温度、pH及盐对植物乳杆菌素L-1作用单核细胞增生李斯特氏菌的影响

本试验分析了透析除盐后的植物乳杆菌素L-1的效价和作用方式，测定了在食品加上过程中常涉及到的温度、pH和盐等生化条件对其作用单核细胞增生李斯特氏菌的影响，并初步探索了pH和盐对植物乳杆菌素L-1吸附作用的影响。结果表明：透析除盐后的植物乳杆菌素L-1的效价可达1280AU／ml，作用方式为杀菌；低温下144h内可以控制住初始菌数，高温下可以短时间内迅速降低初始活菌数；在pH7．0下，该细菌素的抑菌效果最好；无论是TSBYE培养基中还是磷酸缓冲液中，试验所采用的四种盐对植物乳杆菌素L-1的杀菌作用都有一定的拮抗作用，各盐之间和同种盐内不同浓度间差异不显著；对吸附作用的初步研究发现pH对植物乳杆菌素的吸附作用有一定影响，而盐对其影响不显著。     

解淀粉芽孢杆菌发酵液保鲜冷却猪肉的效果研究

实验研究了解淀粉芽孢杆菌发酵液对冷却肉的防腐保鲜效果,对冷却肉的微生物、感官品质和理化指标3个方面进行了检测.结果显示,解淀粉芽孢杆菌发酵液处理组可将冷却肉的保质期延长6d～9d,而且效果优于Nisin.解淀粉芽孢杆菌发酵液对冷却肉中主要污染菌-假单胞菌和潜在致病菌-单增李斯特菌有较好的抑制效果.解淀粉芽孢杆菌发酵液作为冷却肉的生物防腐剂,具有广阔的应用前景.     

一株植物乳杆菌所产细菌素的性质及诱变筛选

以从自制乳酪中分离获得的1株植物乳杆菌为研究对象,其能大量分泌对单核细胞增多性李斯特菌有极强烈抑制作用的细菌素。对其细菌素性质及效价进一步研究发现:所产细菌素具有热稳定性,pH稳定性,在pH2~12之间仍具有一定的抑菌活性。经过细菌素效价实验,确定该菌所产细菌素活力大大高于文献报道的其他同类细菌素,相对Nisin效价为4199 IU/mL,并可与抗生素比较效价,相对利福平效价为458μg/mL。进一步将该植物乳杆菌进行甲基磺酸乙酯(EMS)诱变,以抗生素利福平为标准曲线,最终得到细菌素上清液对单核细胞增多性李斯特菌效价由458μg/mL提高到682μg/mL,比诱变前提高了48%。     

植物乳杆菌素MG及其复合防腐剂对冷却猪肉保质期及品质的影响

采用不同保鲜液对冷却肉进行处理,真空包装后于4℃冷藏15 d,通过评价细菌总数、pH、挥发性盐基氮、感官质量等指标,研究植物乳杆菌素MG及其复合防腐剂对猪肉保质期和品质的影响。结果表明:不进行保鲜防腐处理的对照冷却肉只能保存6 d,500 IU/mL植物乳杆菌素MG处理的冷却肉可保存9 d,500 IU/mL植物乳杆菌素MG与2%乳酸钠处理的冷却肉保质期延长至12 d。     

片球菌素BM-1免疫蛋白对甘露糖磷酸转移酶受体识别特异性研究

利用牛津杯法筛选到对片球菌素BM-1敏感的植物乳杆菌WQ0815和肠膜明串珠菌05-43。并利用Nisin诱导表达系统,在乳酸乳球菌NZ9000中诱导表达两敏感菌株的甘露糖磷酸转移酶系统IICD组分,抑菌实验表明不同来源的IICD组分皆可被片球菌素BM-1识别。进一步将片球菌素BM-1同源免疫蛋白分别与两种IICD组分同时在乳酸乳球菌中表达,抑菌实验表明:免疫蛋白可识别植物乳杆菌来源的IICD组分,不能识别肠膜明串珠菌来源的IICD组分。研究结果为IIa类细菌素的同源免疫蛋白对受体存在特异性识别提供了直接证据。     

