An electrohydraulic shock wave generator was used to study the bactericidal action of shock waves on Escherichia coli ATCC 10536 suspensions in 0.9% (w/v) NaCl solution (initial cell population: 8.2 log10 CFU/ml). The influence of treatment temperature, shock wave energy, number of applied shock waves, the acoustic cavitation produced by the shock wave, and the spark gap-generated light (UV and visible) were analyzed using E. coli cultures in the exponential phase. Part of the experiment was repeated in the stationary phase. Results indicate that light, number of shock waves, cavitation and interactions between them, influence bactericidal activity (P<0.05). The best viability reduction of 4.06 log10 CFU/ml was achieved at 350 shock waves, administered during approximately 14.5 min, with bacteria in the stationary phase by enhancing acoustic cavitation inside the vial, and without protecting the samples from the visible and UV radiation produced by the shock wave-generating spark.
Nanocomposite LDPE films containing Ag and ZnO nanoparticles were prepared by melt mixing in a twin-screw extruder. Packages prepared from the films were then filled with fresh orange juice and stored at 4 °C. Microbial stability, ascorbic acid (AA) content, browning index, color value, and sensory attributes of them were evaluated after 7, 28, and 56 days of storage. Packages containing the nanomaterials, expect 1% nano-ZnO, kept the microbial load of fresh juice below the limit of microbial shelf life (6 log cfu/ml) up to 28 days The least degradation of AA (80.50 mg/100 g), development of brown pigments (OD = 0.23) and losing of color (∆E = 6.0) were observed in pouches containing 0.25% nano-ZnO, after the same time. Sensory attributes were also ranked highest for the juice thus packed in the recent packages after 28 days (p < 0.05). Packages containing nanosilver increased shelf life of fresh juice although part of its sensory attributes were lost.Industrial relevanceCompared with pure packaging materials, antimicrobial nanocomposite packages containing Ag and ZnO as an alternative non-thermal technology can extend the shelf life of fresh orange juice up to 28 days. However, a certain concentration of nano-ZnO in the packages showed less adverse effects on sensory characteristics.
Cultures of Lactobacillus delbrueckii ssp. bulgaricus 11842 grown on whey supplemented with yeast extract were subjected to treatments using sonication, a high-speed bead mill, and a high-pressure homogenizer. The various means of disruption were compared by the release of intracellular β-galactosidase and by scanning electron microscopy (SEM). The β-galactosidase activity was measured using o-nitrophenyl-β-d-galactopyranoside (ONPG). In general, the release of active β-galactosidase was not affected by cell concentrations in the range of 12–46% (wet wt.). The maximum activity was observed after 2–3 min of bead milling and after three passages through the high-pressure homogenizer (135 MPa). The amount of active β-galactosidase released by homogenization after one passage at 200 MPa was comparable to that released between two or three passages at 135 MPa. Sonication was not as effective as the bead mill or the high-pressure homogenizer with respect to the release of β-galactosidase or the break-up of cells as evidenced by SEM and TEM. Both bead milling and high-pressure homogenization appear to be suitable for the large-scale disruption and release of β-galactosidase from L. delbruekii ssp. bulgaricus 11842.
Amaranthus tricolor (Amaranthaceae) is a popular vegetable in China. Separation of lipophilic extracts of the aerial parts of A. tricolor by means of preparative ‘High-speed Countercurrent Chromatography’ (HSCCC) led to the isolation of two chlorophyll breakdown products which were characterized as 132-hydroxy-(132-S)-phaeophytin-a (1) and chlorophyll b methoxylactone (2).The structure of 1 was established using a combination of 1D- and 2D-NMR spectroscopic and mass spectrometric techniques. Component 2 was identified by means of ESI-MS/MS analysis.Industrial relevanceChlorophylls and their degradation products are natural pigments of interesting bioactivities. For industry, recovery of these pigments from waste materials of fruit and vegetable processings could be a promising by-product line. Here we present the isolation of a pure chlorophyll breakdown product which is in principle suited as a nutraceutical ingredient. Large-scale isolation procedures using countercurrent chromatography techniques for chlorophyll related pigments are currently under development.
Labelling with stable isotopes is a powerful technique when used in metabolic studies. However, there is some doubt that absorption from a test meal labelled ‘extrinsically’ with a stable isotope compound will behave in the same manner as the same naturally occurring ‘intrinsically’ labelled compound. Three growing methods were investigated, and a method for growing spinach containing intrinsically labelled 5-methyltetrahydrofolic acid (5-CH3-H4-PteGlu) using as nutrient-flow hydroponic system and a nutrient solution containing 50% of the nitrate as 15N nitrate is described. The resulting plants contained 630 μg kg− 1 5-CH3-H4-PteGlu with 40% of the nitrogen present as 15N. After feeding, appearance of 5-CH3-H4-PteGlu in the plasma derived from the test meal could be identified by liquid chromatography/mass spectrometry.Industrial relevance: This paper deals with the highly relevant question of comparing the absorption of biochemicals – in this case folates – used as food fortificants or supplements with folates occuring naturally in foods. The authors provided data for the successful application of a method for growing spinach containing an intrinsic label for use in folate metabolism studies.
The inactivation effect of 18 T pulsed magnetic fields in combination with selected non-thermal technologies was studied on Escherichia coli ATCC 11775. The bacteria were subjected to a treatment of either ultrasound (20 kHz, 70 W, 242 μm), high hydrostatic pressure (207 MPa, 5 min), pulsed electric field (6.25 kV/cm, 5.6 ms), or anti-microbials (Nisin 77.5 mg/l, lysozyme 1 mg/ml) and 50 magnetic field pulses (18 T, 30 μs). No additional inactivation or cell damage due to exposure to the pulsed magnetic field at 42°C was observed.
Diffusion of beet dye from beet cubes was measured during a 3 min moderate electric field (MEF) process using frequencies ranging from 0 (direct current) to 5000 Hz, and field strengths ranging from 0 (conventional heating) to 23.9 V/cm, while maintaining steady-state temperature at 45 °C throughout the process. Diffusion increased with electric field strength and decreased with frequency. There was no enhanced diffusion from an agar cube or from previously frozen beet tissue. Electroporation is suggested as the mechanism for enhanced diffusion. Mass transfer enhancement appears to be significant when the product initially possesses an intact cell structure. There appears to be a threshold potential above which significant increases in permeabilization occur. Except for DC, this potential is found to depend on frequency—the higher the frequency, the higher the threshold potential for permeabilization.
The effects of ultrasound on milk homogenization and yogurt fermentation were studied. Microscopic photographs were used to check the size distribution of fat globules to evaluate the homogenization effect. The pH change during yogurt fermentation, water holding capacity, viscosity and syneresis for finished yogurt were evaluated. It was found that high amplitude ultrasound has a very good homogenization effect compared with conventional homogenization. Longer exposure times improved the ultrasound homogenization effect. Sonication after inoculation reduced the total fermentation time by 0.5 h. Increasing the ultrasound amplitude level before inoculation significantly improved the water holding capacity and viscosity and reduced syneresis. Sonication after inoculation did not decrease the syneresis effect but did increase water holding capacity and viscosity.
Ultrasound combined with heat treatment has yielded favorable results in the inactivation of microorganisms; however, the composition of food influences the rate of microbial inactivation. The objective of this research was to study the effect of butter fat content in milk on the inactivation of Listeria innocua and compositional parameters after thermo-sonication. Four butter fat contents in milk were evaluated at 63 °C for 30 min of sonication (Hielscher® UP400S, 400 W, 24 kHz, 120 μm amplitude). Results showed that inactivation of Listeria cells occurs first in fat free milk, and that the rate of inactivation decreases with increasing fat content. No degradation of protein content or color variation was observed after the treatments. The pH dropped to 6.22, and lactic acid content showed an increase of 0.015% after the treatment; solids-non-fat, density and freezing point decreased. During storage life, growth of mesophiles was retarded with sonication.Industrial relevanceUltrasound is an emerging technology that has shown positive effects in milk processing. Listeria monocytogenes represent one of the main foodborne pathogenic microorganisms in the food industry. Results of this research show that thermo-sonication is a viable technology capable of inactivating Listeria cells in milk and extending shelf-life without significant nutritional or physicochemical changes.
