Effects of pulsed light treatments on quality and antioxidant properties of fresh-cut mushrooms (Agaricus bisporus)

This study investigated the impact of pulsed light treatments on microbial quality, enzymatic browning, texture and antioxidant properties of fresh-cut mushrooms. The reduction of the native microflora of sliced mushrooms ranged from 0.6 to 2.2 log after 15 days of refrigerated storage by flashing at 4.8, 12 and 28 J cm⁻². Pulsed light treatments allowed extension of the microbiological shelf life of fresh-cut mushrooms by 2–3 days in comparison to untreated samples, while providing a high quality product. The use of high pulsed light fluencies (12 and 28 J cm⁻²) dramatically affected the texture of sliced mushrooms due to thermal damage induced by the treatments. Enzymatic browning was also promoted by an increase in polyphenol oxidase activity when the highest dose of pulsed light was applied. At 28 J cm⁻², phenolic compounds, vitamin C and antioxidant capacity were significantly reduced. Our results suggest that the application of pulsed light at doses of 4.8 J cm⁻² could extend the shelf life of fresh-cut mushrooms without dramatically affecting texture and antioxidant properties.     

Low oxygen levels and light exposure affect quality of fresh-cut Romaine lettuce

Modified atmosphere packaging (MAP) has the potential to extend the shelf-life of fresh-cut lettuce mainly by limiting the oxidation processes. However, exposure to light conditions has been described as causing browning and quality loss. The influence of O₂ partial pressures (pO₂) and light exposure during storage on the shelf-life of fresh-cut Romaine lettuce was studied. Fresh-cut lettuce was exposed daily during storage to different light conditions: light (24 h), darkness (24 h) and photoperiod (12 h light + 12 h darkness). Changes in respiration rate, headspace gas composition, sensory quality, colour, electrolyte leakage, stomatal opening, water loss, texture and compositional constituents related to browning such as vitamin C and individual and total phenolic compounds were evaluated. Different weight samples (75–275 g), packaged with an initial pO₂ of 0.5–2.0 kPa balanced with N₂, reached pO₂ from 0.1 to 1.5 at the steady-state. Atmospheres with low pO₂ (0.2–0.5) at the steady-state preserved lettuce quality by the control of browning and the prevention of off-odours and off-flavours. Light exposure during storage positively influenced the number of open stomata (74% in light vs 24% in darkness) which contributed slightly to weight loss. Consumption of O₂ in samples exposed to light differed significantly from those stored in photoperiod or darkness (10.6 ± 7.0, 18.3 ± 3.5 and 25.8 ± 8.6 nmol O₂ kg^?1 s^?1, respectively). Packages exposed to light showed higher pO₂ compared with packages stored in darkness while those exposed to photoperiod had intermediate values. Moreover, location of the packages in the shelves affected package headspace gas composition and thus, packages near the front of the shelves showed higher pO₂ than those at the back. The different light conditions did not influence the content of vitamin C or the individual and total phenolic compounds. This study shows that under light conditions respiration activity was compensated by photosynthesis resulting in a higher pO₂. Thus, browning of fresh-cut Romaine lettuce can be promoted by light exposure during storage as it increases headspace pO₂.     

Pre-harvest nitrogen and Azoxystrobin application enhances postharvest shelf-life in Butterhead lettuce