乳过氧化物酶体系在冷却猪肉保鲜中的应用研究

为了评定乳过氧化物酶体系对冷却猪肉的保鲜效果,对冷却鲜猪肉分别采用浓度为3μg/ml的乳过氧化物酶体系(LPS)、4μg/ml的LPS、40μg/ml的乳酸链球菌素(Nisin)、3μg/ml的LPS+40μg/ml的Nisin、4μg/ml的LPS+40μg/ml的Nisin等5组不同保鲜剂处理,以蒸馏水处理做对照,测试猪肉在3±0.5℃保存条件下感官指标、理化指标和细菌总数的变化。结果表明:经LPS处理的冷却猪肉在贮藏过程中的感官指标、理化指标和细菌总数的变化比对照组缓慢,差异达到极显著水平(p<0.01),LPS可有效延长冷却猪肉的保鲜期;LPS处理比Nisin处理的保鲜效果更好,差异达到显著水平(p<0.05);当LPS与Nisin复配时,可以达到更好的保鲜效果,猪肉的保鲜期可达20d以上;Nisin可以减轻LPS导致的猪肉脂肪氧化。     

行业动态

植物乳杆菌产细菌素的研究通过鉴定中国农业大学食品科学与营养工程学院主持完成的“植物乳杆菌产细菌素的研究及其在发酵香肠中的应用”项目,已通过了教育部组织的专家鉴定。他们从我国传统宣威火腿中分离筛选到了一株高产细菌素的植物乳杆菌L-1;确立了一条经济合理、适合工业化生产该细菌素的分离纯化技术(工艺)路线;探明了植物乳杆菌细菌素L-1对肉源单核细胞增生李斯特氏病原菌作用机理;利用产细菌素植物乳杆菌L-1作为发酵,剂开发出了2种新型发酵香肠,产品的品质优良,风味和感官特性好。行业动态我国软包装罐头企业首次通过欧洲双认证…     

植物乳杆菌M1-NTG300产细菌素培养条件优化

以植物乳杆菌素的效价作为特征性考察指标,对植物乳杆菌M1-NTG300产细菌素培养条件进行优化。通过响应面分析结合实际值确定培养基最佳组分为:葡萄糖浓度3.5%、蛋白胨浓度3.5%、吐温80浓度0.35%、氯化镁浓度0.20%,此培养条件下植物乳杆菌M1-NTG300所产细菌素的效价为1 269.4IU/mL,细菌素效价提高了19.8%。     

植物乳杆菌P9对小鼠功能性便秘的作用及机制

目的：研究植物乳杆菌P9对小鼠功能性便秘的润肠通便作用及其对肠道菌群的影响。方法：将100只BALB/c雄性小鼠随机分成空白组、模型组、植物乳杆菌P9低剂量组(给予0.42 mg/(kg m_b·d)菌粉(活菌数2.0×1011 CFU/g,下同))、中剂量组(给予0.84 mg/(kg m_b·d)菌粉)、高剂量组(给予2.5 mg/(kg m_b·d)菌粉),每组20只小鼠。将相应剂量的菌粉用无菌去离子水配制成菌悬液,按照10 mL/(kg m_b·d)剂量灌胃15 d,空白组、模型组灌胃等量无菌去离子水。实验第16天,模型组、植物乳杆菌P9干预组以洛哌丁胺4 mg/(kg m_b·d)灌胃诱导小鼠功能性便秘,随机选取10只进行排便实验,检测小鼠首次排黑便时间、6 h排黑便量;剩余10只进行小肠运动实验,测定墨汁推进率,并采用16S rRNA高通量测序技术测定小鼠盲肠内容物菌群组成。排便实验结束后模型组、植物乳杆菌P9干预组剩余小鼠持续灌胃洛哌丁胺4 mg/(kg m_b     

乳酸菌31-1菌株产细菌素的初步研究

从发酵肉制品宣威火腿中分离筛选出一株产细菌素的乳酸茵31-1,对多株植物乳杆菌具有抑菌作用.经排除有机酸等干扰因素,进行初步蛋白质分离提纯后,抑茵活性增强,因此确定该菌株为细菌素产生菌.进而研究了31-1生长过程中细菌素产生的变化情况,结果发现细菌素在对数末期(8h)开始产生,且在稳定期中期(33h)有最大产量,最终31-1产细菌素的效价达到320AU/mL.     

