Differential stilbene induction susceptibility of seven red wine grape varieties upon post-harvest UV-C irradiation

The stilbene induction capacity of the red wine grape varieties 'Tempranillo' (TEM), 'Cabernet Sauvignon' (CAS), 'Merlot' (MER), 'Syrah' (SYR), 'Monastrell' (MON), 'Garnacha' (GAR) and 'Cariñena' (CAR) exposed to post-harvest UV-C irradiation is reported for the first time. The induction of trans-piceatannol, trans-resveratrol and viniferins, among other stilbenes, was characterized using high-performance liquid chromatograph with diode-array and mass spectrometric detection (HPLC-DAD-MS-MS). All the wine grape varieties increased their resveratrol, piceatannol and viniferin content after UV-C treatment with the exception of the variety MON in which only piceatannol was induced. Other stilbenes such as astringin (piceatannol glucoside) or piceid (resveratrol glucoside) were induced to a lesser extent and only in some varieties. The stilbene induction capacity of grapes submitted to UV-C irradiation did not necessarily match the final corresponding maximum stilbene content reached in each variety. The total stilbene induction capacity of the grapes ranged from 2.4-fold (in MER) to 10.9-fold (in both CAS and CAR) with respect to untreated grapes (control). The total stilbene content (mg stilbene/100 g fresh weight, fw) after UV-C irradiation ranged from 1.16 in MON to 3.5 in MER. In general, the maximum induction of specific stilbenes in all the varieties followed the sequence: resveratrol >piceatannol >₁-viniferin >piceid. This maximum induction was 22.7-fold for resveratrol in CAS, 6.4-fold for piceatannol in CAR, 3.8-fold for piceid in TEM and 8.4-fold for ₁-viniferin in both CAS and CAR with respect to the control. The maximum concentration of the specific stilbenes reached after UV-C irradiation was 2.5 (mg stilbene/100 g fresh grape weight) for resveratrol in MER, 0.42 for piceatannol in MER, 0.16 for piceid in MON and 0.39 for ₁-viniferin in CAR. The screening of stilbene induction capacity in red wine grapes treated with UV-C irradiation could be useful for selecting the most suitable variety to produce stilbene-enriched red wines with potentially increased health-promoting properties.     

Degradation of fenthion and fenthion sulfoxide on grapes on the vines and during refrigerated storage

The degradation of the pesticide fenthion and of the metabolite fenthion sulfoxide were studied on two varieties of Vitis vinifera, “Sideritis” and “Opsimo Edessas”, grown in the vineyard of the Agricultural University of Athens. Vines were sprayed with fenthion according to manufacturer instructions. One part of the sprayed grapes remained on the vines and another part was harvested, packed according to the recommended trade practices and stored in a refrigerator at 0 ± 0.5 °C and relative humidity 80%. It was found that, after spraying, fenthion was very quickly transformed on the grapes into fenthion sulfoxide that had a much slower rate of decomposition. Half-lives for the decomposition of fenthion on the trees were found to be 7.6 days for grapes of Sideritis variety and 5.6 days for grapes of Opsimo Edessas variety. Corresponding values for grapes stored in the refrigerator were 42 and 44.7 days. Percentages of fenthion sulfoxide increased up to the 0th day and then decreased steadily due to the decomposition of the pesticide and its metabolite.     

Inactivation of Salmonella typhimurium and Lactobacillus plantarum by UV-C light in flour powder

