Optimization of probiotics in dairy products
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Date
2005-11
Authors
Jansen van Rensburg, L'Zanne
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
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.
Description
Keywords
Lactobacillus rhamnosus, Response surface model, Factorial design, Bifidobacterium, Functional foods, Lactic acid bacteria, Dairy microbiology -- South Africa, Cheese -- Microbiology -- South Africa, Dissertation (M.Sc. (Microbial, Biochemical and Food Biotechnology))--University of the Free State, 2005