Weak organic acid food preservatives exert pronounced culture pH‐dependent effects on both the heat‐shock response and the thermotolerance of Saccharomyces cerevisiae. In low‐pH cultures, they inhibit this stress response and cause strong induction of respiratory‐deficient petites amongst the survivors of lethal heat treatment. In higher pH cultures, 25°C sorbic acid treatment causes a strong induction of thermotolerance without inducing the heat‐shock response. In this study we show that trehalose, a major stress protectant, accumulates rapidly in S. cerevisiae exposed to sorbate at low pH. In pH 3.5 cultures, a 25°C sorbate treatment is as effective as a 39°C heat shock in inducing trehalose. This weak‐acid‐induced trehalose accumulation is enhanced in the pfk1 S. cerevisiae mutant, indicating that it arises through inhibition of glycolysis at the phosphofructokinase step. The more preservative‐resistant food spoilage yeast Zygosaccharomyces bailii differs from S. cerevisiae in that: (1) its basal thermotolerance is not strongly affected by culture pH; (2) it does not display trehalose accumulation in response to 25°C sorbate treatment at low pH; and (3) there is no induction of respiratory‐deficient petites during lethal heating with sorbate. This probably reflects Z. bailii being both petite‐negative and better equipped for maintenance of homeostasis during weak‐acid, pH or high‐temperature stress.