Article

Effect of preliminary and technological treatments on the content of chlorophylls and carotenoids in kale (Brassica oleracea L. var. Acephala)

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Abstract

The level of chlorophylls and carotenoids was measured in fresh kale leaves, and in those after blanching, cooking, freezing, canning or drying. Fresh materials contained 121 mg chlorophylls, 28.1 mg carotenoids and 5.77 mg β-carotene in 100 g fresh matter. Blanching kale leaves did not significantly affect the content of these pigments, while cooking decreased only the level of chlorophylls. The highest losses of chlorophylls and carotenoids occurred in canned kale leaves and the lowest in frozen leaves. After 12-month storage, frozen products contained on average 100 mg chlorophylls and 26.3 mg carotenoids in 100 g fresh matter, while in canned products the above values were 42.1 and 22.1 mg, respectively. The content of chlorophylls and carotenoids in air dried leaves was 646 mg and 158 mg/100 g, respectively. Compared with air-dried leaves, the average levels of chlorophylls and carotenoids in freeze-dried products were 15 and 9% higher, respectively. Chlorophylls and carotenoids are important components of vegetables because they give specific coloration and, as phytochemicals, show protective activity against a variety of degenerative diseases. The results of the investigation showed that of the processes preceding the actual preservation of kale, a significant loss of total chlorophylls was found only after cooking. The processes involved in the thermal preservation of kale leaves, particularly in an aquatic environment, brought about pronounced losses of chlorophyll pigments. Carotenoid pigments, however, proved more stable. Of the evaluated methods used in the preservation of kale leaves, the least loss of pigment was found after freezing and the greatest after canning. Results of this study would have practical applications in kale processing to obtain a product in which a considerable proportion of chlorophylls and carotenoids contained in raw kale leaves are retained.

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... In the present study, the Chl a to b ratio ranged from 2.3 to 2.6, wherein the Chl a content was affected by both the factors (blanching and drying), and Chl b content was affected by only that of the drying method (Table 4). In case of Chl a, blanched NPs were observed to have higher values that can be attributed to the protective effect of blanching that was found to limit enzyme activity and pheophytin formation during drying in mint and basil leaves [43,44]. Table 4. ...
... Chlorophyll a (mg 100 g DW − As for drying method, generally, both chlorophyll a and b were positively influenced by freeze-drying method with higher values than convection-dried powders. This can be attributed to the higher pigment retention in FD powders due to the low temperature drying, resulting in limited damage and better extractability of the chlorophylls as consequence of a more porous product, meaning that solvents can easily penetrate the matrix and extract more phytochemicals [16,44]. Moreover, the low temperatures in freeze drying prevented the degradation of chlorophylls to pheophytins due to heat exposure. ...
... Among the individual chlorophylls, Chl a registered a significant loss in convective-dried NPs due to its thermolabile nature. A similar loss of chlorophylls was observed in oven-dried and freeze-dried nettle and kale leaves by Branisa et al. (2017) [16] and by Korus et al. (2013) [44], respectively. ...
Article
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Stinging nettle (Urtica dioica L.) is a ubiquitous, multi-utility, and under-utilized crop with potential health benefits owing to its nutritional and bioactive components. The objective of the work is to produce powders by drying wild stinging nettle leaves as a storable, low-cost functional additive to be used in bakery and ready-to-cook products. Convective drying (CD) and freeze-drying (FD) were applied on unblanched (U) or blanched (B) leaves, which were then milled to nettle powders (NPs). The obtained NPs were evaluated for selected physicochemical (moisture, color), techno-functional (flow indices, hygroscopicity), and phytochemical (pigments, phenols) characteristics as well as mineral contents. Blanching improved mass transfer and reduced the oxidative degradation of pigments during drying, but it caused a loss of total phenols content, antioxidant activity, and potassium content. As for the drying method, CD resulted in better flow properties (i.e., Carr Index and Hausner Ratio), while FD retained better the color, pigments, magnesium content, phenolic, and antioxidant parameters. Overall, the evaluated processing methods resulted in different technological properties that can allow for better evaluation of NPs as a food additive or ingredient. Among the NPs, blanched and freeze-dried powders despite showing inferior technological properties can be recommended as more suitable ingredients targeted f or food enrichment owing to better retention of bio-active components.
... Although the nutritional and antioxidant qualities of fresh vegetables have been studied in detail, and their beneficial effects are well known, little is known about the effects of different cooking methods on some vegetables (such as Galega kale) or about the amounts of beneficial substances actually consumed (Korus, 2013). ...
... capitata Taste associated with flavour reminiscent of metal or salts Aftertaste Sensation occurring after elimination of the product rubra and that steaming slightly decreased that content. Lisiewska et al. (2009) and Korus (2013) observed that blanching and boiling also increased the water content of kale. However, Lisiewska et al. (2009) found that boiling decreased the water content of New Zealand spinach (Tetragonia expansa Murr.) and spinach (Spinacia oleracea, L.) and increased that of kale. ...
... The chlorophyll content can vary between cultivar, sample origin, growing conditions, year, stage of maturity, senescence and plant part. Values of 1.21 g total chlorophyll g À1 in fresh kale (Korus, 2013) and 1.42 and 1.60 mg total chlorophyll g À1 for curly and smooth Galega kale, respectively (Armesto et al., 2015), have been reported. ...
Article
Kale (Brassica oleracea L. var. acephala) is rich in bioactive phytochemicals such as phenolic compounds and vitamins. However, cooking the plants can cause important changes in composition. The objective of this study was to investigate the effect of some domestic cooking processes (boiling, steaming, microwaving and pressure cooking) on several quality parameters of Galega kale. Boiling had the strongest effect on the antioxidant capacity (the IC50 was four times higher than in the fresh sample), total phenolics (losses of 76.4–77.9%) and colour (ΔE = 17.79–19.12). Microwaving caused the greatest loss of soluble solids (80.8–82.2%). Steaming seems to be the best method for retaining the nutrient and antioxidant capacity of kale (100% ash, 71–77.5% soluble solids, 100% antioxidant capacity, 67–71% total phenolics, 62–71% chlorophyll). However, steamed kale was awarded the lowest sensory scores, indicating the difficulty in reconciling nutritional value and sensorial quality. Use of discriminant statistical techniques enabled the classification of 100% of samples.
... freezing (Korus, 2013). Moreover, its processing into convenience products such as chips, juices, fermented juices and inclusion into other fruit and vegetable beverages has been reported (Šamec et al., 2018). ...
... The high-intensity treatment (TP128), resulted in the highest ΔE* value which depicts a great visible difference (ΔE* > 6.0). For vegetable products, the green color is reported to depend on the level and relative proportion of chlorophyll a and b (Korus, 2013). Thus, this change results from the conversion of green colored chlorophylls a and b to olive brown pheophytin a and b and then into olive brown pyropheophytin a and b due to the high temperature and time of processing (Weemaes, Ooms, Van Loey, & Hendrickx, 1999). ...
... Chlorophyllase catalyzes the conversion of chlorophylls to chlorophyllides and pheophythins to pheophorbides whereas lipoxygenase is responsible for coupled oxidation reactions of unsaturated lipids and chlorophylls leading to chlorophyll bleaching (Gökmen, Savas Bahçeci, Serpen, & Acar, 2005;Weemaes et al., 1999). Besides degradation of chlorophyll, other possible reactions linked to color changes are enzymatic browning, Maillard-associated reactions, carotenoid degradation as well as ascorbic acid degradation reaction formed brown compounds (Korus, 2013;Wibowo et al., 2015). ...
Article
This study focused on investigating quality changes of thermally processed kale purée using an integrated targeted and untargeted approach. Low, medium, and high processing intensities (carried out at 70, 90, and 128 °C) were selected based on predetermined shelf-life targets: frozen-thawed, refrigerated, and ambient storage, respectively. The results show that that physicochemical properties determining consumer acceptability were largely dependent on the treatment intensity. The high intensity treatment resulted in the least favorable quality characteristics (distinct brown color, chlorophyll and vitamin C destruction as well as a phase separation after storage). Enzymes were inactivated with increasing thermal load. Regarding taste related compounds, there was no clear effect of processing and storage on acidity and sugar profiles. The untargeted GC–MS approach showed that increasing the processing intensity resulted in an increase of the formation of furans and sulfides. Storage clearly affected the formation of volatiles that could be, depending on the thermal treatment, attributed to lipid and/or carotenoid oxidation, continuation of Maillard reactions, and enzyme catalyzed reactions. Industrial relevance Compared to other Brassicaceae vegetables such as as broccoli, cauliflower and different types of cabbages, kale so far has received little attention from an industrial processing point of view. However, kale has been reported to contain high nutritional value due to its important content of minerals, bioactive compounds and fibre. With the growing health awareness of consumers and increasingly busy lifestyles, the demand for more convenient fruit and vegetable products with high nutritional content has increased. Therefore, research to obtain more insight on the effect of processing and storage on kale purée is important.
