真空包装冷却猪肉冷藏过程中菌相变化

应用传统微生物培养和PCR-DGGE方法研究真空包装冷却猪肉4℃贮藏过程中的菌相变化。细菌培养计数结果表明,乳酸菌生长迅速,在贮藏后期即超过了细菌总数值。DGGE结合16S rRNA基因序列分析结果表明,贮藏初期肉中初始菌相较复杂,贮藏末期主要是漫游球菌、肉食杆菌、乳杆菌、乳球菌和热死环丝菌成为优势腐败菌。     

真空包装腌萝卜干中腐败微生物的抑制研究

实验用苯甲酸钠、山梨酸钾、尼泊混合酯、脱氢醋酸钠、双乙酸钠5种防腐剂,抗氧化剂植酸,酸味剂富马酸、水分保持剂六偏磷酸钠、乳化剂蔗糖酯以及复合防腐剂对真空包装腌萝卜干中6种腐败微生物(克柔念珠菌、枯草芽孢杆菌、蜡样芽孢杆菌、金黄色葡萄球菌、表皮葡萄球菌和短乳杆菌)进行了抑制试验,并研究了氯化钠、乙醇、pH对腌萝卜腐败微生物的押制作用.结果表明:pH为4.0,6%氯化钠,5%乙醇对腌萝卜干腐败微生物有较好抑制.单一防腐菌抑菌效果不理想.双乙酸钠、富马酸、尼泊混合酯的抑菌效果相对较好,脱氢醋酸钠对表皮葡萄球菌和短乳杆菌的抑制较强.脱氢醋酸钠+富马酸组合、双乙酸钠+富马酸组合、脱氢醋酸钠+双乙酸钠组合综合抑菌效果好.     

不同切割方式对真空包装净菜菌相的影响

以真空包装土豆、胡萝卜和莴苣为原料,研究不同切割方式对真空包装净菜的菌相组成及数量变化的影响.结果表明:不同的净菜中主要微生物包括酵母菌属、乳酸菌属、肠杆菌科、假单胞菌属,微球菌和葡萄球菌属.初始时,不同切割方式对净菜微生物的菌相组成没有影响,但对其数量有显著影响,其中切块的微生物数量最少,切片和切丝根据原料特性不同微生物数量有所变化.腐败后,切割方式对净菜腐败微生物菌相组成和数量均有影响,但微球菌和葡萄球菌属在切丝土豆和切丝胡萝卜中未检出.     

Lactobacillus sakei对真空包装切片火腿的特定腐败研究

研究从真空包装切片火腿中分离得到的腐败菌清酒乳杆菌清酒亚种对该产品品质变化的影响,确定其在低温肉制品中的特定腐败特征。均匀接种104cfu/mL菌悬液于二次杀菌的切片火腿上,真空包装,4℃贮藏,于0、3、7、15、25、35天取样分析:乳酸菌数、pH值、TVB-N值、生物胺变化。结果表明:清酒乳杆菌清酒亚种具有很强的生长竞争力,发酵肉品中的糖类造成pH值下降,形成黏液,并生成酪胺、腐胺等典型腐败生物胺,产生腐败味。L.sakei subsp.sakei是造成真空包装切片火腿发酸变味、发黏起丝、腐败臭味等腐败现象的特定腐败菌。     

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。     

冷藏条件下盐水鸭菌相消长规律研究

采用选择性培养基对真空包装和托盘包装的盐水鸭在低温(4±1℃)贮藏过程中的主要微生物进行了选择性培养,研究了盐水鸭冷藏过程中的菌相消长规律.结果显示:盐水鸭初始菌相以递减的顺序分别是乳酸菌、肠杆菌、假单胞菌和热死环丝菌.盐水鸭在真空包装条件下微生物生长速率要低于托盘包装,乳酸菌和肠杆菌是盐水鸭的优势腐败菌.     

