NISIN: A BACTERIOCIN WITH A POTENTIAL USE IN BREWING

Depending on the amount used and the strain of bacteria involved, nisin either kills lactic acid bacteria or inhibits their growth. In medium inoculated with approximately 10⁵ cells ml^?1 of a sensitive strain of Lactobacillus (BSO 375) nisin, added at levels recommended for commercial use (100 International Units ml^?1, killed all the cells in less than 6 h. In the absence of nisin this inoculum grew to a concentration of 10¹⁰ cells ml^?1 in about 50 h. Lower nisin concentrations killed fewer cells but inhibited the growth of those still viable. For the more resistant strain Lactobacillus (BSO 343) growth was only inhibited at the higher nisin concentrations. Nisin maintained its activity against lactic acid bacteria in brewing fermentations. It had no effect on the growth and fermentative performance of the 9 brewing yeast strains tested, and, in a pilot brewery fermentation, had no deleterious affect on the taste of the beer produced. Nisin could be used either as a preventative measure by regular addition to fermentations, or as a remedial measure once contamination by lactic acid bacteria had been detected.     

Effect of nisin on the growth of Staphylococcus aureus determined by a microcalorimetric method

A novel microcalorimetric technique based on the bacterial heat output was applied to evaluate the biological effect of nisin on the growth of Staphylococcus aureus. The thermogenic curves of S. aureus in the presence of nisin were studied by an LKB-2277 Thermal Activity Monitor. The thermokinetic parameters, such as the growth rate constant (k), the generation times (G), the inhibitory ratio (I), and the half inhibitory concentration (IC50), for the growth of S. aureus at different nisin concentrations were determined. The relationship between the growth rate constant (k) and the concentration of nisin (c) is nearly linear, which can be modeled by the formula k = 0.03794 - 4.005 x 10(-4) x c, with a correlation coefficient of -0.9971. Based on this model, we obtained the critical inhibitory concentration of nisin on the growth of S. aureus at 94.73 IU/mL. We proposed that this microcalorimetric method could be a useful tool in monitoring the biological effect of nisin on microorganisms, and providing valuable information on the study of microorganism metabolisms.     

乳酸链球菌素在即食腊肉制品保藏应用中的研究

采用正交实验、感官评定、破坏性实验及微生物分析等实验手段,全面研究了乳酸链球菌素及相关因素对即食腊肉质量的影响。找出了用乳酸链球菌素保藏即食腊肉的最佳工艺条件。     

以乳链菌肽为主的复合防腐剂对低温火腿肠保质期、色泽和质构的影响

采用正交试验方案筛选得到以乳链菌肽(Nisin)为主的复合防腐剂,可以延缓低温火腿肠中的微生物引起的腐败,保质期达到3个月.在研究Nisin复合防腐剂延长低温火腿肠保质期的同时,分析了添加Nisin等食品添加剂对低温火腿肠色泽和质构的影响.结果表明低温火腿肠的色泽在辅料A0.25～0.50g/kg,辅料B20～25g/kg,辅料C1.5g/kg,辅料D0.15～0.25g/kg时较理想;低温火腿肠的硬度只与辅料A和辅料B二因素有关,当辅料A0.10g/kg,辅料B20g/kg时硬度较大.低温火腿肠的弹性在辅料A0.10g/kg,辅料B1.5g/kg,辅料C0.15g/kg时较好     

综合保鲜技术对冷却牛肉的保质研究

本文筛选了茶多酚、乳酸菌肽、胶原蛋白、壳聚糖等组成的复合天然保鲜膜,结合真空包装技术对冷却牛肉的保鲜效果进行研究。并测定菌落总数、大肠菌群、水分活度、汁液渗出率、pH、嫩度、H2S、TVB-N等指标。主要以TVB-N来判定冷却肉最终新鲜度。结果表明:对照组的保质期仅为6d,试验三、五组均可使冷却肉的保质期达到18d以上,试验五组对冷却肉的保鲜效果明显优于其它组,可使保质期达到21d以上。     

Synergistic effect of nisin and garlic shoot juice against Listeria monocytogenes in milk

