Sourdough is a very interesting natural preservation system to prolong mould free shelf-life of bread. Numerous studies have reported that the antifungal activity of sourdough is mainly correlated with the presence of lactic (LA) and acetic acid (AA), but very few information is available on the effect of undissociated acid concentrations in the aqueous phase of bread (C_HA; mmole/L). This study was conducted to provide additional information about the mode of action of the acids in sourdough bread, enabling a better shelf-life prediction. This study was divided into two parts. In part 1, three industrial biological sourdoughs were characterized (dough yield, pH, a_w, fermentation quotient, microbiota). During 7 weeks, a shelf-life test with natural flora was conducted with daily checks of visible mould growth (21 °C). In part 2, the effect of the acids present in the antifungal active sourdough breads was validated in chemically acidified wheat breads. Complete growth inhibition was observed in full-baked sourdough bread (30 g/100 g dough) containing Lactobacillus sanfranciscensis and Saccharomyces cerevisiae as dominant sourdough micro-organisms, whereas in control bread the shelf-life was limited to 4.4–9.2 days. These full-baked sourdough breads contained 36 mmole undissociated LA/L and 220 mmole undissociated AA/L. The data were used to make General Linear Regression models for shelf-life prediction and resulted in a fit of R² = 0.79 when expressing the shelf-life in function of C_HA,LA and C_HA,AA. In acidified breads, the role of lactic acid was not significant and only impacted shelf-life indirectly through acidification. No difference between antifungal activity of sourdough breads and chemically acidified bread with comparable C_HA,AA concentrations was observed. Shelf-life increased when 150–200 mmole undissociated AA/L aqueous phase in bread was present. To conclude, this study showed the importance of the undissociated acid fraction of acetic acid in relation to bread shelf-life, together with bread pH and moisture content.

酵母是一种非常有趣的天然保存系统，可以延长面包的无霉菌保质期。大量研究报告称，面团的抗真菌活性主要与乳酸（LA）和乙酸（AA）的存在有关，但是关于面包水相中未离解的酸浓度影响的信息很少（C _HA ; mmole / L）。进行这项研究是为了提供有关酸在面包中的作用方式的其他信息，从而可以更好地预测保质期。本研究分为两个部分。在第1部分中，对三种工业生物酵母进行了表征（面团产量，pH，_w，发酵商，微生物群）。在7周内，对自然菌群进行了保质期测试，每天检查可见的霉菌生长（21°C）。在第2部分中，在化学酸化的小麦面包中验证了抗真菌活性酸面团中存在的酸的作用。在含有旧金山乳杆菌和酿酒酵母作为主要酵母微生物的全熟酵母面包（30 g / 100 g面团）中观察到完全的生长抑制作用，而在对照面包中，货架期被限制在4.4-9.2天。这些全熟的酸面团面包包含36 mmole未解离的LA / L和220 mmole未解离的AA / L。数据用于建立通用线性回归模型以预测货架期，并得出R ²的拟合度 当表示C _HA，LA和C _HA，AA的功能的货架期时，= 0.79 。在酸化的面包中，乳酸的作用并不重要，仅通过酸化间接影响保质期。酸面包和化学酸化的面包在具有可比的C _HA，AA浓度时_，其抗真菌活性没有差异。当面包中存在150-200 mmole未解离的AA / L水相时，保质期增加。总而言之，这项研究表明了乙酸的未离解酸部分与面包保质期以及面包的pH和水分含量有关的重要性。