Survival of free and microencapsulated Lactobacillus acidophilus and Bifidobacterium lactis and their effect on texture of feta cheese

The survival and the effect of free and encapsulated probiotic bacteria (Lactobacillus acidophilus DD 910 and Bifidobacterium lactis DID 920) on pH, high salt environment, water-holding capacity, exo-polysaccharide production and influence on the textural attributes of feta cheese were studied over a 7-week storage. Addition of probiotic bacteria either in the free or encapsulated form slowed acid development during storage. Addition of encapsulated probiotic cultures increased water-holding capacity of the cheese due to the production of exo-polysaccharides and the polymer (alginate as encapsulant material) and filler material (Hi Maize(TM) starch) added. There was approximately 2 and 3 log cycle loss in the number of cells with free and encapsulated probiotic cultures respectively over a 7-week period. Microencapsulation did not offer protection to the probiotic bacteria, due to the open texture of cheese, possible disintegration of microcapsules in brine solution and a higher salt uptake when encapsulated cultures were incorporated. The addition of probiotic cultures, either in the free or encapsulated states, did not seem to significantly affect textural parameters such as springiness and cohesiveness of the cheese over the 7-week period. There were, however, significant differences (p<0.05) in the chewiness, gumminess and hardness of the feta cheese when probiotic cultures were incorporated. This study has shown that calcium-induced alginate-starch micro capsules did not offer significant protection to maintain the viability of probiotic bacteria; however, coating of the micro capsules, selection of probiotic strains that are acid and salt tolerant and produces exo-polysaccharides may allow the production of a cheese with greater survival rate of probiotic bacteria and an improved texture.