Influence of Postharvest UV-C Hormesis on the Bioactive Components of Tomato during Post-treatment Handling

Mature green tomato fruit exposed to a pre-determined hormetic dose of UV-C (3.7 kJ/m²) and untreated fruit (control) were stored at 13 °C and 95% relative humidity. After 10, 20, and 30 days of storage, fruits were randomly sampled and transferred to room temperature (23 °C) for 7 and 14 days to allow ripening. Edible pericarp was excised from the equatorial region for subsequent analyses of the antioxidant components. Ascorbic acid and total phenolic contents were higher in the UV-treated tomatoes, but UV treatment significantly reduced the lycopene content of the tomatoes. The UV treatment did not affect significantly the antioxidant activity of the hydrophilic extract, expressed as Trolox equivalent. Both storage and ripening period were found to affect positively all the bioactive components of tomato evaluated in this study. The results suggest the possible existence of a window of opportunity for the development of practices based on storage temperature and duration to preserve the beneficial effects expected from UV-C hormesis and to circumvent its negative impact on lycopene synthesis.     

Starch-based coatings: effect on refrigerated strawberry (Fragaria ananassa) quality

Edible coatings can provide an alternative for extending post-harvest life of refrigerated fruit and vegetables. The influence of different starch-based coating formulations on quality attributes of strawberries stored at 0°C and a relative humidity of 84·8% was studied. Starch sources were classified according to the amylose content in starch, with medium amylose content (potato and corn) and high amylose content (amylomaize and amylose-rich product). Quality of fruits was evaluated by weight loss, firmness retention, microbial decay, surface colour development, titratable acidity and sugar content. The effects of starch amylose content and glycerol (plasticiser) concentration on coating properties were also analysed. The coatings reduced the number of infected fruits and extended storage life of strawberries by retarding senescence. The addition of glycerol improved coating performance, with 20 g litre⁻¹ the most effective concentration. The starch source had a significant effect on surface colour development, weight loss and firmness retention. Coated strawberries produced the lowest ratios of chromaticity parameters (a/b, red/yellow) with regard to the control fruits, thus retarding senescence. High amylose content starches reduced weight loss, maintained firmness and reduced decay better than medium amylose content starches. © 1998 SCI.     

Use of UV-C treatments to maintain quality and extend the shelf life of green fresh-cut bell pepper (Capsicum annuum L.)

Abstract: The objective of this work was to select a Ultraviolet‐C (UV‐C) treatment for fresh‐cut mature green bell pepper, and to evaluate the effect of its combination with refrigeration on quality maintenance. Bell pepper sticks were treated with 0, 3, 10, or 20 kJ/m² UV‐C in the outer (O), inner (I), or both sides of the pericarp (I/O) and stored for 8 d at 10 °C. During the first 5 d of storage, all UV‐C treatments reduced deterioration as compared to the control. The treatment with 20 kJ/m² I/O was the most effective to reduce deterioration, and was used for further evaluations. In a second group of experiments, mature green bell pepper sticks were treated with 20 kJ/m² I/O, stored at 5 °C for 7 or 12 d and assessed for physical and chemical analysis, and microbiological quality. UV‐C‐treated fruit showed lower exudates and shriveling than the control. UV exposure also reduced decay, tissue damage, and electrolyte leakage. After 12 d at 5 °C, UV‐C irradiated peppers remained firmer and had higher resistance to deformation than the control. The UV‐C treatments also reduced weight loss and pectin solubilization. UV‐C exposure decreased the counts of mesophile bacteria and molds, and did not affect acidity or sugars. UV‐C‐treated fruit stored for 0 or 7 d at 5 °C did not show major differences in antioxidants from the control as measured against DPPH^? or ABTS^?+ radicals. Results suggest that UV‐C exposure is useful to maintain quality of refrigerated fresh‐cut green pepper. Practical Application: Exposure to UV‐C radiation before packing and refrigeration could be a useful nonchemical alternative to maintain quality and reduce postharvest losses in the fresh‐cut industry.     

