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.

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.

Evaluation of Pseudomonas graminis CPA-7 as a biopreservation method for fresh-cut pear: Physicochemical, enzymatic, and nutritional quality.

Biological preservation methods with bacterial antagonists have emerged as alternatives to chemical sanitizers for extending shelf-life and reducing the population of pathogenic microorganisms. In addition, calcium plays an important role in maintaining the quality of fruit, and postharvest calcium treatments might determine the potential of fruit for processing. The objective of this work was to evaluate the effect of the postharvest application of calcium and biopreservation with the CPA-7 strain of Pseudomonas graminis on the quality parameters of fresh-cut pears. After harvest, whole pears were dipped in calcium chloride solution (1%, w/v) or water (control) for 10 min at 25 ℃ and stored for five months at temperatures ranging from 0 to -0.5 ℃. Both batches of fruit were minimally processed and dipped in a solution containing CPA-7 and an antioxidant solution or kept untreated, and both groups were stored at 4 ℃ for six days. The postharvest calcium treatment had no remarkable effect on the quality of the whole and fresh-cut pears. The enzymatic activities (PPO, PME and PG) related to browning and softening were constant in fresh-cut pears after storage, and the application of P. graminis CPA-7 had a positive effect on the activity of PPO. Finally, a combined effect of the biocontrol agent and calcium treatment was not demonstrated.

Evaluation of biocontrol capacity of Pseudomonas graminis CPA-7 against foodborne pathogens on fresh-cut pear and its effect on fruit volatile compounds.

The application of microorganisms to control the growth of foodborne pathogens is an alternative to the use of chemical additives. In this work, Pseudomonas graminis CPA-7 was tested as a biocontrol agent against Salmonella enterica and Listeria monocytogenes on fresh-cut pear under conditions that simulate its commercial application at 5 ±â€¯1 °C (under a modified atmosphere and antioxidant solution). The quality of the fresh-cut fruit, including the ethanol and acetaldehyde contents and the volatile profile, was determined. After the storage period, the L. monocytogenes population was reduced by 1-log unit by the presence of CPA-7; however, CPA-7 was not found to have antagonistic activity against S. enterica. The fruit quality (total soluble solids content and titratable acidity) was not negatively affected by CPA-7. The ethanol and acetaldehyde contents increased during the shelf-life of the fruit regardless of the presence of CPA-7. Some volatile compounds were key factors for discriminating samples from the two groups (the control group and the group that was inoculated with CPA-7). Some components are common in the volatile profile of pear (methyl acetate, 3-methylbutyl acetate, 1-butanol, 1-hexanol, and hexanal), and thus increases in their contents could enhance consumers flavour perception.

Evaluation of postharvest calcium treatment and biopreservation with Lactobacillus rhamnosus GG on the quality of fresh-cut 'Conference' pears.

BACKGROUND: Biological preservation with probiotic bacteria has arisen as an alternative to control the growth of foodborne pathogens on food. The objective of this work was to evaluate the effect of postharvest calcium application and biopreservation with Lactobacillus rhamnosus GG on the quality and bioaccessibility of total phenolic content and antioxidant activity in fresh-cut pears. RESULTS: The immersion of whole pears in a calcium chloride solution did not provide added value. Despite the increase in observed activity of PME and PPO enzymes in fresh-cut pears during storage, the browning index and firmness values were constant for all samples. The antioxidant properties, including antioxidant activity, total phenolic content and vitamin C content, were maintained during storage, but a significant decrease was observed after in vitro simulated digestion. Ca/LGG samples showed the lowest calcium content (1.75 ± 0.00 g kg-1 ) after 9 d of storage at 4 °C. In general, the overall visual quality scores were higher in fresh-cut pears treated with L. rhamnosus GG than in non-treated pears, with the highest values in the NoCa/LGG (7.7 ± 0.2) samples after 9 d at 4 °C. CONCLUSION: Fresh-cut pears with a postharvest treatment of calcium and immersed in a solution containing antioxidant agents and probiotic bacteria could be a suitable alternative to dairy products for maintaining the overall quality of fruit for up to 9 d of storage. © 2018 Society of Chemical Industry.