We investigated the growth parameters of Saccharomyces rouxii isolated from spoiled chocolate syrup. The optimum pH range for S. rouxii was 3.5 to 5.5, whereas the minimum and maximum pH values that permitted growth were 1.5 and 10.5, respectively. For cells grown in 0 and 60% sucrose the optimum water activity (a,) values were 0.97 and 0.96, respectively. The optimum temperature for S. rouxii increased with a decreasing a, regardless of whether glucose or sucrose was used as the humectant. The optimum temperatures for S. rouxii were 28°C at an a. of >0.995 and 35°C at an a, of 0.96 to 0.90 in 2x potato dextrose broth with sucrose. Increasing the sorbate concentration (from 0.03 to 0.10%) caused the growth of S. rouxii to become more inhibited between a,s of >0.995 and 0.82. S. rouxii did not grow when the sorbate level was 0.12% (wt/vol). At lower sorbate levels, the effect of sorbate on the growth of S. rouxii depended on

The effects of hydrochloric, citric, lactic, phosphoric and malic acids in combination with potassium sorbate on the growth of Saccharomyces bailii, Saccharomyces acidifaciens (Saccharomyces bailii var. osmophilus), Saccharomyces rouxii and Saccharomyces bisporus were evaluated. Double strength potato dextrose broth supplemented with 58% (wt/vol) sucrose, 14% (wt/vol) glucose, and 0.2% agar acidulated to a pH of 5.0 to a final aw of 0.88 to 0.89 was used as the growth medium. In general, at 0.05% potassium sorbate, S. rouxii and S. bisporus were more resistant than S. bailii and S. acidifaciens to the antimycotic agent independent of the acid used to acidulate the growth medium, whereas 0.1% potassium sorbate inhibited the growth of the four yeast strains. At 0.05% potassium sorbate, growth occurred (1 log number yeast cells/ml) for S. acidifaciens in the lactic acid/sorbate combination after 36 h of incubation, whereas a bacteriostatic relationship existed for the other acids employed. Citric acid potentiated the antimicrobial effectiveness of 0.05% potassium sorbate at pH 5.0 against the growth of S. rouxii and S. bisporus by either delaying the lag phase or reducing the growth rate.

Effects of preconditioning Saccharomyces rouxii to various sucrose and sorbate concentrations were investigated. Cells were preconditioned to 0 and 60% (wt/vol) sucrose without and with 0. 1% (wt/vol) sorbate by a series of four transfers in potato dextrose broth (PDB). The preconditioned cells were inoculated in growth medium containing 0, 30, or 60% (wt/vol) sucrose with 0. 0.05, or 0.1% (wt/vol) sorbate and in chocolate syrup without and with 0.1% (wt/vol) sorbate. Preconditioning of S. rouxii cells to 0 and 60% sucrose offered no advantage for growth in a medium containing 0, 30 or 60% sucrose. When S. rouxii cells were preconditioned in 0.1% sorbate, an increased resistance to sorbate occurred. S. rouxii cells preconditioned in 60% sucrose/0.1% sorbate were more sensitive to sorbate than cells preconditioned in 0% sucrose/0.1% sorbate. Regardless of the sucrose level, S. rouxii cells, preconditioned in 0. 1% sorbate showed an increased resistance to sorbate when inoculated into the growth medium and the chocolate syrup.

Standard Potato Dextrose Agar (PDA) was inferior to PDA/60% sucrose plating medium for enumerating osmotolerant yeasts from a high-sugar food product. The largest disparity in the number of Saccharomyces rouxii cells (>2.00 log number cells/g) recovery by PDA/60% sucrose and standard PDA was during the lag and early log phase. The optimum growth temperatures of S. rouxii propagated in double strength (2X) Potato Dextrose Broth (PDB) were 28°C at 0.995 aw level and 35°C for 0.92 and 0.90 aw levels. No significant (P>0.05) difference was determined between shaking and stomaching for enumeration of S. rouxii, an osmotolerant yeast, from chocolate syrup. Therefore, use of PDA/60% sucrose incubated at 35°C for 5 d is recommended for enumeration of osmotolerant yeasts from a liquid high-sugar product.

With an initial microbial level of ca. 107 microorganisms per g of Ivory Coast cacao beans, 5 kGy of gamma radiation Linder an atmosphere of air reduced the microflora per g by 2.49 and 3.03 logs at temperatures of 35 and 50°C, respectively. Bahia cacao beans were artificially contaminated with dried spores of Aspergilliusflaias and Penicillium citrinurm, giving initial fungal levels of 1.9 x 104 and 1.4 x 103 spores per g of whole Bahia cacao beans, respectively. The average D (values for A. flaiw'is and P. citrinum spores on Bahia cacao beans were 0.64 and 0.88 kGy. respectively.