A fast micromethod for the estimation of nisin activity in a soft cheese

The British Standard protocol currently used to determine the nisin concentration in cheese requires the manipulation of a 40 g sample involves two critical points, pH adjustment and heating/cooling. In this work, we developed a fast micromethod that permits the manipulation of 0.2 g cheese, substitutes the use of 0.02N HCl by 50 mM citric acid and facilitates the handling of many samples in reduced time, and with increased efficiency/yield. This change keeps the pH stable at ~3.4, enough to sidestep the pH adjustment, and nisin antimicrobial activity was stable at boiling temperatures.     

Method development for sensitive determination of nisin in food products by micellar electrokinetic chromatography

A rapid and sensitive micellar electrokinetic chromatography (MEKC) method has been developed for the identification and quantification of nisin in food products. Factors such as micelle concentration, pH, and concentration of the buffer were investigated in order to determine the optimum conditions for the analysis. Using optimised conditions of a background electrolyte containing 50 mM sodium phosphate, 80 mM sodium dodecyl sulphate (SDS) at pH 3.75 enabled the successful detection of nisin within 6 min. Limits of detection (LOD) and quantification (LOQ) were in the range of 0.3–0.8 and 1.0–2.8 mg L⁻¹, respectively. The calibration curves were linear for nisin concentration over the range of 2–60 mg L⁻¹. The relative standard deviation (RSD) of the peak area ratios and migration times for method repeatability (n = 3) were found to be lower than 5% and 1%, respectively. The potential of the proposed method to be used for quantitative determination of nisin concentrations in food materials was demonstrated by spiking food samples including dairy products, salad dressings, alcoholic beverages and canned tomatoes with known concentrations of nisin. Quantitative recoveries ranging from 83% to 104% were obtained in the food matrices.     

Nisin release from films is affected by both protein type and film-forming method

Effects of protein type (wheat or corn) and film-forming method (casting or heat-pressing) on films were evaluated for the retention of biologically active nisin (Nisaplin) and release of activity into water at four different temperatures (5, 25, 35 and 45 °C). Nisin activity was measured using the agar diffusion method against Lactobacillus plantarum 1752. Cast corn zein (CCZ) and cast wheat gluten (CWG) films retained 12.1% (8.1×10⁴ IU/g film) and 15.8% (1.1×10⁵ IU/g film) of the original activity after film formation, respectively. Heat-pressed corn zein (HPCZ) and heat-pressed wheat gluten (HPWG) films retained 6.5% (4.3×10⁴ IU/g film) and 7.4% (4. 9×10⁴ IU/g film) of the original activity after film formation, respectively. The maximum nisin activity found migrating into water at any sampling time was 561 IU/ml (CCZ), 1058 IU/ml (CWG), 309 IU/ml (HPCZ), and 478 IU/ml (HPWG).     

不同阴离子对乳酸链球菌素抑菌稳定性的影响研究

为了改善乳酸链球菌素（Nisin）的抑菌稳定性及扩展其在食品工业中的应用,研究了几种含钠磷酸盐、EDTA二钠和柠檬酸钠对乳酸链球菌素抗菌活性的影响。结果表明,磷酸盐、EDTA二钠、柠檬酸钠对Nisin的抑菌活性保护作用较显著,其保护作用排序为：六偏磷酸钠〉EDTA二钠〉三聚磷酸钠〉柠檬酸钠〉磷酸二氢钠〉磷酸氢二钠。在pH6．8、121℃备件下加热20rain,六偏磷酸钠使Nisin效价仅损失7．25％,EDTA二钠为10.2％。     

冷却猪肉复合抑菌剂的配比优化及保鲜效果研究

为延长冷却猪肉货架期,用琼脂扩散法,模拟冷鲜猪肉原始菌群,采用二次回归通用旋转组合设计,对Nisin、ε-聚赖氨酸和山梨酸钾的复合抑菌剂的抑菌效果进行配比优化试验。结果表明,复合抑菌剂的最佳配比为Nisin 0.15g/L,ε-聚赖氨酸0.45g/L,山梨酸钾0.97g/L;将该复合抑菌剂应用于冷却猪肉,第19天时,冷却猪肉仍然保持在一级鲜度,表明复合抑菌剂对延长冷却猪肉货架期有明显效果。     

Nisin在食品防腐作用中的研究进展

介绍乳酸链球菌素(Nisin)的结构、特性以及抗菌作用机制。并对Nisin的应用局限性和影响因素进行简要说明,例举其在食品防腐中的应用,并对Nisin的发展前景做一展望。     

Nisin、姜油协同高氧气调包装熟肉保鲜效果的研究

将熟猪肉采用Nisin和姜油处理,结合60%O2+20%CO2+20%N2和80%O2+20%CO2高氧气调包装,于低温和常温条件下贮藏,研究高氧气调包装对熟猪肉制品的保鲜效果,以空气包装的熟肉制品为对照。结果表明:高氧气调包装可显著抑制熟肉制品贮藏期间菌落总数的上升和感官品质的下降,贮藏后期能有效抑制TBA值的上升,防止肉制品的氧化;0.05%乳酸链球菌素、0.08%姜油结合80%O2+20%CO2高氧气调包装,可使肉制品达到最佳的保藏效果,低温下(0～4℃)至少可以保藏28d,常温下可以保藏15d。     

Nisin替代部分亚硝对中式香肠品质影响的研究

主要研究通过对比实验,以挥发性盐基氮、过氧化值、pH值、菌落总数及感官评定作为评价指标,探讨了Nisin代替部分亚硝对中式香肠品质的影响。实验结果表明:在其他条件相同的情况下,添加600mg/kg Nisin及40mg/kg亚硝制作的中式香肠,与按90mg/kg添加亚硝制作的中式香肠品质差异不明显。     

单核细胞增生李斯特菌复合抑菌剂的研究

单核细胞增生李斯特菌(Listeria monocytogenes,LM)在0～4℃也能生长,为确保冷却肉卫生安全,必须阻止肉中污染的LM的生长繁殖。本实验通过研究不同抑菌剂对3株LM的最小抑菌浓度(MIC),选取了ε-聚赖氨酸、Nisin、曲酸三种抑菌剂,利用响应面法找出最佳组合。结果表明:ε-聚赖氨酸、Nisin、曲酸对单核细胞增生李斯特菌的最小抑菌浓度分别为50μg/mL、200μg/mL、6.4mg/mL。当ε-聚赖氨酸、Nisin、曲酸的浓度分别为20.5μg/mL、184.6μg/mL、4.37mg/mL时对单核细胞增生李斯特菌的抑制作用最佳。