Inhibition of Listeria monocytogenes LMG10470 by plantaricin UG1 in vitro and in beef meat

The inhibition of Listeria monocytogenes LMG 10470 occurred due to plantaricin UG1, but not to lactic acid produced by Lactobacillus plantarum UG1 or its negatie variant (BAC). Partially purified plantaricin UG1 had a higher antilisterial activity in vitro and in meat than Lactobacillus plantarum UG1 culture. Plantaricin UG1 activity was higher in brain heart infusion (BHI) broth than in minced meat. The inhibitory effect of plantaricin UG1 against L. monocytogenes LMG10470 was dependent on its concentration. The 22,880 AU/mL appeared to be an ideal meat preservative in this experiment.     

Effect of combining nisin and/or lysozyme with in-package pasteurization on thermal inactivation of Listeria monocytogenes in ready-to-eat turkey bologna

Achieving a targeted lethality with minimum exposure to heat and preservation of product quality during pasteurization is a challenge. The objective of this study was to evaluate the effect of nisin and/or lysozyme in combination with in-package pasteurization of a ready-to-eat low-fat turkey bologna on the inactivation of Listeria monocytogenes. Sterile bologna samples were initially treated with solutions of nisin (2 mg/ml = 5,000 AU/ml = 31.25 AU/cm2), lysozyme (10 mg/ml = 80 AU/ml = 0.5 AU/cm2), and a mixture of nisin and lysozyme (2 mg/ml nisin + 10 mg/ml lysozyme = 31.75 AU/cm2). Bologna surfaces were uniformly inoculated with a Listeria suspension resulting in a population of approximately 0.5 log CFU/cm2. Samples were vacuum packaged and subjected to heat treatment (60, 62.5, or 65 degrees C). Two nonlinear models (Weibull and log logistic) were used to analyze the data. From the model parameters, the time needed to achieve a 4-log reduction was calculated. The nisin-lysozyme combination and nisin treatments were effective in reducing the time required for 4-log reductions at 62.5 and 65 degrees C but not at 60 degrees C. At 62.5 degrees C, nisin-lysozyme-treated samples required 23% less time than did the control sample to achieve a 4-log reduction and 31% less time at 65 degrees C. Lysozyme alone did not enhance antilisterial activity with heat. Results from this study can be useful to the industry for developing an efficient intervention strategy against contamination of ready-to-eat meat products by L. monocytogenes.     

Inhibition of Bacillus cereus ATCC 14579 by plantaricin UG1 in vitro and in food

The inhibition of Bacillus cereus ATCC 14579 viable growth by Lactobacillus plantarum UG1 bacteriocin (plantaricin UG1) in vitro and in food (pasteurized milk and minced meat) was studied. The inhibitory effect against B. cereus food-borne pathogen noticed in this study was due to plantaricin UG1, but not due to lactic acid produced by the L. plantarum UG1 culture. Plataricin UG1 negative clone did not affect viable growth of B. cereus in both broth and meat or pasteurized milk. The inhibitory effect of L. plantarum UG1 and its bacteriocion was apparently more in liquid systems (BHI broth & pasteurized milk) than in minced meat. The inhibitory effect of plantaricin UG1 against B. cereus was dependent on its concentration. The 22880 AU/ml concentration appeared to be an ideal preservative against B. cereus ATCC 14579 in liquid systems.     

Nisin-curvaticin 13 combinations for avoiding the regrowth of bacteriocin resistant cells of Listeria monocytogenes ATCC 15313

