滚揉腌制液中添加Nisin对川香鸡柳的保鲜效果

在川香鸡柳滚揉腌制液中添加不同含量的Nisin(0.1、0.2、0.3、0.4g/kg,按鸡小胸质量计),结合托盘包装技术对其进行保鲜研究。通过测定其在(4.0±0.5)℃条件下贮藏期间的菌落总数、水分活度、pH值、色差值、贮藏损失各项指标,分析Nisin对川香鸡柳的保鲜效果。结果表明:滚揉腌制液中添加Nisin能显著抑制川香鸡柳中菌落总数的增长(P<0.05),贮藏第8天时最明显,与对照组相比,处理组菌落总数可降低3.32 lg(CFU/g);Nisin可显著提高川香鸡柳贮藏后期色泽亮度和黄度;显著延缓第8天后pH值的升高(P<0.05);但对水分活度影响不显著。综合各因素,添加0.3g/kg Nisin保鲜效果最佳。在滚揉腌制液中添加Nisin对川香鸡柳具有良好的保鲜效果。     

Nisin的生产、提纯和检测

Nisin是一种由乳酸乳球菌产生的羊毛硫氨酸类细菌素 ,在许多国家被许可作为生物防腐剂。Nisin的产量受许多因素的制约 ,如产生菌性能、培养基组成 (碳源、氮源、磷源和阳离子 )、发酵条件 (pH、温度、搅拌、通风 )、发酵类型 (分批发酵、连续发酵、自由细胞、固定化细胞 )等 ;大规模回收和纯化Nisin主要采用一些基于吸附-解析或者相分配原理的方法 ;最常用的定量检测Nisin的方法主要有生物分析法和免疫检测法 ,采用各种特定nisin抗体的免疫检测方法具有迅速、灵敏、准确等特性并能实现Nisin的在线检测。     

尼辛对常温条件下“月盛斋”酱牛肉货架期的影响

将切片的酱牛内分别浸入4种防腐液(A液为2％醋酸,B液为A液+2％尼辛,C液为B液+1％壳聚糖,D液为C+5％山梨酸)中30～40秒,取出沥干2～3分钟,真空包装,贮藏在30℃,观察不同防腐液对酱牛肉货架期的影响。结果表明:B、C、D3种防腐液均可明显降低肉表面的杂菌(P<0.05)。延长酱牛肉的货架期、其中尤以D液抑茵效果最好(P<0.05)。分析不同防腐液处理的肉上腐败菌系表明;4种防腐液对牛肉的优势腐败菌葡萄球菌、肠杆菌科菌均有较强的抑菌效果,但不能抑制乳酸杆菌的生长。     

石香薷挥发油与几种常用食品保鲜剂对冷切肉保鲜效果的研究

本文研究比较了石香薷挥发油与常用防腐保鲜剂Nisin、山梨酸钾、茶多酚在冷切肉冷藏(00C～40C)过程中的保鲜效果。试验结果表明石香薷挥发油具有较好的综合保鲜效果,与其他保鲜剂相比,在抑制细菌生长、减缓TVB-N的升高、保持蛋白质含量稳定等方面有着显著的效果,与对照组相比,能将冷切肉的保鲜期延长7d。     

白骛鸭常压杀菌保鲜技术的研究

为获得软包装白鹜鸭在常压杀菌工艺下的最佳品质,采用微波脱水与预杀菌处理技术并结合使用乳酸链球菌素(Msin),对产品品质及保鲜防腐的应用效果进行了研究.结果表明,在微波脱水6.5 min后,加入净鸭质量0.02%的乳酸链球菌素和0.08%的柠檬酸,真空包装后采用常压杀菌,使白鸭产品的保鲜防腐效果达到预期目的,且产品的品质、口感和风味均达到最佳.     