The behaviour of spoilage and pathogenic microorganisms was evaluated after high-pressure treatment (600 MPa 6 min, 31 °C) and during chilled storage at 4 °C for up to 120 days of commercial meat products. The objective was to determine if this pressure treatment is a valid process to reduce the safety risks associated with Salmonella and Listeria monocytogenes, and if it effectively avoids or delays the growth of spoilage microorganisms during the chilled storage time evaluated. The meat products covered by this study were cooked meat products (sliced cooked ham, pH 6.25, aw 0.978), dry cured meat products (sliced dry cured ham, pH 5.81, aw 0.890), and raw marinated meats (sliced marinated beef loin, pH 5.88, aw 0.985). HPP at 600 MPa for 6 min was an efficient method for avoiding the growth of yeasts and Enterobacteriaceae with a potential to produce off-flavours and for delaying the growth of lactic acid bacteria as spoilage microorganisms. HPP reduced the safety risks associated with Salmonella and L. monocytogenes in sliced marinated beef loin.
Perishable foods are extremely sensitive to temperature abuse often observed during sea transportation, which regularly involves long transit times. The goal of this study was to compare the effects of the cargo on RFID (radio frequency identification) tag readability to achieve real-time temperature monitoring. A 12 m long refrigerated sea container (68 m3) and a 915 MHz RFID system were used. The container was loaded three times with different food products: canned vegetables, fresh meat and frozen bread. Each load was instrumented with 42 RFID tags evenly distributed throughout the volume. Results showed that canned vegetables provide the best readings (97.6% of tags read), followed by fresh meat (61.9%) and frozen bread (57.1%) respectively. These results validated that radio waves at 915 MHz are absorbed by high water as well as ice contents. However, spacing between metal surfaces and tags can allow excellent RFID readability even if RF reflects on metallic surfaces.Industrial relevanceThe food industry is facing great challenges when it comes to food transportation and distribution. Marine transportation is a slow operation that can expose shipments to a significant range of non-ideal temperatures. Refrigeration units may experience failure during shipment, which inevitably causes losses in quality. The implementation of a real-time temperature monitoring system within a container can provide a good tool to address this issue. Radio frequency technology definitely offers additional benefits such as real-time monitoring as well as tracking and tracing.
Phospholipase A2 is very resistant to thermal and manothermosonication treatments. It is a frequent contaminant of pancreatic proteolytic preparations. Its inactivation in such preparations can be achieved by dissolving the enzymes in buffers at neutral pH prior to its end use to allow the proteolytic action on the lipase. Alternatively, although much more complicated, the application of manothermosonication treatments makes phospholipase susceptible to proteolysis under conditions (buffer, pH and temperature) where the protease was not able by itself to hydrolyze PL.
Background: Many patients prescribed cholesterol-reducing drugs do not achieve target cholesterol levels. Soy protein reduces plasma cholesterols in patients with untreated hypercholesterolaemia. Objective: To test whether Abacor®, a newly developed soy-based dietary supplement, further reduces plasma cholesterol concentrations when given to hypercholesterolaemic patients in statin treatment. Design: In total, 49 patients (m/f=34/15, age 43–79 years) completed the study. All had a plasma LDL cholesterol concentration >3.0 mmol/l at baseline despite statin treatment. Within the study, participants received statin monotherapy for 6 weeks, statin+Abacor® for 6 weeks and finally statin monotherapy for further 6 weeks. Results: The plasma concentrations of total cholesterol and of LDL cholesterol were significantly lower at visit 5 (6 weeks of combination treatment) than the mean value of the concentrations at visit 3 and visit 6 (both after 6 weeks of statin monotherapy), 5.5±0.1 vs. 5.9±0.1 mmol/l, p<0.0004 and 3.3±0.1 vs. 3.6±0.1 mmol/l, p<0.0006. Conclusion: The soy-based dietary supplement Abacor® has a total and LDL cholesterol reducing effect when given as supplement to statins in hypercholesterolaemic patients.
Clostridium perfringens growth from a spore inoculum was investigated in vacuum-packaged, cook-in-bag, marinated chicken breast that included additional 1.0% NaCl. The packages were processed to an internal temperature of 71.1 °C, ice chilled and stored at various temperatures. The total C. perfringens population was determined by plating diluted samples on tryptose–sulfite–cycloserine agar followed by anaerobic incubation for 48 h at 37 °C. At 19 °C, C. perfringens levels were consistently about 2.5 log10 CFU/g until 9.5 h regardless of the presence or absence of Citricidal®. However, storage of the unsupplemented marinated chicken samples and those with 50 or 100 ppm Citricidal® samples at 25 °C for more than 6 h resulted in rapid growth of C. perfringens, exhibiting 2–3 log10 CFU/g increase at 7 h. Citricidal® at 200 ppm significantly (p < 0.05) reduced the growth of C. perfringens at both 19 and 25 °C. The D-values obtained at 90 °C were significantly decreased (p < 0.05) from 14.07 (no Citricidal®) to 9.20 min (200 ppm Citricidal®). Supplementing marinated chicken products with Citricidal® and the temperature abuses had no consistent effect on color, shear force or lipid oxidation. However, the organism may grow to unsafe levels if sous-vide products are poorly handled or temperature abused for a relatively long period. An extra degree of safety may be assured in such products by supplementation with 100 or 200 ppm Citricidal®.Industrial relevance: Since temperature abuse is a common occurrence during trasportation, distribution, storage or handling in grocery stores or by consumers, an extra degree of safety may be assured in marinated chicken products by supplementation 100–200 ppm Citricidal®. In such products, the temperature abuse should not have any consistent effect on color, shear force or lipid oxidation of products.
The use of new technologies in beef production chains may affect consumers' opinion of meat products. A qualitative study was performed to investigate consumers' acceptance of seven beef processing technologies: marinating by injection aiming for increased 1) healthiness; 2) safety; and 3) eating quality; 4) marinating by submerging aiming for increased eating quality; 5) nutritional enhancement and restructuring through enzyme binding; 6) shock wave treatment and 7) thermal processing. Participants' attitudes towards beef, their innovativeness and risk aversion were also assessed. In total, 65 adults (19–60 years old) participated in eight focus groups in Spain, France, Germany and the UK. Results suggested a relationship between acceptance of new beef products, technology familiarity and perceived risks related to its application. Excessive manipulation and fear of moving away from ‘natural’ beef were considered negative outcomes of technological innovations. Beef processing technologies were predominantly perceived as valuable options for convenience shoppers and less demanding consumers. Overall, respondents supported the development of ‘non-invasive’ technologies that were able to provide more healthiness and better eating quality. Excessive intervention in meat production chains was severely criticized and participants expressed their longing to keep beef processing ‘simple and natural’.
