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.     

Low UV-C illumination for keeping overall quality of fresh-cut watermelon

The effects of four pre-packaging UV-C illumination doses (1.6, 2.8, 4.8 and 7.2 kJ m^?2) on quality changes of watermelon cubes stored up to 11 days at 5 °C were studied. Non-treated cubes were used as a control. Higher UV-C doses induced slightly higher CO₂ production throughout the storage period, while no changes in C₂H₄ production were monitored. However, UV-C did not significantly affect the final gas partial pressures within modified atmosphere packages where levels of 3–6 kPa O₂ and 13–17 kPa CO₂ were reached for all treatments. UV-C decreased microbial counts just after illumination. After 11 days at 5 °C, mesophilic, psycrophilic and enterobacteria populations were significantly lower in UV-C treated watermelon. Slight changes in CIE colour parameters were observed. According to sensory quality attributes, control and low UV-C treated cubes (1.6 and 2.8 kJ m^?2) can be stored for up to 11 days at 5 °C while the maximum shelf-life of moderate to high UV-C treated fruit was 8 days at 5 °C. Control cubes showed a 16% decrease in lycopene content after 11 days at 5 °C similar to that found for the high UV-C treatment. However low UV-C treated watermelon cubes preserved their initial lycopene content (2.8 kJ m^?2) or it was slightly decreased (1.6 kJ m^?2). UV-C radiation did not significantly affect the vitamin C content while catalase activity and total polyphenols content considerably declined throughout the storage period. However, total antioxidant capacity markedly increased, independently of UV-C doses. As a main conclusion, UV-C radiation can be considered a promising tool for keeping overall quality of fresh-cut watermelon.     

Neutral and acidic electrolyzed water as emergent sanitizers for fresh-cut mizuna baby leaves

The effects of 40, 70 or 100 mg L^?1 free chlorine neutral and acidic electrolyzed water (NEW and AEW) during the washing and disinfection step, on quality attribute changes during shelf life of fresh-cut mizuna baby leaves, were studied. Physiological, nutritional, enzymatic, sensory, and microbial changes throughout 11 days at 5 °C were monitored. Results were compared to those reached with a conventional industrial treatment of 100 mg L^?1 NaClO at pH 6.5 and with a control washing with deionised water. Both NEW and AEW showed an inhibitory effect on natural microflora growth and retained the main quality attributes. Total chlorophyll content was preserved after shelf life. Initial total phenolic contents ranged between 1868 and 2518 mg CAE kg^?1 fw for AEW 40 and AEW 100 treatments respectively and slightly increased throughout shelf life. In contrast, after shelf life the total antioxidant activity recorded on the processing day decreased around 35%. Throughout shelf life EW induced an increase in catalase activity while superoxide dismutase activity decreased. Scanning electron microscopy of the leaves showed that neither NEW nor AEW affected their surface structure. To the best of our knowledge, the effects of NEW and AEW on bioactive quality parameters, as well as on antioxidant enzyme activities for fresh-cut baby leaves are first reported here. EW provides an alternative sanitizing technique to NaClO for maintaining the quality of fresh-cut mizuna baby leaves up to 11 days at 5 °C.     

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.     

The combined effects of aqueous chlorine dioxide,fumaric acid,and ultraviolet-C with modified atmosphere packaging enriched in CO2 for inactivating preexisting microorganisms and Escherichia coli O157:H7 and Salmonella typhimurium inoculated on buckwheat sprouts

The combined effects of a sanitizer mixture, ultraviolet-C (UV-C), and modified atmosphere packaging (MAP) on the quality of non-inoculated and inoculated (Escherichia coli O157:H7 and Salmonella typhimurium) buckwheat sprouts were examined. Buckwheat sprouts were treated with a sanitizer mixture (comprising 100 mg L⁻¹ aqueous ClO₂ and 0.3% fumaric acid) and 2 kJ m⁻² UV-C, packaged under two different conditions (air and CO₂ gas) and storage for 8 d at 4 °C. The combination of the sanitizer mixture and UV-C treatment reduced the initial counts of preexisting microorganisms in the buckwheat sprouts by 1.9 log CFU g⁻¹ and reduced the initial inoculated counts of E. coli O157:H7 and S. typhimurium on buckwheat sprouts by 3.0 and 2.3 log CFU g⁻¹, respectively. The preexisting microorganisms and inoculated pathogens in buckwheat sprouts packaged under CO₂ gas were significantly reduced during storage following the combined treatment compared to those of the control by above 95%. Differences in Hunter L^*, a^*, and b^* values among the treatments were negligible. The combined sanitizer mixture and UV-C treatment increased the sprout rutin content by 147%, but there was no significant difference in 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity between treatments during storage. Therefore, the combination of sanitizer mixture made from aqueous ClO₂ and fumaric acid, UV-C irradiation, and MAP can improve the microbial safety and quality of buckwheat sprouts.     

