Analytical Characterization of the Widely Consumed Commercialized Fermented Beverages from Russia (Kefir and Ryazhenka) and South Africa (Amasi and Mahewu): Potential Functional Properties and Profiles of Volatile Organic Compounds

Optimisation of Lactobacillus fermentation conditions and its application in the fermentation of salt-free sauerkraut

To identify what are the dominant lactic acid bacteria (LAB) involved in the fermentation of salt-free sauerkraut, and optimize its industrial culture conditions, we isolated and identified a strain of LAB, which is referred to as Lactobacillus sp. DF_001, with the preservation number CCTCC NO: M20232593, from five different regions in Guizhou Province. Industrial culture conditions were optimized using Plackett-Burman and Central Composite design experiments, and the potential role of this LAB in salt-free sauerkraut fermentation was validated. Bioproduction was optimal with a culture time of 66 h, starch/water ratio of 1.7% and inoculum of 0.02%, which gave approximately three-fold higher yield than the basal culture medium DeMan-Rogosa-Sharpe medium (MRS). The LAB was used in small-scale industrial experiments. The Dafang LAB significantly enhanced the sensory score of the salt-free sauerkraut products by about 32% compared to the control group. The total acid content increased by about 32% and the sugar and nitrite contents were reduced by 67.27 and 69.58%, respectively. The total number of bacterial colonies decreased by 37.5%. All other indicators complied with the national standard, providing overall the basis to improve salt-free sauerkraut fermentation.

Fermentation of Rice, Oat, and Wheat Flour by Pure Cultures of Common Starter Lactic Acid Bacteria: Growth Dynamics, Sensory Evaluation, and Functional Properties

Recent consumer demand for non-dairy alternatives has forced many manufacturers to turn their attention to cereal-based non-alcoholic fermented products. In contrast to fermented dairy products, there is no defined and standardized starter culture for manufacturing cereal-based products. Since spontaneous fermentation is rarely suitable for large-scale commercial production, it is not surprising that manufacturers have started to adopt centuries-known dairy starters based on lactic acid bacteria (LABs) for the fermentation of cereals. However, little is known about the fermentation processes of cereals with these starters. In this study, we combined various analytical tools in order to understand how the most common starter cultures of LABs affect the most common types of cereals during fermentation. Specifically, 3% suspensions of rice, oat, and wheat flour were fermented by the pure cultures of 16 LAB strains belonging to five LAB species-Lacticaseibacillus paracasei, Lactobacillus delbrueckii, Lactobacillus helveticus, Streptococcus thermophilus, and Lactococcus lactis. The fermentation process was described in terms of culture growth and changes in the pH, reducing sugars, starch, free proteins, and free phenolic compounds. The organoleptic and rheological features of the obtained fermented products were characterized, and their functional properties, such as their antioxidant capacity and angiotensin-converting enzyme inhibitory activity, were determined.

Changes in Composition of Some Bioactive Molecules upon Inclusion of Lacticaseibacillus paracasei Probiotic Strains into a Standard Yogurt Starter Culture

Incorporation of probiotic Lacticaseibacillus paracasei into a standard yogurt starter culture can drastically improve its health promoting properties. However, besides being an advantage in itself, the incorporation of a new probiotic strain can significantly affect the overall composition of fermented milk. In this article, the effect of incorporation of the L. paracasei probiotic strains (KF1 and MA3) into several standard yogurt starter cultures (consisting of the following strains: Streptococcus thermophilus 16t and either Lactobacillus delbrueckii Lb100 or L. delbrueckii Lb200) was investigated. Such parameters as the degree of proteolysis, antioxidant activity, ACE-inhibitory activity, content of organic acids, profile of FAs and profile of volatile organic compounds were measured, and the influence of the starter culture composition on these parameters was described. It was demonstrated that, at least in the case of the studied strains, yogurt with L. paracasei had an advantage over the standard yogurt in terms of the content of acetoin, acetic acid, butyric acid and conjugated linoleic acid. Moreover, the incorporation of L. paracasei KF1 significantly improved the hypotensive properties of the resulting yogurt. Thus, the presented study provides insight into the bioactive molecules of probiotic yogurt and may be useful for both academia and industry in the development of new dairy-based functional products.