... 2). The mean values obtained were 1.12 g·kg -1 , 0.81 g·kg -1 and 0.33 g·kg -1 of total chlorophyll, chlorophyll a and chlorophyll b, respectively, in agreement with other studies [7,28]. The canning gave rise to important losses of chlorophyll in turnip greens, mainly in chlorophyll b (between 72 % and 82 %), which is in agreement with the known fact that chlorophyll a is more stable than chlorophyll b. ...
... MURCIA et al. [24] found in canned broccoli a decrease in chlorophyll a and b contents of 99.4 % and 96.7 %, respectively. KORUS [28] observed losses of 60 % in canned kale. ...
Article
Canned turnip greens were elaborated industrially using water without added salt and water with different levels of NaCl (0.5 %, 1 % and 2 %) as brine, and a mixture (1 : 1) of NaCl-KCl or NaCl-MgCl2 were considered as a tool of reducing sodium. Colour, nutritional quality and consumer acceptability were analysed monthly for 3 months. Significant losses in moisture content, total soluble solids, pH, antioxidant activity, ascorbic acid, total chlorophyll as well as chlorophyll a and b were detected, but titratable acidity increased. Colour was affected by the loss of lightness and greenness, and the increase in yellowness. Consumers evaluated the overall acceptability and the intensities of 15 sensory characteristics of the six types of canned turnips. The results showed that NaCl (2 %) improved flavour, appearance, odour, colour and texture, preserving organoleptic characteristics better than when no salt was added, or when NaCl (0.5 % or 1 %) or other salts were employed. Partial replacement by KCl or MgCl2 showed the worst punctuations, due to the high scores in texture parameters, such as hardness, fibrosity, astringency or adhesiveness, and in bitter and metallic tastes.
... So, it is possible to conclude that these approaches offer protection to the sample and are advantageous in reducing TAOC degradation during drying of Galega kale. In previous literature, it was referred that in spite of losses in antioxidant content caused by blanching at the preliminary stage of processing in kale samples, dried blanched leaves resulted in lower antioxidant loss (Korus 2011a). Similar results related with metabisulphite pretreatment were found for pumpkin flours (Aydin and Gocmen 2015), carrots (Negi and Roy 2001) and leafy vegetables (Onayemi and Badifu 1987). ...
... The influence of pretreatments on the TPC of dehydrated kale is presented in Fig. 4. Losses of 46 % in TPC were observed for untreated samples, whereas blanched samples generated losses between 44 and 76 %. These results were in agreement with previous literature (Korus 2011a), which reported polyphenol content decreases of 60 and 49 % in nonblanched and blanched kale leaves, respectively. These reductions may be attributed to the connection of polyphenols with proteins or the alterations in the chemical structure of polyphenols which cannot be extracted and determined by available methods (Di Scala et al. 2011). ...
Article
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The objective of this work was to evaluate the effect of six pretreatments on quality and nutritional contents of sliced Galega kale submitted to convective drying. Among all treatments, steam blanching was the most favourable, allowing improvements in retention of vitamin C, total antioxidant capacity and chlorophylls in comparison to the absence of pretreatment. Total phenolic losses were not reduced by steam blanching, but the retention was improved by combining this approach with a previous immersion in a metabisulphite solution. Moreover, steam blanching improved the colour parameters and appearance, providing a final dried product more similar to the fresh sample.
... Many vegetables are cooked before consumption. Traditional cooking methods may positively or negatively affect nutritional and sensory characteristics (Korus, 2013). In addition, different heating conditions have different effects on these characteristics that depend on the vegetable concerned (Miglio, Chiavaro, Visconti, Fogliano, & Pellegrini, 2008). ...
... Our results are consistent with those reported in different studies analyzing the effects of different cooking methods on various Brassica spp. (Korus, 2013;Lisiewska, Gę bczynski, Bernas, & Kmiecik, 2009;Mansour, M.Elshimy, Shekib, & Sharara, 2015;Mondrag on-Portocarrero et al., 2006;Podsę dek et al., 2008). However, Lisiewska et al. (2009) observed that the moisture content of New Zealand spinach (Tetragonia expansa Murr.) and spinach (Spinacia oleracea, L.) decreased after boiling. ...
... Korus (2011) showed that freeze-dried kale leaves contained higher levels of antioxidants than did airdried material: polyphenols, vitamin C, and antioxidant activity expressed as trolox equivalent were, respectively, 36, 15, and 33% higher. Moreover, Korus (2012Korus ( , 2013 also pointed out that the levels of chlorophylls, carotenoids and individual amino acids content were higher in freezedried than in air-dried products, and from a practical point of view, she concluded that blanching was not a necessary procedure before drying kale leaves. Still, there is virtually no data in the literature on the freeze-drying kinetics of whole and pulped kale leaves or the extent to which the temperature of this process impacts on the physicochemical properties of dried kale. ...
... Chlorophylls are pigments abundantly found in green vegetables and are strongly related to the colour characteristics. Hence, they are an important quality parameter, reflecting a certain aspect of the final dried product and thus playing a crucial role in the overall consumer acceptability (Korus, 2013). The average contents of chlorophyll a and chlorophyll b in fresh kale leaves were 510.2 and 282.4 mg 100 g -1 DM, respectively. ...
Article
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Investigations were performed to study the freeze-drying process of kale (Brassica oleracea L. var acephala). The process of freeze-drying was performed at temperatures of 20, 40, and 60°C for whole pieces of leaves and for pulped leaves. The kinetics of the freeze-drying of both kale leaves and kale pulp were best described by the Page model. The increasing freeze-drying temperature from 20 to 60°C induced an approximately two-fold decrease in the drying time. Freeze-drying significantly increased the value of the lightness, delta Chroma, and browning index of kale, and had little influence on the hue angle. The highest increase in the lightness and delta Chroma was observed for whole leaves freeze-dried at 20°C. An increase in the drying temperature brought about a slight decrease in the lightness, delta Chroma and the total colour difference. Pulping decreased the lightness and hue angle, and increased browning index. Freeze-drying engendered a slight decrease in the total phenolics content and antioxidant activity, in comparison to fresh leaves. The temperature of the process and pulping had little influence on the total phenolics content and antioxidant activity of dried kale, but significantly decreased the contents of chlorophyll a and chlorophyll b.
... In light of the above information, it can be concluded that food processing may have both beneficial and detrimental effects on the phytochemicals in vegetables (Bunea et al., 2008;Korus, 2012). The drying operation is usually accompanied by physical, biological, and chemical changes, all of which influence the quality of the products, and ultimately the consumers' choice. ...
... Chlorophyll is highly susceptible to degradation during processing and storage, which depends on numerous factors such as temperature, pH, time, enzymes, oxygen, and light. Carotenoids have proven to be more stable during thermal processing in comparison to chlorophyll but may be isomerized and oxidized under the influence of heat, light, and oxygen, among others (Korus, 2012). ...
Article
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Convective drying is one of the most commonly used methods of food dehydration. This technique allows highly perishable products to be preserved; however, it is simultaneously time‐consuming, energy‐consuming and has a negative impact on the products' quality. In order to eliminate these drawbacks alternative drying methods have been sought. This article concerns the microwave‐assisted convective drying of kale. Eight different drying processes were tested. The influence of both continuous and changeable application of microwaves on process kinetics (drying rate), energy consumption, and quality of product (color and ascorbic acid retention) was analyzed. Additionally, four thin‐layer drying models were used to approximate the experimental data and an effective diffusion coefficient was calculated. It was found that the continuous application of microwaves positively influenced kinetics and energy consumption but may have an adverse effect on the products' quality. In contrast, intermittent‐hybrid schedules were characterized by smaller kinetics advantages but a visibly better quality of product. Practical applications In the face of current environmental problems (reduction of CO2 emissions) and increasing prices for electricity, the high energy consumption in convective processes is encouraging the search for alternative methods of drying food products that are prone to spoilage. Additionally, consumer awareness is growing, which is increasing the demand for high‐quality, safe, food products. This work concerns the optimization of existing technology and the development of new technologies for food drying using microwaves. Microwave radiation is an effective source of energy that allows a significant reduction in drying time and energy consumption; but it can have a negative impact on product quality. The proposed solution is the intermittent use of microwaves; but the matter is not simple because the dielectric properties of food depend on many factors (moisture content, composition, temperature, etc.), which makes the effects of microwave drying difficult to predict. Thus, all research on this topic is valuable.
... Other methods of thermal processing, such as blanching or cooking, decrease chlorophyll content as well. Korus [42] researched the influence of blanching kale before convective drying at 55 • C on total chlorophyll content and noted a decrease of 11%. Araújo et al. [43] also researched the influence of the initial processing and drying conditions on the chlorophyll content of kale. ...
