CPMF2, Flemish Cluster Predictive Microbiology in Foods, Chemical and Biochemical Process Technology and Control Section, Katholieke Universiteit Leuven, 3001 Leuven, Belgium.
Appl Environ Microbiol. 2009 Nov;75(22):7060-9. doi: 10.1128/AEM.01045-09. Epub 2009 Sep 25.
Within the field of predictive microbiology, the number of studies that quantify the effect of food structure on microbial behavior is very limited. This is mainly due to impracticalities related to the use of a nonliquid growth medium. In this study, an experimental food model system for studying yeast spoilage in acid sauces was developed by selecting a suitable thickening/gelling agent. In a first step, a variety of thickening/gelling agents was screened, with respect to the main physicochemical (pH, water activity, and acetic acid and sugar concentrations) and rheological (weak gel viscoelastic behavior and presence of a yield stress) characteristics of acid sauces. Second, the rheological behavior of the selected thickening/gelling agent, Carbopol 980, was extensively studied within the following range of conditions: pH 4.0 to 5.0, acetic acid concentration of 0 to 1.0% (vol/vol), glycerol concentration of 0 to 15% (wt/vol), and Carbopol concentration of 1.0 to 1.5% (wt/vol). Finally, the applicability of the model system was illustrated by performing growth experiments in microtiter plates for Zygosaccharomyces bailii at 0, 0.5, 1.0, and 1.5% (wt/vol) Carbopol, 5% (wt/vol) glycerol, 0% (vol/vol) acetic acid, and pH 5.0. A shift from planktonic growth to growth in colonies was observed when the Carbopol concentration increased from 0.5 to 1.0%. The applicability of the model system was illustrated by estimating mu(max) at 0.5% Carbopol from absorbance detection times.
在预测微生物学领域，定量研究食品结构对微生物行为影响的研究数量非常有限。这主要是由于使用非液体生长培养基的不切实际性所致。在本研究中，通过选择合适的增稠/胶凝剂，开发了一种用于研究酸性酱汁中酵母腐败的实验食品模型系统。在第一步中，筛选了多种增稠/胶凝剂，主要针对酸性酱汁的主要物理化学（pH、水分活度以及乙酸和糖浓度）和流变学（弱凝胶粘弹性行为和屈服应力的存在）特性。其次，在以下条件范围内对选定的增稠/胶凝剂 Carbopol 980 的流变行为进行了广泛研究：pH 值为 4.0 至 5.0，乙酸浓度为 0 至 1.0%（体积/体积），甘油浓度为 0 至 15%（重量/体积），以及 Carbopol 浓度为 1.0 至 1.5%（重量/体积）。最后，通过在微滴定板中进行 Zygosaccharomyces bailii 的生长实验，说明了模型系统的适用性，在 0、0.5、1.0 和 1.5%（重量/体积）Carbopol、5%（重量/体积）甘油、0%（体积/体积）乙酸和 pH 值为 5.0 的条件下进行了实验。当 Carbopol 浓度从 0.5%增加到 1.0%时，观察到从浮游生长到菌落生长的转变。通过从吸光度检测时间估算 0.5% Carbopol 时的 mu(max)，说明了模型系统的适用性。
