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SEM images showing the raw apple, the raw apple dried at 10 MPa, 35° C for 120 min with pure SC-CO2 and rehydrated at 20±2° C, and the raw apple dried for 40 min in EtOH and 10 min in SCCO2 at 10 MPa, 35° C and rehydrated at 20±2° C.
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... Bioactive compounds are present in small amounts in foods and other natural matrices [1] and provide an extra-nutritional contribution to diet due to their beneficial effects on health. Scientific research has recently been focused on the development of new and more advantageous methods for their extraction from food waste [2][3][4][5][6][7][8][9][10], a potential source of useful molecules, in the attempt to provide the food industry with an efficient, cheap, and environmentally friendly solution for waste disposal. ...
... The parameters applied during supercritical fluid extraction (SFE) were found in the literature [1][2][3][4]36]. Ethanol with a percentage of 20% was selected as the extraction co-solvent to help CO 2, which has a low polarity, to favor the extraction of compounds with different polarities from apple peel [5,27]. ...
... Additionally, a mild temperature (60 • C) was selected to avoid thermal degradation of the compounds and preserve the antioxidant properties of the extracts [4,36]. Given these observations, the samples were prepared according to the protocol optimized by Aresta et al. for the determination of polyphenols and vitamins in winemaking by-products by extraction with SC-CO 2 [5]. ...
Supercritical fluid extraction (SFE) was used to extract bioactive compounds from apple (Malus domestica) peel waste from three different Italian cultivars. The bioactive fractions were extracted applying a temperature of 60 °C and a pressure of 250 bar for 15 min with 20% ethanol as co-solvent, at a flow rate of 2 mL/min. The total polyphenol (TP), anthocyanin (TA), ascorbic acid (AA), and antioxidant activity contents (TACs) were measured, while chromatographic analyses were performed to highlight the differences between the extracts. The Stark cultivar had the highest levels of polyphenols, anthocyanins, and ascorbic acid, while the Royal Gala cultivar showed the highest total antioxidant activity. SFE extracts were then tested for their effect on the mitochondrial NADH–ubiquinone oxidoreductase (Complex I) activity on mitochondria isolated from human embryonic kidney cells (HEK239). The Stark extract showed the most positive response in terms of NADH oxidation. The results obtained in this work highlight the potential of apple peel waste as a source of functional phytocompounds and suggest that Stark cultivar extracts may be exploited for pharmacological applications. This study supports the circular bioeconomy by promoting the use of waste products as a valuable resource.
... Drying is one of the most common and effective foodpreserving methods to prevent microbial growth by reducing water activity. 11 Some of the current protein drying methods are convective drying, freeze drying, and spray drying. Convective drying is a commercial method utilized for drying proteins as it is more cost-effective than freeze drying. ...
The aim of this research was to use supercritical carbon dioxide (SC-CO2) drying as a novel approach for generating sorghum protein concentrates/isolates with enhanced functional properties. Sorghum protein extracts were obtained from white whole-grain sorghum flour and were dried by two methods, namely, freeze-drying and SC-CO2 drying. The collected proteins were characterized for their morphology, color, crystallinity, surface hydrophobicity, emulsifying activity index (EAI), creaming index (CI), foaming capacity (FC), foaming stability (FS), protein solubility, chemical interactions, and viscosity. The SC-CO2-dried proteins exhibited higher porosity compared to the freeze-dried ones with smaller particle sizes (∼5.1 vs. 0.4 μm, respectively). The XRD patterns indicated that the SC-CO2-dried proteins had a lower crystallinity than the freeze-dried proteins. However, the surface hydrophobicities of the freeze-dried and SC-CO2-dried proteins were similar. The EAI results showed that the emulsifying activity of freeze-dried protein powder (40.6) was better than that of SC-CO2-dried protein powder (29.8). Nevertheless, the solubility of SC-CO2-dried proteins was higher than that of freeze-dried proteins in most of the pHs investigated. Overall, the proposed SC-CO2 drying method has the potential to generate porous protein powders with improved solubility that can be used in developing functional foods.
... In the last decade, scientific research has focused on new and more advantageous methods for the extraction of bioactive molecules, such as polyphenolic compounds and vitamins, from food waste [1][2][3][4][5]. The main reasons for the growing interest in these matrices are in their properties, namely they provide the food industry with an efficient and environmentally friendly solution for waste disposal and can represent a rich and economical source of useful molecules, if properly treated. ...