Highlighting the Impact of Lactic-Acid-Bacteria-Derived Flavours or Aromas on Sensory Perception of African Fermented Cereals

Sensory characteristics and flavour profiles of lactic-acid-fermented foods are influenced by lactic acid bacteria (LAB) metabolic activities. The flavour compounds released/produced are directly linked to the sensory characteristics of fermented cereals. African fermented cereals constitute a staple, frequently consumed food group and provide high energy and essential nutrients to many communities on the continent. The flavour and aroma characteristics of fermented cereal products could be correlated with the metabolic pathways of fermenting microorganisms. This report looks at the comprehensive link between LAB-produced flavour metabolites and sensory attributes of African fermented cereals by reviewing previous studies. The evaluation of such data may point to future prospects in the application of flavour compounds derived from African fermented cereals in various food systems and contribute toward the improvement of flavour attributes in existing African fermented cereal products.

Nutritional and Phytochemical Composition of Mahewu (a Southern African Fermented Food Product) Derived from White and Yellow Maize (Zea mays) with Different Inocula

Mahweu is an important indigenous beverage for many low-income and undernourished consumers in southern Africa. As a result, the nutritional and phytochemical profile of mahewu samples (obtained using optimized fermentation and boiling conditions from a previous study) as well as their related raw materials (white and yellow maize) were investigated. At these conditions, white and yellow maize mahewu (WM and YM) were prepared utilizing various inocula including sorghum malt, wheat, millet malt, or maize malt, and the pH, titratable acidity (TTA), total soluble solid (TSS), and proximate analysis were determined. The mineral content, amino acid composition, and phenolic compound profile were also investigated using inductive coupled plasma optical emission spectrometry (ICP-OES), high-performance liquid chromatography (HPLC), and ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS), respectively. Fermentation was observed to have influenced the proximate composition of obtained mahewu samples compared to the raw flour with significant (p ≤ 0.05) improvement in protein from 8.59 to 9.7% (YM) and 8.78 to 9% (WM) as well as carbohydrate from 72.27 to 74.47% (YM) and 71.15 to 72.65% (WM). Sodium, magnesium, phosphorous, potassium, calcium, manganese, iron, copper, and zinc were the minerals detected in the mahewu samples, while potassium was the most abundant mineral, having values ranging from 3051.61 to 3283.38 mg/kg (YM) and 2882.11 to 3129.97 mg/kg (WM). Heavy metals detected in this study were all below the recommended tolerable levels by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Arginine and leucine with values ranging from 0.47 to 0.52 g/100 g (YM) and 0.48 to 0.53 g/100 g (WM) as well as 0.91 to 1.04 g/100 g (YM) and 0.95 to 1.01 g/100 g (WM), respectively, were the most abundant essential amino acids, whereas for non-essential amino acids, glutamic acid, aspartic acid, alanine, and proline were observed to be abundant. Based on the different inocula, the derived mahewu samples prepared using either white or yellow maize have varying nutritional and health beneficial components and the choice of inocula might still be determined by consumer preference.

Biochemical and Genomic Characterization of Two New Strains of Lacticaseibacillus paracasei Isolated from the Traditional Corn-Based Beverage of South Africa, Mahewu, and Their Comparison with Strains Isolated from Kefir Grains

Lacticaseibacillus paracasei (formerly Lactobacillus paracasei) is a nomadic lactic acid bacterium (LAB) that inhabits a wide variety of ecological niches, from fermented foodstuffs to host-associated microenvironments. Many of the isolated L. paracasei strains have been used as single-strain probiotics or as part of a symbiotic consortium within formulations. The present study contributes to the exploration of different strains of L. paracasei derived from non-conventional isolation sources-the South African traditional fermented drink mahewu (strains MA2 and MA3) and kefir grains (strains KF1 and ABK). The performed microbiological, biochemical and genomic comparative analyses of the studied strains demonstrated correlation between properties of the strains and their isolation source, which suggests the presence of at least partial strain adaptation to the isolation environments. Additionally, for the studied strains, antagonistic activities against common pathogens and against each other were observed, and the ability to release bioactive peptides with antioxidant and angiotensin I-converting enzyme inhibitory (ACE-I) properties during milk fermentation was investigated. The obtained results may be useful for a deeper understanding of the nomadic lifestyle of L. paracasei and for the development of new starter cultures and probiotic preparations based on this LAB in the future.

