Development of a probiotics rich yogurt dry mix : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Albany, New Zealand

Abstract

The probiotic Lactobacillus acidophilus NCFM has been scientifically studied to confer health benefits in humans when consumed in sufficiently high numbers. The incorporation of the NCFM strain in yogurt has been widely applied due to the popularity of the fermented product. Probiotics and other yogurt microorganisms (Streptococcus thermophilus and Lactobacillus bulgaricus) can remain viable in high concentration when present in liquid or in high water activity products. However, such products are not convenient as they can not be stored at ambient temperature and have limited shelf life. The development of dehydrated yogurt base (DYB) has created opportunities for the delivery of probiotics. DYB is unique to the current market and provides the convenience of ambient storage and long term shelf life. Therefore, the objective of this study was to develop a stable DYB formulation with shelf life of up to 18 months at ambient storage and 2 weeks at 4°C in its ready-to-eat (RTE) form. Full experimental design was used to formulate the DYB. Characterization of DYB and RTE was analysed for physical, microbiological and chemical properties. The Arhenius model was used to predict the shelf-life of DYB. Liquid yogurt was prepared using selected DYB and the products were analysed by sensory consumers. Results showed that the level of oxygen, moisture, fat, sugar and the storage temperature affected the survival of NCFM in DYB. The cell counts of the NCFM however were above 106 cfu/g throughout storage. In liquid yogurt (RTE form), acidity and the initial level of microorganisms used were important in the stability of the NCFM cells during storage. The growth of the starter microorganisms and the NCFM was symbiotic. Based on this information and the sensory analysis, the developed DYB formulation in the current study showed good potential for commercialization.