Differences in pressure tolerance of Listeria monocytogenes strains are not correlated with other stress tolerances and are not based on differences in CtsR

Thirty strains of Listeria monocytogenes were screened for their pressure tolerance phenotype at 400 MPa for 2 min at 21 °C. The strains exhibited reductions ranging from 1.9 to 7.1log₁₀ CFU/ml in tryptic soy broth with 6% yeast extract (TSBYE). The 3 most and the 3 least pressure-tolerant strains were further tested for their thermal resistance (based on their ability to survive at 55 °C), acid tolerance (based on their ability to survive in acidified TSBYE; pH 2.0) and for their nisin sensitivity. No correlation between pressure tolerance and heat, acid or nisin resistances was found. Nucleotide sequence analysis of the ctsR region in these 6 strains demonstrated that this gene codes for a CtsR protein with identical predicted amino acid sequences. The sequences of the 200-bp region located immediately upstream of the ctsR start codon of the different strains were virtually identical and it is therefore likely that differences in pressure tolerance are based on factors other than the stress gene regulator CtsR. The pressure sensitivity of a cocktail of the 2 most pressure-resistant strains and a cocktail of the 2 most-sensitive strains was investigated when the cocktails were inoculated into a real food system consisting of ground chicken meat. We demonstrated that the nature of the suspending substrate or the temperature did not change the expected pressure tolerance of the cocktails.     

Effect of nanovesicle-encapsulated nisin on growth of Listeria monocytogenes in milk

Commercial nisin was encapsulated in nanovesicles (mean diameter 140 nm) prepared from partially purified soy lecithin. Nisin-loaded liposomes and unencapsulated (free) nisin were initially tested in BHI medium and skim milk inoculated with Listeria monocytogenes and incubated for 48 h at 30 °C. At such abuse temperature conditions, free nisin showed better inhibitory than the liposomal counterparts. Subsequently, the effect of encapsulated or free nisin was evaluated in combination with refrigeration (7 ± 1 °C) in both whole (3.25% fat) and skim (0% fat) milk for up to 14 day. A decrease of 3–4 log cycles in L. monocytogenes counts was observed for free and encapsulated nisin at 0.5 mg/ml concentration. Liposome encapsulation of antimicrobial peptides may be important to overcome stability issues and interaction with food components. The utilization of nanovesicle-encapsulated nisin in combination with low temperatures appeared to be effective to control L. monocytogenes in milk, emphasizing the importance of hurdle technology to assure food safety.     

Cinnamon and nisin in alginate-calcium coating maintain quality of fresh northern snakehead fish fillets

Cinnamon (Cinnamomum zeylanicum) and nisin in alginate-calcium coating were used to maintain quality of northern snakehead fish fillets at refrigeration temperature (4 ± 1 °C). Northern snakehead fish fillets were left untreated (CK), or were treated with alginate-calcium coating (Y0), alginate-calcium coating incorporating 10 μL mL⁻¹ cinnamon (Y1), alginate-calcium coating incorporating 2000 IU mL⁻¹ nisin and 150 μg mL⁻¹ ethylene diamine tetraacetic acid (EDTA) (Y2), or alginate-calcium coating incorporating 10 μL mL⁻¹ cinnamon and 2000 IU mL⁻¹ nisin and 150 μg mL⁻¹ EDTA (Y3). Y1 and Y3 had better effects on inhibiting bacterial growth and maintaining values of pH, total volatile base nitrogen (TVB-N) and thiobarbituric acid (TBA) of northern snakehead fish than CK, Y0 and Y2. Lightness (L*) values of fish fillets of all treatments were higher than CK. Cinnamon in alginate-calcium coating treatments could efficiently maintain quality of northern snakehead fish fillets during storage, but colors of fish fillets of Y1 and Y3 were evidently changed due to the color of cinnamon.     

极低频电磁场影响Nisin发酵生产的工艺研究

在发酵罐的外部循环管路上加螺线圈,通过控制磁场的强度、发酵液的循环速度和磁场的暴露时间3个因素来对磁场存在下Nisin的发酵进行研究并寻求其最优工艺.采用响应面法中的中心组合试验设计法得到3个因素的最佳条件,通过对试验数据的分析,在最优条件电流0.43A,气速0.56L/min,暴露时间7 h时,Nisin效价提高27%.     

乳链菌肽(Nisin)发酵培养基的优化

以从新鲜牛奶中筛选出的乳酸链球菌KY-2为出发菌株,采用二剂量法检测发酵液中Nisin效价,通过单因子试验和正交设计对该菌株产Nisin发酵培养基进行优化.结果表明:该茵株产Nisin的最适碳源、氮源和磷源组合为(%):蔗糖0.8,蛋白胨2.0,酵母膏1.0,K2HPO4 0.9.优化后效价为957.95 IU/mL,比优化前(812.11 IU/mL)提高了18.0%.