This research evaluates the potential use of ultraviolet C light (UV-C) as a decontamination method for powdered foods, particularly of refined flour. This technology's lethal effectiveness was evaluated on Salmonella enterica subsp. Enterica serotype Typhimurium and Lactobacillus plantarum in wheat flour, and in laboratory liquid media of different a_w and turbidities to evaluate the action mechanisms of UV-C light in powdered products. Initial results showed a large variability of lethality in flour, obtaining between 0.2 and 3.0 log₁₀ cycles of inactivation. Results obtained in laboratory media and SEM analysis of contaminated flour indicated that the variability was due to a shadow effect on the efficacy of UV-C light and not due to the low water a_w of the flour or starch content. Based on these conclusions, a 2-m vertical tunnel with twelve 480 W UV-C lamps was designed to treat flour by forming a continuous cloud of dust (0.05–2.4 kg/h). Inactivation levels of 4.0 to 1.7 log₁₀ cycles of the population of L. plantarum in flour were achieved at flow rates of 0.2 and 2.4 kg/h respectively, with a maximum residence time of 4 s.Industrial relevanceThis investigation demonstrated the lethal efficacy of the application of UV–C light to inactivate microorganisms, both pathogenic and spoilage, present in flour. 4-log10 cycles of inactivation of both Salmonella Typhimurium and Lactobacillus plantarum were inactivated with UV-C treatments. A UV-C facility was built up which enabled to treat flour in continuous conditions creating a cloud of dust with treatments of 4 s and lethalities of 4-log10 reductions.     

The effects of composite coatings containing chitosan and Mentha (piperita L. or x villosa Huds) essential oil on postharvest mold occurrence and quality of table grape cv. Isabella

The effects of coatings containing shrimp chitosan and the essential oil from Mentha piperita L. (MPEO) or M. villosa Huds (MVEO) to control common mold infections in table grape cv. Isabella (Vitis labrusca L.) that were caused by Aspergillus niger, Botrytis cinerea, Penicillium expansum and Rhizopus stolonifer were evaluated. The effects of the coatings on physicochemical and sensory characteristics of the grapes were also assessed. The coatings containing chitosan (4, 8 mg/mL) and MPEO or MVEO (1.25, 2.5, 5 μL/mL) delayed the mold growth and reduced the incidence of infections caused by all test fungi in grapes during storage at room and low temperatures. The coatings (chitosan 4 mg/mL; MPEO or MVEO 1.25, 2.5 μL/mL) did not negatively affect the physicochemical and sensory characteristics of grapes. From these results, coatings containing chitosan and MPEO or MVEO are potential postharvest treatments to control common mold infections in table grape cv. Isabella.Industrial relevanceIn table grapes, the reduction of losses resulting from fungal rot is a major goal of postharvest technology, which seeks to use effective methods to control the contamination and the growth of phytopathogenic fungi. However, the negative consumer perception of synthetic fungicides used for many years to solve the problem of mold infections in table grapes and the development of fungicide-resistant strains have impelled researchers to study the efficacy of natural compounds against postharvest pathogenic fungi. In this context, edible coatings composed of chitosan and essential oils have been considered as an environmentally friendly and added-value technology to control fungal postharvest decay in table grapes because of their biodegradability and lack of phytotoxicity. In this study, the authors evaluated composite coatings that contained shrimp chitosan and reduced amounts of Mentha (piperita L. or x vilosa Huds) essential oil as postharvest treatment to control the occurrence of mold infections caused by fungi in table grape cv. Isabella (Vitis labrusca L.), and their effects on the quality attributes of this fruit during storage. The tested composite coatings are presented as possible alternative technologies to control fungal infections and related post-harvest losses in table grape cv. Isabella.     

UV-C irradiation as an alternative disinfection technique: Study of its effect on polyphenols and antioxidant activity of apple juice

