Department of Agronomy Food Natural Resources Animal and Environment (DAFNAE), University of Padova, Legnaro, PD, Italy.
Interdepartmental Centre for Research in Viticulture and Enology (CIRVE), University of Padova, Conegliano, TV, Italy.
PLoS One. 2021 Dec 28;16(12):e0261988. doi: 10.1371/journal.pone.0261988. eCollection 2021.
Generally, endospore contamination can occur from different sources during product manufacturing in many industries and therefore lower its quality by affecting physicochemical properties and shelf-life. Bacterial endospores can germinate inside the product and produce several enzymes, which can cause several undesirable changes. This study assessed the spores thermal resistance and applied a microwave decontamination technique toward herbal extracts (Tilia tomentosa and Centella asiatica) containing ethanol or glycerol. Based on 16S rRNA analysis, the detected contaminant endospores belonged to different Bacillus species, namely B. subtilis, B. zhangzhouensis, and B. pumilus. The thermal resistance assessment using inoculated endospores in the actual products revealed B. pumilus T2 as the most resistant endospore to the heat treatments tested in both T. tomentosa and C. asiatica extracts. Finally, a high-performance microwave technique was used to decontaminate T. tomentosa extract against the mixture of Bacillus spores. Results from the microwave technique indicate that the increase of temperature from 100°C to 105°C not only decontaminated the product but also could dramatically decrease the effective thermal treatment time (10 times), which can benefit the product quality. The results provided in this study considerably contribute to improving an original decontamination method for products containing glycerol and ethanol with the most negligible effect on product quality.
一般来说，在许多行业的产品制造过程中，内孢子污染可能来自不同的来源，从而通过影响物理化学性质和保质期降低产品质量。细菌内孢子可以在产品内部发芽，并产生几种酶，从而导致许多不良变化。本研究评估了孢子的耐热性，并应用微波消毒技术对含有乙醇或甘油的草药提取物（毛梾和积雪草）进行处理。基于 16S rRNA 分析，检测到的污染内孢子属于不同的芽孢杆菌属，即枯草芽孢杆菌、樟科芽孢杆菌和短小芽孢杆菌。使用实际产品中接种的内孢子进行耐热性评估表明，在毛梾和积雪草提取物中，B. pumilus T2 是对测试的热处理最具抗性的内孢子。最后，采用高效微波技术对毛梾提取物中的芽孢杆菌孢子混合物进行消毒。微波技术的结果表明，温度从 100°C 升高到 105°C 不仅可以对产品进行消毒，而且可以大大缩短有效热处理时间（10 倍），从而有利于提高产品质量。本研究的结果为改进含有甘油和乙醇的产品的原始消毒方法做出了重要贡献，对产品质量的影响最小。