Article
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The aim of the work was to assess the possibility of obtaining high bioactivity dried kale using a vacuum impregnation as the preliminary processing before the drying. Kale leaves underwent vacuum impregnation in freshly squeezed onion juice and in sodium chloride solution utilising the following impregnation process parameters: At the vacuum stage, 6 kPa reduced pressure for 1 min, dosing the impregnating solution and keeping the sample under vacuum for 2 min, and then 6 min in impregnating solution at atmospheric pressure. Fluidized bed drying of kale was conducted using inert polypropylene balls, utilising a drying air temperature in a range from 70 to 130 °C. The drying kinetics were described, and the dehydrated product’s quality was assessed, on the basis of these selected characteristics: The content of chlorophylls, polyphenols and carotenoids, and antioxidant activity measured with ABTS+, dry matter, water activity and colour. It was determined that protective influence of vacuum impregnation before fluidized bed drying was seen only in the case of using temperatures of 90 and 110 °C. The highest content of bioactive components in dried kale was obtained in the case of using onion juice impregnation and drying at 110 °C.
... Kale (Brassica oleracea var. acephala) is a source of calcium, magnesium, potassium and fiber (LISIEWSKA et al., 2009;SIKORA;BODZIARCZYK, 2012).It also contains high concentrations of ascorbic acid antioxidants (CAMPOS et al., 2009), carotenoids and chlorophyll (KORUS, 2013), substances which reduce the concentration of free radicals in the body and have been proved to prevent certain chronic degenerative diseases (LIGOR et al., 2013). ...
Article
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The aim of this study was to add dehydrated kale (Brassica oleracea var. acephala) to the formulation of a loaf of bread at concentrations of 2.5% and 5%, and submit the products obtained to physico-chemical, sensory and chemical composition analysis. We also designed a control loaf of bread for comparison purposes. The addition of dehydrated kale increased the pH and acidity of the bread; however, it did not affect the specific volume, which ranged from 4.57 to 4.08 cm3/ g, and the water activity, which was 0.95, making it possible to obtain products with satisfactory technological characteristics. In the sensory test, the kale bread showed good acceptance, with mean scores ranging from 6.5 to 8.4, and outstanding softness. The color of the bread with 5% kale was the only attribute that obtained a mean score below the one obtained for the control bread. The addition of dehydrated kale promoted greater increase in the fiber (133-281%), calcium (176-297%), phosphorus (201-232%), potassium (208-318%) and magnesium (181-300%) content of the bread; however, only for copper (140-160%) and manganese (76-118%), were increments sufficient to make the products good sources of these minerals. As regards the level of oxalic acid, the concentrations obtained were far below the level considered as risky to health. Therefore, the addition of dehydrated kale to the formulation of bread resulted in products with good sensory acceptance, increased their nutritional value, and offered consumers a new choice of bread.
... Chlorophyll content is one of the most important biochemical materials, closely related to the photosynthetic process and with protective activity against a variety of degenerative diseases [1]. Changes in the chlorophyll content of leaves may thus indicate effects of disease and nutritional and environmental stresses [2]. ...
Article
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The reflectance properties of leaves are influenced by diverse biochemical components including chlorophyll, one of the key indicators related to plant photosynthesis and plant stress. Although a number of hyperspectral indices have been proposed for quantifying leaf chlorophyll concentrations, their applications are largely restricted to where they were developed and can hardly provide satisfactory results in other cases. In this study, universally applicable hyperspectral indices calculated from both original and first-order derivative spectra were identified for quantifying leaf chlorophyll concentrations in deciduous forests. Using the main criteria of the ratio of performance to deviation (RPD) and the widely applicable information criterion (WAIC), new hyperspectral indices were proposed for quantifying chlorophyll concentrations in four independent datasets. The results revealed that the normalized derivative difference between the green peak (520-540 nm) and the end of the red edge (720-740 nm) were effective. The normalized difference type of index using reflectance derivatives at 522 and 728 nm, dND (522, 728), was the most effective index for quantifying chlorophyll concentrations, with an R² of 0.807 and a lowest root mean square error of 8.67 μg/cm², n = 816. This index was also validated based on a simulated dataset generated from the model of PROpriétés SPECTrales Version 5 (PROSPECT 5). Its applicability for assessing chlorophyll content in various deciduous forests was hence demonstrated. We foresee its wide application in the future.
... Various studies have been done to reduce this postharvest loss. Korus (2013) reported a decrease in the chlorophylls and carotenoids content of air dried Kale (Brassica oleracea L. var. acephala) leaves (water blanched at 96-98°C for 2.5 min prior to air drying at 55°C). ...
... Various studies have been done to reduce this postharvest loss. Korus (2013) reported a decrease in the chlorophylls and carotenoids content of air dried Kale (Brassica oleracea L. var. acephala) leaves (water blanched at 96-98°C for 2.5 min prior to air drying at 55°C). ...
... Plant leaf chlorophyll is considered to be the most important pigment directly related to the photosynthetic capacity and net primary productivity (Croft et al. 2017). It is also an effective bio-indicator of plant growth condition, nutritional status, environmental stress, senescence, and disturbances (Korus 2013;Main et al. 2011). Hence, quantitatively monitoring the spatial-temporal variation of LCC could provide crucial information to understand the ecosystem response to the changes in environmental, meteorological, and ecological factors (Croft et al. 2017;Richardson et al. 2002). ...
Chapter
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USE OF TIME SERIES SENTINEL-2 DATA AND INDICES FOR MANGROVE HEALTH ANALYSIS
... Carotenoids have been proven to be more stable during thermal processing compared with chlorophylls, but may be isomerized and oxidized under the influence of heat, light and oxygen, and others. [9] As expected, the highest value of relative colour change (dE) was observed for CV, whereas the smallest values of this parameter were noticed for nonstationary processes, i.e. IT2 and IT3. ...
Conference Paper
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This paper concerns hybrid drying of kale. Eight different schedules of drying were tested experimentally to find out the influence of microwave enhancement on the kinetics (drying rate and time), energy consumption of convective drying and quality of products. Different power of microwaves and modes of microwave application were tested. Quality of products was assesed through water activity and colour measurements, as well as retention of ascorbic acid. The results obtained in the studies allowed to state that intermittent application of high-power microwave pulses may lead to a meaningful reduction of drying time and high quality of the dry products.Keywords: hybrid drying; intermittent drying; kale; ascorbic acid; colour
... In addition, measurement of chlorophyll is not possible over a large area. In recent years, Xiaoyan et al. hyperspectral imaging technology has been widely used to estimate chlorophyll content of crops because of it is highly efficient, non-destructive, and nonpolluting (KORUS, 2013). ...
Article
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Chlorophyll is a major factor affecting photosynthesis; and consequently, crop growth and yield. In this study, we devised a chlorophyll-content detection model for millet leaves in different stages of growth based on hyperspectral data. The hyperspectral images of millet leaves were obtained under a wavelength range of 380-1000 nm using a hyperspectral imager. Threshold segmentation was performed with near-infrared (NIR) reflectance and normalized difference vegetation index (NDVI) to intelligently acquire the regions of interest (ROI). Furthermore, raw spectral data were preprocessed using multivariate scatter correction (MSC). A correlation coefficient-successive projections algorithm (CC-SPA) was used to extract the characteristic wavelengths, and the characteristic parameters were extracted based on the spectral and image information. A partial least squares regression (PLSR) prediction model was established based on the single characteristic parameter and multi-characteristic parameter fusion. The determination coefficient (Rv 2) and the root-mean-square error (RMSEv) of the validation set for the multi-characteristic parameter fusion model were reported to be 0.813 and 1.766, respectively, which are higher than those obtained by the single characteristic parameter model. Based on the multi-characteristic parameter fusion, an attention-convolutional neural network (attention-CNN) (Rv 2 = 0.839, RMSEv = 1.451, RPD = 2.355) was established, which is more effective than the PLSR (Rv 2 = 0.813, RMSEv = 1.766, RPD = 2.167) and least squares support vector machine (LS-SVM) models (Rv 2 = 0.806, RMSEv = 1.576, RPD = 2.061). These results indicated that the combination of hyperspectral imaging and attention-CNN is beneficial to the application of nutrient element monitoring of crops.
... Information on the amount and distribution of CCC has been utilized to answer many ecological questions related to monitoring and evaluating terrestrial ecosystem properties such as identifying types of vegetation, mapping vegetation cover, and understanding the condition of vegetation [7]. Changes in CCC indicate the effects of disease, nutritional, and environmental stresses [8][9][10][11]. CCC can also be used for forage quality assessment, ecosystem classification, and biomass estimation, as well as being a key input to estimate the indicators for the Convention on Biological Diversity (CBD) such as trends in carbon stocks and patterns in resilience within ecosystems of Aichi target 15, and net primary productivity of Achi target 3 [12]. The spatially and temporally contiguous information on CCC can also be used to support measuring indicators of the sustainable development goals (SDGs) related to the sustainable use of terrestrial ecosystems. ...