Ultraviolet (UV-C) irradiation is a non-thermal disinfection method, effective against a range of bacteria and viruses, which is being considered as an alternative to pasteurization of fruit juices. The objective of this study was to investigate the effect of UV-C irradiation on the polyphenolic content and in-vitro total antioxidant activity of apple juice. UV irradiation doses ranging from 0 to 240 mJ·cm^− 2 were delivered to apple juice and polyphenols, sugars, in-vitro total antioxidant activity and total phenols were profiled. The results demonstrated that UV-C irradiation in apple juices at relevant commercial disinfection doses induced significant reduction in the concentrations of chlorogenic acid, phloridzin, and epicatechin (p < 0.05). The induced changes were relatively minor for the above mentioned polyphenols, except phloridzin (50% reduction) at 240 mJ·cm^− 2. Epicatechin concentrations were reduced significantly (p < 0.05), whereas increase in catechin concentration was observed with increase in UV-C exposure to 240 mJ·cm^− 2. There was a minor reduction in sugar (glucose and fructose) concentrations with increasing exposure levels from 0 to 40 mJ·cm^− 2 (p > 0.05). In contrast, a slight increase in sugar concentrations as increase in UV-C exposure after 40 mJ·cm^− 2 was observed. These changes were not significantly different from control. Total phenolic content was well retained regardless of the UV-C exposure for apple juice. In-vitro total antioxidant activity changed when UV-C exposure exceeded 40 mJ·cm^− 2, but remained unchanged at the maximum UV-C dose of 240 mJ·cm^− 2. These results suggested that UV-C irradiation could be an effective alternative to conventional thermal processing for production of high quality apple juice.Industrial RelevanceThis research paper provides scientific evidence of the potential for UV-C irradiation to achieve meaningful levels of disinfection while retaining important bioactive compounds (polyphenols) in apple juice. In-vitro antioxidant activity and individual polyphenols were well retained at commercially relevant doses of 40 mJ·cm^− 2. From a nutritional perspective, UV-C irradiation is an attractive food preservation technology and offers opportunities for horticultural and food processing industries to meet the growing demand from consumers for healthier food products. Therefore, UV-C irradiated foods could be sold at a premium price to their thermally-processed counterparts, as they have retained their fresh-like properties. This study would provide technical information relevant for commercialization of UV-C treatment of juices.     

Monitoring the process to obtain red wine enriched in resveratrol and piceatannol without quality loss

Stilbene-enriched wine is considered an interesting new food product with added value as a consequence of the numerous health-promoting properties ascribed to it, mainly from its trans-resveratrol content. Postharvest grapes have been treated with ultraviolet-C light to produce stilbene-enriched grapes that were later used in a conventional winemaking process to obtain a red wine enriched in stilbenes.     

Surface UV-C light treatments to prolong the shelf-life of Fiordilatte cheese

The possibility to apply UV-C light technology to control surface contamination and extend the shelf-life of Fiordilatte was investigated. First, cheese was inoculated with Pseudomonas spp., exposed to UV-C light for increasing time up to 750 s to estimate the antimicrobial efficacy of the treatments. UV-C light penetration depth in Fiordilatte was also evaluated. Then, a shelf-life test was carried out on samples exposed to 0.1, 0.6, 1.2 and 6.0 kJ/m² UV-C light, compared to untreated control cheese. The samples were packaged with brine, stored at 9 °C and analyzed for microbial growth, sensory quality and pH. A germicidal effect of about 1–2 log cycles on Pseudomonas spp. and Enterobacteriaceae was observed during storage. UV-C light did not promote changes in terms of color, texture and surface appearance. With a minimum transmittance inside the product, this treatment showed an interesting surface microbial decontamination that prolonged cheese shelf-life.Industrial relevanceConsidering that dairy industry represents one of the most important components of the Italian food system, the present work focused on the utilization of UV-C light to preserve one of the most important milk-derived Italian fresh cheese, Fiordilatte, which totalized a consumption of about 20 kg per capita per year in the world. Interesting results were recorded on treated samples, above all at specific UV-C light fluence values (6 kJ/m²). The control of microbial proliferation in these treated samples allowed prolonging shelf-life by 80% compared to untreated cheese. The technique is very rapid and simple to be scaled up; after proper optimization of light parameters, it could be applied at industrial level to prevent surface post-process contamination of Fiordilatte that generally represents the main factor responsible for product deterioration and its short shelf-life.     

Inactivation kinetics of Listeria monocytogenes,Salmonella enterica serovar Typhimurium,and Campylobacter jejuni in ready-to-eat sliced ham using UV-C irradiation

To investigate the applicability of UV-C irradiation on the inactivation of foodborne pathogenic bacteria in ready-to-eat sliced ham, UV-C treatment was evaluated. Irradiation dose required for 90% reduction of the populations of Listeria monocytogenes, Salmonella enterica serovar Typhimurium, and Campylobacter jejuni were determined to be 2.48, 2.39, and 2.18 J/m². Ready-to-eat sliced hams were inoculated with the pathogens and irradiated with UV-C light of 1000, 2000, 4000, 6000, and 8000 J/m². Microbiological data indicated that foodborne pathogen populations significantly (p < 0.05) decreased with increasing UV-C irradiation. In particular, UV-C irradiation at 8000 J/m² reduced the populations of L. monocytogenes, S. Typhimurium, and C. jejuni in the ham by 2.74, 2.02, and 1.72 log CFU/g. The results indicate that UV-C irradiation can be used as a microbial inactivation method for ready-to-eat sliced ham, and inactivation kinetics of the foodborne pathogens fit the Weibull model better than the first-order kinetics model.     

