Interactions between sanitizers and packaging gas compositions and their effects on the safety and quality of fresh-cut onions (Allium cepa L.)

Recent Advances in Bioactive Compounds, Health Functions, and Safety Concerns of Onion (Allium cepa L.)

Onion (Allium cepa L.) is a common vegetable, widely consumed all over the world. Onion contains diverse phytochemicals, including organosulfur compounds, phenolic compounds, polysaccharides, and saponins. The phenolic and sulfur-containing compounds, including onionin A, cysteine sulfoxides, quercetin, and quercetin glucosides, are the major bioactive constituents of onion. Accumulated studies have revealed that onion and its bioactive compounds possess various health functions, such as antioxidant, antimicrobial, anti-inflammatory, anti-obesity, anti-diabetic, anticancer, cardiovascular protective, neuroprotective, hepatorenal protective, respiratory protective, digestive system protective, reproductive protective, and immunomodulatory properties. Herein, the main bioactive compounds in onion are summarized, followed by intensively discussing its major health functions as well as relevant molecular mechanisms. Moreover, the potential safety concerns about onion contamination and the ways to mitigate these issues are also discussed. We hope that this paper can attract broader attention to onion and its bioactive compounds, which are promising ingredients in the development of functional foods and nutraceuticals for preventing and managing certain chronic diseases.

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.

Predicting the Growth of Listeria monocytogenes and Salmonella Typhimurium in Diced Celery, Onions, and Tomatoes during Simulated Commercial Transport, Retail Storage, and Display

Temperature is arguably the most important factor affecting microbial proliferation in fresh-cut produce. In this study, growth of Listeria monocytogenes in diced onions and celery and Salmonella Typhimurium in diced tomatoes was determined in modified atmosphere packages and snap-fit containers using three fluctuating temperature scenarios for transport, retail storage, and display. As expected, L. monocytogenes growth in diced onions and celery varied depending on the extent of temperature abuse, with exposure to high and intermediate temperature-abuse scenarios generally being growth supportive. A Baranyi primary model with a square-root secondary model for maximum growth rate, and a linear model for maximum population density, were used to estimate Listeria growth under fluctuating temperature. Accuracy and acceptability of the model prediction were evaluated in terms of root mean square error (RMSE) and acceptable prediction zone (APZ), respectively. Overall, growth predictions for L. monocytogenes were more accurate for celery (RMSE, 0.28 to 0.47) than onions (RMSE, 0.42 to 1.53) under the fluctuating temperature scenarios tested. However, both predictions yielded APZ values that ranged from 82 to 100% for celery and 36 to 78% for onions. In contrast, Salmonella Typhimurium populations increased more than 1 log CFU/g in diced tomatoes under the three fluctuating temperature scenarios studied. Overall, these diced products packaged under a high-oxygen atmosphere showed decreased pathogen growth compared with product stored in a passive modified atmosphere. Findings from this study will be particularly useful in assessing the risk associated with consumption of diced celery, tomatoes, and onions and in designing effective packaging strategies to minimize pathogen growth in fresh-cut produce.

Performance of Poly(lactic acid) Surface Modified Films for Food Packaging Application

Five Poly(lactic acid) (PLA) film samples were analyzed to study the gas barrier behavior, thermal stability and mechanical performance for food packaging application. O₂, CO₂, N₂, N₂O, and C₂H₄ pure gases; Air; and Modified Atmosphere (MA, 79% N₂O/21% O₂) were used to analyze the influence of the chemical structure, storage temperature and crystalline phase on the gas barrier behavior. The kinetic of the permeation process was investigated at different temperatures, ranging from 5 °C to 40 °C. Annealing thermal treatment on the samples led to the crystalline percentage, influencing especially the gas solubility process. Thermal properties such as Tg and χc, and mechanical properties such as tensile strength and modulus were remarkably improved with surface PLA modification. A more pronounced reinforcing effect was noted in the case of metallization, as well as improved gas barrier performance. Tensile testing and tensile cycling tests confirmed the rigidity of the films, with about a 20% loss of elasticity after 25 cycles loading.