Nisin在酸奶制品中的应用

酸奶制品在贮存过程中会发生后酸化,为推迟酸化的发生,延长酸奶制吕的保质期,本实验将Nisin(乳酸链球菌素）以不同的剂量（10,20,40IU／ml)添加到酸奶制品中,观测在不同贮存期间酸奶制品的菌数,酸度变化,并对酸奶的感官质量进行评定。实验证明,添加40IU／ml的Nisin于酸奶中,将酸奶的后酸化推迟了3天,且菌数保持在10^7以上,而且感官质量良好。     

乳酸链球菌素在白酒发酵中的应用

乳酸链球菌素应用与白酒发酵,对降低白酒总酸,抑制白酒发酵中乳酸菌的生长繁殖,控制白酒醪液中乳酸、乳酸乙酯的生成有明显的效果。综合使用成本、控制酸度的效果等方面来看,乳酸链球菌素较佳的添加量应该是0.5mg/L,最佳的添加时间应该是投料的同时,用水稀释后均匀加入。     

CLEANSING CONTAMINATED PITCHING YEAST WITH NISIN

The ability of solutions of nisin to cleanse pitching yeast of contaminating gram-positive lactic bacteria (at levels of about 1% by cell numbers) was compared to that of three different acid-washing procedures: ammonium persulphate, acidified ammonium persulphate or phosphoricacid. 1000 international units ml^?1 of nisin killed all the cells of more sensitive bacterial strains in less than 30 minutes, equivalent to the killing ability of the acid-washing procedures, and more than 99·9% of cells of a more resistant strain in 2 hours. Washing contaminated pitching yeast with nisin has several advantages over acid-washing methods. It has no effect on yeast viability and vitality, and, in subsequent fermentations, the yeast shows unchanged flocculation characteristics and fermentative performance.     

Effects of Salmonella bacteriophage,nisin and potassium sorbate and their combination on safety and shelf life of fresh chilled pork

Salmonella is an important foodborne pathogen and a serious threat to human health worldwide. This study was to reduce Salmonella and the spoilage bacteria on fresh chilled pork using bacteriophage, nisin, and potassium sorbate (PS) along with their combinations. Microbial, chemical, and sensory qualities of the fresh chilled pork (artificially contaminated with Salmonella 3 log CFU/g) treated with bacteriophage (9 log PFU/g), nisin (5000 IU/g), PS (2 mg/g) and their combinations were evaluated. The result showed that all the samples treated with phage could significantly (P < 0.05) reduce Salmonella population on fresh chilled pork. The combination treatment of nisin, PS and phage (N-PS-P) could significantly lower total viable counts (TVC), TVB-N and TBARS of the chilled pork during the storage period. The TVC of sample treated by N-PS-P was reduced by 2.3 log CFU/g at 7th day. It was also found through the electronic nose detection that the N-PS-P treatment was able to significantly reduce odour and maintain good sensory of the chilled pork. Hence, the N-PS-P treatment extended the shelf life of fresh chilled pork up to 14 days. No adverse effect of the phage on the chilled pork was observed. In conclusion, this study suggests that the phage and its combination with nisin and PS have great potential to be used as a good preservative for fresh chilled pork.     

Combination of nisin and ε-polylysine with chitosan coating inhibits the white blush of fresh-cut carrots

Effects of the combination of nisin and ε-polylysine with chitosan coating on quality maintenance and white blush inhibition were investigated in fresh-cut carrots. Fresh-cut carrots were treated with 1% lactic acid solution (v/v), 1% chitosan solution (w/v), or 1% chitosan solution containing 64 μg/mL nisin and 250 μg/mL ε-polylysine (LA + CH + Nisin + ε-PL). The samples were packed in polyethylene plastic bags and stored at 4 °C for 9 days. Changes in sensory attributes, physicochemical indices, respiration rate, microbiological counts and white blush were measured. Results showed that LA + CH + Nisin + ε-PL significantly (P < 0.05) inhibited respiration rate, decline of ascorbic acid and growth of microorganism (yeast and mold, total viable counts, total coliforms counts, Staphylococcus aureus and Pseudomonas spp.), and increased total phenol content and phenylalanine ammonialyse (PAL) activity compared with the control after 9-day storage. It was also strongly effective in inhibiting the white blush of fresh-cut carrots. Furthermore, LA + CH + Nisin + ε-PL significantly (P < 0.05) reduced the lignin synthesis in fresh-cut carrots by inhibiting the cinnamate-4-hydroxylase (C4H) and 4-coumarate-CoA ligase (4CL) activity, as well as Dc4CL and DcC4H gene expression. Our results may provide some basis for the use of the combination of nisin and ε-polylysine with chitosan coating as an alternative preservation method for fresh-cut carrots.     

