蒸煮贻贝冰温贮藏保鲜剂的筛选、优化及评价

目的 筛选用于改善冰温贮藏蒸煮贻贝品质、延长蒸煮贻贝保质期的生物保鲜剂,对复合保鲜剂的配方及保鲜工艺进行优化,并评价其保鲜效果。方法 通过测定保鲜剂作用于贻贝优势腐败菌的抑菌圈大小,筛选出抑菌效果较强的保鲜剂,运用响应面法优化复合保鲜剂配方,采用肉汤稀释法测定最小抑菌浓度(minimuminhibitoryconcentration,MIC);利用正交实验确定复合保鲜剂用于蒸煮贻贝保鲜的最佳工艺;通过测定蒸煮贻贝冰温贮藏8 d后的感官评分、pH、挥发性盐基氮(total volatile basic nitrogen, TVB-N)含量、菌落总数、汁液流失率来评价复合保鲜剂的效果。结果 筛选出的3种保鲜剂分别为溶酶菌、乳酸链球菌素和丁香酚,复合保鲜剂对枯草芽孢杆菌和假单胞菌的MIC分别为16、8μg/mL,复合保鲜剂的优化配方(质量分数)为溶菌酶4%、乳酸链球菌素2%和丁香酚0.75%,最佳保鲜工艺为保鲜剂溶液p H 5.5、料液比1:2.5 (m:V)、浸泡时间60 min,采用优化的配方和工艺用于蒸煮贻贝的冰温贮藏,贻贝品质的综合评分为空白样品的2倍。结论 复合保鲜剂可以有效改善蒸...     

Effect of liquid fermented Chinese edible Ganoderma Lucidum fungus on wheat bread: A quality improver and staling inhibitor

People's pursuit to additive-free products inspired us to find natural functional compositions to improve bread quality. Ganoderma Lucidum is used as nutraceutical Chinese traditional edible fungus for thousands of years. In this study, Ganoderma Lucidum fermentation broth were prepared by liquid fermentation to obtain high-yield of functional components like polysaccharides that exhibited water holding ability to restrict water migration and inhibited starch retrogradation in bread crumb. The data demonstrated the fermentation broth added to dough, whether sterilized or not, could improve the bread quality, especially decrease crumb softness. Dose-response relationship was observed, however when the addition amount exceeded the critical concentration, there was no more improvement in bread quality. The detection of volatile organic components in bread indicated Ganoderma Lucidum fermentation broth promoted the generation of the aroma of bread and enriched the flavor. This research suggested Ganoderma Lucidum fermentation broth whether sterilized or not could both improve bread quality and offer a potential strategy of additive-free ameliorant for prolonging bread shelf-life in industrial process.     

Combination effects of ultrasound and citral nanoemulsion against Shigella flexneri and the preservation effect on fresh-cut carrots

This present study evaluated the effect of ultrasound (US), citral nanoemulsion (CLON) and combined treatments on the inactivate effectiveness of Shigella flexneri in phosphate-buffered saline (PBS) and on the surface of fresh-cut carrots. In this study, CLON was produced by ultrasonic nanoemulsification. Results demonstrated that US + CLON treatment significantly (P < 0.05) improved the bactericidal effect against Sh. flexneri, especially 0.15 mg/mL of CLON combined with US (20 kHz, 345 W/cm²) treatment for 9 min decreased the number of Sh. flexneri by 8.55 log CFU/mL. The assay of reactive oxygen species (ROS) and malondialdehyde (MDA) levels indicated that US + CLON aggravated oxidative stress and lipid peroxidation in cell membranes. The leakage of cell constituents (proteins and nucleotide) demonstrated that the permeability and integrity of the cell membrane was significantly (P < 0.05) impaired. Field-emission scanning electron microscopy further showed that US + CLON exacerbates the disruption of the bacteria morphology. Confocal laser scanning microscopic and flow cytometry observed US + CLON treatment enhanced the changes of bacterial cell membrane integrity. Meanwhile, US + CLON was effective in reducing the presence of bacteria on the surface of fresh-cut carrots, and had no negative effects on the quality of fresh-cut carrots in terms of colour, hardness and weight during storage. Overall, this present study revealed ultrasound combined with CLON is a promising and viable cleaning method for improving the microbiological safety of fresh produce.