Minimal processing of mucilage from the pulp of yam (Dioscorea pseudojaponica Yamamoto) using bubble separation and ultraviolet irradiation

Recently the applications of the low starch contents of yam mucilage in nutraceutical and cosmeceutical industries are required. A novel continuous pilot-scale bubble separation system was used for recovering yam slurry mucilage. The objectives of these studies were to follow the previous design for continuously separating, recovering and irradiating yam slurry mucilage for inactivation of microorganisms. The UV-C dose of 32000 μW/sec/cm² at 254 nm has a germicidal effect against microorganisms and is used for the disinfection. Two sets of custom made UV-C irradiators containing four UV-C germicidal lamps were added to the system. The effectiveness of this UV-C irradiator for reducing the aerobic bacteria count (APC) and yeasts and molds (YM) count in yam slurry mucilage was investigated. The results showed UV-C irradiation was successfully applied to reduce the microbial load in the yam slurry mucilage. If the slurry mucilage completes the process for both two sets of UV-C irradiators, a 4.5 log₁₀ APC reduction and a 4.1 log₁₀ YM reduction were achieved after 200 sec irradiation at a UV-C dosage of 32000 μW/sec/cm², resulting in zero cfu/ml APC and YM. Escherichia coli and Salmonella are both negative. This novel continuous UV-C pilot-scale bubble separation technology could be an alternative technology not only separate and recover mucilage but also reduce the microorganisms to acceptable levels.Industrial relevanceThis novel continuous pilot-scale bubble separation system was used for recovering yam slurry mucilage. Recently the applications of the low starch contents of yam mucilage in nutraceutical and cosmeceutical industries are required.This novel continuous UV-C pilot-scale bubble separation technology could be an alternative technology not only to separate and recover mucilage but also reduce the microorganisms to acceptable levels. Actually the pilot scale of this system is going to build in our university. We also try to further use it for non-thermal fermentation. There are many potential industrial applications using this idea.     

Assessment of the protein quality of fourteen soybean [Glycine max (L.) Merr.] cultivars using amino acid analysis and two-dimensional electrophoresis

The protein quality of commercial soybeans varieties can be determined from their total protein content, their amino acid composition and from the ratio of glycinin to β-conglycinin, the major seed storage protein components. In this study 14 commercial soybean cultivars were assessed. There were significant differences in storage protein composition (P < 0.05) and in their valine, proline and phenylalanine contents (P < 0.01 to P < 0.001). Mean protein values among these varieties ranged from 29.8% to 36.1%. The total amino acid nitrogen (AAN) ranged from 89.6 to 95.1 g AA/16 g of nitrogen, corresponding to nitrogen values from 16.5 to 17.9 g AAN/100 g protein. All varieties contained a good balance of essential amino acids (EAA₉), limited only in methionine. Two-dimensional gel electrophoretic (2-DE) separations, led to the establishment of high-resolution proteome reference maps, enabling polypeptide chain identification and calculation of the ratio of the constituent glycinin and β-conglycinin storage proteins of soybean. This method enables the assessment of the genetic variability of the soybean cultivars, which can then be correlated with their protein quality and food processing properties. These three methods can be used as very effective tools for assisting plant breeders in their selection of high quality soybean varieties.     