Article
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Accurate measurement of canopy chlorophyll content (CCC) is essential for the understanding of terrestrial ecosystem dynamics through monitoring and evaluating properties such as carbon and water flux, productivity, light use efficiency as well as nutritional and environmental stresses. Information on the amount and distribution of CCC helps to assess and report biodiversity indicators related to ecosystem processes and functional aspects. Therefore, measuring CCC continuously and globally from earth observation data is critical to monitor the status of the biosphere. However, generic and robust methods for regional and global mapping of CCC are not well defined. This study aimed at examining the spatiotemporal consistency and scalability of selected methods for CCC mapping across biomes. Four methods (i.e., radiative transfer models (RTMs) inversion using a look-up table (LUT), the biophysical processor approach integrated into the Sentinel application platform (SNAP toolbox), simple ratio vegetation index (SRVI), and partial least square regression (PLSR)) were evaluated. Similarities and differences among CCC products generated by applying the four methods on actual Sentinel-2 data in four biomes (temperate forest, tropical forest, wetland, and Arctic tundra) were examined by computing statistical measures and spatiotemporal consistency pairwise comparisons. Pairwise comparison of CCC predictions by the selected methods demonstrated strong agreement. The highest correlation (R2 = 0.93, RMSE = 0.4371 g/m2) was obtained between CCC predictions of PROSAIL inversion by LUT and SNAP toolbox approach in a wetland when a single Sentinel-2 image was used. However, when time-series data were used, it was PROSAIL inversion against SRVI (R2 = 0.88, RMSE = 0.19) that showed greatest similarity to the single date predictions (R2 = 0.83, RMSE = 0.17 g/m2) in this biome. Generally, the CCC products obtained using the SNAP toolbox approach resulted in a systematic over/under-estimation of CCC. RTMs inversion by LUT (INFORM and PROSAIL) resulted in a non-biased, spatiotemporally consistent prediction of CCC with a range closer to expectations. Therefore, the RTM inversion using LUT approaches particularly, INFORM for ‘forest’ and PROSAIL for ‘short vegetation’ ecosystems, are recommended for CCC mapping from Sentinel-2 data for worldwide mapping of CCC. Additional validation of the two RTMs with field data of CCC across biomes is required in the future.
... CCC is an essential input variable to terrestrial biosphere models for quantifying carbon and water fluxes (Luo et al., 2018), primary productivity (Houborg et al., 2013;Peng and Gitelson, 2011), and light use efficiency (Wu et al., 2012). Changes in CCC can be an indicator of plant disease, nutritional, and environmental stresses (Korus, 2013;Zhao et al., 2011;Inoue et al., 2012). Therefore, because of its importance to ecosystem function and its value as an indicator of ecosystem health, CCC is an essential variable to be monitored consistently in space and time (Li et al., 2014;Homolova et al., 2013). ...
Article
The Sentinel-2 Multi-Spectral Imager (MSI) has three spectral bands centered at 705, 740, and 783 nm wavelengths that exploit the red-edge information useful for quantifying plant biochemical traits. This sensor configuration is expected to improve the prediction accuracy of vegetation chlorophyll content. In this work, we assessed the performance of several statistical and physical-based methods in retrieving canopy chlorophyll content (CCC) from Sentinel-2 in a heterogeneous mixed mountain forest. Amongst the algorithms presented in the literature, 13 different vegetation indices (VIs), a non-parametric statistical approach, and two radiative transfer models (RTM) were used to assess the CCC prediction accuracy. A field campaign was conducted in July 2017 to collect in situ measurements of CCC in Bavarian forest national park, and the cloud-free Sentinel-2 image was acquired on 13 July 2017. The leave-one-out cross-validation technique was used to compare the VIs and the non-parametric approach. Whereas physical-based methods were calibrated using simulated data and validated using the in situ reference dataset. The statistical-based approaches, such as the modified simple ratio (mSR) vegetation index and the partial least square regression (PLSR) outperformed all other techniques. As such the modified simple ratio (mSR3) (665, 865) gave the lowest cross-validated RMSE of 0.21 g/m2 (R2 = 0.75). The PLSR resulted in the highest R2 of 0.78, and slightly higher RMSE =0.22 g/m2 than mSR3. The physical-based approach-INFORM inversion using look-up table resulted in an RMSE =0.31 g/m2, and R2 = 0.67. Although mapping CCC using these methods revealed similar spatial distribution patterns, over and underestimation of low and high CCC values were observed mainly in the statistical approaches. Further validation using in situ data from different terrestrial ecosystems is imperative for both the statistical and physical-based approaches' effectiveness to quantify CCC before selecting the best operational algorithm to map CCC from Sentinel-2 for long-term terrestrial ecosystems monitoring across the globe.
... Chlorophyll, the most important pigment of plant is directly related to the photosynthetic capacity and net primary productivity (Croft et al., 2017;Carter and Knapp, 2001), and is essential for powering the biosphere (Richardson et al., 2002). It is also an effective bio-indicator of plant growth condition, nutritional status, environmental stress, senescence, and disturbances (Korus, 2013;Main et al., 2011). Moreover, leaf chlorophyll content (LCC) is closely related to nitrogen nutrition status (Daughtry et al., 2000). ...
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... Plant leaf chlorophyll is considered to be the most important pigment directly related to the photosynthetic capacity and net primary productivity (Croft et al. 2017). It is also an effective bio-indicator of plant growth condition, nutritional status, environmental stress, senescence, and disturbances (Korus 2013;Main et al. 2011). Hence, quantitatively monitoring the spatial-temporal variation of LCC could provide crucial information to understand the ecosystem response to the changes in environmental, meteorological, and ecological factors (Croft et al. 2017;Richardson et al. 2002). ...
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Use of fresh-cut vegetables has increased and new technologies have been applied to preserve the quality during transportation and storage. The aim was to investigate the colour changes during storage of fresh-cut rocket, chicory and Swiss chard leafy vegetables during storage at 4-5°C with or without light (150 µmol m -2 s -1 light intensity per 12 h). Moreover, the effect of wash treatments (water or 150 mg L -1 citric acid, applied at the harvesting time) on colour changes was evaluated. During the experimental period of 12 days the colour changes were monitored by the variations of total chlorophyll, carotenoids and anthocyanins. The potential browning development was assessed by polyphenol measurements. Rocket and chicory stored in light conditions showed leaf yellowing after 4 days, while Swiss chard was affected after 8 days of light storage. On the contrary, dark storage preserved better the visual appearance of the minimally processed leafy vegetables tested. The carotenoids declined after 8 days of storage in all treatments and species used. At the end of the experiment the carotenoids reduction was in average 37-47% respect the initial value. Anthocyanins declined in light stored rocket but did not change in other species or treatments. Total polyphenols did not change during storage in all species tested.
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The effect of oven drying at 50ᵒC ± 1ᵒC for 9 hour, 70ᵒC ± 1ᵒC for 5 hour and freeze drying on retention of chlorophyll, riboflavin, niacin, ascorbic acid and carotenoids in herbal preparation consisting of 8 medicinal plants was evaluated. The medicinal plants selected were leaves of Apium graveolens (saderi), Averrhoa bilimbi (belimbing buluh), Centella asiatica (pegaga), Mentha arvensis (pudina), Psidium guajava (jambu batu), Sauropus androgynous (cekor manis), Solanum nigrum (terung meranti) and Polygonum minus (kesum ). Results revealed that both type and conditions of the drying treatments affected retention of all phytochemicals analysed. Herbal preparation developed using oven drying was found to have inferior phytochemicals content compared to that obtained by freeze dryer. Nevertheless, the herbal preparation developed using all treatments still retain appreciable amount of phytochemicals studied, especially carotenoids, ascorbic acid, niacin and riboflavin and thus have potential for commercial purposes.
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Journal of the Science of Food and Agriculture Vol.83 Nr.14, 1389 - 1402 An extensive study on the effects of blanching/freezing and long-term freezer storage on various bioactive compounds of more than 20 commonly used vegetables was performed. Effects were strongly plant species-dependent. Contents of dietary fibre components either were not affected or increased slightly. Minerals in general were also stable, but some losses of soluble minerals by leaching were observed. Phenolic antioxidants and vitamins were clearly more sensitive. Significant losses (20-30%) of antioxidant activity and total phenolics were detected in many vegetables. A qualitative HPLC profiling method for phenolic antioxidants was developed which proved to be very useful when evaluating the complex behaviour of phenolics during food processing. Up to one-third of vitamin C contents were lost during blanching, and further slight losses were detected during storage. Folic acid turned out to be very sensitive to blanching, with more than half of the vitamin being lost, but was stable during freezer storage. Carotenoids and sterols were not affected by blanching or freezer storage. The usefulness of the applied screening methods for evaluation of the effects of processing on vegetables is shown. Copyright © 2003 Society of Chemical Industry
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The effect of drying, packaging and storage conditions on the retention of β-carotene and ascorbic acid, and browning during storage of savoy beet and amaranth leaves was determined. Higher losses of β-carotene and ascorbic acid were observed in solar drying as compared to cabinet drying. Chlorophyll loss was also higher in solar drying. During storage of dehydrated green leaves a continuous decline in nutrients and chlorophyll, and an increase in browning was observed. Storage at low temperature and packaging in double layers of polyethylene film limited loss of quality parameters.