Two trials were carried out on Butterhead lettuce (March–May 2008 and April–June 2009) to investigate the effect of the application of nitrogen fertilizer (0, 50 and 100 kg ha⁻¹ of N) and of strobilurin (Azoxystrobin, methyl (E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}-3-methoxyacrylate) on (i) yield and morphological traits at harvest, (ii) physical (weight loss and dry matter), visual (chlorophyll content and main colour indices), physiological (relative water content, osmotic potential, and electrolytic leakage), and nutritional (ascorbic acid, nitrate, and polyphenol content) quality of raw material and their changes after storage of fresh-cut leaves. Cool storage lasted 7 and 12 days in the first and second experiment, respectively. In the first cycle, under early-spring conditions, lettuce yield was lower by 38% and, even if the product was lighter coloured [higher L* (+6%) and lower CHL (−21%)], it had lower dry matter content (−32%), higher electrolyte leakage (EL) (+14%) and WL_Trans (+8%) compared with the raw product from the second cycle. In both years, the increase of N supply and the application of Azoxystrobin improved yield (by 8.5% and 10%, respectively). The response in N fertilization was more evident under early-spring (2008) compared to late-spring (2009) conditions (12.3% vs. 4.8%), and when (2008) the highest N rate interacted with the application of Azoxystrobin (+12.9% compared with the other treatments). The nitrate content in leaves was always reduced by Azoxystrobin application (−43%) and increased with the N supply (+53%). In the second experiment, when storage was prolonged for 12 days, strobilurin improved postharvest shelf-life by reducing chlorophyll degradation (−27%), senescence (−19%, measured as EL), and browning (−53%, measured as h° index decrease). Azoxystrobin lowered also the total polyphenol content of raw material (−12.5%), which can be linked to less browning during storage. During postharvest storage, irrespective to the preharvest dose, N supply kept the visual quality and physiological senescence indices constant (L*, h° and EL). The suitability of the Butterhead lettuce to fresh-cut processing depends on climatic growing conditions. Preharvest Azoxystrobin supply improves the nutritional quality of the raw material, reducing leaf nitrate content, and the shelf-life in prolonged storage. The N rate of 100 kg ha⁻¹ of N is suitable under less favourable growing conditions, while the rate of 50 kg ha⁻¹ is better for more favourable climatic conditions, especially if a moderate contribution in available N from soil organic matter mineralization and no leaching from heavy rains is expected.     

Biopreservation of fresh-cut melon using the strain Pseudomonas graminis CPA-7

The use of biopreservation is a promising technique to ensure microbial safety of fresh-cut produce. The objective of this work was to test the effectiveness of the strain CPA-7 of Pseudomonas graminis against a cocktail of Salmonella spp. and Listeria monocytogenes on fresh-cut melon, and evaluate its effect on its quality during shelf-life when tested in conditions simulating commercial application.Fresh-cut melon was artificially inoculated with Salmonella spp. and L. monocytogenes and with or without the biopreservative strain at different concentrations and stored at 20, 10 and 5 °C. Moreover, the effect of the strain was tested in conditions simulating commercial application. Fresh-cut melon was packaged using passive modified atmosphere (MAP) and AIR conditions and stored at 5 and 10 °C. Quality of fresh-cut melon was evaluated in CPA-7 treated and untreated samples. At laboratory scale trials, P. graminis reduced Salmonella and L. monocytogenes growth on fresh-cut melon stored at 5, 10 and 20 °C. Effectiveness depended on their concentration and on storage temperature. At low pathogen concentration and 20 °C, L. monocytogenes growth was reduced between 2.1 and 5.3 log cfu g⁻¹ units after 2 days of storage and Salmonella growth between 2.0 and 7.3 log cfu g⁻¹ depending on CPA-7 dose. At 10 °C, similar reductions of pathogens were observed after 5 days of storage. In studies simulating commercial conditions, packaging atmosphere and temperature influenced P. graminis effectiveness, with better results in samples packaged under AIR conditions and 10 °C. Reduction of pathogen growth was <1-log unit in fresh-cut melon stored in MAP whilst it was >4-log units in AIR. Soluble solids content, titratable acidity, pH and firmness of fresh-cut melon were not significantly different in CPA-7 treated and untreated (control) melon. In general, lightness, chroma and hue values of fresh-cut melon stored in AIR decreased faster in CPA-7 samples than on control ones. At 5 °C, CPA-7 treated melon was visually scored lower than untreated melon. P. graminis has demonstrated promising results at 10 °C, which is a temperature more compromised for safety. Nevertheless more detailed studies on the modified atmosphere are required because AIR packaging is not recommended due to the rapid loss of quality.     

