天然保鲜剂的配比优化及其对牛肉保鲜效果的影响

牛肉贮藏期间易被微生物污染而发生腐败变质。为延长冷鲜牛肉的货架期,使用无毒、健康、安全的天然保鲜剂对牛肉进行保鲜的研究备受关注。本试验采用抑菌试验,以大肠杆菌与金黄色葡萄球菌的对象菌,以抑菌圈直径为检测指标,进行了茶多酚、乳酸链球菌素(Nisin)、壳聚糖三种天然保鲜剂抑菌的单因素试验,得出三种保鲜剂适合的抑菌浓度;采用正交试验优化了三种天然保鲜剂协同保鲜的配比。并以未经保鲜剂处理的冷藏牛肉为对照,进行了该天然保鲜剂对冷藏牛肉保鲜效果的研究。研究结果表明:三种天然保鲜剂协同抑菌的最适配比为:0.10%茶多酚+1.00%壳聚糖+0.08%Nisin,可将牛肉的货架期从5 d延长至11 d。本研究为冷鲜牛肉的保鲜开发出一种天然保鲜剂,对牛肉产业的发展提供一定的技术指导。     

不同保鲜剂对真空条件下冷却羊肉菌相变化的影响

选取Nisin、溶菌酶、乳酸钠、茶多酚、壳聚糖5种天然保鲜剂对冷却羊肉进行保鲜处理,采用选择性培养基对贮藏过程中引起冷却羊肉腐败的主要微生物进行选择性培养,分析研究不同保鲜剂的抑菌效果和对腐败菌相构成的影响。结果表明真空条件下,5种保鲜剂的保鲜效果依次为Nisin>溶菌酶>乳酸钠>茶多酚>壳聚糖,其中Nisin、溶菌酶、乳酸纳的抑菌效果最明显,较适宜作为冷却羊肉真空包装的保鲜剂。     

Nisin、茶多酚、壳聚糖复合保鲜冷却羊肉的配比优化研究

本研究利用响应面法对Nisin、茶多酚、壳聚糖进行复配组合,应用于冷却羊肉中,真空包装后贮藏于3±1℃环境中,3w后测其挥发性盐基氮值,研究其交互作用,确定复合保鲜剂最佳配比。结果表明,三种保鲜剂的抑菌效果依次为Nisin>壳聚糖>茶多酚;Nisin和壳聚糖之间存在极显著的交互效应(p<0.01),茶多酚与Nisin、茶多酚与壳聚糖之间的交互效应不显著(p>0.05);复合保鲜剂Nisin、壳聚糖、茶多酚的最佳配比分别是0.137%、1.395%、0.158%。     

复合天然保鲜剂对低温酱鸭保鲜效果的研究

以低温酱鸭为原料，通过对6种天然保鲜剂进行筛选，选出4种抑菌效果较好的，进一步进行组合实验，根据抑菌率得出抑制酱鸭腐败菌的最佳组合为壳聚糖2．00％、乳酸链球菌素（Nisin）0．01％、茶多酚1．00％、桂皮2．40％。采用此最佳组合的复合天然保鲜剂对酱鸭进行保鲜实验，定期测定其微生物指标和理化指标，结果表明利用优选的组合保鲜剂保鲜，加上真空包装、低温水浴杀菌，可使酱鸭保质期冷藏达2-3个月。     

Nisin、茶多酚、壳聚糖复合保鲜冷却羊肉的配比优化研究

利用响应面法对Nisin、茶多酚、壳聚糖进行复配组合,应用于冷却羊肉中,真空包装后贮藏于3±1℃环境中,三周后测其挥发性盐基氮值,研究其交互作用,确定复合保鲜剂最佳配比。结果表明:三种保鲜剂的抑菌效果依次为Nisin>壳聚糖>茶多酚;Nisin和壳聚糖之间存在极显著的交互效应(P<0.01),茶多酚与Nisin、茶多酚与壳聚糖之间的交互效应不显著(P>0.05);复合保鲜Nisin、壳聚糖、茶多酚的最佳配比分别是0.137%、1.395%、0.158%。     

