Spoilage characteristics of ground beef with added lactic acid bacteria and rosemary oleoresin packaged in a modified-atmosphere package and displayed at abusive temperatures

Lactic acid bacteria (LAB) can reduce Escherichia coli O157:H7 and Salmonella spp. in ground beef during storage. Furthermore, the addition of rosemary oleoresin (RO), a natural antioxidant, to ground beef has been shown to increase shelf life and is commonly used in modified-atmosphere packaged (MAP) ground beef. This study evaluated the effects of LAB and RO treatment on the shelf life and stability of MAP ground beef displayed at abusive (10°C) temperatures for 36 h. Subjective and objective sensory analyses were conducted to determine spoilage endpoints. Trained and consumer panel responses and Hunter lightness (L*), redness (a*), and yellowness (b*) values were not affected (P = 0.62, 0.66, 0.45) by LAB addition, although RO inclusion improved (P < 0.05) lean color. Ground beef with LAB and RO had significantly less (P < 0.0001) thiobarbituric acid reactive substance values than control ground beef, indicating decreased lipid oxidation. Additionally, RO inclusion reduced (P < 0.0001) off odors, as determined by trained and consumer odor panelists. Overall, the addition of LAB did not negatively affect beef color, odor, or oxidative rancidity, suggesting that LAB can be added to ground beef in MAP packaging as a processing intervention without detrimentally affecting shelf life or stability.     

乳酸菌或有机酸盐与尿素复配添加对紫花苜蓿混合青贮的影响

以紫花苜蓿、稻秸和麦麸按质量比8:1:1为混合青贮原料,设计双因素试验,因素A:乳酸菌(LA)和有机酸盐(AS),因素B:尿素添加量分别为1.5(U1)、3.0(U2)和4.5(U3)g·kg-1FW和未添加组(U0).青贮45 d后分析发酵品质、营养品质和有氧稳定性,结果表明:乳酸菌处理组的pH值、粗蛋白含量、中性洗...     

Isolating and evaluating lactic acid bacteria strains for effectiveness on silage quality at low temperatures on the Tibetan Plateau

Four lactic acid bacteria (LAB) strains isolated from straw silages on the Tibetan Plateau were characterized, and their effects on the fermentation quality of Italian ryegrass (Lolium multiflorum Lam.) at different temperatures (10°C, 15°C and 25°C) were studied. These LAB isolates were evaluated using the acids production ability test, morphological observation, Gram staining, physiological, biochemical and acid tolerance tests. All the isolates (M1, LM8, LO7 and LOG9) could grow at 5‐20°C, pH 3.5‐7.0 and NaCl (3.0%, 6.5%). Strains M1, LM8, LO7 and LOG9 were identified as Lactobacillus plantarum, L. coryniformis, Pediococcus pentosaceus and P. acidilactici, respectively, by sequencing 16S ribosomal DNA. The four isolates were added to Italian ryegrass for ensiling for 30 days at various temperatures. Compared with the corresponding control, inoculating with isolates M1, LM8 and LO7 could improve the silage quality of Italian ryegrass at low temperatures, indicated by significantly (P < 0.05) higher lactic acid (LA) contents and ratios of lactic acid/acetic acid (LA/AA), and significantly (P < 0.05) lower pH and ammonia nitrogen/total nitrogen (AN/TN). Compared with other isolates, LM8 performed better at 10°C and 15°C, indicated by the higher (P < 0.05) LA content and ratio of LA/AA, and the lower (P < 0.05) pH and AN/TN.     

乳酸菌胞外多糖

本文综述了目前关于乳酸菌胞外多糖(EPS)的结构、化学组成、影响乳酸菌EPS产生的因素等方面的研究现状及乳酸菌胞外多糖的应用。     

饲用高效乳酸菌与纤维素分解菌混合培养生长特性研究

试验将本课题组分离到的高效乳酸菌A4和A7与两株纤维素分解菌Nf和Y6等比例混合培养在2%蔗糖溶液中,测其生长曲线,探讨这两类菌株混合后的生长特性。试验结果表明：各试验组达到稳定期时高效乳酸菌和纤维素分解菌活菌数等比例增加,可初步判断这两种菌并无相互抑制作用。而试验组（A4+A7）??（Nf+Y6）达到稳定期时间段,总活菌数量都比其他组高。这为将这两种菌混合后作为青贮饲料添加剂提供了试验依据。     