Changes in respiration of fresh-cut butterhead lettuce under controlled atmospheres using low and superatmospheric oxygen conditions with different carbon dioxide levels

The effect of different O₂ levels from 0 to 100 kPa in combination with 0, 10 and 20 kPa CO₂ on the respiration metabolism of greenhouse grown fresh-cut butter lettuce was studied. Controlled atmospheres of 20 or 75 kPa O₂ with 0 or 10 kPa CO₂ showed a constant respiration rate during the first 2–4 days at different temperatures (1, 5 and 9 °C). Therefore, constant respiration rates during a short period of 2–4 days could be considered as valid for a large part of the commercial life of, for instance, a modified atmosphere package development. The fresh-cut lettuce exposed to low O₂ levels (2–10 kPa) combined with moderate to high CO₂ levels (10 and 20 kPa) had a higher respiration rate than when 20–100 kPa O₂ were used. Moderate CO₂ levels (10 kPa) reduced the respiration rates of fresh-cut lettuce 20–40% at 9 °C. This effect was less noticed at lower temperatures. Gas composition with high CO₂ levels (20 kPa) probably caused a metabolic disorder increasing the respiration rate of fresh-cut butter lettuce. It was concluded that 80 kPa O₂ must be used in modified atmosphere packaging (MAP) to avoid fermentation of fresh-cut butter lettuce in combination with 10–20 kPa CO₂ for reducing their respiration rate.     

Impact of a decontamination step with peroxyacetic acid on the shelf-life,sensory quality and nutrient content of grated carrots packed under equilibrium modified atmosphere and stored at 7 °C

Peroxyacetic acid (PAA) is a strong oxidizer and exerts antimicrobial properties. The effect of a decontamination step with 80 and 250 mg L⁻¹ PAA on shelf-life of grated carrots stored under equilibrium modified atmospheric packaging at 7 °C was determined and compared with the shelf-life of unwashed and water-washed carrots. Microbial parameters, including total aerobic plate count, numbers of lactic acid bacteria, Lactobacillae and yeasts, and sensory quality were evaluated. Next to these parameters, atmospheric gas composition, pH and nutrient content were also monitored. The suggested packaging configuration prevented CO₂ accumulation, but at the end of the study anoxic conditions were reached for unwashed carrots and carrots washed with 80 mg L⁻¹ PAA. The microbial shelf-life of water-washed carrots was 4 d based on the yeast count, whereas the flavour was not acceptable after 5 d. The total aerobic plate count and the yeast count determined the shelf-life of carrots treated with 80 mg L⁻¹ PAA on 5 d, whereas the flavour was unacceptable after 7 d. None of the microbial parameters determined the shelf-life of carrots washed with 250 mg L⁻¹ PAA. However, this treatment had already a pronounced adverse effect on the initial sensory quality. Water washing already decreased the content of all individually studied nutrients (−16 to −28%), except for lutein content and the antioxidant capacity. Additional losses after adding PAA on day 0 were found for α-tocopherol and phenols. Regardless of the applied treatment, α- and β-carotene remained stable during storage, whereas ζ-carotene, lutein and α-tocopherol were unstable. The phenol content and the antioxidant capacity of unwashed, water-washed and 80 mg L⁻¹ PAA-treated carrots increased significantly at the end of the storage period, whereas no changes were found in carrots treated with 250 mg L⁻¹ PAA.On the condition that carrots were packed under an adequate EMA, the 80 mg L⁻¹ PAA treatment showed possibilities for extending shelf-life without pronounced effects on nutrient content.     