冷却猪肉中复合保鲜剂配比优化研究

按照五因子二次旋转正交组合设计方案,确定了Nisin、纳他霉素、溶菌酶、茶多酚和壳聚糖复合保鲜冷却猪肉的交互作用,获得最佳配比。结果表明:5种保鲜剂的抑菌效果依次为溶菌酶>壳聚糖>茶多酚>Nisin>纳他霉素;溶菌酶与Nisin、溶菌酶与壳聚糖间存在显著交互效应(P<0.05);浸泡用复合保鲜剂的最佳配比为Nisin0.10%、纳他霉素0.13%、溶菌酶0.20%、茶多酚1.8%、壳聚糖1.8%。     

Nisin、乳酸钠、壳聚糖复合保鲜药膳牛肉丸的配比优化

利用响应面法对Nisin、乳酸钠、壳聚糖进行复配,应用于药膳牛肉丸保鲜,4℃贮藏,7 d后测其TVB-N值,研究交互作用,确定复合保鲜剂最佳配比。结果表明:3种保鲜剂的抑菌效果依次为:壳聚糖Nisin乳酸钠;壳聚糖与Nisin、壳聚糖与乳酸钠有交互作用,对结果影响显著;Nisin与乳酸钠对结果影响不显著;复合保鲜Nisin、乳酸钠、壳聚糖的最佳配比为:以100 g牛肉计,Nisin 0.015 g、60%乳酸钠4.5 m L、壳聚糖0.8 g。     

响应面法优化冰温鸡肉复合保鲜剂研究

为了延长鸡肉货架期,利用Box-Behnken设计对茶多酚、壳聚糖、Nisin进行复配优化,建立以菌落总数对数值为指标的二次多项式回归模型,研究复合抑菌剂对冰温鸡肉的保鲜效果。结果表明:经回归拟合和方差分析,Nisin分别与茶多酚、壳聚糖呈现显著的交互作用(p0.05),优化分析得到复合保鲜剂的最优配比为:茶多酚为0.6700%,壳聚糖为0.1124%,Nisin为0.0174%。通过验证实验,复合保鲜剂处理鸡胸肉菌落总数值比对照组下降了2个对数单位,抑菌效果显著。     

响应面法优化软冷冻肉复合保鲜剂的研究

以新鲜猪腿肉为原料,以菌落总数为评价指标,研究了不同浓度的Nisin、茶多酚和壳聚糖对软冷冻猪肉的保鲜效果,得知三种保鲜剂单一使用最佳浓度分别为:Nisin 0.02%、茶多酚0.5%和壳聚糖2.0%;以贮藏30d的TVB-N值为响应值,采用响应面法中心组合设计实验,得到三种保鲜剂对TVB-N影响顺序为:壳聚糖茶多酚Nisin,且Nisin与茶多酚的交互作用对TVB-N的影响显著(P0.05);三种保鲜剂的最佳配比为:Nisin 0.02%、茶多酚0.42%和壳聚糖2.18%;对复合天然保鲜剂进行验证,测定30d内软冷冻条件下猪肉的各项指标,发现均优于软冷冻对照组的各指标。     

生物保鲜剂对冷却肉保鲜的影响

为了延长冷却肉的保鲜期，研究了乳源抗菌肽和壳聚糖、纳他霉素、苹果多酚、茶多酚、Nisin等生物保鲜剂对冷却肉主要腐败菌的抑制作用，并应用于冷却猪肉和羊肉的保鲜。结果表明：山羊乳酪蛋白胃蛋白酶酶解所得抗菌肽的抑菌活性较高；山羊乳源抗菌肽与壳聚糖对冷却猪肉和羊肉主要腐败菌的抑制作用较强，聚赖氨酸、苹果多酚、茶多酚、Nisin对特定腐败菌的抑制作用各有优、劣，普鲁兰多糖没有抑菌作用；复配最佳保鲜剂组合及质量浓度为抗菌肽（14.25 g/L）、纳他霉素（2.50 g/L）、苹果多酚（4.00 g/L）和壳聚糖（2.28 g/L）。该复配保鲜剂比对照能延长冷却肉货架期4～6 d。     

