COVID-19 is a widespread global pandemic with nearly 185 million confirmed cases and about four million deaths. It is caused by an infection with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which primarily affects the alveolar type II pneumocytes. The infection induces pathological responses including increased inflammation, oxidative stress, and apoptosis. This situation results in impaired gas exchange, hypoxia, and other sequelae that lead to multisystem organ failure and death. As summarized in this article, many interventions and therapeutics have been proposed and investigated to combat the viral infection-induced inflammation and oxidative stress that contributes to the etiology and pathogenesis of COVID-19. However, these methods have not significantly improved treatment outcomes. This may partly be attributable to their inability at restoring redox and inflammatory homeostasis, for which molecular hydrogen (H2), an emerging novel medical gas, may complement. Herein, we systematically review the antioxidative, anti-inflammatory, and antiapoptotic mechanisms of H2. Its small molecular size and nonpolarity allow H2 to rapidly diffuse through cell membranes and penetrate cellular organelles. H2 has been demonstrated to suppress NF-κB inflammatory signaling and induce the Nrf2/Keap1 antioxidant pathway, as well as to improve mitochondrial function and enhance cellular bioenergetics. Many preclinical and clinical studies have demonstrated the beneficial effects of H2 in varying diseases, including COVID-19. However, the exact mechanisms, primary modes of action, and its true clinical effects remain to be delineated and verified. Accordingly, additional mechanistic and clinical research into this novel medical gas to combat COVID-19 complications is warranted.

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The effects of yoghurt fortification with rhubarb (RE), grape seed (GSE), thyme (TE), green tea (GTE) and mint (ME) extracts on the physicochemical, rheological, textural and sensory properties during cold storage were investigated. The syneresis value of the extract‐fortified yoghurts was higher and the colour was lighter in comparison with control sample. The values of texture parameters such as firmness and consistency in RE and TE samples were higher than of CS, and all extract‐fortified samples, except GSE, showed higher cohesiveness and viscosity. The ME‐fortified yoghurt was found tastiest with the highest overall appreciable score. These food‐agriculture wastes could be valorised for improving the nutritional and textural properties of yoghurt.

The acidification and reducing capacities of yoghurt bacteria were evaluated in different plant extract-enriched milk samples. The milk samples enriched with thyme and grape seed extracts exhibited the highest values of acidification capacity for Lactobacillus delbrueckii subsp. bulgaricus (LB) (0.0065 pH unit/min) and Streptococcus thermophilus (ST) (0.0068 pH unit/min). The highest values of reducing capacity were observed in thyme (À0.98 mV/min), grape (À1.92 mV/min) and green tea (À0.75 mV/min)-enriched samples for LB, ST and mixed culture of LB + ST, respectively. The fortification of yoghurt with plant extracts modified the acidification and reducing activities of starters, thus changing the fermentation time and quality attributes of the product.

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Lactobacillus plantarum and Saccharomyces cerevisiae are acid-tolerant microorganisms that are able to spoil citrus juices before and after pasteurization. The growth of these microorganisms in orange juice with and without pasteurization was investigated. Two samples of orange juice were inoculated with ca. 10(5) CFU/ml of each microorganism. Others were inoculated with ca. 10(7) CFU/ml of each microorganism and then thermally treated. L. plantarum populations were reduced by 2.5 and <1 log10 CFU/ml at 60 degrees C for 40 s and at 55 degrees C for 40 s, respectively. For the same treatments, S. cerevisiae populations were reduced by >6 and 2 log10 CFU/ml, respectively. Samples of heated and nonheated juice were incubated at 15 degrees C for 20 days. Injured populations of L. plantarum decreased by ca. 2 log10 CFU/ml during the first 70 h of storage, but those of S. cerevisiae did not decrease. The length of the lag phase after pasteurization increased 6.2-fold for L. plantarum and 1.9-fold for S. cerevisiae, and generation times increased by 41 and 86%, respectively. The results of this study demonstrate the differences in the capabilities of intact and injured cells of spoilage microorganisms to spoil citrus juice and the different thermal resistance levels of cells. While L. plantarum was more resistant to heat treatment than S. cerevisiae was, growth recovery after pasteurization was faster for the latter microorganism.

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