Effect of 1-methylcyclopropene (1-MCP) on softening of fresh-cut kiwifruit,mango and persimmon slices

Ethylene production is enhanced by wounding during fresh-cut processing and the accumulation of this gas within the packages of fresh-cut fruit can be detrimental to their quality and shelf-life. The effect of 1-methylcyclopropene (1-MCP), an ethylene action blocker, applied before or after processing, on the quality of fresh-cut kiwifruit, mangoes and persimmons was evaluated during storage at 5 °C. Fresh-cut ‘Hayward’ kiwifruit slices softened at a slower rate and their ethylene production rate was decreased in response to 1-MCP application (1 μL L⁻¹ for 6 h at 10 °C) either before or after processing. A 2-min dip in 0.09 M (1%, w/v) CaCl₂ synergistically increased the effect of 1-MCP on firmness retention and 1-MCP did not affect the color (L* value) of fresh-cut kiwifruit slices. Softening and browning (decreasing L* value) were delayed when 1-MCP was applied directly on fresh-cut ‘Kent’ and ‘Keitt’ mango slices. Respiration rate of mango slices was not influenced by 1-MCP whereas the ethylene production was affected only towards the end of their shelf-life. Fresh-cut ‘Fuyu’ persimmons treated with 1-MCP after processing presented higher ethylene production rate, slower softening rate and slower darkening of color (decrease in L* value), whereas the respiration rate was not affected.     

Effect of new sanitizing formulations on quality of fresh-cut iceberg lettuce

In the present study, three recently patented decontamination agents: peroxyacetic acid combined with lactic acid, and two different combinations of hydrogen peroxide with citric acid (with and without propylene glycol), were compared with sodium hypochlorite and tap water washing regarding their effect on equilibrium modified atmosphere packaged (EMAP) fresh-cut iceberg lettuce. Effects of these sanitizers on respiration rate, electrolyte leakage, microbial levels, and sensory quality of the product after decontamination and during storage (3 d at 4 °C followed by 4 d at 7 °C) were elucidated. Hydrogen peroxide based sanitizers provoked a significant increase in the respiration rate and the electrolyte leakage of fresh-cut iceberg lettuce compared with tap water washing. Peroxyacetic acid combined with lactic acid resulted in similar results to those of tap water washing for all the parameters analyzed. However, other aspects of the combination of peroxyacetic and lactic acids (e.g. efficacy for cross-contamination avoidance) should be assessed in the future in order to determine its suitability for fresh-cut iceberg lettuce processing.     

Lemongrass essential oil incorporated into alginate-based edible coating for shelf-life extension and quality retention of fresh-cut pineapple

The effects of different concentrations (0.1%, 0.3% and 0.5%, w/v) of lemongrass essential oil incorporated into an alginate-based [sodium alginate 1.29% (w/v), glycerol 1.16% (w/v) and sunflower oil 0.025% (w/v)] edible coating on the respiration rate, physico-chemical properties, and microbiological and sensory quality of fresh-cut pineapple during 16 days of storage (10 ± 1 °C, 65 ± 10% RH) were evaluated. Coated fresh-cut pineapple without lemongrass and uncoated fresh-cut pineapple were stored under the same conditions and served as the controls. The results show that yeast and mould counts and total plate counts of coated samples containing 0.3 and 0.5% (w/v) lemongrass were significantly (p < 0.05) lower than other samples. However, the incorporation of 0.5% (w/v) lemongrass in coating formulation significantly (p < 0.05) decreased the firmness and sensory scores (taste, texture and overall acceptability) of fresh-cut pineapples. Therefore, the results indicate that an alginate-based edible coating formulation incorporated with 0.3% (w/v) lemongrass has potential to extend the shelf-life and maintain quality of fresh-cut pineapple.     

