Exploring natural antifungal preservation strategies to extend bread shelf-life : from baking technology to biopreservation

Mould spoilage of bakery products is a serious problem resulting in a significant volume of food waste. Moreover, the food industry takes a keen interest in replacing chemical preservatives by natural alternatives in order to meet the consumers’ changing requirements as well as the clean label trend. This study focused on exploring natural water or oil soluble compounds with antifungal activity in bread and various baking technologies to reduce fungal growth of primarily Penicillium spp. and Aspergillus spp. The technologies considered included variations in par-baking conditions and the production of composite bread. The antimicrobial efficacy of antifungal compounds was assessed through in-vitro studies and predictive growth/no-growth models. The screening assays were macro-dilution (cf. agar dilution assays) and micro-dilution assays (cf. dilution assay in 96-well plates). Moreover, the effect of the undissociated acid fraction of weak organic acids such as those found in sourdough (e.g. acetic, lactic and phenyllactic acid), expressed in the aqueous phase of bread, became apparent. This provided additional information about the mode of action of the acids, enabling a better shelf-life prediction. Furthermore, the natural compounds were tested in actual dough and bread, assessing the technological quality of both dough and bread. In addition, the antifungal activity of the compounds was investigated by shelf-life and challenge tests. Throughout this work, it was shown that by adjusting the par-baking conditions, bread composition and packaging, it is possible to extend the shelf-life of par-baked bread in a natural way