真空包装牛肉冰温贮藏过程中优势腐败菌的分离鉴定

为确定导致真空包装牛肉腐败的优势致腐菌,将牛肉真空包装后在冰温(-1±1)℃条件下贮藏,利用选择性培养基(CFC培养基、STAA培养基、MRS培养基、VRBDA培养基)分离筛选各类腐败菌,并通过分离纯化、形态学鉴定、16S r DNA序列分析等手段,对冰温贮藏真空包装牛肉的优势腐败菌进行鉴定。结果表明:真空包装牛肉在冰温条件下贮藏至15 d时优势腐败菌为乳酸菌(8.54 lg cfu/g)、假单胞菌(8.28 lg cfu/g),热死环丝菌和肠杆菌也是腐败菌,数量分别为6.51 lg cfu/g和5.31 lg cfu/g。形态和分子学鉴定证实,真空包装牛肉的优势腐败菌株包括变形斑沙雷菌(Serratia proteamaculans)、水生拉恩氏菌(Rahnella aquatilis)、热死环丝菌(Brochothrix thermosphacta)、干酪乳杆菌(Lactobacillus sakei)、分叉肉毒杆菌(Carnobacterium divergens)和脆假单胞菌(Pseudomonas fragi),以及未能鉴定到种的沙雷氏菌属、肉食杆菌属的菌株。     

巴西研究火腿中的乳链菌肽对乳酸菌的抑制效果

<正>在一些气调包装或者真空包装的肉制品腐败微生物中,乳酸菌占主导地位,许多的研究者已经发现清酒乳酸菌会导致肉制品特别是切片熟火腿的变质。巴西科学家对真空包装条件下切片熟火腿的乳酸菌控制进行了研究,他们首先采用部分析因设计在肉汤中加入氯化钠、乳酸钠、异抗坏血酸钠、乳链菌肽和片球菌素等作为抑菌剂,结果表明:乳链菌肽对清酒乳     

贵州少数民族酸肉、酸鱼中乳酸菌的分离鉴定

采用传统微生物分离方法进行乳酸菌纯种分离,利用16S rRNA序列分析方法进行乳酸菌鉴定,从7个酸肉、酸鱼样品中共分离出14株乳酸菌,有乳杆菌属、环丝菌属、乳球菌属3个属,9个种.从其中鉴定出7株乳酸菌,分别是:植物乳杆菌(Lactobacillus plantarum)、消化乳杆菌(Lactobacillus alimentarius)、清酒乳杆菌(Lactobacillus sakei)、泡菜乳杆菌(Lactobacillus kinchi)、清酒乳杆菌亚种(肉)(Lactobacillus sakei subsp.carnosus)、草乳杆菌(Lactobacillus graminis)、弯曲乳杆菌(Lactobacillus curvatus).     

真空包装素皮鸭的初始菌相分析与优势菌初步鉴定

以干豆腐皮为原料,对其进行卤制、蒸煮、冷却、油炸、浸煮、沥干等工序后真空包装于4℃条件下7天保藏,对其初始菌相和保藏期间各种微生物的生长变化进行分析。结果表明:素皮鸭样品的初始菌相以乳酸菌(39%)、假单胞菌(29%)和肠杆菌(24%)为主,其次为球菌(5%)和酵母菌(3%)。在保藏期间的3~7天里,乳酸菌、假单胞菌和肠杆菌一直处于增长趋势,乳酸菌增长快而肠杆菌增长慢,但一直保持增长趋势。因此,导致素皮鸭腐败变质的主要优势菌为乳酸菌、假单胞菌和肠杆菌。     

水产品特定腐败菌研究进展

对国内外水产品特定腐败菌(specific spoilage organism,SSO)的研究进展进行综述。在有氧冷藏中,水产鲜品最常见的SSO 为假单胞菌(Pseudomonas spp.)与腐败希瓦氏菌(Shewanella putrefaciens)。真空冷藏或气调包装水产品的SSO,国内外一致报道的有磷发光杆菌(Photobacterium phosphoreum)、乳酸菌(Lactobacillus)和肠杆菌(Enterobacteriaceae)。温和加工水产品的SSO 的情况较为复杂,通常为乳酸菌(Lactobacillus)、磷发光杆菌(Photobacterium phosphoreum)、肠杆菌(Enterobacteriaceae)等。SSO 的应用领域之一是建立SSO 数学模型,预测产品的腐败进程与剩余货架期;应用领域之二是靶向抑制SSO,延长货架期。     

