Nortjé K, Buys E M, Minnaar A
Department of Food Science, University of Pretoria, South Africa.
Food Microbiol. 2006 Dec;23(8):729-37. doi: 10.1016/j.fm.2006.02.001. Epub 2006 Apr 3.
Moist beef biltong strips (mean moisture content = 53.6%, NaCl content = 1.91% and a(w) = 0.979) was inoculated with Staphylococcus aureus ATCC 9441 (10(6)-10(7) cfu/g), or sprayed with distilled water (non-inoculated controls). Both non-inoculated and inoculated biltong strips were coated with a casein-whey protein (1:1) edible coating followed by irradiation to a target dose of 4 kGy. S. aureus, aerobic plate, yeast and mould counts were performed to determine the effect of gamma-irradiation and the edible coating on inoculated S. aureus and the spoilage flora of the biltong. Moisture and NaCl content, a(w) and pH measurements were also performed. None of the intrinsic properties were affected to a practically significant extent. Irradiation reduced all microbial counts (P < 0.05), i.e. inoculated S. aureus (6 log cycles), aerobic plate count (5-6 log cycles) and yeast and mould counts (1-2 log cycles). Irradiation at 4 kGy is thus effective to ensure safety of moist beef biltong, and provided that initial fungal counts are not excessive, may extend the shelf-life. The edible coating had no significant effect (P > 0.05) on microbial counts, possibly because the high moisture content of the biltong diminished its oxygen barrier properties.
将水分含量为53.6%、氯化钠含量为1.91%、水分活度为0.979的湿润牛肉干条接种金黄色葡萄球菌ATCC 9441（10⁶ - 10⁷ cfu/g），或喷洒蒸馏水（未接种对照）。未接种和接种的牛肉干条均涂有酪蛋白 - 乳清蛋白（1:1）可食用涂层，然后辐照至目标剂量4 kGy。进行金黄色葡萄球菌、好氧平板计数、酵母和霉菌计数，以确定γ辐照和可食用涂层对接种的金黄色葡萄球菌以及牛肉干腐败菌群的影响。还进行了水分和氯化钠含量、水分活度和pH测量。没有任何内在特性受到实际显著影响。辐照降低了所有微生物计数（P < 0.05），即接种的金黄色葡萄球菌（6个对数循环）、好氧平板计数（5 - 6个对数循环）以及酵母和霉菌计数（1 - 2个对数循环）。因此，4 kGy的辐照有效地确保了湿润牛肉干的安全性，并且如果初始真菌计数不过高，可能会延长保质期。可食用涂层对微生物计数没有显著影响（P > 0.05），这可能是因为牛肉干的高水分含量降低了其氧气阻隔性能。
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