Canine intestinal lactic acid bacteria agglutinated with concanavalin A

Twenty-six out of 46 representative lactic acid bacteria (LAB) that we isolated from 36 dogs in a previous study were agglutinated by concanavalin A (ConA) at a concentration of 0.1563 mg/ml, while isolates did not agglutinate without the addition of ConA. Amongst the isolates, L. reuteri, L. mucosae, and E. canintestini agglutinated strongly, while L. gallinarum, L. kitasatonis, L. acidophilus, L. saerimneri, B. animalis ssp. animalis, P. acidilactici, and E. hirae did not agglutinate. ConA-agglutination of LAB was specifically inhibited by D-glucose, D-galactose, and D-mannose at a concentration of 1.563 mg/ml. Among the sugars, ConA-agglutination was strongly inhibited by D-mannose, while the inhibition level by D-glucose and D-galactose were lower than that of D-mannose. ConA- agglutination of all the LAB isolates was inhibited by D-mannose, except for L. reuteri (one species) and L. mucosae (two species). ConA-agglutination of Bifidobacterium spp. was inhibited by only D-mannose. Based on our results, ConA-agglutination of LAB seems to be strain-specific, but not species-specific.     

尖叶胡枝子青贮微生物数量变化及发酵特性

以尖叶胡枝子（Lespedeza hedysaroides）为原料,对其表面附生的2株乳酸菌（LH29、LH33）的生化特性、生长特性、产酸速率进行了研究,经传统鉴定方法及16S rRNA分析方法鉴定,LH29为戊糖片球菌,LH33为植物乳杆菌;发酵初期戊糖片球菌产酸速率优于植物乳杆菌,发酵中后期后者产酸速率优于前者;将SNOW LACT L (SL)和纤维素酶(AC) 2种添加剂添加至尖叶胡枝子中,研究了不同发酵时间微生物数量的动态变化及发酵品质。发酵初期,各种微生物的数量较青贮原料上的数量有较大的增长,发酵第2天,添加AC处理组的乳酸菌数量最高,SL+AC添加组的乳酸菌的数量显著高于对照组（P＜0.05）,发酵第30天,乳酸菌、好氧细菌、酵母菌、霉菌及大肠杆菌的数量有所减少,大肠杆菌减少更明显;各添加组与对照组相比,氨态氮及丁酸含量显著降低（P＜0.05）,乳酸含量明显提高（P＜0.05）。通过Flieg青贮饲料评分方案得出直接青贮饲料的发酵品质较差,等级为劣,而添加AC及SL+AC处理的青贮饲料发酵品质Flieg等级为优。     

乳酸菌的耐酸性机制

<正>乳酸菌是一类能利用可发酵糖产生大量乳酸的细菌的通称。乳酸菌在自然界分布广泛,可栖居于人和动物的肠道以及其它器官内。很久以前人们就利用乳酸菌来发酵动物制品(乳、肉、鱼等)和植物制品(蔬菜、葡萄酒、橄榄等)。随着食品发酵工业的不断发展壮大,开发利用乳酸菌的经济效益也不断在增长。虽然乳酸菌在发酵食品中的含量非常少,但是对食品的感官品质和质量却有决定性作用,因此,发酵剂菌株的质量功能特性和生长特性对于产品的成功发酵是非常必要的。乳酸菌不但包括在食品发酵中使用的一     

短芒大麦草青贮微生物特性研究及优良乳酸菌筛选

以短芒大麦草为研究对象,利用传统培养法从叶围和青贮发酵体系中分离出乳酸菌、大肠杆菌、好氧细菌、酵母菌和霉菌,并计数;结合细菌形态学、生理生化特征及16S rDNA序列分析鉴定分离出的乳酸菌菌株;通过研究乳酸菌的生长曲线、产酸特性及耐酸性,筛选优质乳酸菌。以期探明短芒大麦草叶围及青贮发酵体系中微生物菌群特性及青贮料中乳酸菌多样性,筛选出具有促发酵效果的乳酸菌菌株,为有益微生物饲料研发奠定基础。试验结果表明,短芒大麦草经青贮发酵后各微生物菌群数量发生不同程度变化,乳酸菌数量由0 cfu/g FM增加到4.00×10⁸ cfu/g FM,酵母菌数量由8.50×10⁵ cfu/g FM增加到1.02×10⁸ cfu/g FM,而好氧细菌、大肠杆菌和霉菌数量变化不明显;从短芒大麦草青贮发酵体系分离得到4株乳酸菌,经鉴定Lx36为Lactobacillus pentosus,Lx37为Lactobacillus brevis,Lx53为Pediococcus pentosaceus,Lx54为Lactobacillus parabuchneri;筛选得到1株益于青贮的乳酸菌株Lx36,约在20 h后进入稳定生长期,OD值达到4.21,且发酵12 h的pH仅为4.08,并可以在pH=3.0环境条件下生长。综上所述,青贮发酵是体系中各种微生物相互作用的过程,微生物菌群的数量及变化直接影响青贮饲料发酵品质。短芒大麦草青贮饲料中乳酸菌种类较丰富,筛选得到的戊糖乳杆菌繁殖速度快、产酸能力强同时表现出了较强的耐酸性,具有潜在的生产应用价值,适宜用作促发酵的青贮添加剂菌种。     

