Jaquette C B, Beuchat L R
Center for Food Safety and Quality Enhancement, University of Georgia, Griffin 30223-1797, USA.
J Food Prot. 1998 Dec;61(12):1629-35. doi: 10.4315/0362-028x-61.12.1629.
The potential for growth of enterotoxigenic Bacillus cereus in reconstituted dry foods is a concern, especially when they are consumed by infants or the immunosuppressed. The ability of a four-strain mixture of spores or vegetative cells of psychrotrophic B. cereus to survive in a commercial, dry infant rice cereal as affected by water activity (a(w); 0.27 to 0.28, 0.52 to 0.55, and 0.75 to 0.78), pH (5.6 and 6.7), and temperature (5, 25, 35, and 45 degrees C) was investigated. The rate of death of vegetative cells in dry cereal stored for 36 weeks was not affected by a(w) or pH. Death of spores in cereal stored at 45 degrees C for up to 48 weeks was enhanced at a(w) 0.78 but was unaffected by pH; loss of viability at 5, 25, and 35 degrees C was largely unaffected by differences in a(w). The effect of temperature (8, 15, 21, and 30 degrees C) on outgrowth of spores of B. cereus inoculated at three levels (0.14, 14, and 133 CFU/g, dry weight basis) into cereal reconstituted with apple juice and commercial pasteurized milk (2% fat) was also studied. Outgrowth of spores did not occur in cereal reconstituted with apple juice. Cereal reconstituted with milk and inoculated with 0.14, 14, and 133 spores per g contained >3 log CFU/g within 24, 9, and 6 h, respectively, at 21 degrees C. Populations in cereal reconstituted with milk and inoculated with 133 CFU of B. cereus spores per g reached 7.11, 7.72, and 7.40 log CFU/g within 12, 48, and 72 h when stored at 30, 21, and 15 degrees C, respectively. The organism grew in cereal reconstituted with milk and held at 8 degrees C for 72 h; however, enterotoxin was not detected. In reconstituted cereal inoculated with 133 spores per g, enterotoxin was detected (detection limit 16 ng/g) after 24, 48, and 72 h at 30, 21, and 15 degrees C, respectively, when the population of B. cereus reached >7 log CFU/g. It is recommended that reconstituted infant foods be either consumed immediately or held at < or = 8 degrees C and consumed within 48 h after preparation.
产肠毒素蜡样芽孢杆菌在复水干燥食品中的生长可能性令人担忧，尤其是当这类食品被婴儿或免疫功能低下者食用时。研究了嗜冷蜡样芽孢杆菌的四菌株孢子或营养细胞混合物在商业干燥婴儿米粉中，受水分活度（aw；0.27至0.28、0.52至0.55和0.75至0.78）、pH值（5.6和6.7）以及温度（5、25、35和45℃）影响的存活能力。储存36周的干燥米粉中营养细胞的死亡速率不受水分活度或pH值的影响。在45℃下储存长达48周的米粉中，孢子在水分活度为0.78时死亡加速，但不受pH值影响；在5、25和35℃下活力丧失在很大程度上不受水分活度差异的影响。还研究了温度（8、15、21和30℃）对接种于用苹果汁和市售巴氏杀菌牛奶（2%脂肪）复水的米粉中三种水平（0.14、14和133 CFU/g，以干重计）蜡样芽孢杆菌孢子萌发的影响。用苹果汁复水的米粉中孢子未萌发。用牛奶复水并分别接种每克0.14、14和133个孢子的米粉，在21℃下分别在24、9和6小时内含有>3 log CFU/g。用牛奶复水并接种每克133 CFU蜡样芽孢杆菌孢子的米粉，分别在30、21和15℃下储存12、48和72小时后，菌数达到7.11、7.72和7.40 log CFU/g。该菌在用牛奶复水并在8℃下保存72小时的米粉中生长；然而，未检测到肠毒素。在每克接种133个孢子的复水米粉中，当蜡样芽孢杆菌菌数达到>7 log CFU/g时，分别在30、21和15℃下24、48和72小时后检测到肠毒素（检测限1 ng/g）。建议复水婴儿食品要么立即食用，要么保存在≤8℃并在制备后48小时内食用。
