反复冻融对速冻水饺菌相变化的影响

本文同时采用PCR-DGGE(聚合酶链式反应-变性梯度凝胶电泳)方法和传统平板培养法两种方法研究了反复冻融条件下造成的温度波动对速冻水饺中微生物数量及其种类多样性的影响。并向水饺中人为添加金黄色葡萄球菌,分析反复冻融条件下金黄色葡萄球菌数量的动态变化及其对水饺中菌相的影响。研究结果表明随着反复冻融次数的增加,水饺中的微生物数量均呈显著增加趋势(P0.05),人工接种金黄色葡萄球菌处理组水饺中金黄色葡萄球菌数量从速冻后的3.49 lg CFU/g增加至5.07 lg CFU/g,已经达到了可导致葡萄球菌属中毒的水平(105CFU/g)。PCR-DGGE结果表明,乳酸菌、假单胞菌和热杀索丝菌为反复冻融过程水饺中的优势菌株,葡萄球菌属在后期数量较多成为反复冻融后期的优势菌株,与传统平凡培养方法结果基本一致。

Effect of Multiple Freeze-thaw Cycles on the Microflora of Quick-frozen Dumplings

The effect of temperature fluctuations caused by repeated freeze-thaw cycles on the number and diversity of microorganisms in quick-frozen dumplings was investigated using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and traditional plate culture methods. The dumpling fillers were inoculated with Staphylococcus aureus to analyze the dynamic changes in S. aureus itself and its influence on the dumpling microflora. The results showed that the quantity and diversity of microorganisms in the dumplings increased significantly (p < 0.05) with increasing freeze-thaw cycles. At the last cycle, S. aureus count in the inoculated dumplings increased from 3.49 to 5.07 log10 CFU/g, which reached the minimum count for Staphylococcal toxicity, of 105 CFU/g. PCR-DGGE showed that lactic acid bacteria, Pseudomonadales bacterium and Brochothrix thermosphacta were the dominant strains in the dumplings during the freeze-thaw cycles, while the counts of S. aureus increased and finally became the dominant strain. The results of PCR-DGGE and the traditional culture method were generally consistent.