Characteristics of isolated lactic acid bacteria and their effectiveness to improve stylo (Stylosanthes guianensis Sw.) silage quality at various temperatures

Two lactic acid bacteria (LAB) strains, Pediococcus pentosaceus SC1 and Lactobacillus paraplantarum SC2 isolated from king grass silage, were characterized and their effectiveness to improve the silage fermentation quality of stylo (Stylosanthes guianensis Sw.) was studied. Strain SC1 was able to grow at a high temperature of 45°C, while SC2 did not. SC2 normally grew at a low pH of 4.0, while SC1 could not. These two strains and a commercial inoculant of LAB (L. plantarum, LP) were used as additives to stylo silage preparation at various temperatures (20°C, 30°C and 40°C). All LAB inoculants significantly (P < 0.05) reduced the pH value and ammonia-N content, and increased the ratio of lactic acid to acetic acid and quality score compared with the control. In addition, inoculating LAB strains markedly (P < 0.05) reduced butyric acid content at the temperatures of 30°C and 40°C. Compared to SC2 and LP strains, strain SC1 was the most effective for improving stylo silage quality at 20°C, indicated by the increase in lactic acid, ratio of lactic acid to acetic acid and quality score. At 30°C and 40°C, there were no significant differences among SC1, SC2 and LP treatments in pH values, contents of acetic acid, butyric acid and ammonia-N (P > 0.05).     

西藏地区藏北嵩草附着乳酸茵的理化特性

本研究以藏北嵩草（Kobresia littledalei）上附着的乳酸菌为研究对象，分离得到肠膜明串珠菌肠膜亚种两株，融合魏斯氏菌11株，食物魏斯氏菌6株，然后对这3种试验菌进行不同温度及pH条件下的生长试验、耐盐试验及糖发酵试验等生理生化特性的研究。结果表明，与常规条件下分离得到的相同菌株相比较，青藏高原极端环境中分离的魏斯氏乳酸菌和明串珠菌株都能在4~40 ℃的条件下生长，部分融合魏斯氏菌还可在50 ℃下微弱生长；耐酸碱试验表明，魏斯氏乳酸菌株都能在pH值为3.0和9.5的条件下生长；在耐盐性方面，部分魏斯氏菌可以在18%的NaCl下生长；在碳源利用方面，本研究提取的食物魏斯氏菌可利用半乳糖；融合魏斯氏菌可利用阿拉伯糖、蜜二糖、甘露醇。因此，藏北嵩草中所分离的乳酸菌比常规环境中的乳酸菌有较强的耐温性和耐酸碱性，而且能更广地利用碳源，从而为其在饲料青贮、酸奶发酵等方面的应用奠定基础。     

乳酸菌固态混合发酵研究

以玉米粉、豆粕、麦麸为基质,以保加利亚乳杆菌、嗜酸乳杆菌、嗜热链球菌为发酵菌种,采用固态发酵技术,以活菌数为指标,通过单因素和L9(34)正交试验确定了三种菌混合发酵的最佳条件,并对其发酵产物的常规营养成分进行分析测定。结果表明:固态基质中玉米粉:豆粕:麦麸=1:1:1、培养基初始含水量80%p、H值6.3、接种量为10%、三种菌接种比例为1:1:1、发酵温度40℃时的发酵效果最好。在此条件下,保加利亚乳杆菌数为3.0×109 CFU/g,嗜酸乳杆菌数为4.6×109 CFU/g,嗜热链球菌数为5.8×109 CFU/g,发酵产物粗蛋白质、粗脂肪和氨基酸态氮含量分别是发酵前的1.16、1.12和6.94倍。为开发一种新型生物饲料打下基础。     

优质乳酸菌的应用

人们的认识乳酸菌之前就已利用它们来加工和保存食品。目前，乳酸菌已广泛应用于发酵酸乳、干酪、发酵豆乳、酿造食品、腌渍物、面包、发酵肉制品及食品防腐保藏等方面，乳酸菌不仅可以提高食品保藏性和附加值，而且有其特殖生理活性和保健功能。     

乳酸菌在家禽生产中的应用

乳酸菌是人、畜禽胃肠道以及一些食物中的重要菌群之一,广泛用于食品、饲料和医药等领域,是一类具备多种益生功能的微生物.以乳酸菌为代表的微生态制剂,具有改善机体生长性能、促进机体免疫系统发育防止发生疾病、维持机体胃肠道微生态平衡、提升抗氧化能力、促进机体对营养物质的消化吸收等作用,一直是各大饲料企业以及家禽养殖业关注的焦点...     