Eimeria acervulina is a protozoan parasite that can cause intestinal lesions and reduced weight gain in chickens. E. acervulina oocysts were treated by high hydrostatic pressure and evaluated for pathogenicity, immunogenicity, and structural integrity. Pressure treatment of E. acervulina oocysts at 550 MPa for 2 min at 4, 20 or 40 °C rendered the parasites nonpathogenic to chickens. Pressure treatment at 40 °C also prevented fecal shedding of oocysts. Upon challenge with non-pressurized E. acervulina oocysts, partial immunity was observed with a reduction in lesion severity in chickens that had been inoculated with pressure-treated oocysts. No changes to the fragility and permeability of the oocyst wall or excystation of sporocysts were observed as a result of pressure treatment. Light and scanning electron microscopy revealed no changes to the whole oocyst or sporocysts. Recovery and the morphology of excysted sporozoites were altered by pressure treatment. These results suggest that pressure affects sporozoite integrity.Industrial relevanceHigh-hydrostatic pressure processing has been shown to inactivate various microorganisms and is utilized commercially for enhanced food safety and quality. Some pathogenic microorganisms have been inactivated by HPP yet retain immunogenic properties suggesting potential application for vaccine development. Eimeria acervulina is a poultry pathogen for which new vaccines are sought. E. acervulina is also closely related to Cyclospora cayetanensis, a foodborne human pathogen. HPP was explored for effect on E. acervulina for potential vaccine development for chickens and for insight on HPP effects on parasites for enhanced safety of human foods.
In the present research two objectives were studied. The first was aimed to optimize whey cryoconcentration process by minimizing the amount of the dry matter entrapped in the ice fraction. This was possible by recycling the ice fraction. It was possible to concentrate acidic whey from 5.71 ± 0.01% (w/w) up to 24.68 ±0.03% (w/w) total dry matter using three cryoconcentration cycles and one recycling ice cycle. The second objective was to study the emulsifying and foaming properties of the concentrated whey as function of the cryoconcentration cycle. Results showed that emulsion stability index (ESI) of the cryoconcentrated whey increased by increasing the cryoconcentration cycle whereas the emulsion activity index (EAI) decreased. Foaming ability expressed as nitrogen volume needed to get foam volume three times higher than the initial volume increased by increasing cryoconcentration cycle and foam stability decreased by increasing the cryoconcentration cycle.Industrial relevanceSeveral efforts and studies have been made to increase the use of milk whey, a valuable by-product of cheese processing, especially for human nutrition. In the present work, cryoconcentration technology was used for whey recovery and valorisation as promising ingredient in the food industry.
The effect of partial inactivation with lactic acid (LA), liquid chlorine dioxide (ClO2) and intense light pulses (ILP) on injury and post-treatment growth under increased NaCl concentration and reduced pH values of Listeria monocytogenes strains was investigated. Inactivation levels and the percentage of sub-lethal were dependent upon strain and type of inactivation technique used. Comparison of the mean time-to-detection (TTD) values under suboptimal conditions (increased NaCl concentration or reduced pH) showed that the longest TTD was at every pH observed for the cultures treated with ClO2, followed by LA and ILP. Under increased NaCl concentration LA treated cells required the longest TTD, followed by ClO2 and ILP, respectively. Significant difference in TTD between untreated and cultures treated with ClO2 and LA was observed. Recovery of ILP treated cultures was not always different from untreated cultures. The extended post-treatment effect based on the growth retardation or inhibition of injured cells under sub-optimal conditions is suggested as an important tool in conditioning of microbial food safety.
High pressure processing (HPP) reduces the glycolytic activity of lactic acid bacteria (LAB) and provides a means to control further production of acidic metabolites in fermented dairy products during storage. However, there is limited information on the effects of HPP on specific enzymes of dairy starter bacteria responsible for the metabolism of lactose. The aim of this study was to determine pressure-induced inactivation of glycolytic enzymes in Lactococcus lactis subsp. lactis C10, Streptococcus thermophilus TS1 and Lactobacillus acidophilus 2400. Cultures were grown for 16 h in M17 or MRS broth containing 5% (w/v) lactose at pH 6.5 (maintained by addition of 10 M NaOH). The cells were harvested by centrifugation, washed and resuspended in 100 mM phosphate buffer (pH 6.5) and pressure-treated at 300 and 600 MPa (≤ 22 °C, 5 min). The ability of pressure-treated resting cells of Lactococcus, incubated with 5% (w/v) lactose at 30 °C, to ferment lactose was evaluated by determining titratable acidity (TA) during incubation. The activities of phospho-β-galactosidase (P-β-gal), β-galactosidase (β-gal) and lactate dehydrogenase (LDH) were determined in cell-free extracts of untreated and pressure-treated cells. Resting cells of Lactococcus treated at 600 MPa had a substantially lower rate of acidification than the controls and those treated at 300 MPa. Both P-β-gal and β-gal were significantly inactivated (p < 0.01) in the starter cultures treated at 300 or 600 MPa. The LDH in Lactococcus and Lactobacillus was highly resistant to pressure treatment at 300 MPa. In contrast, the LDH in Streptococcus was almost completely inactivated at ≥ 300 MPa.
The effects of a short-time microwave (MW) treatments on the survival of Alicyclobacillus acidoterrestris spores (105 spores/g) inoculated in a cream of asparagus, along with the oxidation of the fat component (olive oil), were investigated.The samples were MW-treated at 60–100% of power (2450 MHz) for 3–7 min; power and processing time changed according to a Central Composite Design at two variables/five levels. The combinations resulting in a 2-fold reduction in the number of alicyclobacilli spores (100% of power–5 min; 80%–6 min; 80%–7 min) were stored at different temperatures and times (25 °C/27 days, 37 °C/18 days and 50 °C/9 days), to determine the decay of the qualitative characteristics of the lipid fraction. Peroxide value, K232, K270 and Rancimat test (induction time) were chosen as indexes of primary and secondary oxidation. MW-effect on the spores depended upon both the power and the treatment time; moreover the interaction [power] × [time] was the most significant variable. As regards the effect of MW on the lipid fraction, the results suggested that MW affected slightly induction time, peroxide values and spectrophotometric determinations, especially at low powers.Industrial relevanceSince the middle of 1990s, MW-processing has been regarded as a convenient approach for the stabilization of vegetable preserves. In Southern Italy, olive oil is an essential ingredient for this kind of food; however, it is well known that a strong thermal processing as well as not-correct storage could affect it significantly and increase the art of oxidation.This research provides some useful information on the effects of MW for a new product, an asparagus cream, focusing on the influence of this approach on olive oil oxidation, thus suggesting that MW could be a convenient preservation technique.
This study investigates the effects of high-pressure processing on the microbiological, physico-chemical and sensory properties of 3 fermented Spanish dry sausages (salchichón), all high in unsaturated fatty acids. The products, manufactured from the sausage meat and back fat of pigs fed on high-oleic and high-linoleic diets and a control diet, were vacuum-packed prior to high hydrostatic pressure (HPP) treatment (500 MPa, 5 min), and storage at 6 °C for up to 210 days. High-pressure treatment slightly inhibited certain microorganisms, especially yeasts and moulds, and psychotrophic and anaerobic bacteria. Consequentially, microbial counts fell, although injured microorganisms recovered during storage except in the case of the high-linoleic salchichón, in which they remained inactive causing it to register the lowest counts. High-pressure treatment had no noticeable effect on the physico-chemical and sensory properties of the three samples suggesting that it improves the food safety of salchichón with no detrimental effects on organoleptic properties.Industrial relevanceThe problem of safe preservation is increasingly complex for the meat industry as today's products require longer shelf lives and greater assurance of protection from microbial spoilage. High pressure processing is finding increased use in products such as sliced cured meats, where microbial contamination can occur during the slicing process and develop over storage. This study evaluates the microbiological, physicochemical and sensory characteristics of vacuum-packed slices of dry fermented sausage – control (CO), high oleic (HO), and high linoleic (HL) salchichón samples – following high pressure treatment and subsequent chilled storage, contributing thereby to the growing body of knowledge on this new food preservation technology, which produces microbiologically safe food products with long shelf lives, whilst retaining high nutritional and sensory qualities.
