Microwave Treatment vs. Conventional Pasteurization: The Effect on Phytochemical and Microbiological Quality for Citrus-Maqui Beverages.

This study uncovered the impacts of microwave (MW) treatments compared to conventional pasteurization (TP) on the quality of functional citrus-maqui beverages, with added sucrose or stevia. The influence of these thermal treatments on the microbiological burden and phytochemical composition was determined by processing under two MW power levels (600 W and 800 W) and TP at 85 °C for 15 s for 60 days at room temperature (20 °C). The results indicated that, beyond the microbiological quality achieved in the juices treated by both MW and TP technology, there were no differences among the treatments regarding the stability of vitamin C, anthocyanin, and flavanone concentrations. However, anthocyanins were more stable in those beverages with sucrose added, rendering a better red color. Besides, all treatments ensured microbiological stability throughout the entire storage time. In conclusion, MW treatment could be considered as an alternative to TP, which ensures microbial safety, protecting functional compounds associated with health effects.

Limonene nanoemulsified with soya lecithin reduces the intensity of non-isothermal treatments for inactivation of Listeria monocytogenes.

Consumers' demands for ready-to-eat, fresh-like products are on the rise during the last years. This type of products have minimal processing conditions that can enable the survival and replication of pathogenic microorganisms. Among them, Listeria monocytogenes is of special concern, due to its relatively high mortality rate and its ability to replicate under refrigeration conditions. Previous research works have shown that nanoemulsified essential oils in combination with thermal treatments are effective for inactivating L. monocytogenes. However, previous research works were limited to isothermal conditions, whereas actual processing conditions in industry are dynamic. Under dynamic conditions, microorganism can respond unexpectedly to the thermal stress (e.g. adaptation, acclimation or increased sensitivity). In this work, we assess the combination of nanoemulsified D-limonene with thermal treatments under isothermal and dynamic conditions. The nanoemulsion was prepared following an innovative methodology using soya lecithin, a natural compound as well as the essential oil. Under isothermal heating conditions, the addition of the antimicrobial enables a reduction of the treatment time by a factor of 25. For time-varying treatments, dynamic effects were relevant. Treatments with a high heating rate (20 °C/min) are more effective than those with a slow heating rate (1 °C/min). This investigation demonstrates that the addition of nanoemulsified D-limonene can greatly reduce the intensity of the thermal treatments currently applied in the food industry. Hence, it can improve the product quality without impacting its safety.

Antimicrobial activity of nisin, thymol, carvacrol and cymene against growth of Candida lusitaniae.

Yeasts are tolerant to acid pH values, are able to grow in anaerobic media and have minimum nutrition requirements. These capabilities enable them to survive and even grow in foods prepared from acid fruits or vegetables. Among yeasts, Candida is one of the genus most frequently isolated from fruit juices. Bacteriocins and essential oils from spices and aromatic herbs are an alternative to preservatives and other technological treatments and have the advantage that their natural origins do not lead to consumer rejection. However, before the food industry uses them on a large scale, it is necessary to know their effects on microorganisms. The objective of this research was to study the effect of different concentrations of nisin, thymol, carvacrol and cymene on the growth of Candida lusitaniae in pH 5 broth at 25 ℃, and their potential uses as food preservatives. The addition of nisin at the concentrations tested (up to 3 µmol L(-1)) did not affect the yeast growth. Thymol, carvacrol and cymene completely inhibited the yeast growth at concentrations over 1 mM for at least 21 days at 25 ℃. Below this concentration, inhibitions on yeast growth were observed at increasing concentrations. The effect of thymol was also proved in tomato juice. This study indicates the potential use of essential oils for preservation of minimally processed foods.