Lactobacilli and tartrazine as causative agents of red-color spoilage in cucumber pickle products

ABSTRACT:  The cucumber pickling industry has sporadically experienced spoilage outbreaks in pickled cucumber products characterized by development of red color on the surface of the fruits. Lactobacillus casei and Lactobacillus paracasei were isolated from 2 outbreaks of this spoilage that occurred about 15 y apart during the last 3 decades. Both organisms were shown to produce this spoilage when inoculated into pickled cucumbers while concomitantly degrading the azo dye tartrazine (FD&C yellow nr 5). This food dye is used as a yellow coloring in the brine cover solutions of commercial pickled cucumber products. The red color does not occur in the absence of tartrazine, nor when turmeric is used as a yellow coloring in the pickles. Addition of sodium benzoate to the brine cover solutions of a pickled cucumber product, more specifically hamburger dill pickles, prevented growth of these lactic acid bacteria and the development of the red spoilage.     

Lactic acid bacteria in marinades used for modified atmosphere packaged broiler chicken meat products

Lactic acid bacteria (LAB) in some marinades commonly used in Finland for modified atmosphere packaged poultry meat products were enumerated and identified to determine whether the marinades contained LAB species that cause meat spoilage. The concentrations of LAB in 51 marinade samples ranged from less than 100 to 8.0 x 10(5) CFU/ml. Seventeen of the samples produced LAB growth only after enrichment, and in five samples no growth was detected either by direct culturing or enrichment. Eighty-eight randomly selected isolates, 51 from the enumerated plates and 37 from enriched samples, were identified using a database of 16S and 23S rRNA gene HindIII restriction fragment length polymorphism patterns of over 300 type and references LAB strains as operational taxonomic units in numerical analyses. The predominating LAB in the enumerated samples was Lactobacillus plantarum (25 of 51 isolates). Eleven isolates were identified as Lactobacillus paracasei subsp. paracasei, and nine were Lactobacillus parabuchneri. None of these species are considered specific spoilage LAB in marinated modified atmosphere packaged poultry meat products nor have they been reported to dominate in unspoiled late-shelf-life products. These results indicate that even though marinades may contain high numbers of LAB, they are not necessarily sources of specific meat spoilage LAB. Therefore, risks associated with meat quality are not predicted by quantitative enumeration of LAB in marinades.     

Microbial spoilage of date rutab collected from the markets of Al-Hofuf city in the Kingdom of Saudi Arabia

Microbial spoilage was monitored in 520 samples of dates in the rutab stage purchased from retail outlets in Al-Hofuf City, Saudi Arabia, and incubated in the laboratory under different conditions. No spoilage was observed in 130 samples incubated in open containers at 5 or 30 degrees C for up to 60 days. Spoilage occurred in 42 of 130 samples incubated in covered containers at 5 degrees C after about 80 days and was caused mainly by Penicillium spp. and Cladosporium spp. Mixed populations of lactic acid bacteria, yeasts, and molds were mostly responsible for spoilage in about 10 to 14 days of the 130 samples incubated in covered containers at 30 degrees C. The dominant spoilage organisms under these conditions were Lactobacillus delbrueckii subsp. delbrueckii, Lactobacillus fructivorans, Lactobacillus collinoides, Lactobacillus salivarius, Zygosaccharomyces mellis or Zygosaccharomyces rouxii, Candida sphaerica, Candida rugosa, Candida colliculosa, Candida pelliculosa, Candida famata, Pichia anomala, Aspergillus niger, and Penicillium spp. Although some variations among date cultivars in susceptibility to microbial spoilage were observed, moisture content and storage temperature were the most critical factors affecting spoilage.     

Culture media for non-sporulating gram-positive food spoilage bacteria.