Great interest and rapid research efforts on acrylamide in foods followed an announcement in April 2002 by the Swedish National Food Authority and the University of Stockholm. Reduction of acrylamide in high-temperature processing foods, including selection of the raw material and variation of processing parameters, etc. were extensive reported. In this research, effect of some agents on acrylamide formation was investigated. A glucose-asparagines reaction model system was used to test the effect of ferulic acid, catechin, CaCl2, NaHSO3, and l-cysteine on inhibition of acrylamide formation and three efficient inhibitors, NaHSO3, CaCl2 and l-cysteine were screened. The results showed that immersing of the fresh potato chips using different concentration of the agents greatly inhibited acrylamide formation in fried potato crisps, and the efficiency increased as their concentrations increased; among them, l-cysteine is the most efficient agent but CaCl2 is most potential. Effects of these food additives on the texture of fried potato crisps were also studied. It was found that l-cysteine showed little effect on the texture of the crisps and CaCl2 is regarded as the suitable choice because of its low price and the acceptable mouth feel of fried crisps treated by CaCl2, although it increased the brittleness. Moreover, the application of CaCl2 in industrial production of fried potato crisps was also studied. In the blanching process (deactivation process of enzymes at 85 °C), a computerized electrical conductivity detector was used to keep the concentration of CaCl2 at constant and the result showed that immersion of potato slices in CaCl2 solution at 5 g/L reduced acrylamide formation by more than 85% in fried crisps.
Strips of salmon (Salmo salar) skin or whole zebra fish (Brachydanio rerio) were preserved for many weeks by embedment in untreated Sphagnum palustre moss (A), peat derived mainly from Sphagnum mosses (B), acetone-extracted moss (C), or the chlorite holocellulose of the moss (D). Preservation occurred in the presence of oxygen at 20–23°C, and between pH 3.4 and 5.1. Product D, which was a pure, insoluble, white polysaccharide, performed as well or better than the other materials. It contained ∼0.5 mmol g−1 of highly reactive carbonyl groups, and when these were removed by borohydride reduction or condensation with ammonia, the preservative property was lost. Preservation was invariably accompanied by a browning of the dermis and a yellowing of the scales, and was attributed to a Maillard reaction, since neither occurred when the carbonyl groups were removed. A water-soluble fragment (‘sphagnan’) of D, containing 1.0 mmol g−1 of carbonyl groups, had an astringent taste in aqueous solution and produced effects similar to those brought about by embedment in A, B, C or D, albeit more rapidly. Films of mackerel (Scomber scombrus) skin became brown and completely bio-resistant after repeated immersion in aqueous (3% w/v) sphagnan with intermittent drying, whereas similar treatment with borohydride-reduced sphagnan had no effect. Differential thermal analysis (DSC) of the sphagnan-treated skin gave results consistent with tanning by covalent cross-linking. Hence, the chemical and visible color changes associated with embedment in the moss products or immersion in aqueous sphagnan resembled those brought about by exposure to wood smoke. Filleted fish muscle cannot, however, be preserved in these ways because soluble protein diffuses out from the muscle too quickly, and neutralizes the carbonyl groups selectively.
Activation and conformational changes of mushroom polyphenoloxidase (PPO) after high pressure microfluidization treatment were observed by means of UV spectrophotometer, far-UV circular dichroism, fluorescence emission spectra, UV absorption spectra and sulphydryl groups detection. The results indicated that, treated under pressures of 90 MPa, 110 MPa, 130 MPa and 150 MPa one pass, and 150 MPa 1, 2 and 3 passes, respectively, mushroom PPO exhibited an increase in activity. The circular dichroism (CD) analysis demonstrated that some of secondary structures such as α-helix were destroyed. There were some indices that the increase of relative activity was accompanied by a decrease in α-helix content. The fluorescence emission spectra analysis indicated that Trp and Tyr residues in mushroom PPO were more or less exposed to solvent, and the result was in good agreement with that of UV absorption spectra analysis. The sulphydryl groups detection showed that the sulphydryl groups content on the surface of mushroom PPO was increased.Industrial relevanceResults of the present study show that high pressure microfluidization can not be used to inactivate mushroom PPO. However, it provides a new way for enzyme preparation, such as enzyme modification, with higher activity. High pressure microfluidization can be easily operated, with shorter treatment time and higher food safety compared with chemical methods.
Diet rich in fruits and vegetables has been associated with preventing mutagenesis and cancer and other health benefits. In the present study, hexane and chloroform extracts from the fruit rinds of Garcinia pedunculata were tested for their antioxidative and antimutagenic activities. Both the hexane and chloroform extracts showed antioxidant activity studied through beta-carotene-linoleate model system and alpha, alpha-diphenyl-beta-picrylhadrazyl (DPPH) method at various concentrations. At 500 ppm concentration, in case of beta-carotene-linoicate model system, the hexane and chloroform extracts of G. pedunculata showed 60 and 67% antioxidant activity respectively, whereas the free radical scavenging activity was 45% and 65%, respectively with DPPH method. The antimutagenicity of the hexane and chloroform extracts against the mutagenicity of direct acting mutagen sodium azide was determined by the Ames test. Both the extracts showed strong antimutagenicity at or above 1250 mu g/plate in the tester strains of Salmonella typhimurium (TA100 and TA1535). However, the hexane extract showed higher antimunagenic potential than the chloroform extract. Thus, this preliminary study documents for the first time the antioxidant and antimutagenic properties of the extracts from the fruit rinds of G. pedunculata. (c) 2006 Elsevier Ltd. All rights reserved.
Cinnamomum has long been regarded as a food or medicinal plant. Leaves of five species of Cinnamomum, namely C. burmanni, C. cassia, C. pauciflorum, C. tamala and C. zeylanica, were chosen to investigate their antioxidant activities in this study. C. zeylanica exhibited the highest total phenolic content while C. burmanni had the highest flavonoid content among the five species. These five species were then screened for their antioxidant potentials using various in-vitro models such as total antioxidant capability, 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging activity, reducing power and superoxide anion scavenging activity at various concentrations. C. zeylanica showed the highest DPPH radical scavenging activity, total antioxidant activity and reducing power, while C. tamala exhibited the highest superoxide anion scavenging activity. By the analysis of the high performance liquid chromatography coupled to diode array detector (HPLC-DAD), three flavonoid compounds namely quercetin, kaempferol and quercetrin were identified and quantified. This study suggested that Cinnamomum leaf can be used potentially as a readily accessible source of natural antioxidants.Industrial relevanceThis study was focused to evaluate the antioxidant activities of five species of Cinnamomum leaf which is normally used in medicine and also used in food preparation. This study provided an alternative of utilizing Cinnamomum leaf as a readily accessible source of natural antioxidants in food and pharmaceutical industry.
The antioxidant potential of an ethanolic extract of the oyster mushroom, Pleurotus ostreatus, was investigated. The extract exhibited the most potent radical-scavenging activity at a maximum concentration of 10 mg/ml, and the scavenging effects were 56.20% and 60.02% on hydroxyl and superoxide radicals, respectively. The IC50 values of the extract were found to be 8 mg/ml for hydroxyl and superoxide radicals. Ascorbic acid used as a standard was highly effective in inhibiting hydroxyl and superoxide radicals, showing IC50 values of 6 mg/ml and 4 mg/ml respectively. At a maximum concentration of 10 mg/ml, the extract effected 56.12% inhibition of lipid peroxidation and 60.68% chelation of ferrous ions; also, at a maximum concentration 10 mg/ml, the extract manifested significant (p < 0.05) reducing power (1.367) which exceeded even that of butylated hydroxyl toluene (1.192). Increasing concentrations of the extract were found to cause progressively decreasing intensity of fluorescence 2, 3-diazabicyclo [2, 2, 2] oct-2-ene (DBO). In addition, the known antioxidants were identified as components of the extract. The data generated by this study strongly suggest that an ethanolic extract of the oyster mushroom, P. ostreatus, has potent antioxidant activity.Industrial relevanceThe present study suggests that an ethanolic extract of the mushroom, Pleurotus ostreatus, could serve as an easily accessible item of food rich in natural antioxidants, as a possible food supplement or even as a pharmaceutical agent. Hence this study is considerable relevant to the food and pharmaceutical industries.