Some conventional and latent anti-listerial effects of essential oils,herbs, carrot and cabbage in fresh-cut vegetable systems

The anti-listerial effectiveness of selected essential oils (EOs) and shredded fresh herbs (thyme, oregano and rosemary) was examined on a range of modified atmosphere packaged fresh-cut vegetables (lettuce, carrot discs, cabbage and dry coleslaw mix). Anti-listerial effects were in the order: thyme EO > oregano EO > rosemary herb > rosemary EO. While thyme EO demonstrated the best anti-listerial effect, direct application of all the EOs damaged product appearance. Shredded fresh rosemary herb appeared to have a major anti-listerial effect, but shredded fresh thyme and oregano showed no anti-listerial effects. However, fresh rosemary herb was only effective in fresh-cut products when it was stomached with the product prior to microbial analysis. The effectiveness of these antimicrobials varied depending on the product type. Greater anti-listerial effects were recorded on carrot discs and shredded cabbage than on shredded lettuce. Adding shredded carrot to packages enhanced the apparent anti-listerial effects, suggesting a synergistic effect between carrot and rosemary.     

Combination of electrolysed water,UV-C and superatmospheric O2 packaging for improving fresh-cut broccoli quality

The effects of neutral electrolysed water (NEW), ultraviolet light C (UV-C) and superatmospheric O₂ packaging (HO), single or combined, on the quality of fresh-cut kailan-hybrid broccoli for 19 days at 5 °C were studied. As controls, washing with water and sanitation with NaClO were both used. Electrolyte leakage, sensory, microbial and nutritional quality changes throughout shelf-life were studied. At day 15, the combined treatments achieved lower mesophilic and psychrophilic growth compared to the single ones. Single treatments produced higher ascorbate peroxidase (APX) reductions just after its application, while superoxide dismutase (SOD) showed the opposite behaviour. After 5 days at 5 °C, a great increase of APX and guaiacol peroxidase (GPX) activity was observed, NEW + UV-C + HO and HO-including treatments achieving the highest and the lowest APX increases, respectively. UV-C-including treatments produced the highest α-linolenic acid (ALA) decreases ranging 35–38% over control contents on the processing day. NEW-including treatments greatly reduced, throughout shelf-life, ALA and stearic acid (SA) content by 27–44% and 31–61%, respectively. Total phenolic content and antioxidant capacity (1415 mg ChAE kg⁻¹ fw and 287 mg AAE kg⁻¹ fw, respectively) remained quite constant during shelf-life. In general, the treatments and their possible combinations seem to be promising techniques to preserve, or even enhance, the quality of fresh-cut kailan-hybrid broccoli and, probably, other vegetables.     

Physiology of fresh-cut ‘Galia’ (Cucumis melo var. reticulatus) from ripe fruit treated with 1-methylcyclopropene

‘Galia’ (Cucumis melo var. reticulatus L. Naud. cv. Galia) fruit were harvested at the three-quarter slip stage and treated with 1 μL L⁻¹ 1-methylcyclopropene (1-MCP) at 20 °C for 24 h. The fruit were processed and stored as fresh-cut cubes and intact fruit for 10 d at 5 °C. Ethylene production of fresh-cut cubes was approximately 4–5-fold higher than intact fruit at day 1. Afterward, the ethylene production of fresh-cut cubes declined significantly whereas that of intact fruit remained relatively constant at about 0.69–1.04 ng kg⁻¹ s⁻¹. 1-MCP delayed mesocarp softening in both fresh-cut and intact fruit and the symptoms of watersoaking in fresh-cut fruit. Continuously stored fresh-cut cubes and cubes derived from intact fruit not treated with the ethylene antagonist softened 27% and 25.6%, respectively, during 10 d storage at 5 °C while cubes derived from 1-MCP-treated fruit softened 9% and 17%, respectively. Fresh-cut tissue from 1-MCP-treated fruit exhibited slightly reduced populations of both total aerobic organisms and Enterobacterium, although the differences did not appear to be sufficient to explain the differences in keeping quality between 1-MCP-treated and control fruit. Based primarily on firmness retention and reduced watersoaking, 1-MCP treatment deferred loss of physical deterioration of fresh-cut ‘Galia’ cubes at 5 °C by 2–3 d compared with controls.     

