Optimization of probiotics in dairy products
Jansen van Rensburg, L'Zanne
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A literature review regarding the properties of probiotic bacteria were discussed including their therapeutic value, the survival in bio-products and the expansion of the probiotic food range. Cheese offers certain advantages as delivery system for live probiotic bacteria to the human gastro-intestinal tract. Furthermore, the enumeration of probiotics in functional foods was discussed, with special reference made to enumeration media. Probiotic regulations were also discussed, with an in-dept look at regulatory platforms world wide as well as regulations regarding administration levels. Normal practise in the manufacturing of functional food products, is to incorporate the slow growing probiotic cultures, containing beneficial effects, with the fast growing lactic acid bacterial starter cultures, which aid in the speed of the fermentation process. An important parameter in monitoring official levels of viable probiotics, is the ability to count probiotic bacteria differentially, however great controversy exists regarding administration levels as well as standard enumeration media. Nine bacteriological media were subsequently evaluated to assess their suitability and to selectively enumerate L. rhamnosus strain HN001 (DR20TM), in the presence of other lactic acid starter bacteria in South African matured Cheddar cheese. Differences in recovery between the different media as well as the interaction between the media and the availability of oxygen were investigated. MRS-V and BA-R(20%)V agar were ranked as the superior media, while MRS-V agar and aerobic incubation conditions at 43oC for 48h proved to be the most selective medium to enumerate L. rhamnosus in the presence of other cheese starter cultures. Predictive modeling may contribute to a better understanding of and control of microbial processes, and help to clarify in which manner, and to which degree, the food environment will interfere with the functionality of the probiotic strains used. At environmental conditions similar to those during manufacturing, ripening and/or storage processes of cheese, the combined effects of pH, lactic acid, salt (NaCl), and incubation temperatures on the growth of probiotic culture L. rhamnosus HN001 (DR20TM) were investigated in MRS laboratory broth. The developed Response Surface (RS) model provided reliable estimates of the parameters studied and explains approximately 90.7% of the variance within the model data. This model provides a means for rapidly estimating how the probiotic bacterium is likely to respond to any combination of the four variables within the specified ranges and is a valuable tool in enabling its application for shelf-life estimation within a food product. Future research, focusing on Central Composite Designs (CCD) is required in order to optimize the model performance, to subsequently minimize variance associate with the kinetic parameters, but also to estimate optimum responses within the experimenting range. The health benefits of probiotic-containing products are becoming a key factor, affecting consumer choice and therefore the existing limited range of such products needs to be expanded. Cheese may offer certain advantages as carrier system for live probiotic organisms to the human gastro-intestinal tract. The possibility of introducing Lactobacillus rhamnosus strain HN001 (DR20TM) into South African matured Cheddar cheese was explored. The long-term ripening and storage of the organism, the effect on cheese flavor and texture as well as the chemical properties of the cheese were determined. L. rhamnosus strain HN001 (DR20TM) remained highly viable for at least 114 days of ripening, while still satisfying the criteria for probiotic foods. The viability profile of the lactic acid starter bacteria was not substantially affected and a normal, good cheese texture, flavor and appearance were retained. This probiotic adjunct possibly provides control over contaminating secondary flora and limiting flavor defects while delivering a health culture to the consumer.