Functionality and safety of lactic bacterial strains from Korean kimchi

The functional characteristics and safety of five different putative probiotic Lactobacillus plantarum strains and one Leuconostoc citreum strain, isolated from kimchi, were studied. In view of their potential application in food biotechnology, this information was considered necessary, and included the determination of antibiotic resistance, haemolysis, gelatinase activity and biogenic amine production. In addition to a Lactobacillus fermentum strain isolated from pig faeces, two commercial probiotic strains (Lactobacillus rhamnosus GG, ATCC 53103, and Lactobacillus plantarum 299v, both originating from the human intestinal track) were included in the studies for reference purposes. With the exception of L. fermentum, which was resistant to a low concentration (MIC: 30 μg/ml) of tetracycline, all strains were susceptible to the 8 antibiotics tested (erythromycin, gentamicin, ampicillin, tetracycline, chloramphenicol, streptomycin, ciprofloxacin, and benzylpenicillin). All strains survived physiological conditions typical of the upper GIT, comprising a pH of 3.0 for 1 h, and a subsequent 2 h under conditions simulating the duodenum, which included the exposure to 10 % of bile salts. Moreover, all strains were resistant to 0.4 % phenol, and were unable to produce any detectable biogenic amines under the test conditions. These preliminary in vitro tests indicate the safety and functionality of the five selected L. plantarum strains and thus their potential as probiotic candidates.     

Low-cost purification of nisin from milk whey to a highly active product

Nisin is a natural peptide used as a preservative in a variety of food products, in which it inhibits mainly Gram-positive bacterial growth, including multidrug-resistant pathogens. However, its application range depends on the cost-effective production and purification of this molecule. Our group has previously produced nisin by Lactococcus lactis cultivation in milk whey, which is an industrial residue from dairy production. To our knowledge, no report used milk whey as a culture medium, although several investigators have purified nisin using different techniques. We thus aimed to establish a low-cost purification of nisin obtained by this process. Samples were diluted in ammonium sulphate, applied onto HIC columns (butyl sepharose CL 4B matrix), and eluted with Milli-Q water or PBS. Elution fractions were monitored for protein content and nisin antibacterial activity. Water elution resulted in purification factor values (270, commercial nisin; 775, nisin produced in-house) higher than those obtained with PBS elution. We concluded that purification of nisin does not require precipitation with ammonium sulphate, therefore allowing step/cost reduction. Moreover, purification from milk whey using HIC provides nisin with high activity and low salt content, which can further be applied to a variety of areas.     

Effect of elementary and advanced glycation products of nisin on its preservative efficacy and digestibility

Nisin used as a natural preservative in variety of food systems was subjected to glycation at 95 °C in high molar concentration. The elementary glycation end products (EGEs) and the advanced glycated end products (AGEs) formed were tested as compared to non-glycation nisin (NN) for their antibacterial activity against some food spoilage organisms such as Staphylococcus aureus, Bacillus cereus, Micrococcus luteus, Clostridium botulinum and Lactobacillus sake. The extent of hydrolysis of EGEs and AGEs by trypsin was also compared with the (NN) as control. The results have illustrated that antibacterial activity of nisin was substantially affected by the process of glycation in case of all the five organisms selected for the study, suggesting that the glycation of nisin, whether invivo or invitro will adversely affect the preservation of foods. Moreover glycation also reduced the tryptic digestibility of EGEs by 5.2% and AGEs by 50.325% as compared to NN. The data indicated that amount of nisin, if added to carbohydrate consisting foods should be increased accordingly to claim the reported shelf life of the products and food labelling in such products needs cardinal modification. Although hydrolysis of glycated nisin by trypsin is slightly decreased, however; it will not produce any adverse effect on human digestion in view of the minute amount of nisin present in the food system.     

可食性复合膜对冷却肉保水性的影响

以猪背最长肌为原料,以滴水损失、贮存损失、水分含量等为评价指标,研究贮藏温度为0～4℃时不同配方壳聚糖涂膜液对冷却肉保水性的影响。结果表明,各种配方壳聚糖涂膜液处理均可降低冷却肉的滴水损失和贮存损失,减缓水分含量下降速率。     

Polymer films releasing nisin and/or natamycin from polyvinyldichloride lacquer coating: Nisin and natamycin migration,efficiency in cheese packaging

Polyethylene films coated by commercially available polyvinyldichloride (PVdC) as well as nitrocellulose (NC) lacquer with addition of natamycin preparation Delvocid® (16.7% w/w of natamycin in lacquer) were studied at 6 and 23 °C to determine the preservative migration into distilled water. The films released natamycin at maximal level 2.34 ± 0.32 mg/dm². The diffusion coefficient of 0.79 × 10⁻¹⁰ ± 0.29 × 10⁻¹⁰ cm²/s and 1.03 × 10⁻¹⁰ ± 0.17 × 10⁻¹⁰ cm²/s was determined for natamycin transport in PVdC lacquer layer at 6 and 23 °C, respectively. For nitrocellulose lacquer the diffusion coefficient of 0.89 × 10⁻¹⁰ ± 0.16 × 10⁻¹⁰ cm²/s was found at 23 °C. The coextruded polyamide/polyethylene film coated with the PVdC lacquer containing both nisin (16.7% w/w of preparation Nisaplin®) and natamycin (see above) provided inhibitory effect against selected indicator microorganisms (Penicillium expansum, Fusarium culmorum, Lactobacillus helveticus, Listeria ivanovií). This film was unsuitable for the packaging of the surface ripened cheese Olomoucké tvar??ky. On the other hand, it was able to prevent the growth of spoilage microorganisms on the surface of the packaged soft cheese Bla?ácké zlato.