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 Food Microbiology and Food Preservation, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
Food Microbiol. 2020 Jun;88:103407. doi: 10.1016/j.fm.2019.103407. Epub 2019 Dec 19.
Most interesting antifungal compounds from sourdough fermentation are acetic acid (AA) and DL-3-phenyllactic acid (PLA). Although the role of pH on the activity of organic acids has been established long time ago, no information is available on the importance of undissociated acid (HA) expressed on the aqueous phase of bread (C, mmole/L). Mostly, concentrations (mmole/kg dough or bread, C) and pH are given side by side. The aim of this study was to show the importance of C for adequate comparison of in-vitro growth data with bread shelf-life. Growth of Penicillium paneum and Aspergillus niger was recorded using a micro-dilution assay with optical density measurements. Parameters such as a (0.94-0.98), pH (4.6-6.0), temperature (10-30 °C), time (0-8 days) and C (0-300 mM) were varied. Growth/no-growth models were developed and shelf-life tests of par-baked breads of 45 days at 20 °C were conducted. The modelled inhibitory concentrations of undissociated acid were comparable with the shelf-life test of bread: (PLA) 50 versus 39-84 mmol/L; (AA) 110 versus 110-169 mmol/L. This study showed the applicability of G/NG models for bread shelf-life prediction and highlighted the importance of CHA. Moreover, it was found that naturally present PLA in sourdough bread is insufficient to increase bread shelf-life.
发酵面团中最有趣的抗真菌化合物是乙酸（AA）和 DL-3-苯乳酸（PLA）。虽然很久以前就已经确定了 pH 值对有机酸活性的作用，但关于面包水相（C，毫摩尔/升）中未离解酸（HA）的重要性尚无信息。大多数情况下，会给出浓度（毫摩尔/公斤面团或面包，C）和 pH 值并排给出。本研究的目的是表明 C 的重要性，以便将体外生长数据与面包保质期进行充分比较。使用微稀释测定法结合光密度测量记录青霉（Penicillium paneum）和黑曲霉（Aspergillus niger）的生长情况。参数如 a（0.94-0.98）、pH（4.6-6.0）、温度（10-30°C）、时间（0-8 天）和 C（0-300 mM）均有变化。开发了生长/不生长模型，并进行了 45 天 20°C下预烤面包的保质期测试。未离解酸的模拟抑制浓度与面包的保质期测试相当：（PLA）50 与 39-84 mmol/L；（AA）110 与 110-169 mmol/L。这项研究表明了 G/NG 模型在预测面包保质期方面的适用性，并强调了 CHA 的重要性。此外，还发现发酵面团面包中天然存在的 PLA 不足以延长面包的保质期。