Effect of atmospheric modification, 1-MCP and chemicals on quality of fresh-cut banana

Fresh-cut banana slices have a short shelf-life due to fast browning and softening after processing. The effects of atmospheric modification, exposure to 1-MCP, and chemical dips on the quality of fresh-cut bananas were determined. Low levels of O₂ (2 and 4 kPa) and high levels of CO₂ (5 and 10 kPa), alone or in combination, did not prevent browning and softening of fresh-cut banana slices. Softening and respiration rates were decreased in response to 1-MCP treatment (1 μL L⁻¹ for 6 h at 14 °C) of fresh-cut banana slices (after processing), but their ethylene production and browning rates were not influenced. A 2-min dip in a mixture of 1% (w/v) CaCl₂ + 1% (w/v) ascorbic acid + 0.5% (w/v) cysteine effectively prevented browning and softening of the slices for 6 days at 5 °C. Dips in less than 0.5% cysteine promoted pinking of fresh-cut banana slices, while concentrations between 0.5 and 1.0% cysteine delayed browning and softening and extended the post-cutting life to 7 days at 5 °C.     

Evaluation of alternative sanitizers to chlorine disinfection for reducing foodborne pathogens in fresh-cut apple

The risk of undesirable by-products from chlorine disinfection in fresh-cut industries, together with its limited efficacy, has led to a search for alternative agents. The aim of this study was to test several alternative putative antimicrobial substances to reduce Escherichia coli O157:H7, Salmonella spp. and Listeria spp. populations on fresh-cut apple. Carvacrol, vanillin, peroxyacetic acid, hydrogen peroxide, N-acetyl-l-cysteine and Citrox were selected for their results in in vitro assays against E. coli O157:H7 and Listeria spp., to be tested on fresh-cut apple plugs. Apple flesh was inoculated by dipping in a suspension of a mix of the studied pathogens at 10⁶ cfu mL^?1, and then treated with the antimicrobial substances. All treatments were compared to deionized water and a standard sodium hypochlorite treatment (SH, 100 mg L^?1, pH 6.5). Pathogen population on apple plugs was monitored for up to 6 days at 10 °C. Bacterial reductions obtained by peroxyacetic acid (80 and 120 mg L^?1), vanillin (12 g L^?1), hydrogen peroxide (5, 10, 20 mL L^?1) and N-acetyl-l-cysteine (5 and 10 g L^?1) were similar or higher than reduction obtained by SH. In addition, bacterial populations were maintained at low levels throughout storage. No cells of any of the pathogens were detected in the peroxyacetic acid, hydrogen peroxide, Citrox and SH washing solutions after apple treatment. Peroxyacetic acid, hydrogen peroxide and N-acetyl-l-cysteine could be potential disinfectants for the fresh-cut industry as an alternative to chlorine disinfection. However, their effect on sensory quality and effectiveness under commercial processing conditions should be evaluated.     

UV-B light as a factor affecting total soluble phenolic contents of various whole and fresh-cut specialty crops

The effect of ultraviolet-B (UV-B) light treatment on total soluble phenolic (TSP) contents of various whole and fresh-cut specialty crops was evaluated. Whole fruits (strawberries, blueberries, grapes), vegetables (cherry tomatoes, white sweet corn) and root crops (sweet potatoes, colored potatoes), and fresh-cut fruit, vegetables and root crops (apple wedge, iceberg lettuce, broccoli floret and stem, and sliced radish, daikon, and parsnip) were treated with increasing UV-B dose levels (1.3–5.9 kJ m⁻²) and followed by incubation to allow for the samples to respond. TSP levels were measured. The changes in TSP were species-dependent. Whole grapes, blueberries, pink and red cherry tomatoes, white sweet corn, colored potatoes and sweet potatoes did not benefit from UV-B exposure. Strawberries showed a slight, but significant increase in TSP at the highest UV-B dose. UV-B exposure did not affect TSP of apple wedge, broccoli floret and stem, sliced radish and daikon after incubation. Fresh-cut lettuce and parsnip showed significant 1.2 and 2.3 times increase, respectively, in TSP mostly due to the combination effect of wounding and UV-B light exposure after 3 d of incubation. UV-B light exposure (1.3–5.9 kJ m⁻²) can be used as an additional processing step on selected specialty crops to enhance their soluble phenolic contents.     

