Recent Advances in Microbial Fermentation in Foods and Beverages

Abstract

The interest in food microbial fermentation has progressively increased in recent decades. This Special Issue collected original research and review articles dealing with the use of microbial cultures aimed at improving the organoleptic and nutritional properties of both traditional and innovative foods, as well as the use of microbial cultures for health purposes. In detail, three research articles investigated specific aspects of fermentation in the production of traditional foods such as kombucha, Chinese Baijiu and sauerkraut, whereas another study suggested pollen and bee bread as a reservoir of functional yeasts. The effect of a symbiotic beverage on body composition and some biochemical parameters of overweight, obese, or type-2 diabetic women has also been evaluated in the remaining research article. The couple of review articles assessed relevant and timely aspects of microbial fermentation: the first one started from the increasing demand of low-alcohol beverages to analyze current and future biotechnological approaches to reduce alcohol content in wine, whereas the second paper focused on how microbial processes can increase both nutritional and functional value of plant-based fermented foods.

The role of microorganisms in the transformation and conservation of foods has become progressively evident in recent years, pushing the food industry to increase its interest in bacteria, yeasts, and molds. Moreover, in addition to their use for technological purposes, microbial metabolism could result in a nutritional enrichment of fermented foods, as well as a valuable tool to obtain functional foods. It is known, in fact, that activity of enzymes of some microorganisms [1,2] can lead not only to the enrichment of foods, but also to the production of bioactive compounds [3,4].

With this in mind, in this Special Issue we collected seven papers dealing with both the production of traditional fermented foods [5,6,7] and their nutritional/healthy improvement [8,9,10], as well as the identification of a possible source of functional microorganisms, such as yeasts, in bee products [11]. In detail, Yuan and colleagues compared two different methods for the production of Daqu, a crucial starter culture for Chinese Baijiu, analyzing several parameters as physicochemical properties, enzyme activities, flavor components, and microbial diversity. Interestingly, the two approaches resulted in a final product showing different volatile compound compositions, biochemical properties, and microbial profiles, as well as a different process efficiency [6]. Microbial properties, together with other parameters such as pH, total acidity, and mineral composition, were also evaluated in a second paper [5] dealing with another popular fermented food, sauerkraut; in this study white cabbages were fermented with the addition of Salicornia either in the presence or in the absence of calcium chloride. Such a treatment, on one hand, improved product hardness without affecting its microbial and sensorial characteristics; on the other hand, it partially reduced its nutritional value due to lower levels of minerals such as K, Mg, and mainly Zn [5].

Possible beneficial effects of fermented beverages were suggested by a couple of studies dealing with two traditional fermented products, such as kombucha [7] and an aguamiel-based beverage [10]. In the first study, the authors aimed at obtaining a possible functional product by taking advantage of the addition of different ingredients, among which was seaweed, to a symbiotic microbial culture called SCOBY, and evaluating its potential enrichment in both antioxidant and sensorial properties [7]. In the second paper, the Mexican symbiotic aguamiel has been administered for 12 weeks to overweight, obese, and type-2 diabetic women in order to check the effects of this dietary treatment on body composition and biochemical parameters of the enrolled people in either the absence or presence of caloric restriction [10].

The health-promoting and functional properties of fermented plant-based foods were extensively explored in the review by Dhiman and collaborators [9], where, after a detailed introduction on microbial diversity and the functional role of fermentation in the enrichment of the final product, an interesting focus on microbial innovation for next-gen plant-based fermented foods was carried out. Moreover, by discussing not only health benefits and functional properties but also current challenges and limitations in this field, the authors returned a clearer scenario of plant-based fermented foods [9].

Another key aspect in the direction of health-promoting and nutritional improvement of foods and beverages is represented by dealcoholized or low-alcohol beverages. As it is known, in fact, lifestyle changes, together with the enhanced attention to healthy nutrition, have progressively increased the demand for wine with reduced alcohol content. In this regard, besides agricultural and pre-fermentative approaches [12], fermentative strategies can be considered as a promising biotechnological tool to reduce ethanol in wine. Thus, in their paper, Testa and coauthors critically reviewed the literature dealing with the use of non-Saccharomyces yeasts in co-inoculation or sequential inoculation with Saccharomyces yeasts to produce low-alcohol wines [8]. The authors underscored how this approach presents several advantages, such as efficacy, easiness, and limited cost, when compared to other fermentative approaches, such as biomass reduction or arrested fermentation, which usually result in microbiological instability. They finally encourage the continuous search and selection of non-Saccharomyces yeasts to be checked for their use in this specific wine sector.

In this regard, Agarbati and coauthors [11] propose that, in addition to their healthy properties, some bee products, such as pollen and both fresh and aged bread, could be a possible source of functional yeasts. To this aim, they isolated and identified yeast species and checked them for their antioxidant and antimicrobial properties, as well as for their production of polyphenols and phytase activity. The isolation of some yeast strains showing bioactive properties and antagonistic antimicrobial activity, together with preliminary probiotic features, led the authors to candidate bee products as a potential source for functional yeasts [11].

We trust that readers will find the papers collected in this Special Issue as an additional piece in the tangle and increasing puzzle of microbial fermentation of foods and beverages.