... The parameters applied during supercritical fluid extraction (SFE) were found in the literature [1][2][3][4]34]. Having a low polarity, ethanol was selected as extraction co-solvent to help carbon dioxide for vitamin C extraction, while a percentage of 20% was chosen to favor the extraction of polyphenols. ...
This study aimed to extract bioactive compounds from apple (Malus domestica) peel waste using supercritical CO2 extraction. The bioactive fractions from apple peels from the three Italian cultivars were extracted applying a temperature of 60 °C and a pressure of 250 bar for 15 min. 20% ethanol was used as a co-solvent. The extraction process was carried out at a flow rate of 2 mL/min and their total polyphenol (TP), anthocyanin (TA), ascorbic acid (AA), and antioxidant activity contents (TAC) were measured. The extracts from the Stark cultivar had the highest levels of polyphenols, anthocyanins, and ascorbic acid, while the Royal Gala cultivar had the highest total antioxidant activity. Chromatographic analyses were also performed to characterize polyphenols. The extracts were then tested for their effect on the mitochondrial NADH-ubiquinone oxidoreductase (Complex I) activity on mitochondria isolated from human embryonic kidney cells (HEK239) cells, with the Stark extracts showing the most positive response in terms of NADH oxidation. These findings highlight the potential of apple peel waste as a source of functional phytocompounds and suggest the Stark cultivar extracts may have pharmacological applications. This study supports the circular bioeconomy by promoting the use of waste products as a valuable resource.
... Supercritical carbon dioxide (SC-Co 2 ) has been used to dry food because of its low critical temperature of 31.1 C. This property helps dry fruit slices at relatively low temperatures than conventional methods studied in apples (Vetralla, Ferrentino, Zambon, & Spilimbergo, 2018). It has been used for mango slices and persimmon slices drying. ...
In the human diet, bioactive compounds are additional nutrients that are available through fruits. They positively influence human health with their antioxidant activity. To extend shelf life and produce value‐added products, fruits are dried. However, in the process of drying, bioactive compounds are degraded and reduced. In the modern fruit drying facilities, fruits are dried as slices which find their market as snacks and as garnishes for ice creams, yoghurts, and cookies. Hence, it is essential to adopt drying methods that aim at maximum retention of bioactive compounds. Conventional drying methods poorly retain the bioactive constituents and have higher processing time. Potential drying systems that better retain the bioactive compounds include vacuum dryer, hybrid dryer, and freeze dryer. The review focus on different pretreatments and drying methods employed for drying fruit slices with a highlight to the retention of bioactive compounds such as phenols, flavonoids, carotenoids, anthocyanins, and ascorbic acid. The review also gives an outline of the latest techniques to process dried fruit slices with high retention of bioactive compounds.
Practical Applications
Dried fruit slices are valued products from fruits that, after drying, retain a high level of bioactive compounds, fetch a reasonable price in the market. Various drying means for drying fruit slices have been discoursed in the study. Dry fruit makers can choose from various procedures and pretreatments, depending on the costs involved and the technology available. Consumers are watching for healthy snacking options which dry fruit slices can fulfill.
... Supercritical CO 2 (sCO 2 ) has long been used to dry food because it does not leave a residue and it can be used at relatively low temperatures, which preserves the flavor and other properties of the product. Food is a relatively high-value product and the capital and operational costs of sCO 2 dewatering can be justified ( Vetralla et al., 2018 ). We have recently found that sCO 2 dewatering of wood or coal proceeds through one of two mechanisms ( Aggarwal et al., 2019 ;Banerjee et al., 2021 ). ...
Supercritical CO2 (sCO2) displaces water from wastewater, alum, and papermill sludge. The sCO2 appears to enter the sludge matrix through viscous fingering through the entrained water. Because the water removed far exceeds the solubility of water in sCO2, it must be displaced by the sCO2 rather than dissolved out. Adding a small amount of soap to the sludge converts some of the bound water into free water, which can then be displaced by sCO2. Application of the sCO2 in multiple stages greatly enhances dewatering as compared to a single stage process. Approximately 70, 70 and 85% of the initial water can be removed from alum, wastewater and paper sludges, respectively, through a five-stage process. Staged application of sCO2 doubles the efficiency of water removal over a single-stage process of the same duration. It is proposed that when the sCO2 entrained in the sludge is decompressed between stages some of the water is explosively displaced by the expanding CO2.