Nisin (25-100 IU/ml) and curvaticin 13 (160 AU/ml), a bacteriocin produced by Lactobacillus curvatus SB13, were shown to have a bactericidal effect against Listeria monocytogenes ATCC 15313 in TSB-YE broth (pH 6.5), but it was only transitory. Regrowth was not due to the loss of bacteriocin activity. Cells surviving nisin or curvaticin 13 were more resistant to the respective bacteriocin than the parental strain. Survivors to curvaticin 13 were resistant to the class IIa bacteriocins (camocin CP5, pediocin AcH) but remained sensitive to nisin. The frequencies of spontaneous nisin resistants decreased with increasing bacteriocin concentration and the presence of salts (NaCl, K2HPO4). The behaviour of nisin (1000 IU/ml) or curvaticin 13 (640 AU/ml) resistant variants (Nis1000, Curv645) was investigated in the presence of nisin (100 IU/ml) or curvaticin 13 (320 AU/ml) at 22 and 37 degrees C, and compared with that of the parental strain. The effectiveness of nisin was the same at both temperatures, whereas curvaticin 13 displayed a faster bactericidal action at 37 degrees C. Nis1000 cells were less sensitive to curvaticin 13 than the parental strain, whereas Curv640 cells were more sensitive to nisin than the parental strain. Simultaneous or sequential additions of nisin (50 IU/ml) and curvaticin 13 (160 AU/ml) were performed at 22 degrees C in broth inoculated with the parental strain. All combinations induced a greater inhibitory effect than the use of a single bacteriocin. Simultaneous addition of bacteriocins at t0 led to the absence of viable cells in the broth after 48 h.     

不同时间紫外处理对冷鲜猪肉品质变化的影响

目的 探索销售过程中不同时间紫外处理对冷鲜猪肉保鲜的最佳条件。方法 以新鲜猪里脊肉为对象,通过紫外照射0、4、9、24 h/d处理冷鲜猪肉,试验周期为4 d,考察处理前后的挥发性风味物质及感官评定变化规律。同时检测冷鲜猪肉pH、质构分析(textureprofile analysis, TPA)、色差、汁液流失及菌落总数变化,并比较不同紫外处理的保鲜效果。结果 紫外照射9 h的处理组保鲜效果最佳。处理期内前3 d,该组菌落总数最低,冷鲜肉的贮藏pH也是增长最慢的,在色差指标中肉色的亮度明显高于其他组,维持了冷鲜肉原有的色泽,根据TPA结果发现紫外照射后也并未对冷鲜肉的质地产生较大影响。气相色谱-质谱法(gas chromatography-mass spectrometry, GC-MS)结果显示改组不仅提高了生鲜肉醇类、酯类化合物的含量,更促进了庚醛、甲酸辛酯等风味物质的产生。结论 模拟市售情况并添加紫外照射处理冷鲜肉,发现紫外照射处理9 h/d对市售冷鲜猪肉保鲜具有更高的实际应用价值。     

分割托盘小包装冷却肉保鲜技术研究

为有效延长托盘包装冷却肉的货架期,进行了GNa液、Nisin、溶菌酶复合性保鲜实验。试验表明GNa液、Nisin、溶菌酶在非真空托盘包装保鲜的条件下配合性使用,能获得21天的有效保鲜期。试验还发现,GNa液、Nisin和溶菌酶应用于冷却肉的保鲜效果在真空包装和托盘包装的条件下,具有很大的差异,呈现出不同的规律,不仅汁液渗出量少,由于氧的存在,GNa液失去护色的效果,pH值未出现真空状态下的下降-上升-再下降-最后又上升的变化趋势,在托盘包装情况下Nisin抑制脂肪的酸败的效果不能充分发挥出来;同时发现溶菌酶和GNa的配合使用,在非真空托盘包装保鲜条件下,要好于Nisin、GNa的配合效果,GNa液在有氧的短时间内还表现出一定的抑制大肠菌群增殖的效果。     

魔芋涂膜保鲜冷却肉研究

采用改性和不改性的魔芋精粉为涂膜材料,对经75%酒精消毒处理或5‰山梨酸钾溶液处理后的鲜猪肉进行涂膜处理,并与不同浓度的壳聚糖涂膜处理相比较,以冷却肉的pH值、过氧化物酶活性、挥发性盐基氮及细菌总数的变化为指标,评价不同处理的保鲜效果。结果表明:冷却肉采用碱法改性的魔芋精粉溶胶涂膜处理保鲜效果与2%的壳聚糖醋酸溶液保鲜效果接近,明显优于其它处理,一级鲜度货架期可达9d。     

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。     

生物保鲜和辐射保鲜技术在冷却肉上的应用研究

本文利用自制的天然生物保鲜剂,结合真空包装和辐照保鲜技术,从细菌总数、TBA、TVB-N和感官指标等方面,考察了综合保鲜技术对冷却肉的保鲜效果。结果表明,生物保鲜剂和辐照技术对冷却肉的保鲜具有协同作用,经真空包装,保质期可以达到21天以上。