Reduction effect of the selected chemical and physical treatments to reduce L. monocytogenes biofilms formed on lettuce and cabbage

As people shift their attention away from unhealthy foods, healthy fresh produce has become popular. However, fresh produce has contributed to many outbreaks of Listeria monocytogenes, which can form a mature biofilm within 24 h. Recent control strategies have proved ineffective in ensuring safe food production. This study focuses on L. monocytogenes biofilms formed on lettuces and cabbages using a viable plate count method and field emission electron microscopy. We investigated the reduction efficacy of treatment with 200 parts per million (ppm) chlorine, 2% each of citric, lactic, and malic acids, 32 Hz ultrasonication (US), 390 mJ/cm² ultraviolet-C (UV-C), or 750 mJ/cm² cold oxygen plasma (COP) on L. monocytogenes biofilms. Following treatment, the quality of the vegetables was analyzed with standard procedures. UV-C and COP showed the best CFU reduction, regardless of the nature of the vegetable surface, while US failed to produce any significant reduction (P > 0.05). Furthermore, chemical treatments reduced count by < 1 log colony forming unit (CFU)/cm² on lettuces, whereas a > 2 log reduction was observed on cabbages. The effect of chemical treatment largely depended on the particular vegetable, while UV-C and COP achieved high reduction regardless of the vegetable, and had no effect on quality. We, therefore, speculate that UV-C and COP show promise in overcoming L. monocytogenes biofilms on food produce.     

UV-C treatment of soymilk in coiled tube UV reactors for inactivation of Escherichia coli W1485 and Bacillus cereus endospores

Coiled tube UV reactors were used to investigate the influence of tube diameter (1.6 mm ID, and 3.2 mm ID) and Reynolds number (Re) to inactivate Escherichia coli W1485 and Bacillus cereus spores in raw soymilk (RSM). Four levels of Re (343, 686, 1029 and 1372) were tested in RSM inoculated separately with each bacterium and treated in the UV reactors at a constant residence time of 11.3 s with UV-C dose of 11.187 mJ/cm² at 253.7 nm. Inactivation efficiency of both microorganisms increased with Re. Maximum reductions of 5.6 log₁₀ CFU/ml of E. coli and 3.29 log₁₀ CFU/ml of B. cereus spores were achieved in the 1.6 mm ID UV reactor. Inactivation efficiency was higher in the 1.6 mm ID UV reactor than the 3.2 mm ID UV reactor for both the organisms. Effect of UV-C light on lipid oxidation of untreated RSM, measured as malondialdehyde and other reactive substances (MORS) content, was much higher (95 nmol/ml) than the UV-treated (58 nmol/ml) and thermally pasteurized (55 nmol/ml) RSM during the storage period of 7 days. The UV-C treatment can be effectively used for reducing E. coli cells and B. cereus spores in soymilk without compromising its quality.     

Rapid method for resveratrol determination by HPLC with electrochemical and UV detections in wines

The study describes an improved version of the reverse-phase-HPLC method. To determine free resveratrol isomers, the method uses isocratic elution and electrochemical detection with the use of a glassy working electrode at a potential of 0.75 V. The effects of important factors – such as the isomerization of standard resveratrol solution in diffused daylight and its dependence on temperature or resveratrol isomerization in wine samples – were investigated. The equilibrium between trans- and cis-isomer was achieved after a 5-h exposure to the daily diffused light and it was not significantly influenced by the temperature (30–60 °C). Linearity was obtained in the concentration range from 0.01 to 10 mg l⁻¹. The detection limit (S/N=3) was 3 μg l⁻¹ for trans-resveratrol and 15 μg l⁻¹ for cis-resveratrol. The trans- and cis-resveratrol were determined in selected Czech red and white wines and in the extract from Vitis vinifera plant. The concentration of trans-resveratrol ranged from 0.7 to 11 mg l⁻¹, that of cis-resveratrol from 0.6 to 5.1 mg l⁻¹.     

Competitive interactions inside mixed-culture biofilms of Salmonella Typhimurium and cultivable indigenous microorganisms on lettuce enhance microbial resistance of their sessile cells to ultraviolet C (UV-C) irradiation

