Efficacy of propionates and benzoates on the control of growth of Eurotium species in bakery products with near neutral pH

The effects of propionic acid, sodium propionate and benzoic acid on growth of various Eurotium isolates when added to a bakery product analogue were tested under various environmental conditions. The water activity of the products was adjusted to values in the range of 0.75-0.90 aw, and storage temperatures were in the range of 15-30 °C. Propionates were added in concentrations ranging from 0.5 to 5 g kg^-1, while benzoic acid was added in the range of 0.25-1 g kg^-1. It was observed that 0.25 and 0.5 g kg^-1 concentrations sometimes enhanced isolate growth. When using sodium propionate, the highest concentration, 5 g kg^-1, completely inhibited growth under all conditions except for 0.85-0.90 aw at 25-30 °C, while propionic acid completely prevented fungal spoilage regardless of the abiotic conditions assayed. On the other hand, benzoic acid at a given concentration had a wider effectiveness, thus used at 1 g kg^-1 concentration prevented growth under all conditions except for 0.90 aw and 25-30 °C. It was concluded that trying to reduce the applied concentrations of these weak acid preservatives would be counterproductive and that, except for propionic acid, even at the higher permitted concentrations their use is not suitable for these near neutral pH products when their water activity is high (0.90 aw).