Beard B M, Sheldon B W, Foegeding P M
Department of Food Science, North Carolina State University, Raleigh 27695-7624, USA.
J Food Prot. 1999 May;62(5):484-91. doi: 10.4315/0362-028x-62.5.484.
The effect of nisin, added in the form of Nisaplin, on the thermal resistance of bacterial spores and the effects of medium composition, exposure time, and pH on nisin enhancement of heat sensitivity were evaluated. Nisin apparently required specific nutrients to sensitize spores to heat. For example, D130 degrees C values of approximately 10 s were observed in sodium phosphate buffer with and without 6% sucrose with no significant (P> or =0.05) differences detected as a result of increased nisin concentration. In a nutrient-rich chocolate milk model system (CMMS), increasing either the time of exposure to nisin (5, 15, or 24 h) before heating or nisin concentration (0, 2,000, or 4,000 IU/ml) increased the sensitivity of Bacillus stearothermophilus spores to heat. In the CMMS with 10 to 12% fat cocoa powder, increasing nisin concentration (at 5 h of exposure) significantly (P< or =0.05) reduced D130 degrees C values; D130 degrees C values were 21.7, 17.2, and 17.8 s, respectively, for the 0-, 2,000-, and 4,000-IU/ ml nisin treatments. Fifteen and 24 h of exposure further reduced D130 degrees C values in the nisin-containing treatments compared to the control (0 IU of nisin per ml). A lower-fat CMMS (0 to 1% fat cocoa powder) had lower D130 degrees C values (19.3, 15.8, and 14.7 s for the 0-, 2,000-, and 4,000-IU/ml nisin treatments, respectively). Nisin activity was enhanced by lowering pH in the CMMS (10 to 12% fat cocoa powder), with reductions in D130 degrees C values across all pH values (ranging from 18.0% at pH 6.4 to 41.9% at pH 5.0). zD values were 9.6, 9.0, and 8.4 degrees C for the 0-, 2,000-, and 4,000-IU/ml nisin treatments, respectively. Spores of B. licheniformis yielded results similar to those obtained with B. stearothermophilus. For example, decreasing CMMS (10 to 12% fat cocoa powder) pH values from 6.4 to 5.0 produced D100 degrees C values of 3.3, 2.8, and 2.8 min (pH 6.4) and 1.0, 0.8, and 0.8 min (pH 5.0) for the 0-, 2,000-, and 4,000-IU/ml nisin treatments. This study clearly verified that the addition of Nisaplin to dairy-based beverages, such as a chocolate milk drink, or other foods intended to be heated reduces the thermal resistance of selected bacterial spores. Increased spore sensitivity to heat may provide food processors with an opportunity to reduce their thermal processes and expenses while maintaining product quality, functionality, and shelf stability.
评估了以Nisaplin形式添加的乳链菌肽对细菌芽孢耐热性的影响，以及培养基成分、暴露时间和pH值对乳链菌肽增强热敏感性的影响。乳链菌肽显然需要特定的营养物质来使芽孢对热敏感。例如，在含和不含6%蔗糖的磷酸钠缓冲液中，观察到130℃下的D值约为10秒，增加乳链菌肽浓度未检测到显著（P≥0.05）差异。在营养丰富的巧克力牛奶模型系统（CMMS）中，加热前增加乳链菌肽的暴露时间（5、15或24小时）或乳链菌肽浓度（0、2000或4000 IU/ml）会增加嗜热脂肪芽孢杆菌芽孢对热的敏感性。在含有10%至12%脂肪可可粉的CMMS中，增加乳链菌肽浓度（暴露5小时）显著（P≤0.05）降低了130℃下的D值；0、2000和4000 IU/ml乳链菌肽处理的130℃下的D值分别为21.7、17.2和17.8秒。与对照（每毫升0 IU乳链菌肽）相比，暴露15和24小时进一步降低了含乳链菌肽处理中的130℃下的D值。脂肪含量较低的CMMS（0%至1%脂肪可可粉）的130℃下的D值较低（0、2000和4000 IU/ml乳链菌肽处理分别为19.3、15.8和14.7秒）。在CMMS（10%至12%脂肪可可粉）中，降低pH值可增强乳链菌肽活性，所有pH值下130℃下的D值均降低（pH 6.4时为18.0%，pH 5.0时为41.9%）。0、2000和4000 IU/ml乳链菌肽处理的zD值分别为9.6、9.0和8.4℃。地衣芽孢杆菌的芽孢产生的结果与嗜热脂肪芽孢杆菌相似。例如，将CMMS（10%至12%脂肪可可粉）的pH值从6.4降至5.0，0、2000和4000 IU/ml乳链菌肽处理的100℃下的D值分别为3.3、2.8和2.8分钟（pH 6.4）以及1.0、0.8和0.8分钟（pH 5.0）。这项研究清楚地证实，在基于乳制品的饮料（如巧克力牛奶饮料）或其他打算加热的食品中添加Nisaplin可降低所选细菌芽孢的耐热性。芽孢对热敏感性的增加可能为食品加工商提供一个机会，在保持产品质量、功能和货架稳定性的同时，减少热处理过程和成本。
