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Effects of organic acids on thermal inactivation of acid and cold stressed Enterococeus faecium

机译：有机酸对酸热失活和冷应激粪肠球菌的影响

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摘要

In this study the adaptative response to heat (70℃) of Enterococcus faecium using fresh and refrigerated (at 4℃ for up to 1 month) stationary phase cells grown in Brain Heart Infusion (BHI) buffered at pH 7.4 (non-acid-adapted cells) and acidified BHI at pH values of 6.4 and 5.4 with acetic, ascorbic, citric, lactic, malic and hydrochloric acids (acid-adapted cells) was evaluated. In all cases, the survival curves obtained were concave upward. A mathematical model based on the Weibull distribution accurately described the inactivation kinetic. The results indicate that previous adaptation to a low pH increased the bacterial heat resistance, whereas the subsequent cold storage of cells reduced E. faecium thermal tolerance. Fresh acid-adapted cells showed t2.5-values (time needed to obtain an inactivation level of 2.5 log_(10) cycles) ranging from 2.57 to 9.51 min, while non-acid-adapted cells showed t_(2.5)-values of 1.92 min. The extent of increased heat tolerance varied with the acid examined, resulting in the following order: citric ≥ acetic > malic ≥ lactic > hydrochloric ≥ ascorbic. In contrast, cold storage progressively decreased E. faecium thermal resistance. The t_(2.5) values found at the end of the period studied were about 2-3-fold lower than those corresponding to non-refrigerated cells, although this decrease was more marked (about 5-fold) when cells were grown in buffered BHI and BHI acidified at pH 5.4 with hydrochloric acid. These findings highlight the need for a better understanding of microbial response to various preservation stresses in order to increase the efficiency of thermal processes and to indicate the convenience of counterbalancing the benefits of the hurdle concept.
机译：在这项研究中，使用新鲜和冷藏（在4℃下长达1个月）在pH 7.4（非酸适应）缓冲的脑心浸液（BHI）中生长的新鲜和冷藏的固定相细胞对粪肠球菌对热（70℃）的适应性反应细胞），并用乙酸，抗坏血酸，柠檬酸，乳酸，苹果酸和盐酸（适应酸的细胞）评估pH值为6.4和5.4的酸化BHI。在所有情况下，获得的生存曲线都是向上凹的。基于威布尔分布的数学模型可以准确描述失活动力学。结果表明，先前对低pH的适应提高了细菌的耐热性，而随后细胞的冷储存降低了粪肠球菌的耐热性。新鲜的酸适应细胞显示t2.5值（达到2.5 log_（10）周期失活水平所需的时间）范围为2.57至9.51分钟，而非酸适应细胞显示t_（2.5）值为1.92。分钟耐热性的提高程度随所检查的酸而异，其顺序如下：柠檬酸≥乙酸>苹果酸≥乳酸>盐酸≥抗坏血酸。相反，冷藏会逐渐降低粪肠球菌的热阻。在研究期结束时发现的t_（2.5）值比非冷藏细胞低约2-3倍，尽管当细胞在缓冲的BHI中生长时这种降低更为明显（约5倍）然后用盐酸将BHI酸化至pH 5.4。这些发现突出表明，需要更好地了解微生物对各种保存压力的反应，以提高热加工效率，并指出平衡障碍概念所带来的便利。

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  • 来源
    《Food microbiology》 |2009年第5期|497-503|共7页
  • 作者

    Ana Fernandez; Avelino Alvarez-Ordonez; Mercedes Lopez; Ana Bernardo;

  • 作者单位

    Departamento de Higiene y Tecnologia de los Atimentos, Facultad de Veterinaria, Universidad de Leon, Campus de Vegazana s, 24071 Leon. Spain;

    Departamento de Higiene y Tecnologia de los Atimentos, Facultad de Veterinaria, Universidad de Leon, Campus de Vegazana s, 24071 Leon. Spain;

    Departamento de Higiene y Tecnologia de los Atimentos, Facultad de Veterinaria, Universidad de Leon, Campus de Vegazana s, 24071 Leon. Spain;

    Departamento de Higiene y Tecnologia de los Atimentos, Facultad de Veterinaria, Universidad de Leon, Campus de Vegazana s, 24071 Leon. Spain;

  • 收录信息 美国《科学引文索引》(SCI);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    enterococcus faecium; heat inactivation kinetic; organic acids; acid adaptation; cold stress;

    机译：粪肠球菌;热失活动力学;有机酸酸适应冷压力;

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