The microbial starter used to produce kefir beverages, kefir grain, contains a microbial exopolysaccharide called kefiran. Kefir grain consisting of water-insoluble polysaccharides, proteins, and ...fats, which can be applied as a multi-functional biopolymer. The mass of kefir grain can increase in the fermentation process of Kefir, but it is considered very slow. The purpose of this research is to study the impact of ammonium sulfate supplementation and yeast extract on reconstituted skim milk to increase the mass kefir grain and physical properties of kefiran. Results showed that the ammonium sulfate-supplemented substrate increased the mass of kefir grain by 547% in 14 days, with the condition that the substrate must be renewed every 2 days. Refreshing the substrate is considered one of the important factors. Supplementation on substrate did not appear to affect the viability of bacterial and yeast cells. Kefir grain produced from supplemented substrate also yields better thermal stability properties and has more functional groups than without supplementation. Two Lacticaseibacillus rhamnosus (RAL27 and RAL43) and one Limosilactobacillus fermentum (RAL29) were found to produce EPS. The three isolates also showed good skim milk fermentation ability after purification from kefir grain. The kefir grain produced in this study has the potential for wider application. This study also showed that kefir grain can be adjusted in quantity and quality through fermentation substrate engineering.
Fermented Foods: Kefir Julia R. Skinner
EDIS,
07/2024, Letnik:
2024, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Kefir is a fermented dairy beverage made from milk and kefir grains containing yeast and bacteria. This publication describes how kefir is made and its potential health effects for consumers. Written ...by Julia R. Skinner, and published by the UF/IFAS Food Science and Human Nutrition Department, July 2024.
The utilization of pea proteins (PPs) is limited due to their relatively low protein digestibility (∼81%) compared to animal‐based proteins, such as whey. The present investigation involved the ...fermentation of PPs at a concentration of 1% (w/v) using 5% (w/v) water kefir for 60 h at 25°C to improve the functional properties of PPs. The results showed a significant (p < 0.05) increase in lactic acid and acetic acid production during fermentation. These findings suggest that PPs can be effectively fermented using water kefir as a starter culture for the increased protein digestibility of PPs. The PP conformation underwent modifications, including secondary and tertiary protein structure alterations. The total phenolic compounds increased throughout the fermentation, reaching around 695.32 ± 15 mg gallic acid equivalent/100 g after 24 h of fermentation. Furthermore, the fermentation process has culminated in significant (p < 0.05) changes in the surface charge and hydrophobic properties of the fermented PPs, from −38.1 to −45.73 and 362.7 to 550.2, respectively. Fermentation using water kefir is a promising technique for improving the digestibility, protein structure, and nutritional values of PPs.
The microbiota composition of kefir grain and milk kefir was assessed via a metagenomic approach. Significant microorganisms were isolated and identified using molecular methods. A safety assessment ...was conducted based on antibiotic susceptibility and blood hemolysis. Probiotic traits such as resistance to gastric tract conditions, surface characteristics, adhesion to intestinal cells, and antibacterial activity were also assessed. Metagenomic analysis revealed that kefir grains are a more stable community with clear dominant species as compared to milk kefir. Lactobacillus kefiranofaciens BDGO‐A1, Lactobacillus helveticus BDGO‐AK2, and Lactobacillu kefiri strains showed tolerance to acidic pH and the presence of bile salts, adhesion capability to Caco‐2 cells, in vitro antibacterial activity, and the production of antibacterial proteins. In the metagenomic analysis, contigs associated with these species showed the presence of genes involved in exporting polyketide antibiotics and bacteriocin production. To fully exploit the potential probiotic properties of these microorganisms to help human health, further investigation is necessary to elucidate the mechanisms behind the biological activity and the genotypic characteristics of the isolated strains.
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•A total of 715 species were identified within three TKG communities.•Lactobacillus kefiranofaciens is the most dominant species in TKGs (83.3778%).•A total of 33 listed probiotics ...species were identified in TKGs.•There are 16 KOs annotated four approaches participate in β-lactam resistant.
Tibetan kefir grains (TKGs) are distinctive and complex mixtures with protein-lipid-polysaccharide matrices and multiple microorganism species. The objective of this study was to evaluate the microflora composition, probiotic species and functional genes within TKGs. Metagenomic analysis was used to evaluate communities of three TKGs, revealing the presence of 715 species, with Lactobacillus kefiranofaciens as the most dominant species. The relative abundances of acetic acid bacteria and yeast significantly differed among the three TKGs (acetic acid bacteria: p < 0.01; yeast: p < 0.05), and the dominant yeast species also varied across three TKGs. Lactobacillus helveticus was the most abundant listed probiotic species, and its abundance did not significantly differ across three TKGs. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that ko01501 was the most abundant pathway that related to human disease. There are 16 different KOs (KEGG Orthology) in the ko01501 pathway were annotated in TKGs, which helps to resist β-lactam. This study provided a new insight into the microbial community structures and the presence of probiotic species within TKGs and provides a foundation for further targeted studies.
