Application of an innovative water-assisted ultraviolet C light technology for the inactivation of microorganisms in tomato processing industries.

We aimed to study the efficacy of a water-assisted UVC light device (WUVC) as an innovative clean technology for the disinfection of fresh sound tomatoes and processing wash water and water turbidity was evaluated as a critical parameter. First, wash waters with different turbidities (from 0.4 to 828 NTU) were inoculated with Listeria innocua and treated in the WUVC device at different dosages. Secondly, fresh tomatoes, inoculated with L. innocua and non-inoculated ones, were treated using the WUVC device containing wash water of different turbidities for different times. The reduction of L. innocua populations on wash water and on the surface of tomato was influenced by turbidity; lower reduction values were observed at higher turbidities. Washing tomatoes with tap water with UVC lamps off (control treatment, TW) decreased L. innocua population on the surface of tomatoes but did not eliminate those bacteria that went into the water. Contrarily, when UVC lights were on, L. innocua population in wash water after treatment significantly decreased, those in clean water being the lowest populations. Reductions of native microbiota on the clean water treated with the highest UV-C radiation dose were lower than those obtained when tomatoes were artificially inoculated. We demonstrated that high reductions of L. innocua population on fresh tomatoes could be achieved using the WUVC system but some drawbacks related to the increase of turbidity should be solved for its implementation in real conditions.

Water UV-C treatment alone or in combination with peracetic acid: A technology to maintain safety and quality of strawberries.

Disinfection of fruits is one of the most important steps since they are going to be eaten fresh-or minimally-processed. This step affects quality, safety, and shelf-life of the product. Despite being a common sanitizer in the fruit industry, chlorine may react with organic matter leading to the formation of toxic by-products. Alternative sustainable disinfection strategies to chlorine are under study to minimize environmental and human health impact. Water-assisted UV-C light (WUV-C) is proposed here as an alternative sanitizing method for strawberries. In this study, strawberries were washed for 1 or 5 min in a tank with 2 or 4 lamps on, each emitting UV-C light at 17.2 W/cm2, or in a chlorine solution (200 ppm, pH 6.5). Moreover, trials with 4 lamps on, together with a washing solution consisting on peracetic acid at 40 or 80 ppm, were carried out. Overall, quality and nutritional parameters of strawberries after treatments were maintained. Changes in color were not noticeable and fruits did not lose firmness. No major changes were observed in antioxidant activity, organic acid, anthocyanin, vitamin C, and total phenolic content. Yeasts and molds were not affected by the WUV-C treatment, and 5 min were needed to significantly reduce total aerobic mesophylls population. However, reductions of artificially inoculated Listeria innocua and Salmonella Typhimurium after WUV-C treatments were comparable to those obtained with chlorine-wash, which were 3.0 log CFU / g. Moreover, WUV-C light was effective to minimize microorganisms remaining in washing water, avoiding cross-contamination and thus, allowing water recirculation. This effect was improved when combining the action of UV-C light with peracetic acid, showing the suitability of this combined treatment, understood as an alternative to chlorine sanitation, for sanitizing strawberries and keeping the populations of pathogenic bacteria in washing water lower than 0.6 ±â€¯0.1 log CFU / mL.

Bioaccessibility of polyphenols and antioxidant capacity of fresh or minimally processed modern or traditional lettuce (Lactuca sativa L.) varieties.

Modern city lifestyle is characterized by an increased demand for fresh or minimally processed foods. Lettuce (Lactuca sativa L.), mainly iceberg lettuce, is the main vegetable used during the manufacture of fresh-cut salads. The current study evaluated the phenolic content and antioxidant activity of ten fresh and minimally processed lettuce varieties. The phenolic content of selected lettuce samples varied significantly among varieties. Although a higher phenolic content was observed in modern lettuce varieties, when compared to the traditional ones (except for the landrace Francès 219/855), the antioxidant capacity of modern and traditional lettuce varieties was similar. Minimal processing followed by storage for a 7-day period led to an increased phenolic content in varieties Rutilaï RZ, Abago RZ, Maravilla LS044, Francès 219/855, Negre borratger 386/935, and D'hivern LS008, supporting the hypothesis that wounding can induce the accumulation of phenolic compounds in lettuce leaves. For example, the total phenolic content of Francès 219/855 after processing and storage increased from 8.3 to 11.3 mg/100 g (p < 0.05). Accumulation of phenolic compounds after minimal processing was not observed in all the studied samples, suggesting that this effect could be matrix-dependant. The amount of bioaccessible polyphenols was higher after minimal processing and storage. Indeed, the amount of bioaccessible polyphenols after a simulated gastrointestinal digestion of fresh or minimally processed Pelikan lettuce was calculated as 32.6 or 43.3 mg/100 g respectively (p < 0.05), suggesting that the increased amount of polyphenols caused by processing and storage can also lead to a higher amount of bioaccessible phenolic compounds.