Low-intensity light cycles improve the quality of lamb's lettuce (Valerianella olitoria [L.] Pollich) during storage at low temperature

The influence of light on fresh-cut vegetables during storage is controversial, since both positive and negative effects on shelf-life and quality of such products have been observed. In this work, the effect of low-intensity light treatments on lamb's lettuce, a fresh-cut leafy and ready-to-eat vegetable, was investigated during storage at low temperature (6 °C), in comparison with conventional storage (in the dark at 4 °C). Although continuous light treatment (1 cycle of 8 h per day) was deleterious, cycles of light treatments (8 cycles of 1 h per day; 16 cycles of 0.5 h per day) showed positive effects, assessed by evaluating the content of chlorophylls, carotenoids, ATP, glucose and ascorbate. These analyses were performed at the beginning and after 6 days of storage, in comparison with samples stored in the dark at 4 °C. Under low-intensity light treatments, even if performed at a higher temperature (6 °C), the content of such bioactive compounds increased or was at least similar to that found in samples stored in the dark at the same temperature. We suggest that continuous low-intensity light treatments during cold storage of lamb's lettuce are able to promote photosynthesis but, at the same time, induce photo-damage. On the contrary, under intermittent low-intensity light cycles, photosynthesis is only partially activated, while the metabolism of the green tissues is still able to provide carbon moieties for the synthesis of bioactive molecules involved in delaying senescence. Therefore, low-intensity light cycles at 6 °C could contribute to maintain quality of lamb's lettuce, with respect to samples stored in the dark at both 6 and 4 °C. Finally, setting the temperature at 6 °C allows reduction of refrigerator energy consumption during storage.     

Low dose UV-C illumination as an eco-innovative disinfection system on minimally processed apples

In this study, the efficacy of UV-C illumination for inactivate Escherichia coli, Listeria innocua or Salmonella enterica, individually or in a mixture, in vitro and on apple slices was determined. Apple slices inoculated with a 10⁷ cfu/mL suspension of above indicated pathogens were irradiated on both sides with UV-C illumination, with doses of 0.5 and 1.0 kJ/m². UV-C illumination disinfection efficacy was compared to that of washings with sodium hypochlorite at 100 ppm of free chlorine and with distilled water. Bactericidal activity of each treatment was assessed after 30 min and after 7 and 15 days of storage at 4 °C. Results showed that UV-C illumination at 1.0 kJ/m² could be an alternative to the wash with hypochlorite solutions. On the in vitro study, these doses completely inhibited the growth of the three bacteria either as pure cultures or in a mixture. In fresh-cut apple, the pathogens were also affected by the UV-C illumination, the 1.0 kJ/m² dosage being the one that resulted in higher bacteria inhibition in almost every case. The UV-C treatment did not affect the quality properties of fresh-cut apple.     

Pulsed light effects on surface decontamination,physical qualities and nutritional composition of tomato fruit

