科研之友
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摘要
The spoilage potential of Zygosaccharomyces bailii has been widely recognized within the food industry. However, few data are available on the growth characteristics of this yeast at low temperature and in the absence of chemical preservatives. In this study, the growth/no growth boundary of Z. bailii was defined at refrigeration temperature (7 degrees C) and at conditions relevant to high-sugar, low-pH foods (such as ketchup and salad dressing), i.e. pH 3.0-5.0 (five levels), a(w) 0.93-0.97 (five levels) and acetic acid concentration 0-2.5% (v/v; six levels). Yeast growth was followed during 90 days by optical density measurements, and logistic regression models were used to describe the data. Acetic acid had a significant effect on the relation between a(w) and NaCl concentration and this interaction had important consequences for the model development. When data were modelled as a function of a(w) or NaCl concentration, a stimulatory effect by acetic acid was observed. In contrast, as a function of (toxic) Na+ ions, no evidence was found of such a phenomenon. These results indicate that in cases where the relationship between a(w) and solute concentration is not straightforward such as in the presence of acid preservatives, one must be critical towards the interpretation of data and correspondingly, the development of predictive models. On a practical note, the developed models, especially the one incorporating Na+ ions, may be used (1) to assess the stability of shelf-stable acidified foods stored under chilled conditions after opening or (2) to formulate new additive-free products intended for storage at 7 degrees C.
- 出版日期2012-8