Effects of long-term controlled atmosphere storage, minimal processing, and packaging on quality attributes of calçots (Allium cepa L.).

Calçots are the immature floral stems of the second-year onion (Allium cepa L.) resprouts. Modified atmosphere packaging or vacuum packaging are suitable alternatives to preserve fresh-cut vegetables. The objective of this study was to evaluate the effect of postharvest storage time of raw vegetable stored under controlled atmosphere and used packaging system after minimal processing on the quality of fresh-cut calçots. Calçots used for minimal processing were stored under 1.0 kPa O2 + 2.0 kPa CO2 at 1 ℃ for 30 and 60 days. Fresh-cut calçots were packaged using passive modified atmosphere packaging or vacuum packaging and were stored at 4 ℃ for 15 days. Calçots stored under controlled atmosphere for 30 days presented better retention of quality and in turn, being more suitable for minimally processing. Vacuum packaging preserved the physicochemical quality of fresh-cut calçots better after 15 days. Mesophilic aerobic counts were also higher in fresh-cut calçots stored under modified atmosphere packaging, but all counts were below the recommended limits during and at the end of their shelf-life (15 days). The most suitable conservation strategy might be to store whole calçots under controlled atmosphere for 30 days and after minimally processing, packaged under vacuum in order to extend the shelf-life of fresh-cut calçots.

Effect of ultrasound processing on the bioaccessibility of phenolic compounds and antioxidant capacity of selected vegetables.

Ultrasound processing can result in cell wall disruption, facilitating the release of the cellular content. Therefore, we hypothesized that sonication of vegetables could be used as a pre-treatment to increase the bioaccessibility of phenolic and antioxidant compounds. Overall, sonication (40 kHz, 250 W, 4 °C, 20 min) did not affect the main physicochemical parameters of tomato, lettuce, zucchini, and green and red pepper (p < 0.05). The polyphenolic content and antioxidant activity of digestive enzymatic extracts was higher than that of water:methanol extracts (p < 0.05). In addition, sonication resulted in increased bioaccessibility of phenolic compounds in lettuce and green pepper (p < 0.05), while no effect was observed for tomato, red pepper, and zucchini samples suggesting a matrix-dependent effect. The amount of phenolic compounds and antioxidants released by vegetables during a simulated gastrointestinal digestion may be higher than the one that can be expected from measurements in usual aqueous-organic extracts.

Strawberry sanitization by peracetic acid washing and its effect on fruit quality.

The risk posed by outbreaks associated with strawberries together with the safety issues of by-products from chlorine disinfection in the fruit industry has led to a search for alternative sanitizers. The disinfection capacity of peracetic acid (PA) at three concentrations (20, 40 and 80 ppm) and washing times (1 and 2 min) was compared to sodium hypochlorite (200 ppm) (NaClO) treatments and a water control, and its influence on the physico-chemical, biochemical and nutritional quality of strawberries was also studied. Counts on total aerobic mesophilic microorganisms were comparable between NaClO and PA. For yeasts and molds, only NaClO and 80 ppm PA reduced contamination in washing water, but no differences wereobserved in strawberries. Artificially inoculated L.innocua was reduced by at least 4 log cfu/g in strawberry by all the PA treatments, except at 20 ppm PA for 1 min. Total soluble solids, pH, titratable acidity, antioxidant activity and total phenolic content values were maintained after all treatments. Only anthocyanin content was affected. Treatments of 20 and 40 ppm PA did not significantly affect fruit color, and there were no losses on strawberry firmness. PA, as a GRAS substance that has shown potential to reduce microorganisms present in strawberries without any major physicochemical or sensorial alteration, could be a suitable alternative to chlorine disinfection.

