Changes in Microbial, Rheological, and Sensory Characteristics of Probiotic Yogurt Sauce Containing Lactobacillus rhamnosus During Cold Storage

Nowadays, there is a great interest in using yogurt sauce as a flavored dressing for salads and foods. The current study aimed to determine the possibility of producing probiotic yogurt sauce and evaluate its physicochemical, microbiological, sensory and rheological properties throughout refrigeration storage. Lactobacillus rhamnosus was encapsulated with sodium alginate and resistant starch using the emulsion method. The survival of free and microencapsulated L. rhamnosus was studied in simulated gastrointestinal conditions. Two forms (free and microencapsulated) of L. rhamnosus were added to the yogurt sauce. The samples were kept for 30 days at 4 ˚C and evaluated on interval days (1st, 10th, 20th, and 30th) for the above mentioned properties. Survival improvement was demonstrated in microencapsulated L. rhamnosus compared to free L. rhamnosus.  After two hours, the free form of L. rhamnosus showed five logarithmic cycles decreasing in cell viability, while microencapsulated L. rhamnosus presented only one logarithmic cycle reduction. Similarly, on day 30 of storage, the number of viable microencapsulated L. rhamnosus cells in the probiotic yogurt sauce was 6.61 log CFU/g, while the viable count for a sample containing free L. rhamnosus was 5.00 log CFU/g. The produced probiotic yogurt sauce was considered a pseudo-plastic fluid and presented mayonnaise behaviour. Moreover, samples containing microencapsulated probiotic bacteria displayed lower post-acidification values than samples containing free bacteria. The microencapsulation of probiotic bacteria improved the sensory quality of the produced probiotic yogurt sauce.  Hence, producing a probiotic yogurt sauce with desirable properties is possible.