Combination of UV‐C Treatment and Metschnikowia pulcherrimas for Controlling Alternaria Rot in Postharvest Winter Jujube Fruit

The potential of using antagonistic yeast Metschnikowia pulcherrimas alone or in combination with ultraviolet‐C (UV‐C) treatment for controlling Alternaria rot of winter jujube, and its effects on postharvest quality of fruit was investigated. The results showed that spore germination of Alternaria alternata was significantly inhibited by each of the 3 doses (1, 5, and 10 kJ m^?2) in vitro. In vivo, UV‐C treatment (5 kJ m^?2) or antagonist yeast was capable of reducing the percentage of infected wounds and lesion diameter in artificially inoculated jujube fruits, however, in fruit treated with combination of UV‐C treatment and M. pulcherrima, the percentage of infected wounds and lesion diameter was only 16.0% and 0.60 cm, respectively. The decay incidence on winter jujube fruits treated with the combination of UV‐C treatment and M. pulcherrima was 23% after storage at 0 ± 1 °C for 45 d followed by 22 °C for 7 d. None of the treatments impaired quality parameters of jujube fruit. Thus, the combination of UV‐C radiation and M. pulcherrima could be an alternative to synthetic fungicides for controlling postharvest Alternaria rot of winter jujube.     

Inactivation of Escherichia coli Population on Fruit Surfaces Using Ultraviolet-C Light: Influence of Fruit Surface Characteristics

Ultraviolet-C (UV-C 254 nm) light is a possible alternative for chemical disinfection of fresh fruits. However, studies on the influence of surface characteristics on the kinetics of UV-C inactivation of microorganisms on fruits are limited. In this study, UV-C inactivation of generic Escherichia coli (ATCC 23716), a nonpathogenic surrogate strain for E. coli O157:H7, was inoculated onto the skin surface intact pear, pear with surface wounds, and the skin surface of intact peach. Disc shaped (0.057 m diameter?×?0.01 m height) fruit surface were exposed at room temperature to UV-C light ranging from 0 to 7.56?±?0.52 kJ/m² and microbial inactivation kinetics was determined. Maximum reductions of 3.70?±?0.125 log CFU/g were achieved for E. coli on intact pear surfaces (P?<?0.05), with lesser reduction on wounded pear (3.10?±?0.329 log CFU/g) and peach surfaces (2.91?±?0.284 log CFU/g) after 4 min UV-C exposure at 7.56 kJ/m² UV. The Weibull scale factor (α) values of UV-C inactivation for E. coli on an intact pear surface was 0.001?±?0.0007 min (0.235?±?0.001 kJ/m²), wounded pear surface, 0.003?±?0.001 min (0.240?±?0.002 kJ/m²) and peach surface, 0.004?±?0.0004 (0.241?±?0.0008 kJ/m²). The time required for a 90 % reduction in E. coli cell numbers or the reliable life time (t _R) calculated with the Weibull model for intact pear surfaces (0.019?±?0.009 min, 0.268?±?0.017 kJ/m²) was smaller than for wounded pear (0.062?±?0.013 min, 0.348?±?0.024 kJ/m²) and peach surfaces (0.074?±?0.012, 0.371?±?0.012 kJ/m²), suggesting that the wounds on pear surfaces and trichomes (100–1000 μm) on peach surfaces helped to shield and protect microorganisms from UV-C radiation. There was likely a more uniform distribution of bacterial cells onto pear surfaces due to its smaller surface roughness, spreading coefficient, and hydrophobic nature compared to peach. Fourier transform infrared spectroscopy indicate that bacterial membrane damage (phospholipids, protein secondary structures, and polysaccharides) and changes to DNA/RNA in E. coli resulted from UV-C treatment. UV-C can reduce E. coli populations on fresh fruit surfaces, but the efficacy of UV treatment is dependent upon the morphological and surface properties of the fruit and surface integrity.     

THE EFFECT OF ULTRAVIOLET IRRADIATION ON SHELF-LIFE AND RIPENING OF PEACHES AND APPLES

“Loring” and “Elberta” peaches and “Golden Delicious” apples were irradiated with UV (254nm) to doses of 0.84 × 10⁴ to 40 × 10⁴ erg/mm² then stored. “Loring” were stored 10 days and “Elberta” 20 days at 12°C. “Golden Delicious” were stored 30 days at 20–25°C in a dark room. Fruit were examined and differences in percentage rot and in physical-chemical properties determined. Percentage rot decreased with increasing UV dose. Fruit were firmer, pH and soluble solids lower and acidity higher for UV-treated than for nontreated peaches; pH was lower and acidity and ascorbic acid higher in UV treated than in nontreated apples. Percentage weight loss was less for UV-treated apples. The results indicated that UV treatment not only reduced storage rots but also delayed ripening of peaches and apples.     