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Since times immemorial, colors in the living world have always fascinated and amazed humans and left them wonderstruck; the present study has also been inspired by their provocative and conspicuous nature. The structural colors, wherein a variety of optical properties emerge as a result of the physical nature of the surface of the tissue, are, however, excluded from the present review. To give a brief account, two predominant structural colors encountered in the biological systems are Tyndall blue colors and iridescent colors. The former are produced as a result of light scattering by very small particles, examples being the color of human eyes and feathers of many birds. The iridescent colors result from interference with light by thin films or laminations, and examples of such colors are abundant in the animal kingdom, in birds, insects, and fishes. It should be noted that no pigment per se is extractable in either of the structural colors discussed. For a detailed account, the readers may refer to Fox (1). The present review deals with pigments or biochromes, the chemical compounds absorbing specific wavelengths of visible light. A broad spectrum of pigments produced in the biological systems are reviewed in relation to their distribution and occurrence in the living world as well as the types, functions, and applications of the pigments in industry and aquaculture. In the last part, attention is focused on the mechanisms of their biosynthesis.
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Chive leaves for freezing contained 13.9 g dry matter, 133 mg vitamin C, 4.7 mg β carotene, 121 mg chlorophylls (a+b), 40.4 mg nitrates, and 0.19 mg nitrites in 100 g of edible parts. Blanching of the raw material before freezing reduced the level of dry matter by 22%, vitamin C 29%, β carotene 20%, chlorophylls 21%, and nitrates 26%, while that of nitrites increased three times. Freezing and 12-month storage of frozen material caused further losses in the analysed constituents except dry matter. Losses were distinctly higher on freezing non-blanched chive, a further enhancement of losses being observed with a storage temperature at −20°C. After a 12-month storage of frozen chive, the preserved content of vitamin C ranged from 11 to 66%, β carotene 37 to 65%, chlorophylls 65 to 75%, and nitrates 58 to 81%. If the blanching is omitted and the storage temperature is −20°C, a good preservation of vitamin C is not possible even for a period of 3 months. In contrast, the pretreatment of blanching ensures its good preservation at −20°C and at −30°C, and also yields a very good conservation of all the constituents analysed.
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The carotenoid and phenolic acid contents in fresh, stored and processed (blanched, frozen and boiled) spinach were comparatively determined by spectrophotometric and HPLC analyses. The major carotenoids identified after HPLC analysis in saponified samples were lutein (37-53μg/kg), β-carotene (18-31μg/kg), violaxanthin (9-23μg/kg) and neoxanthin (10-22μg/kg). These carotenoids were all affected by storage and/or heating. The content of carotenoids was best preserved after storage for one day at 4°C. The total phenolic content in the fresh spinach was 2088mg GAE/kg FW. After LC-MS analysis three phenolic acids were identified and quantified. These being ortho-coumaric acid (28-60mg/kg FW), ferulic acid (10-35mg/kg) and para-coumaric acid (1-30mg/kg) depending on the sample type. After storage of spinach at different temperatures (4°C or -18°C) the amount of total phenolic compounds decreased by around 20%, while the amount of individual phenolic acids increased by four times on average. Copyright © 2007 Elsevier Ltd. All rights reserved.
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After frozen storage the content of individual carotenoids and flavonoids was determined in organically grown spinach genotypes (Spinacia oleracea L) which differed in leaf colour and shape. The spinach was sorted, washed, blanched in steam for 3 min and frozen in liquid nitrogen. After frozen storage the green colour was determined by sensory evaluation and HunterLab colorimetry. The content of individual chlorophylls, carotenoids and flavonoids was determined using HPLC. Lutein, -carotene, violaxanthin and 9-(Z)-neoxanthin were the main carotenoids in processed spinach. The total content of carotenoids varied from 176.6 mg kg-1 ‘wet weight’ as eaten in the lightest green genotype to 226.3 mg kg-1 ‘wet weight’ as eaten in the darkest green genotype. The highest content of -carotene (83.1 mg kg-1 ‘wet weight’ as eaten) was found in the dark green genotype. The content of lutein and neoxanthin varied significantly between genotypes, and the highest content was found in the dark green genotype (76.0 and 25.4 mg kg-1 ‘wet weight’ as eaten respectively). The total flavonoid content and the relative content of individual flavonoids were found to vary between the six genotypes. Seven main flavonoids were identified.© 2001 Society of Chemical Industry
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Green asparagus spears were blanched for a short or long period by steam, water or microwave in two different systems, and spears were frozen by blast or liquid nitrogen under different conditions. The influence of the process conditions on shear force values (toughness), vitamin C, dietary fibre, chlorophyll and drip loss was investigated. Spears with similar or higher shear force values and lower vitamin C were obtained by microwave blanching than by steam and water. No differences were found in shear force values, vitamin C, chlorophyll and dietary fibre between cryogenic and blast freezing, whereas cryogenic freezing reduced the drip loss significantly. Shear force values increased and vitamin C decreased slightly, whereas dietary fibre and chlorophyll did not change during frozen storage.
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The need to promote the use of indigenous vegetables is gaining momentum, as more of their quality factors (nutritive and medicinal) are unveiled through research. Quality factors are classified as quantitative (ingredients, weight); hidden (nutritive, toxic substances); and sensory (appearance, kinaesthetic, flavor). Organoleptically, vegetables are valued for their supreme flavors and aroma, crisp texture, attractive colors, and their overall appeal to human senses of smell, taste, touch, and sight. The retention of these characteristics in dried reconstituted vegetable is of great importance to human consumption. Fresh jute (Corchorus olitorius L.) leaves, which are used as indigenous vegetables in Kenya, were dried under shade, in the sun, by vacuum, and by freeze drying. The effect of the drying methods on the quality of the vegetables was then evaluated. Freeze-dried vegetable was found to have the best quality in terms of color, ascorbic acid content, and reconstitution characteristics.
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A general mechanistic model was developed to describe chlorophyll degradation to pheophytin, chlorophyllide, and pheophorbide in coleslaw, pickles, and olives. Kinetic constants were determined for each commodity. The comparison of in vitro chlorophyllase catalytic constants from greened rye seedlings and in vivo rate constants determined from our whole tissue studies suggests that the conversions of chlorophyll to chlorophyllide and pheophytin to pheophorbide in coleslaw, cucumbers, and brined olives were the result of chlorophyllase activity. We developed a general model that allows for the quantitative comparison of chlorophyll degradation between commodities and thus enhances qualitative comparisons between commodities. In turn, the qualitative comparison could be useful in understanding and controlling the fate of chlorophyll in processed foods. Keywords: Chlorophyll; degradation; kinetics; model; coleslaw; pickles; olives
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Carotene content was altered during the processing of sweet potatoes. The change was dependent upon the treatment employed: blanching (4.0-11.9% increase), lye peeling and pureeing (10.4% increase), steam injection (8.0% loss), canning (19.7% loss), dehydration (20.5% loss), microwaving (22.7% loss), and baking (31.4% loss). Increases in carotene content were attributed to an enhanced extraction efficiency of heat-treated samples. Heat processing induced the formation of predominately the 13-cis-β-carotene isomer, and the quantity formed was related to the severity and length of the heat treatment.
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Major constituents of the extracts from five green vegetables (broccoli, cabbage, spinach, brussels sprouts, kale), several of which are members of the genus Brassica (Cruciferous), have been separated by high-performance liquid chromatography (HPLC) on a C-18 reversed-phase column. Three classes of compounds were shown to be present. In the order of chromatographic elution, these were xanthophylls, chlorophylls and their derivatives, and the hydrocarbon carotenoids (carotenes). The xanthophylls were identified as neoxanthin, violaxanthin, lutein epoxide, and lutein. Several mono cis isomers of xanthophylls were also shown to be present in the extracts from these vegetables. The chlorophylls were identified as chlorophylls b and a and their decomposition products pheophytins b and a. The only hydrocarbon carotenoids present in these vegetables were all-trans-β-carotene and its 15,15′-cis isomer. β-Apo-8′-carotenal and decapreno-β-carotene have been employed respectively as internal standards for quantification of xanthophylls and carotenes. The effect of cooking on the qualitative and quantitative distribution of carotenoids in some of the vegetables has been discussed.