Effect of radiation intensity on the outcome of postharvest UV-C treatments

Studies on the use of UV-C radiation of fresh produce have focused on the selection of appropriate doses (energy per unit area) for different commodities, but little attention has been placed on the effect of radiation intensity (dose per unit time). In this study, tomatoes (Solanum lycopersicum cv. Elpida) and strawberries (Fragaria × ananassa cv. Camarosa), were harvested (breaker and 100% of surface red color respectively) and treated with 4 kJ m⁻² of UV-C, at low (3 W m⁻²) or high (33 W m⁻²) radiation intensities. Untreated fruits were used as controls. After the treatments and at different storage times the incidence of postharvest rots and the changes in fruit physical and chemical properties were determined. UV-C treatments reduced decay, with the effects being were more marked in fruit exposed to high intensities. Mold counts were unaffected by the treatments, suggesting that improved disease control did not result from greater germicide effect. In both fruit species exposure to UV-C radiation delayed ripening, evidenced as lower color development, pigment accumulation and softening. UV-C-treated fruit maintained better quality than the control. In strawberry, high intensity treatments were more effective to prevent deterioration than in tomato where the differences between UV-C treatments were subtler. Soluble solids, titratable acidity and ethanol soluble antioxidants were not affected regardless of the UV-C intensity. Consumer tests showed higher preference of fruit treated at high UV-C intensity. Results show that in addition to the applied dose, radiation intensity is a main factor determining the effectiveness of UV-C treatments and should not be over-sighted. For a given dose, increasing radiation intensity may in some cases maximize the benefits of UV-C on fruit quality, while significantly reducing the treatments time.     

Controlling sprouting in potato tubers using ultraviolet-C irradiance

Legislation limiting the use of chlorpropham (CIPC), the major potato sprout suppressant, has led to a need for new technologies to extend storage life of tubers. Ultra violet C (UV-C) has been used postharvest to reduce disease incidence on many crops, yet its use and efficacy as a sprout suppressant has not been investigated. The aim of this project was to identify the optimum dose and treatment timing of UV-C treatment on potato tubers as an alternative method of sprout suppression to reduce the dependence on chemical sprout suppressants. Up to six potato cultivars over two seasons were treated with varying doses of UV-C ranging from 0 to 30 kJ m⁻² either at harvest or at first indication of dormancy break. The tubers were stored at 9 °C and sprout growth and incidence assessed. Treatment with moderate UV-C doses (5–20 kJ m⁻²) suppressed sprout length and sprout incidence in a range of cultivars. Periderm DNA damage and programmed cell death were not detected in response to any of the UV-C doses. The inactive ABA metabolite, ABA-GE, increased in response to 10 or 20 kJ m⁻² within 72 h of treatment. Multivariate analysis showed a negative relationship between ABA metabolites and sprout growth/incidence during storage. This study found that UV-C reduced sprout growth in potato with no deleterious effects on tuber quality. This suggests potential for further development as an alternative or supplement to conventional sprout suppressant technologies.     

UV-C treatment delays postharvest senescence in broccoli florets

Central broccoli heads (cv. de Cicco) were harvested and treated with UV-C light (4, 7, 10, or 14 kJ m⁻²). All treatments delayed yellowing and chlorophyll degradation at 20 °C but the irradiation dose of 10 kJ m⁻² allowed retaining the highest chlorophyll content yet had lower amounts of pheophytins than every treatment other than 7 kJ m⁻². This dose was selected to analyze the effect of UV-C on postharvest broccoli senescence at 20 °C. The UV-C treatment delayed yellowing, chlorophyll a and b degradation, and also the increase in pheophytins during storage. The activity of chlorophyll peroxidase and chlorophyllase was lower in UV-C treated broccoli. Instead, Mg-dechelatase activity increased immediately after the treatment, but after 4 and 6 d this activity was lower in UV-C treated florets than in controls. Treated broccoli also displayed lower respiration rate, total phenols and flavonoids, along with higher antioxidant capacity. The results suggest that UV-C treatments could be a useful non-chemical method to delay chlorophyll degradation, reduce tissue damage and disruption, and maintain antioxidant capacity in broccoli.     