UV-C radiation as a novel technique for keeping quality of fresh processed ‘Lollo Rosso’ lettuce

Fresh processed ‘Lollo Rosso’ lettuce (Lactuca sativa) was exposed to different doses (0.4, 0.81, 2.44, 4.07, and 8.14 kJ/m²) of ultraviolet-C (254 nm, UV-C) radiation, and stored up to 9 and 10 days at 5 °C. While minimal processing did not induce significant increases in respiration rate, UV-C radiation did. Consequently, gas composition within bags containing radiated and control lettuce pieces changed according with the increase in respiration rate. All UV-C radiation doses decreased growth of psychrotrophic bacteria, coliform, and yeast, but only significant differences were found when the highest level was applied. UV-C radiation seemed to stimulate the growth of lactic acid bacteria, probably due to reduced growth of competitive flora. After 7 days of storage the highest dose resulted in increased tissue brightness, and browning was reduced when 2.44, 4.07, and 8.14 kJ/m² were applied. UV-C radiation at an appropriate dose could reduce microbial loads without adversely affecting sensorial quality of ‘Lollo Rosso’ lettuce.     

Alleviation of chilling injury in postharvest tomato fruit by preconditioning with ultraviolet irradiation

BACKGROUND: Tomato fruit is usually stored at low temperatures for delayed ripening and extended shelf life. However, tomato fruit is susceptible to chilling injury when exposed to low temperatures. In this study, the potential effects of preconditioning with UV‐C or UV‐B irradiation on chilling injury of postharvest tomato fruit were investigated. RESULTS: Mature–green tomato fruit were exposed to 4 kJ m^?2 UV‐C or 20 kJ m^?2 UV‐B irradiation and stored for 20 days at 2 °C and subsequently 10 days at 20 °C. UV irradiation was effective in reducing chilling injury index and delaying ethylene peak. Furthermore, UV irradiation preserved storage quality as manifested by reduced weight loss, better retention of firmness, and higher contents of total soluble solids, soluble protein and soluble sugar during subsequent storage at 20 °C. UV‐C irradiation significantly delayed the development of the red colour after 10 days of storage at 20 °C. On the other hand, UV irradiation decreased total phenolics content and antioxidant capacity, suggesting possibly reduced stress response to low temperature resulted from enhanced physiological adaptation by UV preconditioning. CONCLUSION: Our results suggest that preconditioning with UV‐C or UV‐B irradiation in appropriate doses had a positive effect on alleviating chilling injury in postharvest tomato fruit. Copyright © 2012 Society of Chemical Industry     

Methyl jasmonate reduces chilling injury symptoms and enhances colour development of ‘Kent’ mangoes

Treatment of mango (Mangifera indica cv ‘Kent’) fruits with methyl jasmonate (MJ) vapour for 20 h at 20 °C reduced chilling injury (CI) symptoms and enhanced skin colour development. MJ at 10^?4 M was the most effective concentration for reducing CI and decay in fruits stored at 5 °C followed by 7 days at 20 °C (shelf‐life period). The use of 10^?5 M MJ enhanced yellow and red colour development of mangoes stored at 20 °C. These fruits possessed higher L*, a* and b* values than untreated fruits and those treated with 10^?4 M MJ. Ripening processes were inhibited by cold storage (5 °C) in control fruits. After cold storage and shelf‐life period, fruits treated with 10^?5 M MJ ripened normally and contained the highest total soluble solids (TSS). These fruits also maintained higher sugar and organic acid levels than fruits subjected to other treatments. We concluded that MJ treatment could be used to reduce decay and CI symptoms and also to improve colour development of mango fruits without adversely affecting quality. © 2001 Society of Chemical Industry     

Evaluation of Alternaria mycotoxins in strawberries: quantification and storage condition

