Characteristics of lactose-free/low-lactose fermented dairy products containing microorganisms that are part of the kefir grain consortium: Scoping review

Abstract

Introduction: There are a significant number of scientific publications dedicated to the analysis of lactose-free and low-lactose fermented milk products, primarily in the context of studying specific microorganisms or starter cultures and their functioning under conditions of limited lactose content. Nevertheless, the synthesis of accumulated data has not been sufficiently highlighted, considering that a large part of the research was conducted over the past 10 years, and an intensive examination of this issue has only begun in the recent past.Purpose: To systematically and critically analyze scientific research that sheds light on the specifics of fermented milk products with a reduced lactose level, focusing on a comparative study of standard fermented milk products and their low-lactose or lactose-free modifications. Special attention is paid to fermented milk products containing microorganisms that are part of the kefir fungus consortium.Materials and Methods: Sources for the review were selected from the Scopus, ScienceDirect, RISC (Russian Index of Science Citation), and Google Scholar databases. Out of 208 publications relevant in terms of keywords, 34 were selected for analysis. The main criterion for selecting articles was a description in them of studies on the use of low-lactose or lactose-free milk as a medium for cultivating starter cultures. This review of the subject area is based on the PRISMA-ScR protocol.Results: Many scientific studies indicate that the prepared low-lactose or lactose-free fermented milk products exhibited similar or improved physicochemical and organoleptic characteristics compared to standard fermented milk products. In experiments aimed at evaluating microbiological characteristics, it was observed that the concentration of lactic acid bacteria in the analyzed products either matched, was lower, or was higher than in traditional fermented milk products. In some publications, scientists found that the final fermented milk product had deteriorated organoleptic and physicochemical parameters. However, all reviewed low-lactose or lactose-free fermented milk products met the standards and regulatory requirements of the countries in which the respective research was conducted.Conclusion: The development of low-lactose and lactose-free fermented milk products is a relevant direction in the food industry, considering their similarity to conventional products and adaptability for consumption by individuals with varying degrees of lactose intolerance. There are nuances related to the duration of the fermentation process, organoleptic characteristics, acidity level, syneresis, preservation, and growth dynamics of microorganisms. These features can be dictated by specific strains of microflora used in the starter and, most often, their influence remains minimal. The results obtained in this study may be useful for selecting starter cultures when designing various fermented milk products, including yogurt, fortified yogurt, kefir, ayran, ryazhenka, and acidophilus. For a deeper understanding of the interaction of the modified glucose-galactose medium with various strains and species of lactic acid bacteria, further experimental work is needed, considering that the activity of these bacteria directly determines the quality characteristics of the final fermented milk product.