UV-C inactivation of Escherichia coli and dose uniformity on apricot fruit in a commercial setting

A UV-C treatment system (two treatment chambers connected by an inclined belt to rotate apricots between chambers) was tested in a commercial setting. Escherichia coli ATCC 25922, used as a surrogate for E. coli O157:H7 to determine the system's antimicrobial efficacy, was inoculated onto fruit surfaces at a population of 6.8 log CFU/fruit. UV-C dosage was evaluated by attaching film dosimeters to six fixed locations on each apricot. Results suggested that reduction of inoculated E. coli ATCC 25922 populations on the apricot fruit by UV-C treatment was small (only 0.5–0.7 logs). There were large variations in UV-C doses among varying apricot surface locations. Approximately 1/3 of apricots had individual surfaces receiving less than 0.2 kJ m⁻² UV-C exposure, even though fruit received, on average, more than 1 kJ m⁻². Low reductions of E. coli may be attributed, in part, to non-uniform UV-C exposure. This study demonstrates the need to use a fruit rotation device more capable of delivering uniform UV-C dosage to the surface of apricots for inactivating bacteria in a commercial setting.     

Performance of fogged disinfectants to inactivate conidia of Penicillium digitatum within citrus degreening rooms

Fogging with formaldehyde of citrus packinghouses when the fruit are absent is a practice to control conidia of Penicillium digitatum (Pers.) Sacc., the cause of citrus green mold. Replacements for formaldehyde in these facilities are needed because of worker and environmental health issues. To evaluate the effectiveness of candidate sanitizers, craft wood sticks with conidia of P. digitatum were attached throughout commercial citrus ethylene degreening rooms and either water alone or the sanitizers were applied. The rooms were 20 ± 2 °C and humidified to 85–90% relative humidity. Aldehydes, peroxygen compounds, sodium hypochlorite, chlorine dioxide, quaternary ammonium, alcohols, one phenolic compound, and one organic acid were applied with a compressed air assisted atomizer or fan atomizer in a volume of approximately 6 L per 100 m³ of room volume dispensed over a 3 h period. Rates applied were expressed as active ingredient per m³ of room volume. All were compared to formaldehyde applied at 1.98 g m⁻³ of room volume. After 24 h, the craft wood sticks were retrieved, and germination of the conidia assessed. Five sanitizers reduced germination of conidia by more than 95% and equaled formaldehyde in effectiveness. They were (effective rates): (1) glutaraldehyde (0.1 g m⁻³); (2) hydrogen peroxide (4.4 g m⁻³); (3) Citrisol (1.0 g m⁻³), a proprietary mineral oxychloride oxidizer; (4) acetic acid (5.3 g m⁻³); and (5) peracetic acid (2.4 g m⁻³). The toxicity of effective sanitizers was determined by exposure of P. digitatum conidia for 10 min to concentrations of each and the proportion of survivors used to estimate EC₅₀ and EC₉₉ concentrations. The toxicity of the sanitizers in this assay did not predict their effectiveness when applied by fogging, probably because other factors, such as distribution, persistence, droplet size, or vapor pressure also influenced their effectiveness.     

Influence of UV-C treatment on antioxidant capacity,antioxidant enzyme activity and texture of postharvest shiitake (Lentinus edodes) mushrooms during storage

Shiitake (Lentinus edodes) mushrooms were exposed to UV-C light (4 kJ/m²) and stored in modified atmosphere packaging (MAP) prior to 15 days at 1 ± 1 °C and 95% relative humidity plus 3 days at 20 °C. Mushroom firmness, total phenolics, total flavonoids, ascorbic acid and H₂O₂ contents, superoxide anion (O₂⁻) production rate and activities of catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) were measured. UV-C treatment resulted in maintenance of a high level of firmness during 15 days at low temperature and reduced the decrease in firmness during shelf-life storage. Furthermore, treated samples showed higher total flavonoids, ascorbic acid, and delayed the increases in both O₂⁻ production rate and H₂O₂ contents. However, no clear treatment effects were seen in total phenolics contents. The treatment also increased the antioxidant enzyme activities of CAT, SOD, APX and GR throughout the storage period. These results indicate that postharvest application of UV-C radiation can delay softening and enhance antioxidant capacity in shiitake mushrooms.     