Pulsed light (PL) is a nonthermal food technology with a potential as postharvest decontamination strategy for fruit and vegetables. The feasibility of PL in extending shelf-life of food products while assuring appropriate quality is still under investigation. The effect of pulsed light (PL) on surface decontamination (natural and inoculated microorganisms), physical (colour, texture and weight) and nutritional quality (ascorbic acid and major carotenoids) was investigated in red-ripe tomatoes during 15 days of storage at 20 °C. The application of PL treatments at fluences of 2.68 and 5.36 J/cm² reduced microbial loads during storage of whole tomatoes. One log₁₀ reduction on the microflora present in both skin and peduncle scar parts of the tomato was obtained with a fluence of 4 J/cm². Fluences of 2.2 J/cm² allowed a 2.3 log₁₀ reduction of Saccharomyces cerevisiae inoculated onto the tomato surface. Softening, increased loss of weight, and wrinkles on the tomato surface appeared after 3 days on PL treated tomato fruit. Ascorbic acid levels remained unchanged during storage. Total lycopene, α-carotene and β-carotene contents and lycopene isomerisation percent were higher in tomato extracts prepared with fresh tomato fruit treated with a high PL dose of 30 J/cm². An increase in the bio-accessibility of lycopene was observed in hot-break purees prepared with fresh tomatoes treated at 5.36 J/cm² and stored 15 days. In conclusion, PL treatment of fresh tomato would result in a reduction in microbiological contaminants without compromising the nutritional value; but it did induce some appearance defects.     

Direct non-thermal plasma treatment for the sanitation of fresh corn salad leaves: Evaluation of physical and physiological effects and antimicrobial efficacy

Current problems with outbreaks of serious infections caused by human pathogens on fresh-cut greens highlight the need for new, optimized postharvest sanitation treatments to effectively meet recent food safety standards. In contrast to various chemical treatments, non-thermal plasma (NTP) has a high potential as a gentle target sanitation technique. However, possible interactions between NTP and the physiology of treated fresh products have not been investigated in detail. Here, chlorophyll fluorescence image analysis (CFIA) was used to study the potential impacts of non-thermal plasma on the photosynthetic activity of highly perishable corn salad leaves as a model produce. For this purpose, an atmospheric pressure plasma jet, driven at radio frequency, and transforming argon with flow rates of 20 L min⁻¹ into non-thermal plasma at 10, 20, 30, and 40 W generator power was applied for various times to the surface of corn salad leaves. Thermographic measurements indicated maximum temperatures of 39.0 °C, 44.4 °C, 60.1 °C, and 66.0 °C, respectively, on treated leaf surfaces. CFIA revealed that treatment at moderate generator power of 20 W for up to 1 min was the maximum setting for quality retention. Furthermore, the microbial inactivation efficiency of the plasma jet system at these operating parameters was successfully tested on Escherichia coli bacteria, inoculated on corn salad surface at 10⁷ cfu cm⁻² and 10⁴ cfu cm⁻². At 20 W, bacteria with lower initial load could be inactivated by 3.6 (±0.6) log-cycles within 15 s of treatment duration; whereas at the higher initial load of 10⁷ cfu cm⁻², bacteria were reduced by 2.1 (±0.2) log-cycles after 30 s.     

Extending the shelf life of fresh-cut eggplant with a soy protein–cysteine based edible coating and modified atmosphere packaging

The effect of a soy protein-based edible coating with antioxidant activity, and conventional and superatmospheric modified atmosphere (MA) packaging, on the quality of fresh-cut ‘Telma’ eggplants, was evaluated during storage. In a first experiment, eggplant pieces were dipped in either a coating composed of soy protein isolate (SPI) and 0.5% cysteine (Cys), or water as an uncoated control. Samples were packed in trays under atmospheric conditions to reach a passive MA (MA-P) or two gas mixtures (MA-A: 15 kPa CO₂ + 5 kPa O₂; MA-B: 80 kPa O₂) and were stored at 5 °C. Atmospheric conditions were used as the control conditions (Control). The coated samples packed under MA-B and Control conditions resulted in the highest whiteness index (WI) values during storage, whereas MA-A did not improve the shelf-life of minimally processed eggplants and had the lowest WI values. The MA-B and atmospheric control conditions helped to maintain firmness, whereas the coating helped to maintain the weight loss under MA-A and MA-B. The maximum commercial shelf-life was reached on day 6 for the coated samples packed under atmospheric conditions. In a second experiment, the commercial shelf-life of fresh-cut eggplants was extended to 8 and 9 storage days by increasing the Cys content in the edible coating from 0.5 to 1% under MA-B and Control storage conditions, respectively.