McKechnie, Sandra (2005) Improvement in viability of Lactobacillus Acidophilus in yogurt by stress adaptation. PhD thesis, Victoria University.

Abstract

The main factor claimed to be responsible for the loss of viability of probiotic organisms during storage is the decrease in intracellular pH caused by accumulation of organic acids in the yogurt. This leads to inactivation of essential metabolic pathways, deprivation of ATP to the cell, and eventually, cell death. A strategy to improve the viability of Lb. acidophilus in yogurt is to adapt the organism to the harsh environments that normally cause loss in viability. This has been achieved by culturing cells in an environment that allows them to prepare for normally lethal conditions. Acquired acid tolerance was previously reported for Lb. acidophilus following cell conditioning at moderate pH followed by a challenge in normally lethal pH conditions. The primary objective of the work in this thesis was to design a protocol for preparing probiotic cultures for yogurt manufacture that would improve their viability during long-term refrigerated storage.

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