Two peptide fractions (P1 and P2) were isolated from Cantonese sausages at different drying periods by ultrafiltration. P1 possessed a stronger 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity in the first 18 h of drying and a weaker activity during the rest period, comparing with P2. The analysis of amino acid composition indicated that histidine was the major amino acid in both peptide fractions, which content was changed during the process. In addition, Glu, Gly, Arg were important constituent amino acids in both peptide fractions. A significant (P < 0.05) decrease of >10 kDa peptide fraction and increases of 2–3 and <2 kDa peptide fractions were detected when comparing with peptides at 0 h. However, no significant difference was found for all the peptide fractions at different drying periods, except for 2–3 kDa peptides. A significant (P < 0.05) correlationship was found between lipid oxidation and antioxidant activities.Industrial relevanceCantonese sausage has gained much popularity and acceptance in China and many other countries. In this work, two peptide fractions were isolated from Cantonese sausage. A good antioxidant activity was observed for each peptide fraction. Endogenous peptides resulting from proteolysis offer a promising approach to improve lipid stability for meat industry. It is helpful to retard lipid oxidation in order to improve its quality.
The antagonistic effect of the indigenous microflora on pathogens was investigated by using Salmonella Typhimurium, Staphylococcus aureus and Listeria innocua as challenge microorganisms. 18 strains strongly adherent to the leaves of iceberg lettuce were selected and their taxonomic status was determined with the aid of APT NE20, BBL CRYSTAL (TM) E/NF systems and 16 S rDNA sequencing. In the majority of cases (15/19), the identification by biochemical testing did not agree with that of 16 S rDNA sequencing. Six strains exerted antagonistic effects on S. Typhimurium and L. innocua, when overnight cultures or cell free culture supernatants were investigated in the agar diffusion test. In vivo experiments showed that the inoculation of lettuce with P putida LTH 5878 by dipping and pre-incubation decreased the numbers of S. Typhimurium, L. innocita and S. aureus below the level of detection (< 100 cfu/g) after storage for 7-8 d at 4 degrees C. The dependency of the antagonistic efficacy on the numbers of P. putida LTH 5878 was determined using point inoculation. The study of the effect of the pseudomonades/pathogen ratio on the reduction of pathogens showed that the antagonistic activity of Pseudomonas is stronger against S. Typhimurium than against L. innocita. A major reduction was achieved for the counts of L. innoctia at ratios of greater than 100: 1 whereas for S. Typhimurium a ratio of 0.1:1 was already effective. The sensory properties of the inoculated and stored lettuce were in general better than those of the untreated control. (c) 2006 Elsevier Ltd. All rights reserved.
We describe the influence of high pressure (200–600 MPa) on surface tensions and surface shear viscosities of protein layers adsorbed at pH 6.5 or 8.0 from mixtures of sulfated polysaccharides with β-lactoglobulin (β-Lg), bovine serum albumin (BSA), ovalbumin (OVA) or 11S globulin Vicia faba under low ionic strength conditions favouring electrostatic interaction. Time-dependent measurements at the air–water interface for pressure-treated pure β-Lg, OVA or 11S showed a lowering of the surface tension while pressure-treated BSA gave a higher surface tension value. Native β-Lg, OVA and 11S formed highly-viscous films at the n-tetradecane–water interface and pressurisation of these proteins induced even more viscous films that increased in apparent viscosity over a period of several hours. Under similar experimental conditions, untreated BSA formed a less viscous film that weakens after pressure treatment. The experimental interfacial tension data obtained for β-Lg+dextran sulfate (DS) are consistent with weak electrostatic complexation, whereas mixtures of BSA or OVA with dextran sulfate or 11S with ι-carrageenan (ι-CAR) are consistent with strong protein–polysaccharide complex formation in bulk solution. While the interaction of proteins with the polysaccharides has only a small influence on the surface viscosities of the adsorbed proteins, trends are consistent with strongest interaction for the most sulfated polysaccharide (DS).
This study was conducted to determine the effect of both soy protein and glycerol contents on physico-chemical properties of soy protein isolate-based edible (SPI) films. The aim of this study was to better understand the influence of SPI and GLY contents on the behavior of the physico-chemical properties of soy protein isolate-based films. Films were casted from heated (70 °C for 20 min) alkaline (pH 10) aqueous solutions of SPI at 6, 7, 8, and 9 (w/w %), glycerol (50%, w/w, of SPI) and SPI at 7 (w/w %), glycerol (40, 60, 70 %, w/w of SPI). Water vapor permeability (WVP), was measured at 25 °C and for four different relative humidities (30–100%, 30–84%, 30–75%, 30–53%). Surface properties and differential scanning calorimetry were also measured. Varying the proportion of SPI and GLY had an effect on water vapor permeability, wetting and thermal properties of SPI films. A synergistic effect of glycerol and protein was observed on the water vapor permeability. Glycerol and RH gradient strongly enhance the moisture absorption rates and permeability of SPI based films. SPI content weakly increases the WVP and does not modify the surface properties. The temperature of denaturation of soy protein decreases glycerol content except for the higher concentration whereas it increases with protein ratio.Industrial relevanceThis topic of research aims to control mass transfers within composite foods or betweenfoods and surrounding media (for instance the headspace in packagings). The targeted applications from this work deals with the food product coating or the coating of paper-based packaging for limiting both the loss of water and flavors by cheese based products. This will allow to maintain the weight of the cheese during “ripening” and commercialization, and also to prevent (off-) flavour dissemination from very odorant cheese as produced in France and Poland.
Different applications of cold and warm tap water (4 °C and 50 °C) with and without chlorination, respectively, in the washing of uncut peeled carrots (Daucus carota L.) were conducted, and their effects on sensory and microbiological properties during storage for 9 days at 4 °C were assessed. To minimise cross-contamination of almost sterile inner root parts with the highly contaminated outer cortex during processing the peeled carrots were washed prior to cutting. The washing treatments were carried out using a commercial processing line, thus facilitating the scale-up to industrial production. Populations of aerobic mesophilic bacteria, lactic acid bacteria and enterobacteria on these minimally processed carrots were determined, and the sensorial quality of shredded carrots was evaluated by a sensory panel throughout storage. Additionally, colour, texture, sugars, and trichloromethanes were analysed. Washing uncut carrots with cold chlorinated water (200 mg/l, 4 °C) and warm tap water (50 °C) ensured sugar retention and reduced aerobic mesophilic bacteria by 1.7 and 2.0 log10 colony forming units per gram (cfu/g), respectively, while washing with warm chlorinated water (200 mg/l) resulted in a 2.3 log10 cfu/g reduction. By-product formation due to chlorination was negligible. Sensorial properties of the latter samples were slightly affected. It was shown that both washing uncut knife-peeled carrots with cold chlorinated water (4 °C) and warm tap water (50 °C), respectively, provided good microbiological safety paired with improved sensorial properties. Moreover, fresh-like character of the products was retained, as indicated by the persisting respiration of the living tissues.
