Dipartimento di Scienze Agrarie, Alimentari ed Ambientali, Università Politecnica delle Marche, 60131 Ancona, Italy.
Dipartimento di Scienze Agrarie, Alimentari ed Ambientali, Università Politecnica delle Marche, 60131 Ancona, Italy.
Int J Food Microbiol. 2021 Mar 2;341:109048. doi: 10.1016/j.ijfoodmicro.2021.109048. Epub 2021 Jan 19.
Yeasts are the leading cause of spoilage in yogurt. Considering the high demand from consumers to use natural products as an alternative to additives, essential oils (EOs) could be a promising solution to guarantee high microbiological standards. The present study highlighted the in vitro antifungal potential of cinnamon, ginger, lemongrass, mandarin, orange, lemon and lime EOs against spoilage yeasts isolated from yogurts prepared with pasteurized buffalo milk. A total of 74 isolates represented by 14 different species of Candida, Rhodotorula, Debaryomyces, Kluyveromyces and Yarrowia genera were subjected to a disc diffusion assay, showing lemongrass EO to have the highest antifungal activity (40.97 ± 9.86 mm), followed by cinnamon (38.46 ± 6.59 mm) and orange (12.00 ± 4.52 mm) EOs. Yarrowia lipolytica was less susceptible to lemongrass EO than Candida sake and Yarrowia deformans isolates. Ginger EO exhibited the lowest efficacy. A minimum inhibitory concentration (MIC) assay showed the ability of lemongrass and cinnamon EOs to inhibit the growth of all selected isolates at concentrations between ≤0.31 and 1.25 μL/mL. Therefore, for the first time, the two best-performing EOs (lemongrass and cinnamon) based on in vitro assays were assessed for their potential roles as preservatives in an in vivo yogurt model prepared at the laboratory scale. Since some limitations, such as the inhibition of lactic acid bacteria by cinnamon EO, consequently leading to fermentation failure as well as species-specific antifungal activity of lemongrass EO, were observed, further studies are needed to explore the possibility of using a slightly higher concentration of lemongrass EO and/or combinations of different EOs and/or their components. Finally, since yogurt spoilage could also be prevented by correct sanitation procedures of the production environment, the sanitizers commonly used in the food industry were tested against all isolates, showing the high efficiency of alcohol-based sanitizers and the ineffectiveness of chlorine-based sanitizers.
酵母是酸奶变质的主要原因。考虑到消费者对使用天然产品替代添加剂的高需求，精油（EOs）可能是保证高微生物标准的有希望的解决方案。本研究强调了肉桂、生姜、柠檬草、橘子、橙子、柠檬和酸橙 EOs 在体外对巴氏杀菌水牛乳制备的酸奶中分离出的腐败酵母的抗真菌潜力。共有 74 株菌，代表了 14 种不同属的念珠菌、红酵母、德巴利酵母属、克鲁维酵母属和假丝酵母属，进行了圆盘扩散试验，结果表明柠檬草 EO 具有最高的抗真菌活性（40.97±9.86 mm），其次是肉桂（38.46±6.59 mm）和橙子（12.00±4.52 mm）EO。与 Candida sake 和 Yarrowia deformans 分离株相比，柠檬草 EO 对 Yarrowia lipolytica 的敏感性较低。生姜 EO 的功效最低。最低抑菌浓度（MIC）试验表明，柠檬草和肉桂 EO 能够在浓度为≤0.31 至 1.25 μL/mL 之间抑制所有选定分离株的生长。因此，这是首次根据体外试验评估了两种表现最佳的 EO（柠檬草和肉桂）作为实验室规模制备的体内酸奶模型中的防腐剂的潜力。由于观察到一些局限性，例如肉桂 EO 抑制乳酸菌，导致发酵失败，以及柠檬草 EO 的种特异性抗真菌活性，因此需要进一步研究以探索使用稍高浓度的柠檬草 EO 和/或不同 EO 及其成分的组合的可能性。最后，由于正确的生产环境卫生程序也可以防止酸奶变质，因此测试了食品工业中常用的消毒剂对所有分离株的效果，结果表明基于酒精的消毒剂效率很高，而基于氯的消毒剂无效。