Salmonella Typhimurium (ST) is one of the leading causes of foodborne diseases in fresh produce, such as lettuce. Despite this, the role of the possible interactions between lettuce indigenous microorganisms and ST on their ability to form biofilm on lettuce and subsequently on the sensitivity of their sessile cells to ultraviolet C (UV-C) irradiation, remains relatively unexplored. Here, the interaction of a mixed-culture of ST and cultivable indigenous microorganisms (CIMs) was examined, as well as the efficacy of UV-C. Initially, the CIMs were isolated and cultured with ST at 15 °C either planktonically or left to form biofilms on stainless steel (SS) and lettuce leaves. Microbial growth, biofilm formation, and survival following UV-C treatment were monitored using traditional plate count methods while biofilm formation, production of extracellular polymeric substance (EPS), and stomatal colonization were also observed by field emission scanning electron microscopy (FESEM). Internalization strength, color, and texture were analyzed by standard methods. Results revealed that the mixed-culture of ST and CIMs presented significantly (p < 0.05) decreased biofilm formation on lettuce leaves compared to mono-cultures (i.e. ST or CIMs alone), which indicated competitive interaction between them, while no interactions were observed for biofilms on SS and for the planktonic cultures. It was also demonstrated that a mixed-culture biofilm on lettuce presented significantly higher resistance (p < 0.05) to UV-C treatment compared to mono-culture biofilms, but such an effect was not observed for biofilms formed on SS and for the planktonic cultures. The Weibull model fitted well to microbial inactivation curves with R² values that ranged from 0.90 to 0.97. Regarding the mixed-culture conditions, a UV-C fluency of 35 mJ/cm² was required to achieve a 5.0 log CFU/mL or cm² reduction in planktonic and biofilms on the SS for the mixed-culture, while 360 mJ/cm² was required to reduce biofilm cell number by approximately 2.0 log CFU/cm² on lettuce. Furthermore, FESEM analysis indicated higher EPS production, and greater stomatal colonization on lettuce mixed-cultures compared to mono-cultures. Finally, internalization strength was significantly higher (p < 0.05) for the mixed-culture on lettuce, thus supporting the notion that internalization in lettuce is a factor that contributes to microbial UV-C resistance. The absence of adverse effects of UV-C on the color and texture of the lettuce suggests it as an alternative means of eliminating ST.     

Comparison of UV-C and thermal treatments for the preservation of carrot juice

The aim of the present study was to investigate the effectiveness of UV-C and thermal treatments on the shelf life of carrot juice. Carrot juice samples were exposed to UV-C radiation and thermal treatment. After the treatments, all carrot juice samples were stored at 4 °C for 16 days. Parameters taken into account were: physicochemical [colour values (L*, a*, and b*) and browning index, viscosity, optical density, density, pH, turbidity], microbiological [total plate count mesophilic, total plate count psychrotrophic, lactic acid bacteria Enterobacteriaceae and yeast and moulds) and sensory attributes. Results showed that the shelf life of carrot juice samples was 4 days for the fresh (control samples) and increased to 12 days for the thermally and UV-Ctreated, respectively. In addition, no significant changes occurred in the investigated physicochemical parameters, while sensory characteristics were not downgraded by UV-C treatment. Present results obtained, support the use of UV-C technology for improving shelf life stability of carrot juice.     

High voltage electric discharges assisted extraction of phenolic compounds from grape stems: Effect of processing parameters on flavan-3-ols,flavonols and stilbenes recovery

This work aimed at providing some novel aspects pertaining to flavan-3-ols, flavonols and stilbenes extraction from grape stems using high voltage electrical discharges (HVED). Treatment time, pH and ethanol concentration affecting the extractability of these compounds were optimized through response surface methodology. The results from the optimized extraction technique (pH = 2.5; Time = 4.0 ms: Ethanol = 50%) were compared to a conventional hydro-alcoholic extraction.HVED improved significantly the extraction of flavan-3-ols and flavonols but was less efficient on stilbenes. The efficiency of HVED is directly correlated with the other processing conditions (pH, ethanol concentration). Prolonged HVED treatment at low pH value was a positive combination for flavan-3-ols. The proposed procedure (pH = 2.5; Time = 4.0 ms; Ethanol = 50%) allowed the release of almost 35% of additional phenolic compounds, which can be attributed to a better extractability of flavan-3-ols (+ 21%) and of flavonols (+ 12%), compared to conventional hydro-alcoholic extraction.     

Focusing on bioactive compounds in grapes: stilbenes in Uvalino cv.