Alternariol (AOH), alternariol methyl ether (AME) and tentoxin (TEN) are Alternaria mycotoxins produced by the most common post-harvest pathogens of fruits. The production of these metabolites depends on several environmental factors, mainly temperature, water activity, pH and the technological treatments that have been applied to the product. In this study, the occurrence of AOH, AME and TEN was evaluated in strawberries samples stored at different temperatures ranges (at 22 ± 2 or 6 ± 2°C) and different periods (up to 1 month) simulating the current practice of consumer’s storage conditions. Sample extraction was performed using a liquid–liquid extraction method prior to LC-MS/MS analysis. AOH was the most prevalent mycotoxins with a 42% at strawberries stored at (22 ± 2)°C and 37% stored at (6 ± 2)°C. The highest AOH levels were found in samples conserved at (22 ± 2)°C ranging between 26 and 752 ng g^–1. AME levels ranged between 11 and 137 ng g^–1, which were found mainly in stored samples at (6 ± 2)°C for more than 28 days. None sample presented levels of TEN in either of the studied conditions.     

Changes in red pepper antioxidants as affected by UV-C treatments and storage at chilling temperatures

Chilling injury (CI) is one of the main factors limiting refrigeration in several horticultural commodities of subtropical and tropical origin such as pepper. Short UV-C treatments before low temperature storage have been shown to reduce CI. In this work we wanted to test whether or not the reduced susceptibility to CI in UV-C treated fruits was associated with increased levels of antioxidant compounds and enzymes. Red peppers (Capsicum annuum L.) were treated with UV-C radiation (10 kJ/m²) and stored at 0 °C for 21 d. During storage we analyzed chilling injury development, ascorbic (AA) and dehydroascorbic acids and DPPH radical scavenging capacity. We also followed superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX) activities. CI increased rapidly when the fruit was stored for longer than 14 d, but was significantly lower in UV-C treated peppers. Exposure to UV-C did not alter fruit color but reduced weight loss. Although AA and DPPH radical scavenging capacity were lower in the control, this occurred towards end of storage, when CI was already advanced. In contrast, SOD, CAT and APX activities were higher in UV-C treated fruits during the first 2 weeks of storage when the symptoms became visible. Results show that UV-C exposure prevents CI and weight loss in red pepper and suggest that this might be related to increased activity of antioxidant enzymes.     

Influence of postharvest UV‐C treatment on refrigerated storage of minimally processed broccoli (Brassica oleracea var. Italica)

Minimally processed broccoli was treated with UV‐C light (8 kJ m^?2) and subsequently stored for 21 days at 4 °C. The UV‐C treatment delayed yellowing and chlorophyll degradation during storage. Treated broccoli florets displayed lower electrolyte leakage and respiratory activity, indicating higher tissue integrity. Treated samples showed higher phenolic and ascorbic acid contents as well as higher antioxidant activity than controls. Treated samples also had a higher content of soluble sugars, but no differences in the content of soluble proteins between control and treated samples were detected. The UV‐C treatment also affected bacterial and mould populations. After 21 days at 4 °C the number of colony‐forming units of both populations was lower in treated than in control broccoli florets. The results suggest that UV‐C treatment reduces tissue damage of minimally processed broccoli during storage at 4 °C, thus maintaining nutritional quality and reducing microbial growth. Copyright © 2007 Society of Chemical Industry     

Improving Storability of Fresh Strawberries with Controlled Release Chlorine Dioxide in Perforated Clamshell Packaging

Fresh strawberries have short shelf life because of rapid weight loss, softening, and decay. The objective of this research was to study the response of strawberries to ClO₂ when applied to the fruit using a controlled release pad. Four experiments were conducted over 2011 to 2013. Strawberries were packed in perforated commercial clamshells, with or without ClO₂ treatments, and stored at 1 and 6 °C for up to 14 days and at 10 and 20 °C for up to 7 days. The effect of ClO₂ on strawberries was assessed by measuring decay incidence, weight loss, firmness, volatile composition, and stomate activity during storage. Chlorine dioxide treatments induced closing of stomata, markedly slowed weight loss and softening, and reduced decay incidence of strawberry fruit at 10 °C or lower temperatures, but not at 20 °C. Fruit flavor profiles were not affected by ClO₂ treatment.     

