共查询到19条相似文献,搜索用时 746 毫秒
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试验主要研究了预冻温度、预冻时间、保护剂配方、保护剂与菌泥比例、物料厚度等真空冷冻干燥工艺参数对植物乳杆菌MA2活性的影响,并对真空冷冻干燥过程中菌粉的含水量进行了动态监测,绘制了物料升温曲线图,最终确定了合适的真空冷冻干燥工艺为预冻温度70℃;预冻时间2h;保护剂与菌泥的比例为1∶3;保护剂配方为脱脂奶粉10%,海藻糖1.5%,甘油0.5%,山梨醇2%,麦芽糊精1%;冻干厚度为1.5cm,该工艺条件下植物乳杆菌MA2真空冷冻干燥后的菌体存活率达61%,活菌数为1.50× 1012cfu/g.经复水试验证明,真空冷冻干燥后的菌体活性保持良好,证明该工艺具有良好的应用推广前景. 相似文献
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以棘孢木霉(Trichoderma asperelham)为真空冷冻干燥菌种,以菌种存活率、椪柑橘瓣降解时间为评价指标,通过单因素试验研究保护剂添加量、菌液浓度和预冻时间对棘孢木霉真空冷冻干燥效果的影响,在此基础上,采用正交试验优化其真空冷冻干燥工艺,结果表明最佳工艺条件为:保护剂添加量为20%、菌液浓度为1×10~8个/mL、预冻时间为24 h,在此工艺条件下菌株的存活率达到81.25%,橘瓣降解时间最低达到31 min。工艺优化后使得菌种存活率和菌株活性都保持较高水平,其发酵液降解橘瓣所需时间较短,该工艺可用于棘孢木霉的冻干处理。 相似文献
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目前细胞的冻结损伤机制假说主要有2种:IIF(intracellular ice formation)机制和溶质效应损伤机制。这两种损伤机制在冻干过程中共同时细胞产生损伤作用,进而影响双歧杆菌的形态、生理生化性质、分子生物学性质等,导致其在冻干过程中活菌数减少、活力下降。影响双歧杆菌抗冻性的因素有:微生物生理状态、细胞大小、细胞浓度、pH值、冷冻干燥保护剂、预冻温度、降温速率、冷冻干燥条件、细胞含水量等,因此应根据双歧杆菌的冻干损伤机制和抗冻因素来对其冻干实施保护,以提高工业化冻干菌粉的产率。 相似文献
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《食品与发酵工业》2017,(3):14-19
真空冷冻干燥是乳酸菌菌粉制备的关键技术手段,在冻干前须将菌泥与保护剂混匀并进行预冻。文中系统研究了菌泥与保护剂混匀过程中的代谢产酸情况,及产酸引起的pH值降低对预冻的影响。测定了不同菌泥添加保护剂后在室温和冷藏温度下的产酸速率,以及不同pH值下冷冻后菌株的存活率,分析了不同pH值条件下冷冻对菌株ATP酶、β-半乳糖苷酶、乳酸脱氢酶及细胞膜完整性和流动性的影响。结果表明,菌泥与保护剂混合后,室温环境下的产酸速率很快,可在短时间内将菌悬液的pH值降至4.0。而pH值降低确实会对冷冻菌株的存活产生影响,pH值在降至4.0时,菌株冷冻存活率显著降低。低pH值条件下的冷冻,会损伤ATP酶、β-半乳糖苷酶及降低细胞膜的流动性,是导致冷冻存活率降低的原因。因此,为提高真空冷冻干燥的菌株存活率,首先须控制菌泥与保护剂混合时的温度和时间,确保预冻阶段乳酸菌无损失。 相似文献
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Thermal processing of vegetables has pronounced effects on the cell structure, often lowering the final textural properties of the product. In order to investigate the effect of thermal processing on carrot, slices were subjected to different blanching and freezing treatments before frozen storage. Microwave-, steam- or water-blanched material was frozen and then stored at −24 °C. Steam-blanched carrots were subjected to blast freezing or cryogenic freezing at different temperatures before frozen storage. The influence of these process conditions on the texture (maximum load and slope), microstructure, dry matter, sugars, carotene and drip loss was investigated. Microwave blanching differed from the other blanching methods by resulting in a heterogenic cell structure. The content of dry matter, carotene and sucrose was higher following microwave blanching. Blast freezing resulted in low maximum load which seemed to be caused by major tissue damage. Concerning cryogenic freezing, lowering the temperature from −30 °C to −70 °C resulted in better preservation of the native microstructure together with an increase in maximum load, which was most pronounced after one month of storage. No significant effect was observed when lowering the temperature from −30 °C to −70 °C for any of the other measured parameters. © 1999 Society of Chemical Industry 相似文献
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The effect of 14 microbial inoculants on the fermentation and nutritive value of alfalfa silages was studied under laboratory conditions. The first cut (477 g of dry matter/kg) and second cut (393 g of dry matter/kg) of a second-year alfalfa stand were ensiled in 2 trials. In both trials alfalfa was harvested with standard field equipment. All inoculants were applied at 1.0 × 106 cfu/g of crop. Uninoculated silages served as controls. After inoculants were added, the chopped forages were ensiled in 1.0- and 0.5-L anaerobic glass jars, respectively, at a density of 500 g/L. Each trial had 15 treatments (uninoculated control and 14 inoculants), with 4 silos per treatment. Silos were stored for a minimum of 30 d at room temperature (∼22°C). In first-cut silage, all inoculants but one reduced pH relative to the uninoculated control, and all but 2 of the homofermentative strains shifted fermentation toward lactic acid. In second-cut silage, the epiphytic lactic acid bacterial population was 2.7 × 107 cfu/g, and only commercial inoculants produced significant shifts in fermentation. Overall, microbial inoculants generally had a positive effect on alfalfa silage characteristics in terms of lower pH and shifting fermentation toward lactic acid with homofermentative lactic acid bacteria or toward acetic acid with heterofermentative lactic acid bacteria, Lactobacillus buchneri. These effects were stronger in the commercial products tested. In spite of the positive effects on silage fermentation, 48-h in vitro true DM digestibility was not improved by inoculation with lactic acid bacteria. 相似文献