Influence of Chemical Preservatives on Survival and Growth of Z ygosaccharomyces Rouxii  YSa40 in Glycerol-Based Pineapple Model Systems and Intermediate Moisture Pineapple Products

Abstract

This study investigates the growth and survival of Zygosaccharomyces rouxii (a xerotolerant yeast) in the glycerol-based intermediate moisture food (IMF) pineapple model systems (0.87 aw/pH 4.1 GLY/CPB/BM and 0.87 aw/pH 4.5 GLY/CPB/ BM) containing various levels of chemical preservatives (sodium benzoate, potassium metabisulphite and potassium sorbate) used singly or in combination. Comparing the two different levels used singly, the three preservatives were more effective in inhibiting yeast growth at a higher 0.1% (w/w) than at a lower 0.01% (w/w) level of the preservative, with potassium metabisulphite showing most inhibitory effect at 0.1% (w/w) level. When the combinations of two to three preservatives at 0.01% (w/w) level were evaluated, a synergistic growth inhibitory effect was achieved. Combination of three preservatives was more effective compared to a combination of any of the two preservatives. At different pH values, preservatives used singly or in combination were shown to be more effective in inhibiting growth at lower pH value of 4.1 than at a higher pH value of 4.5. Taste evaluation of six formulated acidified 0.87 aw/pH 3.7 glycerol-based IMF pineapple products showed all formulations to be acceptable. However, microbial challenge studies showed that of all the six taste-acceptable glycerol-based IMF pineapple products, only the product that contained 0.1 % (w/w) potassium metabisulphite was shelf-stable up to 6 months of storage at 30C and may be commercially viable. PRACTICAL APPLICATIONSThe results of this study will benefit the food industry wherein preservation of intermediate moisture pineapple-based products or other intermediate moisture products is required to overcome contamination problems, especially from xerotolerant yeasts.

Mechanisms of Repair of Low Water Activity and pH-Injured Z ygosaccharomyces rouxii YSa40 in Glycerol and Sucrose/CPB Liquid Holding System

“…; Kuang et al . ). This included the determination of selected a w levels based on solute/water sorption isotherms (using solute: GLY, SUC and glucose [GLU]) and the accuracy checks on a w and pH values.…”

“…Experimental results were ascertained based on previously reported method using Grubbs' test (Grubbs ; Kuang et al . ). Of the three sets of individual experiments, the set with experimental results which showed no significant difference in the mean values, as identified by Grubbs' test, was chosen as the representative.…”

“…; Kuang et al . ), stress system (0.64 a w /pH 3.5 GLY/CPB), LH systems (0.87 a w /pH 3.5 GLY and SUC/CPB) and paired plating media. The paired plating media consisted of 0.94 a w /pH 3.5 sugars (SUC and GLU)/BM agar (lactic acid) and 0.94 a w /pH 3.5 GLY/BM agar (lactic acid).…”