Rana Faheem Sakhawat Ali

Survival Of Probiotic Bacteria In Commercial Infant Foods And Their Antimcrobial Activity Against Food Borne - 2011

Novel bio-therapeutic agents (Probiotics) are live microorganisms that, when administered in adequate number provide health benefits to the consumer. Functional foods contain viable probiotic bacteria in sufficient population. Some manufacturing companies of multi national fame claim the presence of probiotics in their dairy and cereal products especially for the consumption of infants and growing children of different age groups. But neither a legal definition nor specific regulations governing probiotic food exist. There is no approved list of human foods and any bacterial strain of a known species that is traditionally used can be added. Pakistani parents spent huge amount to purchase the different infant formulas for the better nourishment of their children. Any information basing on scientific grounds which confirms the presence or absence of gut friendly bacteria will be of great value for the general consumers. It is important to ensure a high survival rate of these bacteria during the product shelf life to maintain consumer confidence in probiotic products.
This study is presented to assess the viability, label correctness and diversity of Lactobacillus and Bifidobacterium species in powder milk and cereals recommended for infants. The viability of the probiotic microorganisms was evaluated throughout the shelf life. Antibacterial activity of the recovered strains was also measured against the common food borne pathogens. Isolation, identification and count of micro-organisms was carried out by serial ten fold dilutions prepared in PBS solution using the pour plate technique. Strains were propagated by inoculating the Lactobacillus in de Man Rogosa-Sharpe (MRS) and Bifidobacterium species in Reinforced Clostridium Agar under anaerobic conditions at 42°C.Typical cell morphology, colony characteristics and biochemical tests are used for the identification of isolates. Survival rate of the microorganisms was calculated by the viable cell count which represents the original concentration of probiotics in the infant formulation. Out of the total 45 analyses it is concluded that cereal food contains Bifidobacterium species only and the number of Bifidobacterium species in all three products is more than the Lactobacillus species. Moreover, survival rate of both organisms showed a decline pattern in the terminal stage of shelf life.
Lactobacillus and Bifidobacterium species were identified and differentiated by the application of various biochemical tests including Catalase test, Carbohydrate fermentation profile and growth response at different temperature and NaCl concentration. Gram positive and catalase negative isolates fermented the glucose without the production of CO2.
Isolates were tested for their antimicrobial activity using the Stab overlay, Cross streak and Agar well diffusion method against the common food borne pathogenic bacteria i.e. E.coli, Staphylococcs aureus, Salmonella species and Bacillus subtilus. After the completion of experiments it is concluded that Bifidobacterium species have more inhibition effect against the pathogens as compare to Lactobacillus species. Overall effect of isolates was mild to strong inhibition. Bacillus subtilus was resistant to probiotics as compare to the rest of three pathogenic bacteria.

Department of Dairy Technology


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