Effects of gamma and UV-C irradiation on the postharvest control of papaya anthracnose

Anthracnose is the main postharvest disease in papaya fruit. Today, there is considerable interest on alternative methods of control to promote resistance against pathogens and supplement or replace the use of fungicides. The goal of this work was to evaluate the effects of gamma and UV-C irradiation on Colletotrichum gloeosporioides, the causal agent of anthracnose. Mycelial growth, sporulation, and conidial germination were evaluated in vitro after fungal exposition to different irradiation doses. In the in vivo assays, ‘Golden’ papaya fruit were inoculated through subcuticular injections of a conidial suspension or mycelium discs. Next, fruit were submitted to different irradiation doses (0, 0.12, 0.25, 0.5, 0.75, and 1 kGy), using Co⁶⁰ as source, or UV-C (0, 0.2, 0.4, 0.84, 1.3, and 2.4 kJ m⁻²). To check the possibility of resistance induction by irradiation, papayas were also inoculated 24, 48, or 72 h after the treatments. The fruit were stored at 25 °C/80% RH for 7 days and evaluated for incidence and rot severity. The results showed that the 0.75 and 1 kGy doses inhibited conidial germination and mycelial growth in vitro. All doses increased fungal sporulation. The 0.75 and 1 kGy doses reduced anthracnose incidence and severity, but did not reduce them when the fruit were inoculated after irradiation. All UV-C doses inhibited conidial germination and those higher than 0.84 kJ m⁻² inhibited mycelial growth. The 0.4, 0.84, and 1.3 kJ m⁻² UV-C doses reduced fungal sporulation in vitro. There was no effect of UV-C doses and time intervals between treatment and inoculation on anthracnose control and fungal sporulation in fruit lesions. Moreover, all UV-C doses caused scald on the fruit. Thus, gamma irradiation can contribute for the reduction of postharvest losses caused by anthracnose and reduce the use or doses of fungicides on disease control.     

Effect of UV-C treatments on phenolic compounds and antioxidant capacity of minimally processed Satsuma mandarin during refrigerated storage

The effect of UV-C treatments (0.75, 1.5 and 3.0 kJ/m²) on fruit quality, phenolic compounds and antioxidant capacity of minimally processed Satsuma mandarin during 12 days of storage at 4 °C was studied. The results showed that UV-C treatments had no adverse effects on quality attributes, ascorbic acid, phenolic acids and antioxidant capacity of mandarin segments. Significant increases of flavonoids (22.20% and 21.34% for narirutin, 11.75% and 33.25% for hesperidin) and total phenolics (5.73% and 8.13%) were found in 1.5 and 3.0 kJ/m² UV-C treated fruit at 3 days of storage. Further study confirmed that the increase of flavonoids occurred during the first 3 days and diminished after 4 days of storage. UV-C dose at 3.0 kJ/m² did not further improve the increase of flavonoids, and 0.75 kJ/m² had no significant effects on phenolics. Proper application of UV-C treatment could be a new way to enhance the functional quality of minimally processed citrus fruit.     

UV-C light inactivation kinetics of Penicillium expansum on pear surfaces: Influence on physicochemical and sensory quality during storage

UV-C inactivation kinetic data of Penicillium expansum on intact and wounded pear disks were determined. P. expansum conidia (0.5 mL, 1.6 × 10⁷ CFU/mL) were spot inoculated onto intact and wounded pear tissue with skin (excised disks), treated with UV-C doses ranging 0.101–3.06 kJ/m² at 23 °C and surviving conidia were enumerated. Changes in selected physicochemical parameters and sensory quality following UV-C treatment of whole pears were determined immediately after treatment, and 4 and 8 weeks of storage at 4 °C. A greater UV-C intensity was required for similar inactivation levels of P. expansum populations on wounded pear disks (3.1 kJ/m² for 2.7 log reduction) compared to intact pear disks (1.7 kJ/m² for 2.8 log reduction). No significant difference in % weight loss, or soluble solids content and texture was observed between UV-C treated and untreated pears. However, browning was observed on UV-C treated pear surfaces after 4 and 8 weeks along with changes in flavor and texture. An increase in consumer preference was noticed for the untreated control pears after 4 weeks storage.     

