Ascorbic acid enhances destruction of Escherichia coli O157:H7 during home-type drying of apple slices
Ascorbic acid enhances destruction of Escherichia coli O157:H7 during home-type drying of apple slices
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DOI：
10.4315/0362-028x-64.8.1244
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发表时间：
2001-08-01
影响因子：
2
通讯作者：
Sofos, JN
中科院分区：
文献类型：
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作者：
Burnham, JA;Kendall, PA;Sofos, JN
对接种在两种温度下脱水的苹果片进行了预干燥处理对大肠杆菌O157：H7的杀灭效果进行了评价。半圆片(0.6厘米。去皮和去核的嘎拉苹果在四菌株O157：H7复合接种剂中浸泡30min。接种的切片(8.7至9.4logCFU/g)不进行预干燥处理(对照组)，在3.4%抗坏血酸溶液中浸泡15分钟，或在88℃蒸汽漂白3分钟，然后在57.2℃或62.8℃干燥长达6小时。将样品接种在胰酶大豆(TSA)和山梨醇麦康基(SMAC)琼脂上，直接计数存活细菌数量。蒸汽漂白改变了初始接种量+0.3~-0.7logcfu/g，而浸泡在抗坏血酸溶液中使接种量降低了1.4~1.6logcfu/g。对照样品脱水6h，平均细菌数量在57.2℃时降低了2.9logcfu/g(TSA或SMAC)，在62.8℃时分别降低了3.3(SMAC)和3.5(TSA)logCFU/g。干燥6h后，蒸汽漂白切片的平均接种量在57.2℃时分别为2.1(Smac)和2.0(TSA)logcfu/g，在62.8℃时为3.6(TSA或Smac)logcfu/g。相反，经抗坏血酸处理的苹果片在57.2℃下脱水3h后，初始细菌数量下降了5.0(SMAC)和5.1(TSA)logcfu/g，在62.8℃下脱水3h后，初始细菌数量下降了7.3(SMAC)和6.9(TSA)logcfu/g。无论干燥温度或所使用的琼脂介质如何，在干燥6小时后，用抗坏血酸处理的切片的减少量在8.0到8.3logCFU/g的范围内。将苹果片在3.4%抗坏血酸溶液中浸泡15min后干燥，结果表明，预干燥处理可增强国产苹果干燥产品上的大肠杆菌O157：H7的破坏作用。
Destruction of Escherichia coli O157:H7 was evaluated on inoculated apple slices dehydrated at two temperatures with and without application of predrying treatments. Half-ring slices (0.6 cm. thick) of peeled and cored Gala apples were inoculated by immersion for 30 min in a four-strain composite inoculum of E. coli O157:H7. The inoculated slices (8.7 to 9.4 log CFU/ g) either received no predrying treatment (control), were soaked for 15 min in a 3.4% ascorbic acid solution, or were steam blanched for 3 min at 88 degreesC immediately prior to drying at 57.2 or 62.8 degreesC for up to 6 h. Samples were plated on tryptic soy (TSA) and sorbitol MacConkey (SMAC) agar media for direct enumeration of surviving bacterial populations. Steam blanching changed initial inoculation levels by +0.3 to -0.7 log CFU/g, while immersion in the ascorbic acid solution reduced the inoculation levels by 1.4 to 1.6 log CFU/g. Dehydration of control samples for 6 h reduced mean bacterial populations by 2.9 log CFU/g (TSA or SMAC) at 57.2 degreesC and by 3.3 (SMAC) and 3.5 (TSA) log CFU/g at 62.8 degreesC. Mean decreases from initial inoculum levels for steam-blanched slices after 6 h of drying were 2.1 (SMAC) and 2.0 (TSA) log CFU/g at 57.2 degreesC, and 3.6 (TSA or SMAC) log CFU/g at 62.8 degreesC. In contrast, initial bacterial populations on ascorbic acid-pretreated apple slices declined by 5.0 (SMAC) and 5.1 (TSA) log CFU/g after 3 h of dehydration at 57.2 degreesC, and by 7.3 (SMAC) and 6.9 (TSA) log CFU/g after 3 h at 62.8 degreesC. Reductions on slices treated with ascorbic acid were in the range of 8.0 to 8.3 log CFU/g after 6 h of drying, irrespective of drying temperature or agar medium used. The results of immersing apple slices in a 3.4% ascorbic acid solution for 15 min prior to drying indicate that a predrying treatment enhances the destruction of E. coli O157:H7 on home-dried apple products.