The spoilage association especially of protein-rich foods can be dominated by Gram-positive bacteria, notably lactic acid bacteria (LAB) which affect vacuum packaged refrigerated processed meats and some dairy products. New food ecosystems are being created by novel packaging and processing technologies, resulting in spoilage associations differing from those previously reported. In addition, improvement in identification methods, allow the detection and isolation of 'novel' bacterial groups, e.g., Carnobacterium spp. This review considers the genera Aerococcus, Brevibacterium, Brochothrix, Carnobacterium, Kurthia, Lactobacillus, Leuconostoc, Microbacterium, Micrococcus, Pediococcus and Propionibacterium. Strictly selective procedures, including incubation temperature and atmosphere, are not yet available for the genera Aerococcus, Brevibacterium, Microbacterium and Micrococcus, and only with some limitations for Kurthia and Propionibacterium. On the other hand, a causative role in food spoilage has not been established clearly for all those groups, some of which may be 'opportunistic' in their behaviour. The LAB groups Lactobacillus, Leuconostoc and Pediococcus ('LLP-Group') often share similar habitats and show similar physiological behaviour on a number of elective and selective media. Modifications to increase selectivity have been based mainly on de Man, Rogosa and Sharpe (MRS) or Rogosa agar, and include pH reduction, supplementation with chemical preservatives (e.g., sorbic acid and nitrate) and the use of reduced atmospheres or suboptimal incubation temperatures. Carnobacteria differ from other LAB in their non-aciduric nature, and selective plating procedures use high-pH media (pH 8-9) by which competitors (mainly lactobacilli) are eliminated.     

Spoilage of value-added, high-oxygen modified-atmosphere packaged raw beef steaks by Leuconostoc gasicomitatum and Leuconostoc gelidum

Moisture-enhancing and marinating of meats are commonly used by the meat industry to add value to raw, retail products. Recently in Finland, certain value-added beef steak products have proven to be unusually susceptible to microbial spoilage leading to untoward quality deteriorations during producer-defined shelf-life. This study was conducted to evaluate the role of lactic acid bacteria (LAB) in the premature spoilage of value-added beef packaged under high-oxygen modified atmospheres. Spoilage was characterised by green discolouration and a buttery off-odour. The predominant LAB in eight packages of spoiled, marinated or moisture-enhanced beef steaks were identified by reference to a 16 and 23S rRNA gene restriction fragment length polymorphism pattern (ribotype) database. Leuconostoc gasicomitatum, Leuconostoc gelidum, Lactobacillus algidus, Lactobacillus sakei and Carnobacterium divergens were found to predominate in the LAB populations at numbers above 10(8) CFU/g. Inoculation of moisture-enhanced steaks with LAB strains and strain mixtures originating from the spoiled products demonstrated the spoilage potential of L. gasicomitatum and L. gelidum isolates. These two species produced green surface discolouration and buttery off-odours similar to these found in the spoiled, commercial products.     

Identification of lactic acid bacteria involved in the spoilage of pasteurized “foie gras” products

The spoiling microflora of a re-packaged French “foie gras” product was studied. A total of 54 isolates, originating from two different factories, were identified using phenotypical and molecular methods (partial 16S rDNA sequencing). Weissella viridescens was the main species detected in the products from factory 1 (64% of the isolates). These products had a low lactic acid concentration and were considered as non-spoiled. The microflora of factory 2 was dominated mainly by the genus Lactobacillus (95% of the isolates), and the high lactic acid concentration of these products was linked with a strong spoilage. Among the 30 Lactobacillus strains, three species were predominant: Lactobacillus sakei (nine isolates), Lactobacillus coryniformis (eight isolates) and Lactobacillus paraplantarum (five isolates). Challenge tests were performed to confirm the involvement of the Lactobacillus strains in the spoilage of the product. Sterile “foie gras” samples were inoculated with 14 LAB strains from the collection. The most acidifying strains belonged to the species L. sakei, Lactobacillus plantarum and L. paraplantarum. This confirmed the role of the strains from the Lactobacillus genus as the main spoilers of “foie gras” products and will be useful to design new quality protocols and extend the shelf-life of these products.     

