【作者】 王俊国；

【导师】 张和平；

【作者基本信息】 内蒙古农业大学 ， 农产品加工及贮藏工程， 2003， 硕士

【摘要】 本课题对含Nisin脱脂乳粉的制备及应用进行了系统的研究，主要研究结果如下： 以乳酸乳球菌PCM2379为出发菌株，经紫外线及氯化铯复合诱变使其产Nisin能力提高了32％。以脱脂乳为基础培养基，通过添加酵母粉，及在发酵过程中调控pH值，使产Nisin能力提高了3倍，达到1800IU／ml。 在杀菌后，将含Nisin的脱脂乳真空冷冻制成粉。脱脂乳粉中Nisin的热变性属于1.8级反应。在70℃、80℃、90℃、100℃条件下其D值分别为184.91min、77.18min、21.53min、9.37min，在此温度范围内Z值为22.52℃，表观活化能为122.033KJ／mol。采用LTLT(63℃ 30min)和HTST(85℃15s)巴氏杀菌，其效价分别下降到86.82％、98.2％，采用UHT(115℃ 10min、130℃2s)灭菌其效价分别下降到3.43％、80.58％。 将含Nisin的脱脂乳粉分别添加到原料乳、鲜乳、酸奶中，观察其在乳制品中的应用：添加30-70IU／ml的Nisin可使原料乳中的细菌、芽孢菌的生长明显受到抑制，酸度变化明显缓慢，但低温菌生长受影响不大；添加35IU／mlNisin可明显延长鲜乳的保质期2-3倍；即使添加少量Nisin(5IU／ml)也会影响酸奶的发酵过程。更多还原

【Abstract】 This research subject is to prepare skimed milk powder containing Nisin and toapplicate it in dairy products. Research results are as follow:A mutant strain with hight yield of Nisin was obtained from lactococcus lactis 2379 by many mutagenetic treatment with ultraviolet ray and CsCL. Compared with primitive strain , the Nisin potency of the mutant strain was increased by over 32%. Through neutralize test to control pH changes during fermentation, the strain produced at least 3-fold greater bacteriocin in skimed milk culture supplemented with yeast extract} and the Nisin potency was 1800IU/ml. After pasteurized, the skimed milk powder containing Nisin was prepared by using lyophilization. Thermodynamic analysis indicated that the number of reaction degree of heat denaturation of Nisin in skimed milk powder was n=1.8. At temperatures of 70℃, 80℃ ,90℃, 100℃, D values for Nisin denaturation were 184.91min, 77.18min, 21.53min,and 9.37min respectively. With this temperature range,Z value was 22.52, and the apparent active energy was 122.033KJ/mol. LTLT(63 ℃ ,30min)and HTST(85℃ ,15s)pasteurization made the Nisin potency decrease to 86.82%and 98.2%,UHT(115℃ 10min, 130℃2s )sterilization made the Nisin potency decrease to 3.43% and 80.58%. Concentration of 30-70IU/ml Nisin in raw milk was able to inhibit the growth of bacteria and spores-forming bacteria, but the effect of Nisin on the growth of psychrotrophic bacteria was weak; Concentration of 35IU/ml Nisin was able to extend the shelf-life of sterilized milk up to 30 days at 4℃, three times longer than the control group; during fermentation, concentration of 5IU/ml Nisin was able to inhilit the growth of lactic bacteria.更多还原