The aim of this research was to determine the synergistic effect of nisin and garlic shoot juice (GSJ) against Listeria monocytogenes ATCC 19118 found in whole (3.5%), low (1%) and skim (no fat content) milk. Garlic shoot juice (GSJ) at concentrations of 2.5%, 5% and 10% revealed strong and similar patterns of antilisterial effect against L. monocytogenes ATCC 19118 in all categories of milk. Nisin only at concentrations of 62.5, 125, 250 and 500 IU/ml displayed a strong antilisterial effect as compared to the control group. Also, the synergistic combinations of GSJ (2.5%, 5%) and nisin (62.5, 125, 250 and 500 IU/ml) had a remarkable antilisterial activity in all categories of whole, low and skim milk after 14 days. Results of this study indicated the synergistic effect of GSJ and nisin as a potential antilisterial agent for the food industry.     

乳链菌肽效价测定方法的研究

对琼脂扩散法测定乳链菌肽效价的条件进行了研究,利用标准曲线的斜率和y轴截距评价测定的精确度和灵敏度。结果表明,当使用检测培养基（一）,溶壁小球菌作为检测指示菌,菌悬液浓度约107ctu／ml,检测培养基琼脂浓度0.75％,琼脂层厚度2mm时,测定结果有较高的精确度、灵敏度;吐温20的添加使精确度略有下降。     

Applicability of lactic acid and nisin to improve the microbiological quality of cold-smoked rainbow trout

 The effect of lactic acid and nisin whey permeate on the microbiological and sensory quality of cold-smoked rainbow trout was studied. Lactic acid and whey permeate were mixed with salt solution and injected into fish fillets in concentrations of up to 2.5 g/kg lactic acid, 30 g/kg whey permeate and 20 g/kg sodium chloride. After smoking at 28  °C for 6 h the fillets were sliced, vacuum packed and stored at 3  °C. The aerobic and anaerobic/facultative anaerobic counts were measured after 1, 8, 15, 22 and 29 days of storage. The influence of the treatment on the sensory characteristics was analysed after 8 and 22 days by sensory profiling. A triangle test was used in order to ascertain at which stage the sensory quality of the samples changed during storage. Bacterial counts of smoked fish stored for 29 days were lowest in those samples containing a combination of lactic acid, sodium chloride and nisin whey permeate. Lactic acid alone did not affect the odour or flavour characteristics of the fish but did affect their texture as determined by sensory evaluation making it less elastic when stored at +3  °C for 8 days. A combination of lactic acid and nisin whey permeate enhanced the characteristic fishy flavour of the product. Differences between treatments in elasticity and fishy flavour were not detected after 22 days of storage. According to the triangle test, the samples from all treatments remained unchanged over the first 15 days. Received: 23 March 1998 / Revised version: 19 June 1998     

不同培养基质和食品添加剂对金黄色葡萄球菌P型肠毒素分泌的影响

本研究以产生金黄色葡萄球菌新型肠毒素P的食品源分离株SA-106为研究对象,采用平板计数和酶联免疫方法研究菌株在LB培养基、脱脂乳和无菌熟猪肉中的生长及肠毒素SEP的动态分泌;同时探索食品添加剂茶多酚和Nisin对菌株SEP蛋白分泌影响。结果表明菌株SA-106在LB液体培养基和脱脂乳中生长时,细菌均能在12 h左右进入生长稳定期,在细菌生长过程中,肠毒素SEP蛋白分泌呈持续增加趋势,在检测的第120 h分别达到10.28μg/mL和6.59μg/mL;菌株在猪肉中生长时,24 h左右进入稳定期,在检测的第48 h时,SEP分泌量可达到9.12μg/g。通过比较发现,菌株SA-106在熟猪肉和LB培养基中生长,SEP蛋白分泌量较高,在脱脂乳中SEP蛋白分泌量稍低,说明不同培养基质对肠毒素蛋白P的分泌强度有影响;另外,茶多酚和Nisin的添加对细菌的生长和肠毒素SEP的产生有一定抑制效果。研究结果对葡萄球菌肠毒素P的产生和控制提供一定参考。