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An HPLC study of 18 of the fresh vegetables (raw and cooked) most frequently consumed in Spain was done to determine their carotenoid composition. The results are grouped according to the color of the edible portion of each: green, red-orange, or yellowish-white vegetables. Beta-Carotene and lutein were found to be present in all of the vegetables analyzed except the sweet red pepper, which contains zeaxanthin but not lutein. Lutein and zeaxanthin are present in five of the vegetables analyzed, with the highest concentration of both of these components being found in spinach. In green and yellowish-white vegetables, lutein predominates over beta-carotene. Red-orange vegetables show a wider carotenoid profile, in which the lutein levels are surpassed by other carotenoids (e.g., lycopene in tomatoes, alpha- and beta-carotene in carrots). Boiling was not found to alter the carotenoid profile of the samples, but the amounts of carotenoids quantified were higher when compared to those in raw samples.
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The kinetics of chlorophyll degradation and visual green color loss in pureed green peas with 80% moisture (w/w) were determined at 70, 80 and 90 C. The –a value from a tristimulus colorimeter was chosen as the physical property and a technique based on fractional conversion was developed in the determination of kinetic parameters of visual green color loss. The degradation of chlorophyll a, chlorophyll b and greenness followed a first order reaction and the temperature dependence of these reactions indicated an Arrhenius relationship. The activation energies were 19.5, 17.1 and 18.2 kcal/mol, respectively.
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Carotenoids form one of the most important classes of plant pigments and play a crucial role in defining the quality parameters of fruit and vegetables. Their role in the plant is to act as accessory pigments for light harvesting and in the prevention of photo-oxidative damage, as well as acting as attractants for pollinators. Their function as antioxidants in the plant shows interesting parallels with their potential role as antioxidants in foods and humans. Carotenoids are products of the isoprenoid biosynthetic pathway. The enzymes leading to carotenoid biosynthesis have all been characterised, and more recently the genes encoding these enzymes have been cloned from bacteria, fungi and plants. New information on enzyme activities and the factors leading to the regulation of the pathway is reviewed. Vitamin A deficiency is a widespread problem in the developing world, causing blindness, particularly in the young. This has driven research into finding ways of introducing provitamin A carotenoids into staple crops, and this has recently been achieved in rice and canola through genetic manipulation. The fact that carotenoids show protective activity in vitro and in vivo against a variety of degenerative disease end points has also give impetus to studying whether increasing intakes of the commonly consumed carotenoids would have public health benefits in the developed world. Human intervention studies have been undertaken using supplements of β-carotene rather than utilising foods with enhanced carotenoid levels, but no potential benefit has been shown. Indeed, there is evidence of an increased health risk from the consumption of β-carotene supplements. These observations suggest that the threshold between the beneficial and adverse effects of some carotenoids is low and provides a strong stimulus to further understanding the functional effects of specific carotenoids. Specific needs for future research are identified in the review.© 2000 Society of Chemical Industry
Article
The concentrations of total phenolics, carotenoids, and chlorophylls of fresh and dried sea buckthorn leaves were determined. Overall, drying of leaves resulted in a decrease in the concentrations of these phytochemicals. The degree of reduction depended on the drying time, temperature, or specific component type. For the phenolics, a greater reduction in concentration was observed in the leaves dried at higher temperatures (80 °C or 100 °C) for longer times (to equilibrium moisture contents of 1% to 3%) compared with those dried at lower temperatures (50 °C or 60 °C). For the leaves dried to higher final moisture (5% to 8%), all drying temperatures resulted in a similar final phenolic concentration. The carotenoid and chlorophyll concentrations in the leaves decreased with the increasing temperatures. However, higher temperatures such as 80 °C or 100 °C resulted in similar carotenoid and chlorophyll concentrations in the leaves. Nonetheless, dried sea buckthorn leaves were of a high nutraceutical quality comparable to those of frequently consumed vegetables.
Article
Thermal degradation of chlorophylls and chlorophyllides in spinach puree was studied from 100 to 145°C (2–25 min) for chlorophylls and from 80 to 115°C (2.5–39 min) for chlorophyllides. The derivatives formed were: pheophorbides, pyropheophorbides, pheophytins and pyropheophytins. Degradation kinetics of chlorophylls and chlorophyllides followed a first-order kinetic model. Reaction rate data showed that the a form of both chlorophylls and chlorophyllides degraded more rapidly than the b form. Chlorophyllides were less stable than chlorophylls. Activation energies ranged from 15.0 to 22.8 Kcal/mol. A kinetic compensation effect was observed for both chlorophylls and chlorophyllides with an isokinetic temperature of 160.8°C. The relative stability of these compounds suggests that methods to maximize chlorophyllides would not be effective for improving green color stability.
Article
The reduced ascorbic acid and β-carotene contents of “retail market-fresh” (RMF) and “fresh-frozen” (FF) green beans and broccoli in a simulated handling system were determined. Changes in ascorbic acid content in the two vegetables during a retail market period and frozen storage followed different patterns. In green beans, ascorbic acid content decreased during refrigerated storage for up to 7 days, but in broccoli there was a significant increase. Blanching resulted in a loss of approximately 40% of the ascorbic acid in broccoli. Ascorbic acid content of FF green beans stored at-20C for 16 weeks was approximately twice that in RMF green beans, but in FF broccoli stored under the same conditions it was only about half that of RMF broccoli. β-carotene content of green beans and broccoli did not change during either the retail market simulation of frozen storage and did not differ from that of fresh.
Article
Broccoli (cv. Empress) obtained from a local supplier was blanched within 15 h of harvest. It was blanched by four methods in covered containers: conventional boiling water (1900 mL, 4 min) (BW), steam (300 mL water, 4 min) (ST), microwave heated in 1 L glass containers (60 ml water, 4 min, 700 W) (MW), and microwave heated in 1 L Seal-a-MealTM bags (45 ml water, 4 min) (MWB). Aliquots were frozen at -18C for 4 weeks. Fresh unblanched broccoli peroxidase activity ranged from 389 to 829 units/min; activity was essentially zero immediately after all blanching treatments. The highest reduced ascorbic acid (RAA) content occurred in fresh unblanched broccoli. Some peroxidase regeneration occurred during frozen storage. Immediately after blanching, all blanched broccoli had lower RAA content than control broccoli. MW-blanched broccoli retained the greatest amount of RAA and had appearance, visual color, texture scores, and chroma of florets and stems equivalent to ST-blanched broccoli. MW-blanched broccoli had flavor and general acceptability scores similar to BW-blanched broccoli. After 4 weeks in frozen storage, MW-blanched broccoli had the highest RAA content.
Article
Lipidic extract from tomato peels, or tomato peels plus stalks, dissolved in ethanol were submitted to illumination. Lycopene, β-carotene, phytoene and phytofluene isomerisation and degradation, during storage at room temperature for 28 days, were studied. Degradation of chlorophylls a and b were analysed in lipidic extracts from stalks. Total lycopene and all-E-lycopene degradation was found to fit to a first-order model. The degradation rate constant was lower in extracts from peels −0.0137 (all-E-lycopene) and −0.0737 (total lycopene), than in those from peel plus stalk −0.0415 (all-E-lycopene) and −0.0854 (total lycopene). Z-lycopene isomers showed an inconsistence change during storage, in all analysed samples. Concentration of β-carotene from extracts of tomato peels plus stalks decreased slightly during storage. Phytoene and phytofluene degradation were not significantly affected by both storage conditions and chlorophylls. The obtained results showed that some compounds from stalks, such as chlorophylls, could favour lycopene and β-carotene degradation during storage under illumination.
Article
The growing body of epidemiological and experimental evidence associating diets rich in fruits and vegetables with prevention of chronic diseases such as cancer has stimulated interest in plant food phytochemicals as physiologically active dietary components. Chlorophyll and its various derivatives are believed to be among the family of phytochemical compounds that are potentially responsible for such associations. Dietary chlorophyll is predominantly composed of lipophilic derivatives including chlorophyll a and b (fresh fruits and vegetables), metal-free pheophytins and pyropheophytins (thermally processed fruits and vegetables), as well as Zn-pheophytins and Zn-pyropheophytins (thermally processed green vegetables). Water-soluble derivatives including chlorophyllides, pheophorbides, as well as a commercial-grade derivative known as sodium copper chlorophyllin (SCC) also contribute to the diversity of dietary chlorophyll derivatives. Although the use of chlorophyll derivatives, especially SCC, in traditional medical applications is well documented, it is perhaps the potential of chlorophyll as a cancer preventative agent that has drawn significant attention recently. Biological activities attributed to chlorophyll derivatives consistent with cancer prevention include antioxidant and antimutagenic activity, mutagen trapping, modulation of xenobiotic metabolism, and induction of apoptosis. Although most research has focused on commercial-grade SCC, the extent to which natural chlorophyll derivatives modulate biomarkers of cancer risk is also being explored. Recent research efforts have also included investigation of the impact of digestive factors on chlorophyll structure and bioaccessibility as a means to better understand the extent to which these pigments may be bioavailable in humans and therefore have more systemic impact in the prevention of cancer.