This research aimed to evaluate the effects of using either grain or commercial starter culture on the antioxidative capacity of cow and ewe milk kefirs. The antioxidant capacity of kefir samples ...during fermentation and 21 d of storage was assessed by using 3 assays: 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical cation decolorization; 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radical scavenging activity assay; and Fe+3-reducing power (ferric reducing antioxidant power assay, FRAP). Vitamin E and β-carotene contents were also quantified. All kefir samples exhibited varying values for DPPH, ABTS, and FRAP assays depending on the starter culture and milk type. Vitamin E and β-carotene contents were similar in all kefir samples during storage. The results of this study suggest that milk type (cow or ewe) and culture type (kefir grains or commercial starter) were the significant parameters for the antioxidative activity of kefir.
Water kefir is a sourish, slightly alcoholic, and carbonated drink in which different dried fruits are added to the sucrose-containing solution and fermented using water kefir grains. Kefir grains in ...polysaccharide structure include Lactic Acid Bacteria (LAB), yeasts, and/or acetic acid bacteria that use sucrose as an energy source. Water kefir grains contain a varying number of microbiota with various microbiological compositions, depending on their origin. The present study metagenomically determined the microbial flora of water kefir grains obtained from five different commercial sources. According to the metagenomic composition results obtained with the selected specific primers, the dominant bacterial species in water kefir grains were determined to be Lactobacillus ruminis and Bacillus methanolicus, and the most common species were Lactococcus lactis and Enterococcus faecium. Achromobacterx ylosoxidans were detected in only one sample. Pichia kudriavzevii was the dominant yeast species, and Saccharomyces cerevisiae, Eremothecium cymbalariae, Candida glabrata, and Ogataea parapolymorph were seen as common yeast species in all kefir yeasts. Other yeast types showed differences. It was revealed that natural water kefir grains contained probiotic bacteria including Lactobacillus ruminis, so kefir produced using these types of grains can exert functional properties. Another important conclusion is that, albeit, at low levels, kefir grains contain strains that have probiotic potential, including Lactococcus lactis, Enterococcus faecium, and Lactobacillus reuteri.
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•Water kefir is a sourish, slightly alcoholic, and carbonated drink.•Microbiota of five different water kefir grains.•Metagenomic composition of water kefir microbiota.•Comparison of bacteria and yeast content of water kefir.
Kefir is a homemade viscous and slightly effervescent beverage obtained by milk fermentation with kefir grains, which are built up by a complex community of lactic acid and acetic acid bacteria and ...yeasts confined in a matrix of proteins and polysaccharides. The present review summarizes the role of kefir micro‐organisms in grain assembly and in the beneficial properties attributed to kefir. The use of both culture‐dependent and independent methods has made possible to determine the micro‐organisms that constitute this ecosystem. Kefir consumption has been associated with a wide range of functional and probiotic properties that could be attributed to the micro‐organisms present in kefir and/or to the metabolites synthetized by them during milk fermentation. In this context, the role of micro‐organisms in kefir health promoting properties is discussed with particular attention to the contribution of yeast as well as bioactive metabolites such as lactic and acetic acid, exopolysaccharides and bioactive peptides. Even though many advances on the knowledge of this ancient fermented milk have been made, further studies are necessary to elucidate the complex nature of the kefir ecosystem.
Kefir grains consist of rich bacterial and fungal microflora responsible for the production of this traditional fermented milk beverage with unique flavour properties. Here, a pyrosequencing approach ...was applied for the identification of microbial flora of four kefir grains collected from different regions of Turkey and the volatile compounds in kefir samples produced with these grains were determined. Lactobacillus kefiranofaciens presented in all grains at important levels and Enterobacter, Acinetobacter, Enterococcus and Pseudomonas spp. were observed in traditional kefir grains. The fungal microflora of kefir grains was dominated by yeast species and Dipodascaceae family was dominant and Saccharomyces cerevisiae presented in all grains. Other yeast species belonging to Kazachstania, Candida, Issatchenkia and Rhodotorula species were also detected in kefir grains. Volatile compounds of kefir samples were also diverse related to the microbial diversity of kefir grains. This study revealed the rich microflora of Turkish kefir grains and their interactions with the aromatic properties of kefir.
•A pyrosequencing approach was applied for the identification of bacterial and fungal microflora of four Turkish kefir grains.•Lactobacillus kefiranofaciens was the dominant kefir associated bacterial strain in kefir grains.•Yeast strains dominated the fungal microflora in which Dipodascaceae family was dominant.•Richness in microflora resulted in a diverse volatile compounds in kefir samples produced with these grains.
Kefir, a fermented dairy beverage, exhibits antimicrobial activity due to many metabolic products, including bacteriocins, generated by lactic acid bacteria. In this study, the antimicrobial ...activities of artisanal kefir products from Fusion Tea (A), Britain (B), Ireland (I), Lithuania (L), the Caucuses region (C), and South Korea (K) were investigated against select foodborne pathogens. Listeria monocytogenes CWD 1198, Salmonella enterica serovar Enteritidis ATCC 13076, Staphylococcus aureus ATCC 25923, and Bacillus cereus ATCC 14579 were inhibited by artisanal kefirs made with kefir grains from diverse origins. Kefirs A, B, and I inhibited all bacterial indicator strains examined at varying levels, except Escherichia coli ATCC 12435 (non-pathogenic, negative control). Kefirs K, L, and C inhibited all indicator strains, except S. aureus ATCC 25923 and E. coli ATCC 12435. Bacteriocins present in artisanal kefirs were determined to be the main antimicrobials in all kefirs examined. Kefir-based antimicrobials are being proposed as promising natural biopreservatives as per the results of the study.
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