Mian M A, Fleet G H, Hocking A D
Department of Food Science and Technology, University of New South Wales, Kensington, Australia.
Int J Food Microbiol. 1997 Apr 1;35(2):103-7. doi: 10.1016/s0168-1605(96)01208-1.
The effects of seven diluent types on the viability of yeasts enumerated from foods and in pure culture were studied. The diluents were laboratory glass distilled water; saline water (0.85% NaCl), sodium phosphate buffer (0.1 M, pH 7.0), 0.1% peptone, 0.1% yeast extract, 0.1% peptone in 0.1 M sodium phosphate buffer, pH 7.0, and 0.1% malt extract. For all foods studied, dilution in 0.1% peptone gave the highest counts, with saline and phosphate buffer diluents giving lower counts than those obtained with distilled water. When seven species of yeast were enumerated in pure culture, highest counts were obtained using 0.1% peptone as the diluent and, with three exceptions, all species gave higher counts when diluted in diluents other than distilled water. When yeast suspensions were held in diluents for up to 2 h before plating, cell death occurred. The extent of death was highest in distilled water, saline and phosphate buffer diluents. Cell death also occurred in 0.1% peptone, yeast extract and malt extract, but to a lesser degree.
研究了七种稀释剂类型对从食品中分离出的酵母以及纯培养酵母活力的影响。这些稀释剂分别是实验室玻璃蒸馏水；盐水（0.85%氯化钠）、磷酸钠缓冲液（0.1M，pH7.0）、0.1%蛋白胨、0.1%酵母提取物、pH7.0的0.1M磷酸钠缓冲液中的0.1%蛋白胨以及0.1%麦芽提取物。对于所有研究的食品，用0.1%蛋白胨稀释得到的菌落数最高，盐水和磷酸盐缓冲液稀释剂得到的菌落数低于用蒸馏水得到的菌落数。当对七种酵母进行纯培养计数时，使用0.1%蛋白胨作为稀释剂得到的菌落数最高，除了三个例外，所有酵母在除蒸馏水以外的稀释剂中稀释时菌落数都更高。当酵母悬液在接种前在稀释剂中保存长达2小时时，细胞会死亡。在蒸馏水、盐水和磷酸盐缓冲液稀释剂中细胞死亡程度最高。在0.1%蛋白胨、酵母提取物和麦芽提取物中也会发生细胞死亡，但程度较小。