Article
Enzyme extracted carotenoid pigments from orange peel, sweet potato and carrot samples were freeze-dried and stored at 25oC light, 25oC dark, 4oC and 40oC. Colour losses of freeze dried pigments under these storage conditions were compared with the non-dried samples. For the freeze dried samples, the highest pigment loss was in carrot pigments stored at 40oC (98.1%) while the lowest loss was in sweet potato pigments stored in 4oC (11.3 %) during 45 days of storage. For all three samples, pigment loss was minimum at 4oC and maximum at 40oC as expected. Storage under light did not have significant effect on the carotenoid loss compared with the samples stored at dark. Freeze-drying lowered the pigment loss for all samples under all storage conditions.
Article
Summary  The β-carotene content of young tender leaves of Guku (Bidens pilosa) was found to be 64 μg g-1 in fresh samples. The extractable β-carotene content of Guku leaves boiled for 20 min was 31% greater than that in leaves blanched for 1 min. Boiling for up to 60 min resulted in a 6% decrease of β-carotene compared with the concentration in blanched leaves. Drying in the sun and in the shade resulted in losses of β-carotene of 92% and 93% respectively. After 6 days of refrigeration of unblanched leaves, about 38% of the β-carotene was lost. There was no appreciable change in the levels of β-carotene after the blanched leaves had been kept frozen at -18d̀C for 5 weeks. Blanched mature leaves had 62% more β-carotene than young leaves.
Article
Effect of acid and microbial growth on green color degradation of blanched broccoli (Brassica oleracea) during storage at 7C was studied. When broccoli was submerged in McIlvaine's buffer at pH 3–8, color degradation accelerated as pH decreased, as expected. High Performance Liquid Chromatography (HPLC) was used to show that the color degradation was due to the conversion of chlorophyll to pheophytin only. Pheophytinization followed a first order reaction. the logarithm of the reaction rate constants were linearly correlated to the environmental pH, up to pH 7. Acids containing a benzene ring caused a faster color change than acids with a simple carbon chain due to their hydrophobicity. Microbial growth accelerated color change by producing acid and produced what appear to be holes in the surface of the broccoli, as shown by Environmental Scanning Electron Microscopy (ESEM).
Article
Chlorophylls a and b and pheophytins a and b were quantitaty determined in raw, frozen (after blanching for 60, 120 or 150 s) and canned florets and stems of broccoli. The chlorophyll a and b contents were 0.11 and 0.043 g kg−1 fresh weight respectively in raw florets and 0.036 and 0.018 g kg−1 respectively in stems. About 37.8% and 61.1% losses were incurred during the freezing process in florets and stems respectively, and 98.5% after canning as a consequence of industrial processing. After different blanching times the losses of chlorophyll a in frozen florets varied between 17.7 and 66.4%, while the losses of chlorophyll b varied between 23.2 and 48.8%. In the losses ranged from 55.5 to 75% and from 50 to 88.9% for chlorophylls a and b respectively. These losses resulted in an increase in pheophytin a and b levels in both florets and stems.© 2000 Society of Chemical Industry
Article
The investigation concerned white and green cauliflowers: a traditional technology of freeze – blanched cauliflower, a modified technology of freeze – cooked cauliflower, and two temperatures of frozen storage at −20 and −30 °C for 0, 4, 8, and 12 months. Compared with the white cauliflower, the green variety was characterized by significantly greater contents of dry matter, vitamin C, carotenoids, β-carotene, polyphenols and a higher antioxidative activity at all the stages of evaluation. Depending on the investigated sample, after 12 months of refrigerated storage, cauliflower prepared for consumption retained 29–50% of vitamin C, 73–100% of carotenoids, 53–125% of β-carotene, 69–85% of polyphenols and 26–40% of antioxidative activity in comparison with the raw material. After a 12-month storage, the product obtained using the modified technology contained significantly more vitamin C and in general showed a higher antioxidative activity than did with the traditional product. The lower storage temperature resulted in significantly better retention of vitamin C and also – in some samples – a better retention of carotenoids, β-carotene, and polyphenols. A higher sensory quality was found in products of green cauliflower obtained according to the traditional technology.
Article
Chlorophylls a, b and pheophytins a, b were quantitatively determined in raw, frozen and canned spinach. About 15.9% was lost during the freezing process and 99.9% after canning as a consequence of the heating used in industrial processing. Pheophytins a and b (3.28 and 3.00 mgkg−1) were the predominant chlorophyll degradation derivatives for samples stored in a refrigerator at 8°C for three weeks. The degradation limit of stored samples was around 13–15 days with 2.54 and 1.30 mg kg−1 for pheophytins a and b, respectively. Lipid peroxidation during spinach senescence, as a consequence of being cold stored or processed, increased particularly during the canning process with 3.40 μmol equivalent MDA.
Article
The investigation concerned frozen broccoli produced using a traditional method, i.e. from the raw material blanched before freezing, and a modified method of freezing cooked broccoli. In comparison with blanched broccoli the material cooked before freezing contained more dry matter, carotenoids and beta-carotene and less vitamin C and polyphenols; its antioxidative activity was also poorer. In frozen products stored for 0, 4, 8 and 12 months at − 20 or − 30 °C and then cooked, a steady decrease was observed in the content of all the constituents. Compared with the raw material cooked broccoli stored for 12 months contained 29–33% of vitamin C, 54–66% of polyphenols, 80–97% of carotenoids, 69–80% of beta-carotene and showed a 29–35% decrease in the antioxidative activity. A higher or similar level of the above properties was found in samples cooked before freezing as compared with blanched goods; a higher level was ascertained in samples stored at − 30 °C compared with those stored at − 20 °C. The same sensory quality was found for frozen goods obtained with both methods. Frozen products and ready-to-eat frozen products stored at − 30 °C had higher sensory quality.Industrial relevanceReady to eat vegetable products are more and more popular among individual consumers and catering services. The present work compared quality of traditional frozen broccoli and ready to eat frozen broccoli, both prepared for consumption. After long term frozen storage a higher or similar level of antioxidants was found in ready to eat type as compared with traditional type, and sensory quality of both types was at least good. Products stored at − 30 °C retained more antioxidants and revealed better sensory quality than ones stored at − 20 °C.
Article
The aim of the work was to compare the contents of chlorophylls, total carotenoids, and beta-carotene in the leafy part and in whole plants (leaves with petioles and stems) of dill harvested at the 25 cm stage of growth. Changes in the levels of these compounds in the technological process of freezing and refrigerated storage were also determined. The investigation concerned two kinds of raw material (leafy parts and whole plants), different treatments before freezing (blanching or non-blanching of the raw material), differentiated temperature of storing frozen products (−20 °C and −30 °C), and a storage time of 12 months. Analyses of the frozen products were conducted every 3 months. In 100 g fresh matter of dill leaves the content of dry matter was 12.89 g and of chlorophylls was 144 mg with a ratio of chlorophyll a to b of 1:0.33, that of carotenoids, 30.3 mg and of beta-carotene, 5.00 mg. In whole plants, the contents of comparable components were 26, 40, 38, and 41% smaller, respectively, the ratio of chlorophyll a to b being slightly lower (1:0.39). Blanching, freezing, and in storage of refrigerated products, irrespective of temperature, did not change the contents of components analysed in the first 3 months. During the successive months of storage, blanching favourably affected the preservation of total carotenoids and beta-carotene while the lower temperatures of storage had a beneficial effect on chlorophyll content. The components analysed were preserved in leaves to only a slightly higher extent than in whole plants. If good (90%) preservation of chlorophylls, carotenoids, and beta-carotene were to be used as a criterion of valuation, the dill could be stored for up to 6 months at −20 °C without blanching. For storage periods above 6 months, blanching is necessary, the preservation of analysed components being better at a lower temperature of storing.
Article
The quality of dasheen leaves (Colocasia esculenta Linn Schott var. esculenta) dried at temperatures ranging from 40 to 70 ° C and under both natural and forced convection conditions was studied, in an attempt to develop a dehydrated product from this popular vegetable, often used in soups and commonly called ‘callaloo’. The effects of various pre-treatments on the quality of dasheen leaves dried at 60 °C and under natural and forced convection were also studied, viz.: steam blanching, water blanching and blanching in 0.06% magnesium carbonate at near boiling prior to immersion in a mixed chemical bath consisting mainly of sucrose. Drying of the fresh leaves to a moisture content of 2.0–6.2% db and at the highest temperatures of 60 and 70 °C resulted in undesirable colour changes from green, typical of the fresh vegetable to unattractive olive-brown or brown discolourations. Chlorophyll loss for leaves dried under natural convection was substantial compared with drying under forced convection, where drying times were substantially reduced. Ascorbic acid losses were severe irrespective of convection mode. Blanching of dasheen leaves in water or in an alkali bath followed by sucrose infusion and prior to drying at 60 °C resulted in superior products which, unlike the steam-blanched or unblanched leaves, showed minimal loss of green colour as reflected by chlorophyll and pheophytin contents as well as hue angle measurements.