牛肉火腿切片的腐败微生物鉴定及贮藏过程中的品质变化

对牛肉火腿切片的腐败微生物进行了鉴定。结果表明,腐败产品中的细菌主要是乳杆菌属兼性异型发酵菌——干酪乳杆菌(Lactobacillus casei)。干酪乳杆菌发酵产酸、产气是牛肉火腿切片胀袋、出水的根本原因。并研究了贮藏过程中不同包装、温度、光照条件对品质变化的影响。光照对真空包装的牛肉火腿切片的脂肪氧化及色泽变化影响都较小,但对气调包装的a值影响较大,造成褪色明显。保持低温环境对于抑制乳杆菌的生长繁殖,延长产品货架期具有重要作用。     

Effect of high pressure treatment on microbial populations of sliced vacuum-packed cooked ham

In this study, culture-dependent and culture-independent approaches were used to reveal the microbial diversity and dynamic changes occurring in sliced vacuum-packed cooked ham after high pressure processing (HPP, 400MPa or 600MPa for 10min at 22°C) during refrigerated storage over 90days. Direct extraction of genome DNA and total RNA from meat samples, followed by PCR-denaturing gradient gel electrophoresis (DGGE) and RT-PCR-DGGE on 16S rDNA V3 region, was performed to define the structure of the bacterial populations and active species in pressurized cooked ham. Results showed that HPP affected differently the various species detected. The predominant spoilage organisms of cooked ham, such as Lactobacillus sakei and Lactobacillus curvatus, were found to be very sensitive to pressure as they were unable to be detected in HPP samples at any time during refrigerated storage. Weissella viridescens and Leuconostoc mesenteroides survived HPP at 600MPa for 10min at 22°C and were responsible for the final spoilage. An RNA-based DGGE approach clearly has potential for the analysis of active species that have survived in pressurized cooked ham. High pressure processing at 400 or 600MPa for 10min at room temperature (22°C) has a powerful inhibitory effect on the major spoilage bacteria of sliced vacuum-packed cooked ham. High pressure treatment may lead to reduced microbial diversity and improve the products' safety.     

Inactivation of food spoilage bacteria by high pressure processing: Evaluation with conventional media and PCR–DGGE analysis

Microbial diversity and dynamic changes of sliced vacuum-packed cooked ham during refrigerated storage (0–90 days) after high pressure processing (400 MPa at 22 °C for 10 min) was investigated by using culture-dependent and culture-independent approaches. Isolation of genome DNA and total RNA directly from meat samples, followed by PCR–denaturing gradient gel electrophoresis (DGGE) and RT-PCR–DGGE on 16S rDNA V3 region, was performed to describe the structure of the bacterial community and active species in pressurized sliced cooked ham. The DGGE profile showed that most spoilage bacteria including Lactococcus garvieae, Weissella cibaria, Lactobacillus sakei, Lactobacillus curvatus, Weissella paramesenteroides, Leuconostoc carnosum and Lactococcus lactis subsp. lactis were completely inactivated after high pressure processing (HPP), whereas Weissella viridescens and Weissella minor survived HPP and induced the final spoilage. The microbial diversity of HPP samples during the whole refrigerated storage period was extremely simple. Our results clearly indicated that HPP was an efficient method for avoiding the growth of the major spoilage bacteria and could be used to prolong the shelf-life of sliced vacuum-packed cooked ham.     

Shelf-life extension of cooked ham model product by high hydrostatic pressure and natural preservatives

The inactivation of different spoilage organisms and surrogate pathogens in a cooked ham model product by high pressure (HP) treatment (100–700 MPa, 5–40 °C, 10 min) was investigated. A 5 log reduction could be achieved at ≥ 600 MPa at ≥ 25 °C. Subsequently, the shelf-life of packaged sliced product was studied during storage (7 °C) after treatment at 600 MPa (10 °C, 10 min) in combination with caprylic acid and Purasal^®. Without HP treatment, a plate count of 6 log CFU/g was reached after 40 days, both in presence and absence of antimicrobials. HP treatment delayed this initiation of spoilage to 59 days in absence of antimicrobials. However, microbial growth was completely suppressed during at least 84 days in the HP treated products containing caprylic acid or Purasal^®. HP treatment increased drip loss but had no or little effect on colour and sensorial evaluation by a taste panel. However, the antimicrobials had a negative influence on the flavour and aroma at the concentrations used.