Polyamine Accumulation Following Hot-Water Dips Influences Chilling Injury and Decay in'Friar' Plum Fruit

Mature‐green (Prunus salicina Lindl. cv.‘Friar’) plums were treated in water at 40°C for 40 min, 45°C for 35 min, 50°C for 30 min or 55°C for 25 min, stored at 0°C for 35 d plus 9 d of ripening at 20 to 25°C. During cold storage, putrescine and cadaverine accumulated most compared to spermine and spermidine, especially in fruits treated at 45 or 50°C, compared to other treatments. Chilling injury (CI) and decay symptoms were severe in fruits of control, 55 and 40°C‐treated fruits. Decay incidence was also high in fruits stored at room temperature. Chilling injury and decay symptoms were retarded in fruits treated at 45 and 50°C, which also maintained increased polyamines and low ethylene. By the end of their shelf life, only 45 and 50°C‐HWD treated fruits were fit for market.     

Inhibition of mold growth on the surface of dried persimmons using combined treatments of UV-C light and clove oil

The efficacy of clove oil, UV-C light and their combination for the inhibition of mold growth on the surface of dried persimmon fruits during the storage period of 28 days at 20 °C were investigated in this study. The inactivation kinetics of UV-C resistant mold cultures inoculated to dried persimmon surfaces were determined at UV-C doses in the range of 0.6–12.0 kJ/m². Disc diffusion and microdilution methods were used to evaluate the antifungal activity of the clove oil against Rhizopus oryzae, Alternaria tenuissima and Aspergillus niger previously isolated from dried persimmon fruits. Minimum inhibitory concentrations of clove essential oil against R. oryzae, A. tenuissima and A. niger were 1.56% (v/v) and the minimum fungicidal concentrations were 6.25% (v/v), 3.12% (v/v) and 6.25% (v/v), respectively. UV-C treatments showed limited reductions in the number of molds inoculated to dried persimmon discs regardless of the UV-C dose. Combined treatments of UV-C and clove oil resulted in maximum reductions of 0.64 and 0.68 log cfu/cm² for R. oryzae and A. niger, respectively. Sensory evaluation results showed that all the treatments could maintain the appearance and texture of samples, moreover the highest sensory evaluation score was obtained for the clove oil (1.56% v/v) treatments in terms of flavour and overall acceptability. Application of clove oil (1.56% v/v) to dried persimmon fruits was extended the product shelf life at least 28 days. By using combination of UV-C light and clove oil treatments, the inhibition of mold growth on the surface of dried persimmons has been achieved.Industrial relevanceUltraviolet technology is a non-thermal food processing technology as an alternative to chemicals while maintaining the quality of the food. The results obtained in this study demonstrate that combined treatment of UV-C and clove oil are a promising technology to inhibit fungal growth as well as to enhance sensory quality of dried persimmon fruits. Application of clove oil to dried persimmon fruits produced a novel and value-added product that can be preferred by consumers.     

Quality Improvement of Fresh-Cut Endive (<Emphasis Type="Italic">Cichorium endivia</Emphasis> L.) and Recycling of Washing Water by Low-Dose UV-C Irradiation

Superficial short-wavelength ultraviolet (UV-C) treatment (1.2 kJ/m²) of fresh-cut endive was combined with conventional cold (4 °C, 120 s) and innovative warm (45 °C, 120 s) water washing prior to and after irradiation in order to improve its microbial and sensory quality including physiological properties. UV-C doses applied exerted only minor physiological stress on the plant tissue, irrespective of the washing procedure as indicated by largely unaltered headspace gas compositions, chlorophyll fluorescence maximum quantum yields (F _v/F _m), and retention of chlorophylls and β-carotene. Independent of the washing procedure applied, phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) activities were slightly inhibited by UV-C irradiation. As a result of UV-C irradiation, significantly improved microbiological and sensory quality was retained during the entire storage period, particularly, when applied after washing. Being applicable in organic fresh-cut production, UV-C represents a valuable alternative to chlorine application to washing water. The most efficient decontamination (2.1 log₁₀ units) of fresh-cut endive was achieved by combining warm water washing with subsequent UV-C irradiation. Furthermore, when UV-C lamps were integrated into the water tank of a continuous industrial washing machine, the microbial loads of the process water were also significantly lowered. Accordingly, in-line UV-C decontamination of process water may be instrumental in minimizing both fresh water consumption and the risk of cross-contamination.     

