Research Unit of Cereal and Feed Technology, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium; Laboratory of Applied Mycology (MYCOLAB), Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium.
Research Unit of Cereal and Feed Technology, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Valentin Vaerwyckweg 1, 9000 Ghent, Belgium.
Int J Food Microbiol. 2020 May 16;321:108551. doi: 10.1016/j.ijfoodmicro.2020.108551. Epub 2020 Feb 8.
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; 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, 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 R = 0.79 when expressing the shelf-life in function of C and C. 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 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.
天然发酵剂是一种非常有趣的天然保鲜系统，可以延长面包的无霉货架期。许多研究报告称，发酵剂的抗真菌活性主要与乳酸（LA）和乙酸（AA）的存在有关，但关于面包水相中非离解酸浓度（C；mmol/L）对面包货架期的影响的信息非常有限。本研究旨在提供关于发酵剂面包中酸作用模式的更多信息，从而能够更好地预测货架期。本研究分为两部分。在第 1 部分中，对三种工业生物发酵剂（面团产率、pH 值、α、发酵商、微生物区系）进行了表征。在 7 周内，通过每天检查可见霉菌生长（21°C）进行了天然菌群的货架期测试。在第 2 部分中，验证了存在于具有抗真菌活性的发酵剂面包中的酸的作用。在含有乳酸乳杆菌和酿酒酵母作为主要发酵剂微生物的全烘焙发酵剂面包中观察到完全生长抑制，而在对照面包中货架期限制在 4.4-9.2 天。这些全烘焙发酵剂面包含有 36mmol 非离解 LA/L 和 220mmol 非离解 AA/L。这些数据用于制作货架期预测的通用线性回归模型，结果表明，当以 C 和 C 的函数表示货架期时，拟合度 R = 0.79。在酸化面包中，乳酸的作用并不显著，仅通过酸化间接影响货架期。观察到具有可比 C 浓度的发酵剂面包和化学酸化面包的抗真菌活性没有差异。当面包中存在 150-200mmol 非离解 AA/L 水相时，货架期会增加。综上所述，本研究表明了面包货架期与非离解乙酸酸分数、面包 pH 值和水分含量之间的关系。
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