Article
Two types of parsley — the Hamburg cv Berlińska and leafy type cv Paramount — were frozen and stored at temperatures of −20 and −30 °C for 9 months. One half of the material was blanched before freezing and the other half was non-blanched. In 100 g fresh leaves of Hamburg parsley there were 20.0 g of dry matter, 310mg of vitamin C, 7.5mg of β-carotene, 203mg of chlorophyll, 30.8 mg NNO3 and 0.078 mg NNO2. For the leafy type the corresponding values were 17.3 g, 257 mg, 9.4mg, 68.5mg, and 0.077mg. The material blanched before freezing showed significant losses in the contents of vitamin C (47–51%), nitrates (22–33%), and nitrites (43–55%) and distinctly smaller ones but also significant in the case of dry matter. During freezing and storage of frozen products there were losses in vitamin C, β-carotene, and chlorophyll while the levels of nitrates and nitrites were variable. Particularly great losses of vitamin C and β-carotene were observed in the non-blanched frozen leaves stored at −20 °C. After 9 months' storage, frozen products preserved 10–44% of vitamin C, 37–91% of β-carotene, 78–95% of chlorophyll, and 78–153% of nitrates. Of the types of parsley analyzed the Hamburg type was a better raw material for freezing because of a significantly higher content of vitamin C and chlorophyll and significantly less nitrates in frozen products. When the storage temperature was −30 °C, the blanching of leaves was not necessary, although it helped their pressing into cubes.
Article
Leaves of savoy beet (Beta vulgaris var bengalensis), amaranth (Amaranthus tricolor) and fenugreek (Trigonella foenum graecum) were subjected to different blanching and drying treatments to establish the retention of β -carotene, ascorbic acid and chlorophyll. The vegetables were blanched at 95±3 °C in (i) water, (ii) water followed by potassium metabisulphite (KMS) dip, (iii) salt solution, (iv) salt solution followed by KMS dip, and (v) mixture of sodium bicarbonate, magnesium oxide and KMS and dried in (a) sun, (b) shade, (c) solar drier, (d) cabinet drier, and (e) low temperature drier. Method (ii) was found most suitable for blanching and selected for subsequent drying and method (e) had least drastic effect on β -carotene, ascorbic acid and chlorophyll content of the processed product.
Article
Roasted and ground coffee was stored at constant O2partial pressure (0.5–21.3 kPa), aw(0.106–0.408) and temperature (4–35°C). Product acceptability was monitored by use of a modified Weibull Hazard sensory method where the end of shelf-life was the time at which 50% consumers found the product unacceptable. The effect of O2, awand temperature was studied from a kinetics standpoint. Oxygen increase from 0.5 to 21.3 kPa accelerated deterioration 20-fold. A water activity increase of 0.1 led to a 60% increase in deterioration suggesting non-enzymatic browning activity, while a temperature increase of 10°C rose the rate of deterioration about 15–23%. The activation for shelf life was ≅13 kJ/mole indicating diffusion within the glassy matrix is controlling deterioration.
Article
The herbs of lemon balm, oregano, and peppermint were analysed immediately after harvest and after drying to determine their antioxidant activity and content of total phenolics, l-ascorbic acid, and carotenoids. The strongest inhibition of linoleic acid (LA) peroxidation was found for fresh and dried oregano. For peppermint and lemon balm it was significantly lower and decreased after drying. The ability to scavenge the free radical DPPH (2,2-diphenyl-1-picrylhydrazyl) was very high in almost all tested samples, exceeding 90%. The three species tested had a very high content of total phenolics and drying of oregano and peppermint resulted in their considerable increase. The highest content of ascorbic acid was determined in fresh peppermint and lemon balm and carotenoid content was at a similar level in all the species tested. Drying caused great losses of these compounds.
Article
Antioxidant defence to oxidative stress is achieved by both enzymatic and non-enzymatic reactions. Vitamins C and E and vitamin precursors (e.g. carotenoids) that reduce the rate of initiation or prevent the propagation of free radicals are notable non-enzymatic antioxidants. Of the vitamins, vitamin E is especially important in the prevention of lipid peroxidation, whereas vitamin C reacts effectively with Superoxide and hydroxyl radicals. Vitamin C also plays an important role in reducing semi-stable chromanoxyl radicals and regenerating vitamin E. However, for some vitamins, the oxidativeantioxidative balance may favour pro-oxidant activity under specific conditions. In many cases, this activity has been attributed to the interaction of vitamins with transition metals under certain conditions, which results in the production of a Superoxide ion (O2·−), a hydroxyl radical (·OH) and hydrogen peroxide (H2O2) from the Fenton reaction. The physiological significance of this potential pro-oxidant activity of nutrient vitamins remains to be determined.
Article
An objective method to define the shelf-life of Equilibrium Modified Atmosphere (EMA) packages of minimally processed vegetables is presented. The changes in sensory quality and proliferation of human pathogenic and spoilage micro-organisms on three lightly processed and packaged products as a function of storage temperature were measured. Sensory quality limited the shelf-life of mixed lettuce and cucumber slices before the limiting effects of microbial proliferation. Shelf-life periods were: for EMA-packaged cucumber slices, stored at 2, 4, 7 and 10 °C, 4, 7, 5 and 4 days, respectively; for EMA-packaged mixed lettuce 9, 7, 5 and 3 days, respectively. For bell peppers, on the other hand, the shelf-life was limited by microbial proliferation due to a lower initial microbial quality of the product and extensive availability of water and nutrients. The pH of the product, microbial load and storage temperature had a profound effect on the proliferation of the psychrotrophic pathogens Listeria monocytogenes and Aeromonas caviae. Cucumber slices, stored at 7 and 10 °C, had >2 log units growth of L.monocytogenes during the defined shelf-life. A limited though significant growth of both pathogens was noticed on the mixed lettuce, stored at elevated temperatures (7 and 10 °C). On bell peppers, a decrease in L. monocytogenes and survival of Aer. caviae was detected. Realistic criteria of presence of L. monocytogenes on day 0 (production day) must guarantee microbial safety during the shelf-life of the product, especially when storage temperatures are elevated (7 and 10 °C). In order to guarantee the quality of the fresh-cut produce, it is recommended to keep the product at 4 °C.
Article
The present investigation was conducted to study the concentration of ascorbic acid and beta-carotene in spinach and amaranth leaves as affected by various domestic processing and cooking methods which included storage of leaves in polythene bags or without packing for 24 and 48 hours in refrigerator at 5 degrees C; at 30 degrees C in polythene bags; drying (sun and oven); blanching (5, 10, 15 min); open pan and pressure cooking. Ascorbic acid content of fresh leaves was 624.1 to 629.0 mg and beta-carotene content was 35.3 to 53.1 mg/100 g dry weight. The percent loss of ascorbic acid ranged from 1.1 to 6.3 and 55.3 to 65.9 while lower losses (0.0 to 1.3 and 1.5 to 2.1) of beta-carotene were observed in leaves stored in refrigerator and at 30 degrees C, respectively. A markedly greater reduction in ascorbic acid and beta-carotene was observed in dried, blanched and cooked leaves. The study recommended the storage of leaves in refrigerator, drying in oven, blanching for shorter time and cooking in pressure cooker for better retention of these two vitamins.
Article
The present investigation was conducted to study the effect of selected processing and storage methods on the concentration of ascorbic acid and beta-carotene in Bathua and fenugreek leaves. Methods included storage of leaves with or without polythene bags for 24 and 48 h in a refrigerator at 5 degrees C; at 30 degrees C in polythene bags; drying (sun and oven); blanching (5, 10, 15 min); open pan and pressure cooking. Ascorbic acid content of fresh leaves was 220.97 to 377.65 mg and beta-carotene content was 19.00 to 24.64 mg/100 g, DW. The percent loss of ascorbic acid ranged from 2.03 to 8.77 and 45.15 to 66.9 while lower losses (0.0 to 1.75 and 1.63 to 2.84) of beta-carotene were observed in leaves stored in the refrigerator and at 30 degrees C, respectively. A markedly greater reduction in ascorbic acid and beta-carotene was observed in dried, blanched and cooked leaves. The study data suggest that storage of leaves in refrigeration, drying in oven, blanching for a short time and cooking in a pressure cooker results in better retention of these two vitamins.