Pre-harvest calcium application increases biomass and delays senescence of broccoli microgreens

Microgreen consumption has been steadily increasing in recent years due to consumer awareness of their unique color, rich flavor, and concentrated bioactive compounds. However, industrial production and marketing is limited by their short shelf-life associated with rapid deterioration in product quality. This study investigated the effect of pre-harvest calcium application on the post-harvest quality and shelf-life of broccoli microgreens. Broccoli microgreen seedlings were sprayed daily with calcium chloride at concentrations of 1, 10 and 20 mM, or water (control) for 10 days. The fresh-cut microgreens were packaged in sealed polyethylene film bags. Package headspace atmospheric conditions, overall visual quality and tissue membrane integrity were evaluated on days 0, 7, 14, and 21, during 5 °C storage. Results indicated that the 10 mM calcium chloride treatment increased the biomass by more than 50%, and tripled the calcium content as compared to the water-treated controls. Microgreens treated with 10 mM calcium chloride spray exhibited higher superoxide dismutase and peroxidase activities, lower tissue electrolyte leakage, improved overall visual quality, and reduced microbial growth during storage. Furthermore, calcium treatment significantly affected expression of the senescence-associated genes BoSAG12, BoGPX6, BoCAT3 and BoSAG12. These results provide important information for commercial growers to enhance productivity and improve postharvest quality and shelf-life, potentially enabling a broadening of the retail marketing of broccoli microgreens.     

Effect of modified atmosphere packaging and storage temperature on volatile composition and postharvest life of minimally-processed pomegranate arils (cvs. ‘Acco’ and ‘Herskawitz’)

This study investigated the effects of passive modified atmosphere packaging (MAP), storage temperature (5, 10 and 15 °C) and duration of 14 days on the postharvest quality attributes, compositional change in flavour attributes and microbiological quality of minimally processed pomegranate arils (Punica granatum L.), cvs ‘Acco’ and ‘Herskawitz’. Volatile compounds were extracted via headspace solid phase micro-extraction (HS-SPME) and analyzed by gas chromatography–mass spectrometry (GC–MS). A total of 17 and 18 volatiles were detected and identified in the headspace of pomegranate juices of ‘Acco’ and ‘Herskawitz’, respectively. Based on the physicochemical attributes and microbial evaluation, the postharvest life of MA-packaged ‘Acco’ and ‘Herskawitz’ was limited to 10 days due to fungal growth ≥2 log CFU g⁻¹ at 5 °C. However, the concentration (%) and compositional changes in volatile compounds indicated that the flavour/aroma life (7 days) was shorter than the postharvest shelf-life based on appearance and other physicochemical (10 days) for both cultivars.     

Surface decontamination of fresh-cut apple by UV-C light exposure: Effects on structure,colour and sensory properties

The effect of UV-C light treatments at 1.2, 6.0, 12.0 and 24.0 kJ/m² was studied with reference to germicidal efficiency and changes in fresh-like appearance of fresh-cut apple. Independently of UV-C light fluence, all treatments imparted the same germicidal effect with 1–2 log reduction in total viable counts. Treatments at a fluence exceeding 1.2 kJ/m² caused the loss of compartmentalisation of surface apple cells, activating dehydration and oxidative phenomena. By contrast, mild treatments resulted in apple slices much more stable than the untreated control in terms of microbial growth and development of browning and off-flavours. These effects were attributed not only to the direct inactivation of spoilage microrganisms and enzymes by UV-C light, but also to the formation of a thin, dried film on the surface of the product. This edible protective film inhibited microbial growth and hindered dehydration during storage but was too thin to be perceived by consumers. UV-C light exposure was demonstrated to be an effective non-visible technology for food surface decontamination, but only if applied at mild intensity.     

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 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.     

Effect of cyclic exposure to ozone gas on physicochemical,sensorial and microbial quality of whole and sliced tomatoes

The effect of a humidified flow of ozone-enriched air applied cyclically (4 ± 0.5 μL L⁻¹ of O₃ for 30 min every 3 h) on metabolic behaviour and sensorial and microbial quality of whole and fresh-cut ‘Thomas’ tomatoes stored up to 15 days at 5 °C was examined. The application of O₃ initially stimulated the respiration rate in a way similar to a stress, although after 2 days, the metabolic activity decreased to a rate lower than that of control (air flow). In O₃-treated whole and sliced tomatoes a higher sugar (fructose and glucose) and organic acid (ascorbic and fumaric) content was found. The kind of cut (whole or slices) did not affect the sensitivity of tomato to O₃. In whole tomatoes, O₃ maintained the tissue firmer than in control fruit while no influence was found on slices. The O₃ treated fruit retained a good appearance and overall quality in slices but experienced a reduced aroma. Also, O₃ substantially reduced microbial counts, being more noticeable on bacteria (1.1–1.2 log₁₀ units) than on fungi (0.5 log₁₀ units). This effect was higher when the storage time was longer and when a higher O₃ level (7 μL L⁻¹) was used. O₃ did not cause any damage or off-flavour in slices or whole tomatoes. In conclusion, the assayed O₃ treatment can be useful for maintaining quality and reducing microbial populations in whole and sliced tomato.