Validation of in-vitro antifungal activity of the fermentation quotient on bread spoilage moulds through growth/no-growth modelling and bread baking trials

• Published in: Food science & technology 2020-01, Vol.117, p.108636, Article 108636
• Main Authors: Debonne, Els, Maene, Peter, Vermeulen, An, Van Bockstaele, Filip, Depredomme, Laura, Vermeir, Pieter, Eeckhout, Mia, Devlieghere, Frank
• Format: Article
• Language: English
• Subjects: Acetic acid; Bread; Fermentation quotient; Growth/no-growth models; Shelf-life
• ISSN: 0023-6438; 1096-1127
• DOI: 10.1016/j.lwt.2019.108636

The main objectives were to investigate the antifungal effect of lactic (LA) and acetic acid (AA) and the fermentation quotient (FQ, mol/L ratio of LA over AA) towards Penicillium paneum and Aspergillus niger through growth/no-growth modelling of in-vitro data and to validate its effect in chemically acidified bread by performing challenge tests. Results have shown that AA has strong antifungal activity towards both bread moulds, albeit that P. paneum is ten times more resistant compared to A. niger. Complete growth inhibition of A. niger on chemically acidified bread was observed during 35 days at 21 °C for concentrations of AA ≥ 33 mmol/kg dough or ≥165 mmol undissociated AA/L water phase in bread. Whereas for A. niger the FQ must be close to zero and the concentration of AA in bread 33 mmol/kg dough to achieve complete growth inhibition, very high concentrations of AA and LA were needed to prevent growth of P. paneum (>100 mmol/kg dough). The acids also affected yeast activity in dough resulting in lower specific volumes and harder bread crumb. To conclude, the antifungal activity of the FQ cannot be generalized because its antifungal power depends on the sensitivity of the mould species towards LA and AA. •The antifungal effect of the fermentation quotient was investigated in-vitro and in bread.•Growth/no-growth models were developed as function of lactic and acetic acid.•Acetic acid showed strong antifungal activity towards Aspergillus niger.•Penicillium paneum was ten times more resistant towards acetic acid than A. niger.•Growth of A. niger on bread was prevented for more than 35 days using 33 mmol acetic acid/kg dough.