Nutritional values of raw and cooked 'calçots' (Allium cepa L. resprouts), an expanding crop.

BACKGROUND: 'Calçot' is the Catalan name for the immature floral stems of second-year onion resprouts of the Blanca Tardana de Lleida (BTL) landrace. Highly appreciated for their sensory attributes, these resprouts are typically consumed after roasting on an open fire. Now new preparations are appearing, helping to expand the market for 'calçots'. This study aimed (i) to compare the nutritional and sensory characteristics of BTL 'calçots' versus other onion varieties; (ii) to analyze the effects of cooking and / or in vitro gastrointestinal digestion on the nutritional properties of 'calçots'; and (iii) to determine the influence of the environment on the antioxidant properties of 'calçots'. RESULTS: The nutritional and sensory characteristics of both raw and cooked 'calçots' differed between varieties, with the exception of some minerals. Flavonoid content decreased by 85% during cooking, and total phenolic content decreased by 30%. By contrast, antioxidant activity increased after cooking. Most traits had a nonlinear response to heating, and differences between varieties generally decreased after cooking. Location also had a strong effect on antioxidant activity. In vitro digestion of cooked 'calçots' sharply decreased antioxidant activity after the intestinal phase. The only significant genotypic correlation between sensory and nutritional quality was the correlation between sweetness and ash content (R = -0.97). CONCLUSION: Cooked BTL 'calçots' are within the limits of the onion domain for nutritional properties, and the variability reported for onion bulbs is also present in resprouts. The effects of the environment, cooking, and in vitro digestion clearly overlap the genetic effects. © 2019 Society of Chemical Industry.

A comprehensive study on the main physiological and biochemical changes occurring during growth and on-tree ripening of two apple varieties with different postharvest behaviour.

Apple quality and the storage potential likely depend on a range of physiological and biochemical events occurring throughout fruit development and ripening. In this study, we investigated the major physiological (ethylene production and respiration) and biochemical changes (related to sugar and malic acid content as well as antioxidant metabolism) occurring during growth and on-tree ripening of two apple varieties ('Granny Smith' (GS) and 'Early Red One' (ERO)) with known differences in their postharvest behaviour, mainly firmness loss and susceptibility to superficial scald. Our results demonstrate that the higher storability and the limited loss of firmness of 'GS' fruit was associated to a higher acid content, mainly malic acid, that seemed to be regulated already at fruit set (20 DAFB). The reduced loss of firmness during storage in 'GS' was also associated to the fruit inability to produce ethylene upon harvest resulting from very low 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) activity. Sugar accumulation, on the other hand, was similar among both varieties as was also observed for the rate of fruit growth or the fruit respiration pattern. In addition, the higher susceptibility of 'GS' if compared to 'ERO' to superficial scald was not associated to peroxidative damage (malondialdehyde accumulation) nor to higher levels of the sesquiterpene α-farnesene but rather mediated by a fruit antioxidant imbalance resulting from higher H2O2 levels and lower antioxidant (peroxidase) enzymatic capacity. The interplay between ethylene, respiration and antioxidants or sugars and organic acids during apple growth and development is further discussed.

Effects of thermal and non-thermal processing of cruciferous vegetables on glucosinolates and its derived forms.

Brassica vegetables, which include broccoli, kale, cauliflower, and Brussel sprouts, are known for their high glucosinolate content. Glucosinolates and their derived forms namely isothiocyanates are of special interest in the pharmaceutical and food industries due to their antimicrobial, neuroprotective, and anticarcinogenic properties. These compounds are water soluble and heat-sensitive and have been proved to be heavily lost during thermal processing. In addition, previous studies suggested that novel non-thermal technologies such as high pressure processing, pulsed electric fields, or ultraviolet irradiation can affect the glucosinolate content of cruciferous vegetables. The objective of this paper was to review current knowledge about the effects of both thermal and non-thermal processing technologies on the content of glucosinolates and their derived forms in brassica vegetables. This paper also highlights the importance of the incorporation of brassica vegetables into our diet for their health-promoting properties beyond their anticarcinogenic activities.