The microbiological and sensory qualities of yoghurts and their changes after of "best before" date

The aim of the work was determined of microbial and sensory quality of selected white yoghurts in the course of their shelf-life. The samples of yoghurts were produced in dairy Olma, joint-stock company Olomouc. The selected white yoghurts Revital Active (in addition of probiotic culture composed of Bifidobacterium sp., Lactobacillus acidophilus and Lactobacillus rhamnosus), Klasik, Bio yoghurt Via Natur, Silueta light (0.1% fat, sugarless) and Florian were assessed in fresh condition and after an expiration date. Total counts of microorganisms, lactic acid bacteria, yeasts, moulds and coliform bacteria have been checked in the samples of yoghurt. Texture, aroma, taste, acidity and total sensation were assessed by sensory analyse. Titrating acidity was carried out in accordance with CSN ISO 57 0530. The counts of lactic acid bacteria ranged from 105 CFU/g to 107 CFU/g and total counts microorganisms ranged from 108 CFU/g to 109 CFU/g at the beginning of best before date. The lowest counts of lactic acid bacteria were detected in Bio yoghurt (4.62 × 105 CFU/g). The counts of microorganisms in the samples of yoghurt were similar or with certain difference all the time of best before date. The counts of undesirable microorganisms (i.e. coliform bacteria, yeasts and moulds) weren‘t detected. Sensory assessment confirmed that white yoghurts are satisfactory and fulfil qualitative expectation also over all negative changes along storage.