125th Anniversary Review: Microbiological Instability of Beer Caused by Spoilage Bacteria

Beer has been generally recognized as a microbiologically stable beverage. However, microbiological incidents occasionally occur in the brewing industry. The microbiological instability of beer is often caused by bacteria consisting of four genera, Lactobacillus, Pediococcus, Pectinatus and Megasphaera. Lactobacillus and Pediococcus belong to the lactic acid bacteria (LAB), whereas Pectinatus and Megasphaera form a group of strict anaerobes that are known as intermediates between Gram‐positive and Gram‐negative bacteria. The frequencies of beer spoilage incidents caused by these four genera have been reported to exceed 90% in Europe and therefore Lactobacillus, Pediococcus, Pectinatus and Megasphaera are considered to be the principal spoilage agents in the brewing industry. Thus, this review consists of three parts involving these four genera. The first part describes spoilage LAB in alcoholic beverages with some emphasis on beer spoilage LAB. In this part, the emergence and evolution of these spoilage LAB is discussed, the insight of which is useful for developing quality control methods for these beverages. The second part is devoted to the hop resistance in beer spoilage LAB. This area of research is evolving rapidly and recent progress in this field is summarized. The third part concerns Pectinatus and Megasphaera. Although this group of beer spoilage bacteria has been described relatively recently, the incident reports in Europe increased in the early 1990s, reaching around 30% of spoilage incidents. Various aspects of Pectinatus and Megasphaera, ranging from their taxonomy and beer spoilage ability to detection and eradication methods are described.     

The spoilage microflora of cured, cooked turkey breasts prepared commercially with or without smoking

Lactobacillus sakei subsp. carnosus was predominant in the spoilage flora of sliced, vacuum-packed, smoked, oven-cooked turkey breast fillets which developed mild, sour spoilage flavors after 4 weeks storage at 4 degrees C. In contrast, Leuconostoc mesenteroides subsp. mesenteroides predominated in the spoilage flora of sliced, vacuum-packed, unsmoked, boiled turkey breast fillets from the same plant which were also stored at 4 degrees C. The spoilage flora of the unsmoked breasts grew faster than that of the smoked breasts and was more diverse. Lactobacillus sakei, Weissella viridescens and an atypical group of leuconostoc-like bacteria were also members of the unsmoked turkey breasts flora. Consequently, the unsmoked breasts spoiled after 2 weeks at 4 degrees C: the packs swelled and the meat developed strong sour odors and flavors and abundant slime. Except for the unidentified leuconostocs, which apparently survived boiling of the unsmoked turkey, all the spoilage organisms contaminated the meats during the slicing and vacuum packaging operations. From their biochemical reactions and cellular fatty acid profiles, the atypical leuconostocs were more closely related to Leuconostoc carnosum than W. viridescens. Carnobacteria and Brochothrix thermosphacta were present in relatively large numbers on the raw turkey, but were not numerous in the spoilage flora of the cooked, vacuum-packed meat products.     

Shelf life of modified atmosphere packed cooked meat products: addition of Na-lactate as a fourth shelf life determinative factor in a model and product validation

Cooked meat products are often post-contaminated because of a packaging and/or slicing step after the pasteurisation process. The shelf life is therefore limited and can be extended by adding Na-lactate. A previously developed model for the spoilage of gas packed cooked meat products, including temperature, water activity and dissolved CO2 as independent variables, was extended with a fourth factor: the Na-lactate concentration in the aqueous phase of the meat product. Models were developed for the maximum specific growth rate mu(max) and the lag phase lambda of the specific spoilage organism Lactobacillus sake subsp. carnosum. Quadratic response surface equations were compared with extended Ratkowsky models. In general, response surface equations fitted the experimental data best but in the case of mu(max) the response surface model predicted illogical growth behaviour at low water activities and high Na-lactate concentrations. A extensive product validation of the mathematical models was performed by means of inoculated as well as naturally contaminated industrially prepared cooked meat products. The deviations of the experimentally determined versus predicted growth parameters in inoculated cooked meat products were in general small. Both types of models were also able to predict the shelf life of naturally contaminated cooked meat products, except for paté where an under-estimation of the shelf life was predicted by the response surface equations. The validation studies revealed higher accuracy of the extended Ratkowsky models in comparison to the response surface equations. A significant shelf life extending effect of Na-lactate was predicted, which was more pronounced at low refrigerated temperatures. A synergistic effect has also been noticed between Na-lactate and carbon dioxide which, at least partly, could be explained by the pH-decreasing effect of CO2.