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.     

Combined use of UV‐C irradiation and heat treatment to improve postharvest life of strawberry fruit

The effects of UV‐C (4.1 kJ m^?2) and heat treatment (45 °C, 3 h in air) either separately or combined on the quality of strawberries (Fragaria × ananassa cv Seascape) at the 75 or 50% surface red ripening stage were assessed, the latter stage being used only in the firmness test. In addition, the development of surface fungal infections was followed and in vitro germination assays on conidia of Botrytis cinerea and Rhizopus stolonifer performed. Both heat and combined treatments, decreased hue and delayed changes of the L* parameter. All treatments reduced the accumulation of anthocyanins. Control fruit softened most while fruit treated by the combined method were the firmest. The combined treatment reduced fungal infections and delayed in vitro germination of Botrytis cinerea conidia. After 2 days at 20 °C, treated fruit had lower amount of phenolics than the control. Neither the heat nor UV‐C irradiation modified the total sugar content, although the combined treatment decreased it slightly relative to the control. Titratable acidity increased through storage at 20 °C in all fruit, but no differences between control and treated fruit were detected. The combination of UV‐C and heat treatments enhanced the benefits of applying each treatment separately, and could be useful to improve and extend strawberry fruit postharvest life. Copyright © 2004 Society of Chemical Industry     

Use of UV-C treatment to inhibit the microbial growth and maintain the quality of Yali pear

Abstract: The effects of UV-C radiation on microbial growth in vitro (Monilinia fruticola) and in inoculated Yali pears (Pyrus bretschneideri Rehd.) were investigated. Moreover, postharvest quality and the activities of defense and antioxidant enzymes were analyzed after the pears were exposed to UV-C irradiation at an energy level of 5 kJ m⁻².The results showed that spore germination of M. fructicola was significantly inhibited by each of the 3 doses (1, 5, and 10 kJ m⁻²) in vitro. In the in vivo assays, lesion diameter on the fruit being inoculated before or after the UV-C treatment was both significantly lower than that on the fruit of control. Meanwhile, the activities of phenylalanine ammonia lyase, β-1,3-glucanase, superoxide dismutase, catalase, and glutathione reductase were induced to high levels by UV-C treatment. We conclude that UV-C treatment could reduce postharvest disease by the germicidal and induced effects and maintain the quality by enhancing the antioxidant enzyme activities. Practical Application: UV-C radiation has recently been proposed as a new technology to avoid chemical fungicides. However, there are few studies regarding the effect of UV-C treatment on Yali pear. In this study, we found that 5 kJ m⁻² UV-C irradiation can control postharvest disease and maintain the quality of Yali pear. This method may be applied to reduce the decay of Yali pears during exporting and storage.     

Effect of UV‐C radiation on quality of minimally processed spinach leaves

BACKGROUND: The fresh‐cut vegetable industry commonly uses sodium hypochlorite (NaOCl) for disinfection. However, certain problems with NaOCl usage have led to the investigation of alternative sanitisation treatments. In this respect, UV‐C radiation could be of interest. RESULTS: The effect of four pre‐packaging UV‐C radiation doses (0, 4.54, 7.94 and 11.35 kJ m^?2) and two storage temperatures (5 and 8 °C) on the quality of minimally processed spinach (Spinacia oleracea L.) leaves was studied over a period of 13 days. UV‐C radiation decreased mesophilic and psychrophilic counts just after its application compared with conventional sanitisation washing (150 mg L^?1 NaOCl). However, UV‐C had no residual effect on microbial growth from 6 to 13 days at 5 and 8 °C. During shelf‐life a slight loss of lightness was found, probably related to superficial tissue damage induced particularly in higher‐UV‐C treated leaves. Total antioxidant activity and polyphenol content decreased gradually throughout storage, being more evident in higher‐UV‐C treated leaves stored at 8 °C. The general trend was to maintain the initial chlorophyll content during shelf‐life. CONCLUSION: Low to moderate UV‐C radiation can be an effective alternative to chlorine for sanitising minimally processed spinach leaves and preserving their quality. Copyright © 2008 Society of Chemical Industry