In Vitro and In Vivo Antihypertensive Effect of Milk Fermented with Different Strains of Common Starter Lactic Acid Bacteria

Currently, functional dairy products pave a promising way for the prophylaxis of essential hypertension, and the search for new strains capable of producing such products is a constant challenge for scientists around the world. In this study, the antihypertensive properties of milk fermented with several strains of traditional yogurt starters (Lactobacillus delbrueckii strains Lb100 and Lb200; Lactococcus lactis strains dlA, AM1 and MA1; Streptococcus thermophilus strains 159 and 16t) and one strain of non-conventional probiotic starter (Lacticaseibacillus paracasei ABK) were assessed. The in vitro assessment using angiotensin-converting enzyme inhibition assay was performed for all fermentation products, and the best performed products were tested in vivo using Spontaneously Hypertensive Rat (SHR) animal model. In addition, for the best performed products the fatty acid (FA) composition and FA-related nutritional indices were determined. As a result, the milk fermented with two strains (Lb. delbrueckii LB100 and Lc. lactis AM1) demonstrated significant antihypertensive effect during both in vitro and in vivo experiments. Moreover, the milk fermented with Lb. delbrueckii Lb100 demonstrated significantly better FA-related nutritional indexes and lowered total cholesterol in SHRs upon regular consumption. The obtained results can be used in the future to develop new starter cultures producing effective functional antihypertensive dairy products.

Microbial Communities of Artisanal Fermented Milk Products from Russia

Fermented milk products (FMPs) have numerous health properties, making them an important part of our nutrient budget. Based on traditions, history and geography, there are different preferences and recipes for FMP preparation in distinct regions of the world and Russia in particular. A number of dairy products, both widely occurring and region-specific, were sampled in the households and local markets of the Caucasus republics, Buryatia, Altai, and the Far East and European regions of Russia. The examined FMPs were produced from cow, camel, mare’s or mixed milk, in the traditional way, without adding commercial starter cultures. Lactate and acetate were the major volatile fatty acids (VFA) of the studied FMPs, while succinate, formate, propionate and n-butyrate were present in lower concentrations. Bacterial communities analyzed by 16S rRNA gene V4 fragment amplicon sequencing showed that Firmicutes (Lactococcus, Lactobacillus, Streptococcus, Lentilactobacillus and Leuconostoc) was the predominant phylum in all analyzed FMPs, followed by Proteobacteria (Acetobacter, Klebsiella, Pseudomonas and Citrobacter). Lactobacillus (mainly in beverages) or Lactococcus (mainly in creamy and solid products) were the most abundant community-forming genera in FMPs where raw milk was used and fermentation took place at (or below) room temperature. In turn, representatives of Streptococcus genus dominated the FMPs made from melted or pasteurized milk and fermented at elevated temperatures (such as ryazhenka, cottage cheese and matsoni-like products). It was revealed that the microbial diversity of koumiss, shubat, ryazhenka, matsoni-like products, chegen, sour cream and bryndza varied slightly within each type and correlated well with the same products from other regions and countries. On the other hand, the microbiomes of kefir, prostokvasha, ayran, cottage cheese and suluguni-like cheese were more variable and were shaped by the influence of particular factors linked with regional differences and traditions expressed in specificities in the production process. The microbial diversity of aarts, khurunga, khuruud, tan, ayran and suluguni-like cheese was studied here, to our knowledge, for the first time. The results of this study emphasize the overall similarity of the microbial communities of various FMPs on the one hand, and specificities of regional products on the other. The latter are of particular value in the age of globalization when people have begun searching for new and unusual products and properties. Speaking more specifically, these novel products, with their characteristic communities, might be used for the development of novel microbial associations (i.e., starters) to produce novel products with improved or unique properties.