... For the purpose of commercial drying, scCO 2 is widely used for the drying of gels [25] and also there are studies that reported its practical application for the preservation of decellularized esophageal scaffolds [26]. Application of scCO 2 in food drying is still limited to few products at the small pilot scale [22,24,[27][28][29] and additional studies are still needed for scCO 2 -drying technology to be developed at industrial scale. The pilot scale scCO 2 -drying unit used in this study still has a low technology readiness level and requires further work in order to reach industrial application [30], first of all to validate its effectiveness in various working regimes [31]. ...
The aim of this study was to compare the sensory quality and acceptance of dried ready-to-eat beetroot snacks as a result of different drying methods applied: supercritical CO2-drying (scCO2-drying), frying, and freeze-drying. Descriptive sensory analysis, quality rating (10 assessors), and consumer acceptance testing (n = 102) were performed. Mean overall quality scores within the range of “very good” quality were found only in non-precooked scCO2-dried samples which were characterized by typical magenta color, low level of shape and surface deformations, pronounced brittleness and crispiness, and good rehydration during mastication. The other samples were in the range of “good” quality. The pre-cooking step before scCO2-drying negatively influenced the sensory quality parameters, particularly appearance. Around 60% of tested consumers showed a preference for the fried and non-precooked scCO2-dried samples. The drivers of liking were mostly related to the characteristics of the product, which was salted, fried, and crispy, with an oily and overburnt flavor, i.e., the product most similar to commercial potato chips products. Freeze-drying had a negative effect primarily on appearance and flavor. According to the sensory evaluation conducted, direct scCO2-drying without a pre-cooking step showed itself as a promising alternative drying technology in the production of dried beetroot snacks.
... Sc-CO 2 drying induces minor capillary stresses with respect to conventional methods because the vapor-liquid interface is avoided, allowing the maintenance of the original structure (Baldino et al. 2015;García-González et al. 2015;Özbakır and Erkey 2015). The technology is well known for aerogel preparation (Maleki et al. 2014), but food applications are still limited to a few case products: carrots (Brown et al. 2008), basil (Bušić et al. 2014), coriander , apples (Vetralla et al. 2018;Djekic et al. 2018;Tomic et al. 2019), chicken breasts (Morbiato et al. 2019), and mangoes and persimmon (Braeuer et al. 2017). So far, a few studies have reported a correlation between process variables and the Sc-CO 2 dried product. ...
Supercritical CO2 food drying technique was investigated on red bell pepper with a lab-scale reactor equipped with CO2 recirculation. Box–Behnken design was used as experimental design to analyze the impact of temperature (313–333 K), pressure (10–14 MPa), CO2 flow rate (80–220 kg/h), and treatment time (6 and 16 h) on the final water activity. The results demonstrated that temperature was the most influential variable, reaching the lowest value of water activity (aw = 0.262) at 333 K, 12 MPa, and 100 kg/h. Efficient drying with a similar final water activity could be achieved at the lowest temperature considered (313 K) and longer drying time (16 h) with an appropriate combination of pressure (14 MPa) and flow rate (160 kg/h). Sc-CO2 samples showed similar values of color changes compared with freeze-dried samples with main differences corresponding to the “a” and “b” axes, i.e., in red and yellow. Textural properties of Sc-CO2 dried samples were not statistically different compared with freeze-drying. Sensory evaluation showed promising evidence for the use of supercritical CO2 as an alternative drying method to produce dried bell pepper products.
... On the other hand, the color and chlorophylls content of dried basil samples by freeze-drying were better than the supercritical and conventional drying techniques (Bušić et al., 2014). Vetralla et al. (2018) suggested that the treatment of apple slices by SCCO2 had inactivated polyphenol oxidase, which significantly gave treated slices higher lightness compared to non-treated ones ( Figure 5). (Vetralla et al., 2018) Dehydration rate SCCO2 as a pretreatment for drying of apple slabs has shown fast dehydration rate comparing to the non-treated slabs. ...
... Vetralla et al. (2018) suggested that the treatment of apple slices by SCCO2 had inactivated polyphenol oxidase, which significantly gave treated slices higher lightness compared to non-treated ones ( Figure 5). (Vetralla et al., 2018) Dehydration rate SCCO2 as a pretreatment for drying of apple slabs has shown fast dehydration rate comparing to the non-treated slabs. Furthermore, for an optimum rate, the increase in pressure demonstrated to be more functional than temperature increasing (Lee et al., 2011). ...
