Dept. of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Canada; Dept. of Food, Environmental and Nutritional Sciences, University of Milan, Milan, Italy.
Dept. of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Canada.
Int J Food Microbiol. 2019 Aug 2;302:8-14. doi: 10.1016/j.ijfoodmicro.2018.09.007. Epub 2018 Sep 11.
Fungal spoilage of bread remains an unsolved issue in bread making. This work aims to identify alternative strategies to conventional preservatives in order to prevent or delay fungal spoilage of bread. The minimum inhibitory concentration (MIC) of bacterial metabolites and chemical preservatives was evaluated in vitro, and compared to their in situ activity in baking trials. Calcium propionate, sorbic acid, 3-phenyllactic acid, ricinoleic acid, and acetic acid were tested both individually and in combination at their MIC values against Aspergillus niger and Penicillium roqueforti. The combination of acetic acid with propionate and sorbate displayed additive effects against the two fungi. For these reasons, we introduced sourdough fermentation with specific strains of lactobacilli, using wheat or flaxseed, in order to generate acetate in bread. A combination of Lactobacillus hammesii and propionate reduced propionate concentration required for shelf life extension of wheat bread 7-fold. Flaxseed sourdough bread fermented with L. hammesii, excluding any preservative, showed a shelf life 2 days longer than the control bread. The organic acid quantification indicated a higher production of acetic acid (33.8 ± 4.4 mM) when compared to other sourdough breads. Addition of 4% of sucrose to sourdough fermentation with L. brevis increased the mould free shelf-life of bread challenged with A. niger by 6 days. The combination of L. hammesii sourdough and the addition of ricinoleic acid (0.15% or 0.08%) prolonged the mould free shelf-life by 7-8 days for breads produced with wheat sourdoughs. In conclusion, the in vitro MIC of bacterial metabolites and preservatives matched the in situ antifungal effect. Of the different bacterial metabolites evaluated, acetic acid had the most prominent and consistent antifungal activity. The use of sourdough fermentation with selected strains able to produce acetic acid allowed reducing the use of chemical preservatives.
真菌对面包的破坏仍然是面包制作中的一个未解决的问题。本工作旨在寻找替代传统防腐剂的策略，以防止或延迟面包的真菌变质。评估了细菌代谢物和化学防腐剂的最低抑菌浓度 (MIC)，并将其与烘焙试验中的原位活性进行了比较。丙酸钙、山梨酸、3-苯乳酸、蓖麻油酸和乙酸分别以 MIC 值单独和组合测试，以对抗黑曲霉和青霉。乙酸与丙酸和山梨酸的组合对这两种真菌均表现出相加作用。出于这些原因，我们引入了使用小麦或亚麻籽的特定乳酸菌发酵酸面团，以在面包中生成乙酸。使用 L. hammesii 和丙酸的组合可将小麦面包保质期延长所需的丙酸浓度降低 7 倍。用 L. hammesii 发酵的不含任何防腐剂的亚麻籽酸面团面包的货架期比对照面包长 2 天。有机酸定量分析表明，与其他酸面团面包相比，乙酸的产量更高（33.8±4.4 mM）。在 L. brevis 发酵酸面团中添加 4%的蔗糖可将黑曲霉挑战的面包无霉货架期延长 6 天。用 L. hammesii 酸面团和添加蓖麻油酸（0.15%或 0.08%）的组合可将小麦酸面团面包的无霉货架期延长 7-8 天。总之，细菌代谢物和防腐剂的体外 MIC 与原位抗真菌效果相匹配。在所评估的不同细菌代谢物中，乙酸具有最显著和一致的抗真菌活性。使用能够产生乙酸的选定菌株进行酸面团发酵，可以减少化学防腐剂的使用。