The aim of this work was to evaluate the effect of different homogenization pressures on the rheological properties of model dairy emulsions. Solutions of sodium caseinate and whey protein concentrate at 2% + 1% and 2% + 2% (w/v) were emulsified with milk fat at the final contents of 5%, 8% and 15% (w/v). Raw and pasteurized emulsions were subjected to conventional (15/3 MPa) and high pressure (97/3 MPa and 147/3 MPa) homogenization. Differences in viscosity were observed according to fat content, protein ratio, heat treatment and pressure homogenization conditions. Gel networks formed in 8% and 15% fat content emulsions after pasteurization and high pressure homogenization. Gel strength was mostly affected by protein and fat contents.Dynamic high pressure may be used to produce emulsion gels with modulated structures which could be exploited low fat formulations.Industrial relevanceTexture influences people's acceptance of food and may be more important than the flavor in some products. Gelation of emulsions was observed after pasteurization and high pressure homogenization treatments, depending on fat and protein contents. Dynamic high pressure may be an alternative tool to improve viscoelastic properties and mouth feel of emulsions by providing a weak gel structure in the system. These characteristics can be exploited for low fat and low additive formulations.
The effects of alternative decontamination processes to chlorine: ozonated-water (1 ppm/5 min), hot water (100 °C/45 s) and ultrasonication (45 kHz/1 min), applied pre- or post-cut in the technological diagram of minimal processing of carrots were tested. Ultrasonication in chlorinated-water and thermo-ultrasonication as combined processes applied just in pre-cut carrot were also tested. The initial microbial load reduction, soluble solids content, pH and sensorial attributes of shredded carrot just after processing were evaluated. Decontamination processes applied on pre-cut carrot provided maintenance of fresh-like sensorial quality, regardless the type of treatment, due to diminished leaching phenomena which is critical for shredded carrot. Chlorination, ozonization and ultrasonication achieved ca. 1 Log10 reduction of initial microbial load. No additional decontamination effect in combined processes was observed. The use of heat in pre-cut carrot proved to be the most efficient process regarding microbial reduction (3 Log10 units) providing, as well, an acceptable fresh-like quality product.Industrial relevanceThe major constraint for marketability of minimally processed shredded carrot is its limited shelf-life due to rapid microbial growth and colour loss (decrease of orange intensity and/or whitening of the shreds). These questions arise from the practical experience of a fresh-cut industry directly involved in the R&D research project which supported this study. Chlorine solutions have been widely used to sanitize fruit and vegetables in the fresh-cut industry. However, reduced microbiological efficiency allied to the eventual formation of carcinogenic chlorinated compounds pointed out the need for alternative methodologies. The present work aimed the evaluation of clean alternative decontamination processes applied both to pre- and post-cut carrot for the production of shredded carrot, operating under conditions of industrial practice at pilot-plant scale.
In this study, the effects of microwave treatment on hazelnuts artificially contaminated with aflatoxigenic fungi were evaluated qualitatively and quantitatively. The physical quality attributes (color, moisture loss, and sensory attributes) of microwave treated hazelnuts were also evaluated. A significant 3-log reduction in Aspergillus parasiticus contamination was observed after 120 s treatment, no or similar changes were observed during the storage of microwave treated hazelnuts under the storage conditions. While taste and odour of microwaved in shell hazelnuts were unaffected during treatment and subsequent storage, microwave treatment duration of 120 s was found to be capable of reducing fungal count of A. parasiticus on in-shell hazelnut without any noticeable change in nutritional and organoleptic properties of nuts. Based on this and the earlier study, a hybrid process is proposed, where UV-C surface treatment and vacuum assisted microwave are combined with air drying to increase the shelf life and control the quality.Industrial relevanceA hybrid industrial process is proposed, where UV-C surface treatment and vacuum assisted microwave treatment are combined to increase the shelf life and control the quality of hazelnuts.
The shelf life of mushrooms packaged using different polymer top-films (PVC, PET with different levels of perforations) was investigated using hyperspectral imaging (HSI). Packaged mushrooms were stored at 4 ± 0.2 °C for 14 days and weight loss, Hunter L, a, b values, maturity index and in-pack gas composition (% CO2 and O2) were also measured. The results obtained showed that the PET film perforated with small holes (1 mm in diameter) was generally superior in terms of maintaining overall mushroom quality. Regression models were built to correlate HSI data with measured quality parameters. Prediction maps were generated from hyperspectral data to show the model performance at pixel level. Results presented in this work show hyperspectral imaging can be used to evaluate the effect of different packaging systems on mushroom quality and that perforated PET packaging film is a viable alternative to the conventional PVC packaging, facilitating an increase in shelf life from 10 to 14 days.Industrial relevanceThe present study demonstrates HSI can be used for rapid evaluation of mushroom quality facilitating non-destructive evaluation of the effect of packaging systems on mushroom shelf-life. In addition, this work suggests an effective packaging solution to extend shelf life of mushrooms during storage. The proposed solution potentially improves the packaging recyclability as the same polymer material (PET) is used for the tray and top film, compared to conventional mushroom packaging where PVC is used for the top film and polypropylene (PP) for the tray.
Freshness of common mushrooms was related to the internal atmosphere composition during modified atmosphere packaging (MAP) experiments at 20 °C and 80% RH with stretchable polyvinylchloride (PVC) film, paper, and the same paper coated with a wheat gluten solution. MAP with the stretchable film led to a detrimental deterioration of mushrooms after only one day of storage: dark brown blotches appeared and almost 30% of mushrooms exhibited open veil. This was due to the formation of condensed water at the inner surface of the material and onto mushrooms combined to a high O2 partial pressure (16 kPa) in the headspace. Wheat gluten (WG) coated paper was the most effective to improve the shelf-life of mushrooms since it allowed the preservation of a fair colour, unbroken veils, and an acceptable texture during 3 days. This beneficial effect was attributed to the combination of a medium CO2 (9.5 kPa) and low O2 (2.5 kPa) partial pressure, without condensation. The main drawback of using WG-coated paper was its high water vapour permeability that led to an important weight loss (3.8 wt.% on day 3). However it did not affect the overall quality of mushrooms within the storage duration.
Polyethylene-based films coated with nisin loaded HPMC films were put in contact with food simulants, i.e. agarose gels with 5 or 30% (w/w) fat. Nisin desorption from the multi-layer films and diffusion in agarose gels were monitored by ELISA (Enzyme Linked ImmunoSorbent Assay). The data obtained after 2 or 6 days of contact between antimicrobial films and agarose gels were employed to determine nisin mass transfer by numerical modeling following Fick's second law. The values were in the range from 0.87 × 10− 3 m s− 1 to 4.30 × 10− 3 m s− 1 and 6.5 × 10− 11 m2 s− 1 to 3.3 × 10− 10 m2 s− 1, for nisin apparent desorption and diffusion coefficients, respectively. The diffusion process was governed by interactions between food matrix simulant and nisin. Moreover, it was observed that the polymer in the coating did not modify plastic film initial mechanical resistance and water vapor permeability.Industrial relevanceThis paper concerns active packaging, considered as a new approach to preserve food shelf life. Active packaging is a real gain for plastic and Food industrials. The paper deals with coating as a manner to activate packaging. The impact of coating on film properties is investigated.Also, predictive models are proposed to determine antimicrobial agent desorption and diffusion during some storage conditions.