In food technology, researches work hard to find new technologies which could substitute the conventional industrial processes and could achieve their various purposes. Mainly, these researches look forward to reduce the environmental threatening, to alleviate the usually encountered negative effects during and after processing of foodstuffs, and for the obtainment of novel product to meet the needs of expanding food markets. Supercritical fluid technology is one of the new researched subjects for the development or even the replacement of existing technologies. Since the used substances (CO2) are inexpensive and not toxic, the supercritical fluid technology is considered as an economical and green technology which is ready to invade several applications. As it is known, drying is among the thermal processes applied for the preservation of food and increasing its shelf life. Because of the habitual thermal drawbacks of drying, many studies have tried to apply the supercritical fluids for the dehydration of foodstuffs. In order to know the latest studies done on the dehydration using this non-thermal technology, it was reviewed here in this paper the main supercritical drying processes and the main obtained results for fruits and vegetables. It was concluded that this technology till now reached an important development, due to its positive effects in reducing the microbial charge, to preserve the nutritional value and the bioactivity of dried food. Despite all of that, the investigations on supercritical fluid technology should continue to make clear all its advantages, even disadvantages, and conditions for more and large scale of drying applications in the food industry.
... The state of the art of scCO 2 drying in food is still limited to few products at the lab/pilot scale (Braeuer, 88 Schuster, Gebrekidan, Bahr, Michelino, Zambon et al., 2017;Michelino, Zambon, Vizzotto, Cozzi & 89 Spilimbergo, 2018;Vetralla, Ferrentino, Zambon & Spilimbergo, 2018) and additional studies are needed for 90 a further industrial development of scCO 2 technology. The current technology readiness level of the pilot 91 scale unit for supercritical fluid drying is still low and requires further research in order to achieve its 92 industrial application (Djekic, Tomic, Smigic, Udovicki, Hofland & Rajkovic, 2018). ...
The aim of this study was to analyze the stability of sensory properties and secondary metabolites in supercritical-CO 2 (scCO 2 ) dried ‘Elstar’ apple cuts/snacks during twelve months of storage at ‘room’ temperature. Air-drying and freeze-drying were used as reference methods. ScCO 2 -dried apple packed in aluminum-polyethylene bags under nitrogen gas retained a high sensory and nutritional quality, and acceptance level until the end of the observed period. The overall acceptance scores of these apples after 6 and 12 months of storage remained in the range of neutral consumer attitude “neither like nor dislike”. Packaging under nitrogen gas preserved the content of flavonols (≥0.14 g/kg), dihydrochalcones (≥0.10 g/kg), hydroxycinnamic acids (≥0.18 g/kg), triterpenes (≥5.72 g/kg), and proanthocyanidins (≥0.08 g/kg) in dried apple irrespective of the drying method applied. The comparison with the conventional drying processes demonstrated that scCO 2 -drying represents a promising alternative technology for the production of dried apple snacks. The study was assisted by the evaluation of consumer attitudes towards dried fruit and drying technologies. Freeze-drying, air-drying and scCO 2 -drying were recognized by the tested consumers as trustful drying-processes, with expressed interests in buying scCO 2 -dried products if the technology was scientifically proven as excellent in preserving nutrients, color and taste of food products.
... Indeed, water is not removed by vaporization or sublimation, but is dissolved in the SC−CO 2 [28], avoiding the formation of the vapourliquid interfaces and capillary stress (that usually result during airdrying), thus assuring preservation of structure and less shrinkage. Specifically, evidences in literature are shown for the drying of herbs [29,30], vegetables [31] and fruits [32][33][34] and also for the preparation of aerogel [35] and decellularized dried scaffolds [36,37]. Our group has recently demonstrated that SC−CO 2 drying can dry and pasteurize the food in one step, showing high inactivation for both natural present microorganisms [38] and inoculated pathogens [39]. ...
This work explores the feasibility to apply supercritical CO 2 (SC−CO 2 ) drying alone or in combination with High-Power Ultrasounds (SC−CO 2 +HPU) to improve the shelf life and safety of raw chicken meat. SC−CO 2 +HPU drying process revealed the fastest water removal and higher rehydration capacity. A complete inactivation (6 log CFU/g) of mesophilic bacteria and yeasts and moulds was achieved with both the SC−CO 2 processes, while oven drying at 75 °C, used as control, showed only a limited inactivation (4 log CFU/g). The SC−CO 2 processes were efficient also for the inactivation of inoculated Salmonella. The retention of Vitamins B1, B2, B3 and B12 after the SC−CO 2 drying demonstrated the preservation of fresh like properties in terms of nutrients. Colour analysis showed a change in colour comparable to traditional cooking techniques. Results demonstrate that SC−CO 2 -based processes may be used as innovative technologies to dry chicken and make it microbiologically safe, while maintaining nutritional properties.