Industrial relevance

With a steadily increasing number of commercial applications being introduced on the market, HP pasteurization is growing out of its infancy. To further support this development, there is a need of integrated studies that translate fundamental scientific findings from simplified laboratory model systems to the complexity and scale of real food products. In this work, we determined HP processing conditions to control spoilage and pathogenic bacteria in a cooked ham model product, and subsequently conducted a large pilot scale experiment comprising a total of 432 individual packages of sliced cooked ham product, in which the microbiological, physicochemical and sensorial quality was evaluated during refrigerated storage after HP treatment. In addition, the usefulness of the natural preservatives caprylic acid and lactate-diacetate as an additional hurdle was also studied. This study is one of the most comprehensive available in the literature to document the shelf-life extension that can be achieved with HP treatment of cooked ham.     

Effective use of nisin to control lactic acid bacterial spoilage in vacuum-packed bologna-type sausage.

Lactic acid bacteria (LAB) commonly cause spoilage in minimal heat-treated vacuum-packed cured delicatessen meats. Predominant species are Lactobacillus sake and L. curvatus. LAB strains isolated from spoiled products of this type (liver sausage, ham and bologna sausage) were found to be sensitive to low nisin concentrations (maximum of 1.25 microg g(-1)). Addition of 25 microg g(-1) nisin (as Nisaplin) inhibited the growth of LAB spoilage organisms inoculated into vacuum-packed pasteurized bologna-type sausages stored at 8 degrees C. Control sausages became spoiled (>10(8) LAB CFU g(-1)) by day 7, whereas sausages containing nisin remained unspoiled for >50 days. The effect of three types of phosphates (used as emulsifiers) on nisin activity in the sausages was compared. LAB growth rate was fastest in samples containing orthophosphate, and slowest in sausages containing diphosphate. The shelf life was also greatly extended in the latter. Fat content also affected nisin activity. Nisin activity (as indicated by LAB inhibition) was greatest in samples containing 15% > 25% > 37% (wt/wt) fat. In a sausage formulation containing 37% fat and incorporating diphosphate as emulsifier, levels of nisin as low as 2.5 microg g(-1) showed antibacterial effects. A nisin level of 6.25 microg g(-1) totally inhibited LAB growth for over 4 weeks and 25 microg g(-1) for 5 weeks. Spoilage control was achieved in the same sausage formulation but with 25% (wt/wt) fat; 12.5 microg g(-1) nisin prevented LAB growth for 5 weeks.     

Interactive inhibition of meat spoilage and pathogenic bacteria by lysozyme,nisin and EDTA in the presence of nitrite and sodium chloride at 24 degrees C

To develop a nisin- and lysozyme-based antimicrobial treatment for use with processed ham and bologna, in vitro experiments were conducted to determine whether inhibition enhancing interactions occur between the antimicrobials lysozyme, chrisin (a commercial nisin preparation), EDTA, NaCl and NaNO₂. Inhibitory interactions were observed between a number of agents when used against specific pathogenic and spoilage bacteria. The observed interactions included lysozyme with EDTA (Enterococcus faecalis and Weissella viridescens), chrisin with EDTA (all Gram-positive organisms), EDTA with NaCl (Escherichia coli, Salmonella enterica serovar Typhimurium, Serratia grimesii), EDTA with nitrite (E. coli, Lactobacillus curvatus, Leuconostoc mesenteroides, Listeria monocytogenes, S. Typhimurium), chrisin with nitrite (Lc. mesenteroides, L. monocytogenes), and NaCl with nitrite (S. Typhimurium, Shewanella putrefaciens). Previous reports have described interactions between nisin with EDTA that resulted in enhanced antimicrobial effect against Gram-negative bacteria, or lysozyme with nisin against Gram-positive bacteria. These interactions were not observed in these experiments. We observed that unlike previous studies, these experiments were conducted on growing cells in nutrient broth, rather than under conditions of nutrient limitation. We propose that screening of antimicrobials for use in food systems in nutrient-deficient systems is inappropriate and that new protocols should be developed.     