The use of edible coating has proved a valuable tool in improving the efficiency of osmotic dehydration (OD) of plant material. In this study the impact of edible coating with or without an anti-microbial agent (A–M) on microbial growth was investigated. Potato cylinders (15 × 57 mm — D × L) were used as a model plant material. Calcium alginate (CA) coating was applied with or without incorporation of potassium sorbate (PS), at 0.3% of sample weight (before coating). OD took place for 3 h in stirred jars using sucrose solution at 50 °Brix and 40 °C. Microbial growth (Aerobic Plate Count — APC) was monitored both during OD (3 h) and during refrigerated storage at 5 °C (14 days). During OD, a significant reduction of the initial microbial load (ML) in the control (non-coated) treatment was observed, possibly due to a microbial “wash-out” effect. Both coating treatments resulted in a marginal decrease of initial ML in the OD product, suggesting some kind of protection against this effect. During refrigerated storage, the use of coating resulted in reaching the growth plateau several days earlier, which lead to significant reduction of maximum ML, compared to the control treatment. Besides this benefit, coating with A–M helped extend the lag phase and postpone time to reach maximum load by almost 4 days, compared to the simple coating treatment. These results can support further work on the use of more effective types and concentrations of preferably natural anti-microbials to achieve satisfactory stabilization of osmo-dehydrated/refrigerated products, without a negative impact on their minimal processing profile.
A curved ultrasonic transducer was devised to standardise biofilm removal for hygiene testing in internal or curved food contact surfaces. Meat biofilms made with Escherichia coli and Staphylococcus aureus on stainless steel sheets were studied. Ultrasounds (10 s at 40 kHz) alone failed to completely remove biofilms: 49 ± 5% and 39 ± 5% recovery rates were obtained for E. coli and S. aureus biofilms, respectively. A combined treatment, which involved the application of ultrasounds to EDTA and/or in enzymes solutions, allowed to remove up to 75 ± 4% and 100 ± 15% of E. coli and S. aureus biofilms, respectively. This application was in agreement with an industrial control i.e. a combined treatment: ultrasound generation in enzymes preparation restricted to an active chamber area with a fast and good reproducible recovery.Industrial relevanceThe biofilm phenomenon has been under intensive research for several years in food industry. A curved ultrasonic transducer was devised to standardise biofilm removal for hygiene testing in internal or curved food contact surfaces. This apparatus uses the mechanical effects of ultrasonic cavitation produced at 40 KHz (10 s) for the non-destructive detection of biofilms in food processing equipment. We report the utilisation of a combined treatment, which involved the application of ultrasounds to EDTA and/or in enzymes solutions on meat biofilms made with E. coli and S. aureus on stainless steel sheets. This application was in agreement with an industrial control i.e. a combined treatment: ultrasound generation in EDTA and/or enzymes preparation restricted to an active chamber area with a fast and good reproducible recovery.
In this study the impact of different decontamination agents (water, peroxyacetic acid, sodium hypochlorite, neutral electrolyzed oxidizing water and gaseous chlorine dioxide) on the microbial and sensory quality as well as the nutrient content of minimally processed leek was investigated. Washing with 250 mg/L peroxyacetic acid and contact with 1.59 mg/L chlorine dioxide gas reduced the native microflora with 1.52 and 1.48 log cfu/g respectively whereas the other treatments did not induce a reduction that was significantly higher than the one achieved after washing with water. None of the treatments had a significant effect on the sensory quality of the raw fresh-cut leek, whereas a treatment with 200 mg/L sodium hypochlorite or with 250 mg/L peroxyacetic acid changed the sensory quality of cooked leek significantly when compared with water washing. Apart from the effect of leaching of nutrients into the wash water, the supplementary effect on nutrient content caused by adding a decontamination agent was limited with the exception of some isolated cases such as the significant losses of vitamin C (23%), tocopherols (11–18%) and violaxanthin (66%) after a treatment with respectively chlorine dioxide, 250 mg/L peroxyacetic acid and electrolyzed oxidizing water.
Shredded Cheddar and Mozzarella cheeses were powder coated electrostatically and non-electrostatically with a mixture of natamycin and powdered cellulose, using a tumble drum or belt conveyer. Natamycin content and shelf life of the cheese samples were determined. Dustiness during the coating process was measured in both laboratory and commercial settings. Electrostatic coating by the drum method resulted in an increase in natamycin transfer efficiency over non-electrostatic coating and over liquid coating. The shelf life of the cheese coated electrostatically in the drum was significantly longer than that of non-electrostatically coated and of liquid coated cheese. The drum method of coating was more effective than the belt method both electrostatically and non-electrostatically. Electrostatic coating decreased dustiness significantly over non-electrostatic coating. Using electrostatics for coating shredded cheese will reduce waste and worker exposure to dust inhalation.
A continuous process for the production of foamed food from an emulsion was studied at pH values in the range of 4.2 to 6.6 using an apparatus which simulates the behaviour of an industrial scraped surface heat exchanger. The effect of pH on the rheological properties of the emulsion showed that the consistency factor (k) and the viscoelastic shear modulus (G′) of the emulsion could be increased by a factor of 5 when pH was decreased from 6.6 to 4.2 due to a change of colloidal interactions between proteins and texturing agents. An increase of rotational speed of impeller from 200 rotations per minute to 800 rpm resulted in a reduction in mean bubble diameter (d32) in foams for a given emulsion. At a fixed rpm, the mean bubble diameter and the bubble size distributions increased with decreasing pH. On the other hand, the solidity of the foam was decreased by an increase in pH from 4.2 to 6.6. Weber number (We) explains that foaming is the combined effect of process parameters and physicochemical properties of the emulsion. We numbers at pH 6.6 and 5.2 were 0.6 and 1.1, respectively, representing the minimum and the maximum in the pH range studied. This variation of We number with pH could be observed probably because the viscoelastic character of the continuous phase was ignored for bubble division.
As focus on the potential applications of microbubbles increases, information about the efficiency of generation methods and their effects on the properties and stability of microbubbles is crucial in the selection of an appropriate method to generate microbubbles with the desired properties. This paper evaluates the generation efficiencies of two commonly used methods, mechanical agitation and sonication, in two surfactant systems. The results demonstrated that sonication was more effective than mechanical agitation in the generation of microbubbles in terms of higher gas hold-up, smaller bubble size, and larger interfacial area. Analysis of the changes in bubble size over time revealed that the existence of a critical diameter for the shrinkage of microbubbles. The behavior of microbubbles and the critical diameter depended on the generation method employed and the surfactant used.Industrial relevanceMicrobubble technology has gradually become accepted as a cost-effective and environmentally friendly technology with great potential within almost every field of the food industry. Selection of a suitable method to generate microbubbles with the desired properties is crucial. Mechanical agitation and sonication are two commonly used methods for microbubble generation. However, systematic information on their generation efficiency and effects on the properties of microbubbles is not available. Thus, a comparative study was conducted in this paper.
The dielectric breakdown of gas bubbles entrapped in liquid food flowing through the cavity of a pulsed electric field treatment chamber has been a limiting factor in this non-thermal food preservation technology. Prediction of electric field enhancement due to gas bubbles is an important tool in the design, modification, and optimization of the treatment chamber's electrode geometry and pressurization. Simulation of the electrostatic characteristics of a coaxial treatment chamber with specified voltage of 25 kV, filled with dielectric material with conductivity of 0.6 S/m containing gas bubbles, evidenced a significant perturbation in the electric field. The magnitude of electric fields generated inside the bubbles was almost two times higher than in the homogeneous food. Without pressurization (atmospheric conditions), the dielectric breakdown strength of the gas-filled bubbles was exceeded, thus indicating the risk of arcing. A system pressurization of approximately 8 atm could be sufficient to limit arcing when small gas bubbles (∼1 mm) are present. The presence of gas bubbles caused the field magnitude to decrease significantly near the boundary of the bubble, thus threatening the uniformity of the PEF treatment across the chamber gap. This perturbation in the electric field was more significant when more than one bubble was present or when smaller gaps were used. The dielectric breakdown threshold at a given pressure is more likely to be exceeded by bigger bubbles (>1 mm) entrapped in a fluid processed in smaller treatment chamber gaps (3 mm), than by smaller bubbles (<0.5 mm) in bigger gaps (5 mm). Simulations like those used in this research can be conducted to evaluate and optimize process homogeneity and safety, by studying the effects of different treatment chamber configurations, gaps, food products, number of gas-filled bubbles, or other suspended elements in the food.
