Effect of baking conditions and storage on the viability of Lactobacillus plantarum supplemented to bread

- Viability of probiotics decreased from 109 CFU/g to 104∼5 CFU/g in bread after baking.
- Different baking conditions affected the survival curves of probiotics during baking.
- Higher survival of probiotics was obtained in bread crust than crumb under certain condition.
- Low moisture content and dense structure of crust may increase heat-resistance of bacteria.
- Bacterial viability increased to 108 CFU/g in crust and 106 CFU/g in crumb during storage.

Bread is an interesting non-dairy-based vehicle for probiotics delivery given its daily consumption worldwide. The incorporation of probiotics in bread is challenging due to the high baking temperatures. In this study the influence of various baking conditions and subsequent storage on survival of a model strain Lactobacillus plantarum P8 is systematically investigated. Bread samples with varying dough weight (5, 30, and 60 g) were baked at different temperatures (175, 205, and 235 ○C) for 8 min, and the residual viability of bacteria was determined every 2 min. Under all baking conditions, the viability of probiotics decreased from 109 CFU/g to 104∼5 CFU/g after baking. For specific conditions a difference in bacterial viability between bread crust and crumb was observed, which was explained by the different temperature-moisture history and developed microstructure during baking. Remarkably, during storage bacterial viability increased by 2-3 log to 108 CFU/g in crust and 106 CFU/g in crumb, respectively. The re-growth of probiotics was accompanied by a decrease in pH of the bread and an increase of the total titratable acidity. The results of this work provide valuable experimental data for further modelling and optimization studies, which then could contribute to the development of probiotic bakery products.