RESUMEN
In this work, the influence of high-power ultrasound (HPU) followed by pulsed electric field (PEF) in the hurdle concept (HPU + PEF) on the content of biologically active compounds (BACs) and antioxidant activity in strawberry juices stored at 4 °C/7 days was investigated. The HPU was performed with an amplitude of 25% and pulse of 50% during 2.5, 5.0 and 7.5 min, while the PEF was performed with an electric field strength of 30 kV cm-1 and frequency of 100 Hz during 1.5, 3 and 4.5 min. The results obtained indicate that the synergy of the mechanisms of action for technologies in the hurdle concept plays a critical role in the stability of BACs and antioxidant activity. Juices treated with HPU + PEF hurdle technology and kept at 4 °C for 7 days showed a statistically significant decrease in all BACs, antioxidant capacity and pH. Shorter HPU + PEF treatment times favored the preservation of BACs in juices. Regarding total phenolic compounds, flavonols, condensed tannins and antioxidant capacity, optimization of hurdle parameters showed that a shorter HPU treatment time of 2.5 min provided the best yield of these compounds. In summary, by optimizing and adjusting the parameters of the HPU/PEF technology, it is possible to produce functional strawberry juice.
RESUMEN
This study evaluated the efficiency of UV radiation doses (4.68-149.76 J/cm2) and nisin (50-200 ppm) and their combination in comparison with thermal pasteurization on the microbial inhibition kinetics and physicochemical properties of tangerine juice. It was noted that UV-149.76 J/cm2 and nisin (NS) at 200 ppm in conjunction exhibited the highest log reduction in spoilage and pathogenic microbes including Escherichia coli, Lactiplantibacillus plantarum, and Saccharomyces cerevisiae, yeast and molds, and total plate count in tangerine juice. Additionally, the first-order kinetic model provides a better fit for spoilage and pathogenic strains compared with the zero-order model (higher coefficient of determination, R2), particularly for E. coli. UV and NS showed insignificant effects (p > 0.05) on pH, TSS, and TA values compared with pasteurization. However, there were notable differences observed in color analysis, total phenolic compound, total flavonoid content, vitamin C, carotenoid content, and antioxidant activity using DPPH and FRAP assays. The optimized UV + NS samples were subjected to refrigerated storage for 21 days. The results revealed that during the entire storage period, the pH values and the TSS values slightly decreased, and the TA values increased in the treated samples. The UV + NS treatment insignificantly impacted the color properties. The total phenolic, total flavonoid, and carotenoid contents, and vitamin C decreased over time for all sample treatments, whereas the antioxidant properties exhibited varying outcomes, compared with an untreated control and pasteurization. Therefore, UV radiation and nisin (UV-149.76 J/cm2 + NS-200 ppm) in combination could serve as a viable alternative to traditional heat pasteurization of fruit juice during cold storage.
RESUMEN
The application of several sublethal stresses in hurdle technology can exert microbial stress resistance, which, in turn, might enable foodborne pathogens to overcome other types of lethal stresses, such as the gastrointestinal barriers. The present study evaluated the survival of Salmonella Typhimurium and Listeria monocytogenes during simulated digestion, following exposure to combinations of water activity (aw), pH and storage temperature stresses. The results revealed that both pathogens survived their passage through the simulated gastrointestinal tract (GIT) with their previous habituation to certain hurdle combinations inducing stress tolerance. More specifically, the habituation to a low temperature or to a high pH resulted in the increased stress tolerance of Salmonella, while for Listeria, the cells appeared stress tolerant after exposure to a high temperature or to a low pH. Nonetheless, both pathogens expressed increased sensitivity after habituation to growth-limiting hurdle combinations. The survival of stress-tolerant pathogenic cells in the human GIT poses major public health issues, since it can lead to host infection. Consequently, further research is required to obtain a deeper understanding of the adaptive stress responses of foodborne bacteria after exposure to combinations of sublethal hurdles to improve the existing food safety systems.
RESUMEN
Cauliflower is a rich source of proteins, carbohydrates, vitamins and minerals and also a very important vegetable having maximum availability in tropical climate from November to February which causes glut in the market and consequently producers do not get remunerative prices. The partially blanched cauliflower pieces of 3-4 cm long having stalk upto 2 cm in length are steeped in different levels of sodium chloride (NaCl, 2-6 %) and acetic acid (1-2 %) along with 350 ppm sulphur dioxide (SO2) using modified response surface methodology (RSM). The cauliflower samples steeped in 4 % NaCl, 1 % acetic acid and 350 ppm SO2 were rated best with maximum mean overall acceptability (OAA) score (6.90) and minimum mean preference (6.25) to the experimental run consisting of 6 % NaCl, 2 % acetic acid and 350 ppm SO2 was noted after 120 days of storage. There has been sharp decrease in pH values after 15 days of storage in all the experimental run of preserved cauliflower samples. The maximum mean decrease in hardness values (15.20-0.55 g.cm) was obtained in steeped cauliflower samples consisting of 6 % NaCl, 2 % acetic acid and 350 ppm SO2 during storage for 120 days at room temperature. The decrease in extent of browning, ascorbic acid and total carotenoids content in cauliflower samples was reported in all the experimental runs during 120 days of storage at room temperature. The optimum concentration for maximum desirability in the preservation of cauliflower consisted of 3.5 % sodium chloride and 1.1 % acetic acid and 350 ppm SO2.