Kim Dong-Hyeon, Chon Jung-Whan, Kang Il-Byeong, Kim Hyunsook, Kim Hong-Seok, Song Kwang-Young, Seo Kun-Ho
KU Center for Food Safety, College of Veterinary Medicine, Konkuk University, Hwayang-dong, Gwangjin-gu, Seoul 143-701, Republic of Korea.
Department of Animal Science and Technology, Konkuk University, Hwayang-dong, Gwangjin-gu, Seoul 143-701, Republic of Korea.
J Food Prot. 2015 Sep;78(9):1651-5. doi: 10.4315/0362-028X.JFP-15-119.
Kefir is a type of fermented milk containing lactic and acetic acid bacteria and yeast. In this study, we evaluated the antimicrobial activity of kefir supernatant against Cronobacter sakazakii in powdered infant formula (PIF). In a spot-on-lawn test, the growth of 20 C. sakazakii strains, including 10 clinical and 10 food isolates, was completely inhibited in the presence of kefir supernatant. Significant differences in the diameters of inhibition zones were observed upon treatment with kefir compared with the results for Lactobacillus kefiri and Candida kefyr culture supernatants or solutions of lactic and acetic acid and ethyl alcohol in the agar well diffusion test (P < 0.05). The addition of 100 μl of kefir supernatant to 1 ml of nutrient broth completely inhibited the growth of C. sakazakii, as evaluated by spectrophotometry. The antimicrobial activity of kefir supernatant in experimentally contaminated PIF was also tested; we found no viable C. sakazakii cells remaining in PIF rehydrated with 30% kefir supernatant solution for 1 h, demonstrating that the antimicrobial activity of kefir supernatant against C. sakazakii could be applied in real food samples.
开菲尔是一种含有乳酸菌、醋酸菌和酵母菌的发酵乳。在本研究中，我们评估了开菲尔上清液对婴儿配方奶粉（PIF）中阪崎肠杆菌的抗菌活性。在点种法试验中，在开菲尔上清液存在的情况下，20株阪崎肠杆菌菌株（包括10株临床分离株和10株食品分离株）的生长被完全抑制。在琼脂扩散试验中，与开菲尔乳杆菌和开菲尔假丝酵母培养上清液或乳酸、醋酸和乙醇溶液处理的结果相比，用开菲尔处理后观察到抑菌圈直径存在显著差异（P<0.05）。通过分光光度法评估，向1 ml营养肉汤中添加100 μl开菲尔上清液可完全抑制阪崎肠杆菌的生长。我们还测试了开菲尔上清液在实验污染的PIF中的抗菌活性；我们发现，用30%开菲尔上清液溶液复水1小时的PIF中没有残留的阪崎肠杆菌活细胞，这表明开菲尔上清液对阪崎肠杆菌的抗菌活性可应用于实际食品样品中。
