Antimicrobial efficacy of preservative combinations in South African brown bread

Rope and mould spoilage decrease the shelf life of bread and may result in substantial monetary losses to producers. Five test bakes were carried out to determine the efficacy of sodium diacetate or vinegar in combination with calcium propionate, in inhibiting rope and mould spoilage of brown bread. Their effect on yeast activity was also evaluated. Baked loaves were stored at 30 degrees C and analysed for 6 days post-baking by duplicate plate counting, viable staining using 0.5% tetrazolium salt solution, mould-free shelf life determination and pH measurement. Changes in bacterial counts over time were used to rank treatments statistically. Vinegar combined with calcium propionate at 0.10% each achieved the longest rope-free shelf life, while 0.30% calcium propionate resulted in the longest mould-free shelf life. A combination of sodium diacetate and calcium propionate at 0.10% each showed the lowest reduction in yeast activity.