Amaguaña R M, Hammack T S, Andrews W H
U.S. Food and Drug Administration, Division of Microbiological Studies, Washington, DC 20204, USA.
J AOAC Int. 1998 Jul-Aug;81(4):721-6.
Foods analyzed for Salmonella spp. by the procedure in the U.S. Food and Drug Administration's Bacteriological Analytical Manual are preenriched at a 1:9 test portion/broth ratio. Various thickening agents preenriched at this ratio become viscous and nonpipettable after 24 h incubation at 35 degrees C. The effects of 3 factors (presence of inorganic salts, adjustment of pH, and presence of enzymes) on the viscosity of the test portion/preenrichment mixtures of various thickening agents during incubation were determined. Reduction of the viscosities of these thickening agents was accomplished as follows: carboxymethylcellulose gum, addition of cellulase to a final concentration of 0.10% in lactose broth preenrichment and incubation with no pH adjustment; gum ghatti, addition of NaCl to a final concentration of 0.10% in lactose broth preerichment and adjustment of the pH to 6.5; and gelatin, addition of papain to a final concentration of 0.10% in lactose broth preenrichment and adjustment of the pH to 6.8. With these modified preenrichments, one Salmonella spp. cell/25 g (representing an approximate most probable number value of 0.04 cell/g) was generally recovered from the thickening agents.
按照美国食品药品监督管理局《细菌学分析手册》中的程序对沙门氏菌进行分析的食品，其预增菌时的检验样品与肉汤比例为1:9。在此比例下预增菌的各种增稠剂在35℃培养24小时后会变得粘稠且无法用移液器吸取。测定了3个因素（无机盐的存在、pH值的调节和酶的存在）对培养期间各种增稠剂的检验样品/预增菌混合物粘度的影响。降低这些增稠剂粘度的方法如下：羧甲基纤维素胶，在乳糖肉汤预增菌中添加纤维素酶至终浓度0.10%，且不调节pH值进行培养；印度树胶，在乳糖肉汤预增菌中添加NaCl至终浓度0.10%，并将pH值调节至6.5；明胶，在乳糖肉汤预增菌中添加木瓜蛋白酶至终浓度0.10%，并将pH值调节至6.8。通过这些改良的预增菌方法，通常能从增稠剂中检出1个沙门氏菌细胞/25克（相当于约0.04个细胞/克的最可能数）。
