Analysis of Chemical Composition and Characterization of Bacterial Population of Kefir from Different Regions of Chile

Introduction: Kefir is a beverage produced from the fermentation of milk by a mixture of lactic and acetic acid bacteria and yeast embedded in a natural polysaccharide-protein matrix. In Chile, kefir is typically made at home where it is known as “yogurt de pajaritos”, or “yogurt made by the little beings,” highlighting the lack of awareness of the wider public on how kefir is produced. Its consumption has been associated with health benefits, but it is scarcely consumed and not widely available in the market. 

Purpose: To investigate potential differences in the chemical composition of Chilean kefir and the microbiological composition of kefir grains from diverse geographical areas of Chile. 

Methods: Whole UHT milk was inoculated (10% w/v) with kefir grains obtained from three different geographical areas of Chile. Samples were incubated at 26°C until pH 4.5 was reached and then analyzed for total dry matter, fat, protein and ash contents (AOAC). Microbiological characterization of the kefir grains was carried out by nested PCR targeting the 16S rDNA V3 region. Denaturing gradient gel electrophoresis (DGGE) of the PCR products was performed. Finally, purification and sequencing of the gel bands was completed by a commercial service. 

Results: Differences (p < 0.05) were found between the three kefir samples for total solids (10.55 - 9.99 g/100g^-1), protein (2.86 - 2.71 g/100g^-1), ash (0.67 - 0.55 g/100g^-1) and carbohydrates (4.2-3.53 – g/100g^-1); no difference was found between the fat contents. Sequencing of the selected bands showed that Lactobacillus kefiranofaciens, Lactobacillus helveticus and Lactobacillus crispatus were present in all the samples.

Significance: The potential antimicrobial and probiotic activity of the kefir grain microbiota will be studied. By characterizing the kefir produced in Chile and the microorganisms forming part of the kefir grains, a commercial starter culture to produce a standardized kefir drink providing potential health benefits could be developed.