Growth and survival of Lactobacillus reuteri RC-14 and Lactobacillus rhamnosus GR-1 in yogurt for use as a functional food

Both Lactobacillus reuteri RC-14 and Lactobacillus rhamnosus GR-1 are considered probiotic agents with therapeutic properties. To prepare mother cultures for these organism bacteria, four formulations were made with milk (1% fat) with 0.33% yeast extract (T1); 0.4% inulin (T2); 0.33% yeast extract and 0.4% inulin (T3); and one with no additives (T4). The media were inoculated with 1% probiotic cultures and incubated anaerobically at 37 C overnight. Low-fat (1%) probiotic yogurts were made. Survival of L reuteri RC-14 and L. rhamnosus GR-1 was monitored after 1, 7, 14, 21, and 28 days of storage at 4 C. In all treatments, L rhamnosus GR-1 survived significantly better (P<0.05) than L reuteri RC-14. Survival was highest in media T1 and T3. This study shows that yogurt has the potential to deliver probiotic bacteria to consumers, with L rhamnosus GR-1 providing excellent shelf life. Industrial relevance: This study is of relevance to food industry because it deals with the effectiveness of dairy products as a good-vehicle for delivering probiotic microorganisms to consumers. The fermentation of milk into yogurt has gained widespread consumer acceptance in North America and its consumption has increased significantly over the past few years. The normal yogurt cultures, Lactobacillus delbreukii subspecies bulgaricus and Streptococcus thermophilus, are not bile resistant or acid tolerant and thus cannot survive in the intestinal tract, although they may help to lessen the symptoms of lactose intolerance. Various strains of lactic acid bacteria are considered probiotics. Two of the most documented probiotic strains, Lactobacillus reuteri (formerly fermentum) RC-14 and Lactobacillus rhamnosus GR-1 can colonize the intestine and vagina and reduce recurrences of bacterial vaginosis, yeast vaginitis and urinary tract infections. They are bile resistant and survive passage through the human gastrointestinal tract without induction of systemic immune or inflammatory responses. There is no published information on the growth and survival of L. rhamnosus GR-1 and L reuteri RC-14 in yogurt. The incorporation of L rhamnosus GR-1 and L reuteri RC-14 in yogurt is an innovative idea. This research developed a new probiotic yogurt with sufficient viable counts of L rhamnosus GR-1 accompanied by L reuteri RC-14. The use of probiotic bacteria, especially those with proven therapeutic effects, in dairy products has attracted a lot of attention from dairy industry and health/wellness industry, and this type of product can provide a bridge between the two industries. (C) 2008 Elsevier Ltd. All rights reserved.