Phenolic compounds belonging to the group of stilbenes have recently received a particular attention as bioactive compounds because of their role in plant physiology and for their antioxidant properties. Monomer stilbenes in grapes are mainly present as glycosides. The aim of this work was the identification and quantification of monomer stilbenes (as both free and glycosilated form) in Uvalino grapes, a grapevine variety known for its significant content in stilbenes. Their content in grapes was determined during ripening and overripening stages, in comparison with other phenolic compounds. Piceid (cis and trans form), piceatannol (cis and trans form), cis resveratrol and trans-pterostilbene were identified and quantified in grape skin. Piceid was the most abundant stilbene as both cis and trans forms. As for anthocyanins, the synthesis and the stilbenes accumulation started during veraison, and then, the content of these molecules remained constant with the exception of piceid, whose content slightly increased until harvest. Therefore, stilbenes accumulation seems not to be affected by anthocyanins synthesis. On the contrary, proanthocyanidins, flavonols and hydroxycinnamyl tartrates decreased during ripening. When withering was applied to grapes as a post-harvest treatment, the content of anthocyanins, proanthocyanidins and of the most abundant stilbenes increased, while flavonols and hydroxycinnamyl tartrates decreased. The results suggest that degradation processes during withering are probably weaker or absent in the case of stilbenes, anthocyanins and proanthocyanidins.     

Changes in firmness,cell wall composition and cell wall hydrolases of grapes stored in high oxygen atmospheres

To investigate the effects of high oxygen (O₂) atmospheres on the firmness of ‘Kyoho’ grapes (Vitis vinifera L. X V. labrusca L.), changes in cell wall constituents and hydrolase activities were examined during 60 days of controlled atmosphere storage in air (control), 40% O₂ + 30% CO₂ or 80% O₂ (high O₂) at 0 °C and 95% relative humidity. Grapes stored in high O₂ retained greater firmness than grapes stored in air. The cell wall contents of high O₂-stored fruits contained less water-soluble pectin (WSP), more Na₂CO₃ soluble pectin (SSP) and higher hemicelluloses than air-stored fruits. The levels of cellulose and CDTA-soluble pectin (CSP) did not significantly change. The effects of high O₂ on enzyme activity were dramatic for polygalacturonase and β-galactosidase, moderate for cellulase, and very low for pectinesterase. No pectate lyase was detected. Taken together, WSP, SSP and hemicelluloses appeared to have major structural roles in retaining the firmness and preventing the deterioration of fruits kept in high O₂.     

Processing of clear and turbid grape juice by a continuous flow UV system

The inactivation of inoculated (S. cerevisiae) and spoilage microorganisms, i.e. yeasts and lactic acid bacteria (LAB), in clear and turbid grape juice was investigated using a pilot scale UV system. The biodosimetry method was used for UV dose prediction in a continuous flow UV reactor. Weibull model was applied for fitting the inactivation data. The flow rates (774, 820 ml/min) in this system were very close to the ones used in fruit juice processing. S. cerevisiae in clear juice was reduced by 3.39 ± 0.04 at 65.50 mJ/cm² of UV dose. 1.54 ± 0.04 and 1.64 ± 0.03 log CFU/ml reductions were obtained for spoilage yeasts and LAB in turbid juice at UV dose of 78.56 and 67.97 mJ/cm², respectively. The soluble solids (°Brix) and pH of grape juice samples were not affected by UV-C treatment (p > 0.05). Although the color parameters slightly were changed after irradiation, the color of PCGJ and FSTGJ did not show visual difference compared to the untreated samples.Industrial relevanceUV light has a potential to reduce the levels of microbial contamination in liquid foods. Although grape juice has many beneficial health effects, it has a fairly short shelf life. Therefore, pasteurization is required. But the thermal pasteurization has some undesired effects on the juice quality. Consumer demands for high quality fruit juice with fresh-like characteristics have markedly expanded in recent years. In the current study, the microbial inactivation efficiency of a pilot scale UV system for non-thermal treatment of clear and turbid grape juice was evaluated under conservative conditions. Most of the physicochemical properties of grape juice samples were not significantly affected from UV-C treatment (p > 0.05). This would be a major advantage in the processing of nutritious juice products.