Development of a PCR-culture technique for rapid detection of yeast species in vacuum packed ham

A rapid assay for detection of yeast species in vacuum packed ham has been developed based on the polymerase chain reaction (PCR) coupled to a 24 h pre-enrichment at 25 °C. DNA was isolated from yeast inoculated ham samples and amplified using primers specific for the 18S rRNA gene sequences of yeasts. A detection limit of 10(2) CFU/cm(2) was achieved following enrichment of samples experimentally inoculated with three yeast species frequently associated with meat products spoilage: Debaryomyces hansenii, Yarrowia lipolytica, and Kluyveromyces marxianus. Likewise, commercial sliced and vacuum packed ham samples were analysed using the PCR-culture technique. The results obtained in this work show that PCR amplification of a conserved region of the 18S rRNA gene in the yeast species could be potentially used as a rapid tool for detection of low levels of viable spoilage yeasts in meat products.     

Control of Pathogenic and Spoilage Microorganisms in Fresh‐cut Fruits and Fruit Juices by Traditional and Alternative Natural Antimicrobials

ABSTRACT: Traditional antimicrobials have been extensively used for many years. However, consumers are currently demanding wholesome, fresh‐like, and safe foods without addition of chemically synthesized preservatives. The application of novel natural antimicrobials to assure safety of fresh‐cut fruits and unpasteurized juices while preventing quality loss is a promising alternative. The effectiveness of these natural substances added to fruit derivatives has been studied by different researchers. Antimicrobials of animal (lactoperoxidase, lysozyme, and chitosan), plant (essential oils, aldehydes, esters, herbs, and spices), and microbial origin (nisin) can be used to effectively reduce pathogenic and spoilage microorganisms in fresh‐cut fruits and fruit juices. Nevertheless, the use of these compounds at a commercial level is still limited due to several factors such as impact on sensory attributes or, in some cases, regulatory issues concerning their use. Therefore, extensive research on the effects of each antimicrobial on food sensory characteristics is still needed so that antimicrobial substances of natural origin can be regarded as feasible alternatives to synthetic ones.     

乳酸链球菌素对乳酸菌抑菌作用的研究

目的：为了观察Nisin 对乳酸菌的抑菌效果,探讨Nisin 作为食品级载体筛选方法的最佳抑菌浓度和持续时间。方法：采用试管稀释法和纸片扩散法检测Nisin 对乳酸菌的抑菌浓度,并根据乳酸菌的OD600nm 作出生长曲线,以研究Nisin 对乳酸菌的抑菌效果。结果：Nisin 对乳品工业常用乳酸菌具有较强的抑菌作用,仅某些乳酸乳球菌对Nisin 表现出抗性;Nisin 对乳酸菌有较持久的抑菌效果,可达30～48h 以上。结论：该实验为Nisin 作为食品级载体筛选方法的最佳抑菌浓度和持续时间提供了依据。     

Antimicrobial Activities of Nisin,Tea Polyphenols,and Chitosan and their Combinations in Chilled Mutton

Antimicrobial activities of nisin, tea polyphenols (TPs), and chitosan, and their combinations were evaluated against both Gram‐positive bacteria (GPB) and Gram‐negative bacteria (GNB) by the agar dilution method. Results showed that the MIC of nisin was 2.44 to 1250 mg/L for GPB and reached 5000 mg/L for GNB. The MICs of TPs and chitosan were 313 to 625 mg/L and 469 mg/L for GNB, and 156 to 5000 mg/L and 234 to 938 mg/L for GPB, respectively. These results indicated that TPs and chitosan exhibited inhibitory effects against both GPB and GNB, whereas nisin inhibited the growth of GPB only. Based on the orthogonal test of their MICs, and evaluation of preservative effect and sensory attributes in chilled mutton, the optimum combination was chosen as 0.625, 0.313, and 3.752 g/L for nisin, TPs, and chitosan, respectively. By using the optimum treatment, the shelf life of chilled mutton was extended from 6 to 18 d at 4 °C in the preservative film packages. These results indicate that the combination of nisin, TPs, and chitosan could be used as preservatives to efficiently inhibit the growth of spoilage microorganisms and pathogens in meat, thus improving the safety and shelf life of chilled mutton.