Minced albacore muscle was treated with high-hydrostatic pressure at 275 and 310 MPa for 2, 4, and 6 min and their effects on shelf life at 4 and − 20 °C were studied. Physical (texture, color), chemical (moisture and lipid content, pH, lipid oxidation, electrophoresis), and microbiological analyses were carried out. Pressure increased pH, protected from lipid oxidation, maintained low microorganisms levels, changed the color of the muscle, and induced the formation of high molecular weight polypeptides most likely through disulfide bonding promoting texture improvement of samples. Pressure improved the shelf life of minced albacore muscle for > 22 days at 4 °C and > 93 days at − 20 °C.
Changes in physicochemical properties of raw-appearing restructured models made from hake (Merluccius capensis) muscle, using cold gelation technology by addition of sodium alginate and microbial transglutaminase (MTGase), were studied during frozen storage at − 15 °C.Among the more interesting results, addition of MTGase produced more protein aggregation in models processed by muscle homogenization and thus the protein network that formed in the gel was better than in samples with added sodium alginate. All samples presented enhanced changes in mechanical properties such as gel strength in the course of frozen storage. The protein network that formed was better organized as shown by the ultrastructure analysis and by protein aggregation data from the beginning of storage, and as a result Water Binding Capacity was greater in restructured models processed by muscle homogenization. Some of the models studied presented lipid oxidation during frozen storage, slightly more in the ones with MTGase added.Industrial RelevanceThe industrial relevance of the present work is to establish bases for using fish fillet trimmings and minced muscle to prepare restructured products that can be commercialized in a raw state and that could also support frozen storage in order to prolong the self-life in the market. The models studied here are not final products but the base with which to prepare them. One possibility of them is to process this kind of products with technologies normally used in whole fish muscle such as smoked fish fillets, carpaccios or marinated products. In addition, these raw restructured products can be commercialized to be cooked as a normal fresh fish fillet or pieces of fillet in a variety of preparations, and also products that contain a high amount of salt. Samples elaborated by binding larger muscle fragments imitate well the original fibrousness of the muscle so that it could be used to elaborate products similar to hamburgers or others that will be fried in batter.
Two alkali-soluble polysaccharide fractions (ASPs I and II) were extracted from longan fruit pericarp in this work. The results of chemical composition indicated that ASP I and II fractions comprised mainly of polysaccharides, proteins and lignins. Four monosaccharides, namely Xyl, Ara, Glc and Gal, were identified for both ASPs I and II. Xyl was the dominant monosaccharide in the two alkali-soluble polysaccharides with relative molar percentages of >60%. It constructed the backbone in combination with Ara for both ASPs I and II. The analysis of glycosidic linkage indicated that Xyl had two linkages,→3)-Xyl-(1→ and →3, 4)-Xyl-(1→. The substitution at C-4 position indicated that Xyl was of pyranose structure. The infrared spectra of ASPs I and II showed the characteristic bands at approximate 897 cm− 1 which indicated the β-linkage configuration of Xyl.Industrial relevanceHemicellulose has been suggested as an important polysaccharide with good pharmaceutical properties, including immune modulation and anti-cardiovascular diseases. In this work, alkali-soluble polysaccharides were extracted from longan fruit pericarp and fractionated. The structural characteristics were identified by gas chromatography/mass spectrometry and infrared spectrophotometry. The results will be helpful for application of hemicellulose in functional food industry.
The effects of pulsed electric field (PEF) treatments at field intensities of 25–37 kV cm− 1 and final PEF treatment temperatures of 15 °C and 60 °C on the inactivation of alkaline phosphatase (ALP), Total Plate Count (TPC), Pseudomonas and Enterobacteriaceae counts were determined in raw skim milk. At 15 °C, PEF treatments of 28 to 37 kV cm− 1 resulted in 24–42% inactivation in ALP activity and < 1 log reduction in TPC and Pseudomonas count, while the Enterobacteriaceae count was reduced by at least 2.1 log units to below the detection limit of 1 CFU mL− 1. PEF treatments of 25 to 35 kV cm− 1 at 60 °C resulted in 29–67% inactivation in ALP activity and up to 2.4 log reduction in TPC, while the Pseudomonas and Enterobacteriaceae counts were reduced by at least 5.9 and 2.1 logs, respectively, to below the detection limit of 1 CFU mL− 1. Kinetic studies suggested that the effect of field intensity on ALP inactivation at the final PEF treatment temperature of 60 °C was more than twice that at 15 °C. A combined effect was observed between the field intensity and temperature in the inactivation of both ALP enzyme and the natural microbial flora in raw skim milk.Industrial relevanceMilk has been pasteurised to ensure its safety and extend its shelf life. However, the need for retaining heat-sensitive nutrient and sensory properties of milk has resulted in interest in the application of alternative technologies. The results of the current study suggest that PEF as a non-thermal process can be employed for the treatment of raw milk in mild temperature to achieve adequate safety and shelf life while preserving the heat-sensitive enzymes, nutrients and bioactive compounds.
The present study investigated the effect of active and modified atmosphere packaging, container oxygen barrier and storage conditions on quality retention of raw ground almonds. Ground almond kernels were packaged in: a) polyethylene terephthalate//low density polyethylene (PET//LDPE), and b) low density polyethylene/ethylene vinyl alcohol/low density polyethylene (LDPE/EVOH/LDPE), under N2 or with an oxygen absorber and stored either under fluorescent light or in the dark at 4 or 20 °C for a period of 12 months. Quality parameters monitored were: peroxide value (PV), hexanal content, color, fatty acid composition and volatile compounds. Of the sensory attributes color, texture, odor and taste were evaluated. PV ranged between 0.26 for fresh almonds and 19.98 meq O2/kg oil for almonds packaged in PET//LDPE pouches under N2 exposed to light at 20 °C after 12 months of storage. Respective values for hexanal were < 28.5 µg/kg and 9.38 mg/kg. Polyunsaturated fatty acids (PUFA) and saturated fatty acids (SFA) increased with a parallel decrease of monounsaturated fatty acids (MFA) after 12 months of storage in samples stored with the oxygen absorber while in samples packaged in PET//LDPE under N2, a decrease in PUFA and MUFA with a parallel increase in SFA was recorded. Likewise, volatile compounds such as aldehydes, ketones, alcohols, acids, alkanes and aromatic hydrocarbons increased during storage indicating enhanced lipid oxidation. Color parameters L⁎, a⁎ and b⁎ remained unaffected in all treatments including the oxygen absorber while under a N2 atmosphere L⁎ parameter showed a small but statistically significant (p < 0.05) decrease with a parallel increase (p < 0.05) of a⁎ and b⁎ values after 12 months of storage. The most pronounced color changes occurred for samples in PET//LDPE pouches irrespective of lighting conditions at 20 °C. Raw ground almonds retained acceptable quality for ca. 6–7 months packaged in PET//LDPE and ca. 8 months packaged in LDPE/EVOH/LDPE pouches under N2 irrespective of lighting conditions at 20 °C while at 4 °C shelf life was extended by an additional month as compared to storage at 20 °C. Use of the oxygen absorber provided a shelf life of at least 12 months for all samples irrespective of container oxygen barrier, lighting conditions and storage temperature.Industrial relevanceThe use of oxygen absorbers is very effective in extending the shelf life of ground almonds commercially for at least 12 months irrespective of packaging material barrier to O2, lighting conditions and storage temperature.