为实现植物乳杆菌在苹果汁中的发酵增殖及低温贮藏期间的活性保持,测定苹果汁先后添加无机盐、营养因子和微量元素后菌株的增殖浓度,并比较发酵果汁在添加不同保护剂后4℃冷藏期间的活菌数。发现KH2PO4、柠檬酸钠、酵母粉和MnSO4是植物乳杆菌在苹果汁中发酵增殖的关键因子,其添加量分别为5、7、5和0.05 g/L时菌株发酵12 h活菌数达(3.4±0.2)×109 CFU/mL,且抗性糊精更有利于菌体的活性保持。发酵结束离心收集菌体,以不同浓度的抗性糊精为保护剂制备粒径大小不同的海藻酸钠微胶囊,测定其在果汁中冷藏期间的活菌数。结果表明,抗性糊精浓度为200 g/L,粒径为4 mm的微胶囊显著提高植物乳杆菌在发酵苹果汁中的活性保持,冷藏21 d后存活率达(81±3.1)%。该研究解决了植物乳杆菌在发酵苹果汁高密度增殖的难题,且为含活性菌发酵果蔬汁的研发提供了指导方法。
Proliferation of Lactobacillus plantarum in apple juices and corresponding viable preservation during low-temperature storage was studied. The amounts of viable bacteria in fermented apple juices were determined after adding inorganic salts, nutrient factors and trace elements, respectively, and the survival rate of L. plantarum in was assayed as a function of different protective agents. It was found that 5 g/L potassium dihydrogen phosphate, 7 g/L sodium citrate, 5 g/L yeast powder, and 0.05 g/L manganese sulfate promoted L. plantarum proliferation in apple juices to (3.4±0.2)×109 CFU/mL. Resistant dextrin was more beneficial for maintaining the vitality. The sodium alginate microcapsules with different particle sizes were prepared with resistant dextrin of different concentrations as protective agents, and the microcapsule with 4 mm particle size and 200 g/L resistance dextrin significantly improved the survival rate of L. plantarum to (81±3.1)% after 21 d storage at 4 ℃.This study solved the problem of high-density proliferation of L. plantarum in fermented apple juices, which provides guidance for developing fermented fruit and vegetable juices containing viable lactic acid bacterium.
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