Yoghurt has been known as an excellent source for delivering viable lactic acid bacteria (LAB) in concentrations providing benefits to the human host and microbiome. Different gastrointestinal tract (GIT) simulators have been developed and are successfully used to determine the viability of LAB from fermented dairy products in vitro studies. Commercial yoghurts were tested for digestibility using the GIT IT system Labfors 5 (INFORS HT, Switzerland). The length for both the gastric phase and the small intestinal phase was 120 min each. Yoghurt LAB colony-forming units were analysed prior to the GIT simulation test, as well as after the simulation test. The survival rate of LAB was evaluated based on the differences in the viable LAB count at the beginning and at the end of the experiment. Tested yoghurts’ LAB were tolerated in the simulated gastric and small intestinal phases. Samples collected prior to and after the intestinal phase revealed that LAB had adapted and started to grow within 120 min. Our results showed the ability of LAB to recover in the intestinal phase which has been explained by the food matrix, which protects the bacteria from the elimination effect of intestinal secretions. In addition, differences in survival rates of LAB significantly influenced the overall LAB colony-forming units in the gastrointestial tract. The chemical composition of the product has an influence on the survival rate of LAB, and it should be studied more thoroughly. In vitro studies are quite different from the assay in vivo studies; however, this information provides significant data about the viability of LAB from regularly consumed products and helps to modulate the influence of LAB on human microbiota.

Organic fermented milk products are an area of interest combining functional properties and sustainable practices. Limited information is available regarding the specific components of organic milk that may impact the growth of lactic acid bacteria. This study emphasised the differences in bioactive compounds between organic and conventional milk and their potential influence on lactic acid bacteria growth. Analysis of organic (n = 15) and conventional (n = 15) farm milk using GC-MS revealed differences in fatty acid (FA) concentrations, mainly mono-, polyunsaturated fatty acids, and conjugated linoleic acid. Individual FA, such as stearic, linoleic, and oleic acids, were up to 33.6%, 31.0%, and 25.23% higher in conventional milk. Detection of the whey proteins using the enzyme-linked immunosorbent assay (ELISA) showed lysozyme content was up to 40.6% higher in conventional (22.04 µg L⁻¹) than in organic (15.68 µg L⁻¹) milk. Conversely, lactoferrin content was 20.4% higher in the organic (45.27 µg L⁻¹) than in conventional (36.04 µg L⁻¹). No difference in the content of immunoglobulin A was found. The higher concentrations of lysozyme, mono- and polyunsaturated fatty acids in conventional milk could enhance a higher inhibitory activity against lactic acid bacteria compared to organic milk.

In recent years, the demand for organic fermented dairy products has been growing. Lactic acid bacteria (LAB) are of major interest in the food industry due to their ability to form the quality and functionality of fermented products. A significantly higher LAB cell count is presented in organic (ORG) fermented products such as yoghurt and kefir, than their conventional (CONV) counterparts. There is still a lack of information on the possible explanation and evidence of ORG milk as a better medium for LAB growth. The aim of the present review is to summarise the results of research articles on the milk compounds and their effect on LAB growth, and to identify differences between ORG and CONV milk that may provide a plausible explanation for their influence on LAB growth in ORG milk. The monographic method was used in this study. According to the previous research, significant differences were established in a content and range of carbohydrates, nitrogen sources, fats, macro elements and microelements, as well bioactive compounds in ORG and CONV milk. The composition of ORG milk may have potential benefits for the development of LAB due to the higher concentration of peptides and long-chain polyunsaturated fatty acids in it.