猪源乳酸菌的分离、筛选、鉴定及产酸性能的研究

试验旨在分离、筛选出具有强抗逆性、产酸能力强的同源菌株。从28日龄断奶健康仔猪粪便分离得到30株乳酸菌,应用体外筛选法,筛选出在pH值2.5处理2h后的菌株13株;将此13株菌株通过浓度为0.2%胆盐后剩7株。采用牛津杯法进行抑菌试验,从7株菌中筛选出对大肠杆菌、沙门氏菌有较强抑菌作用的4株,分别为R11、R15、R18、R22,对此4株菌株进行产酸试验验证,都表现出强的产酸能力。对这4株菌进行鉴定性试验,结果R11为屎肠球菌,R15为鸡肠球菌,R18为嗜酸乳杆菌,R22为口乳杆菌。     

耐低温乳酸菌的分离与优化培养

从青贮玉米(Zea mays)以及新鲜泡菜中分离乳酸菌,通过初筛和复筛获得1株产酸能力较强的耐低温乳酸菌L2;对其进行了形态学描述和生理生化鉴定,对照伯杰式手册确定其种属;采用Box-Behnken实验设计进行培养条件优化实验,确定了该菌的最佳发酵条件。结果表明,该菌的最佳发酵条件为接种量3.1%、初始pH6.4、培养温度18.4 ℃。     

Oxalate-degrading capacities of lactic acid bacteria in canine feces

In this study, lactic acid bacteria in canine feces were isolated and identified, and their oxalate-degrading capacities were evaluated. The oxalate-degrading capacities were determined for 24 of 47 (51.06%) lactic acid bacteria isolates. Of these, 8 isolates [Leuconostoc mesenteroides (RL75), Lactococcus garvieae (CD2), Lactococcus subsp. lactis (CS21), Enterococcus faecium (CL71 and CL72), and Enterococcus faecalis (CD14, CS62, and CD12)] degraded more than 5% of the oxalate present, while the others degraded less than 5% of the oxalate in vitro. Isolates that degraded more than 5% of the oxalate present were selected for further examination. The oxalate-degrading capacities of individual isolates, a mixture of Enterococcus, a mixture of Lactococcus, and a mixture of the eight isolates were evaluated in media containing different concentrations of glucose (sufficient, insufficient, or no glucose). In comparison with the control medium, all of the individual isolates and mixtures of isolates could degrade oxalate in all three groups (P<0.05). In most cases, the isolates growing in medium with 20 g/L of glucose had higher oxalate-degrading capacities than those growing in medium with 2.5 g/L of glucose or no glucose. The mixture of all isolates showed higher oxalate-degrading capacity than the individual isolates and other mixtures. The oxalate-degrading capacities of the isolates were isolate dependent.     

Identification of lactic acid bacteria isolated from corn stovers

One hundred and twenty‐six strains were isolated from corn stover in Henan Province, China, of which 105 isolates were considered to be lactic acid bacteria (LAB) according to Gram‐positive, catalase‐negative and mainly metabolic lactic acid product. Analysis of the 16S ribosomal DNA sequence of 21 representative strains was used to confirm the presence of the predominant groups and to determine the phylogenetic affiliation of isolates. The sequences from the various LAB isolates showed high degrees of similarity to those of the GenBank type strains between 99.4% and 100%. The prevalent LAB, predominantly Lactobacillus (85.6%), consisted of L. plantarum (33.3%), L. pentosus (28.6%) and L. brevis (23.7%). Other LAB species as Leuconostoc lactis (4.8%), Weissella cibaria (4.8%) and Enterococcus mundtii (4.8%) also presented in corn stover. The present study is the first to fully document corn stover‐associated LAB involved in the silage fermentation. The identification results revealed LAB composition inhabiting corn stover and enabling the future design of appropriate inoculants aimed at improving the fermentation quality of silage.     

乳酸菌青贮添加剂的研究与应用

很多添加剂被用来促进青贮发酵过程,其中研究最广泛的就是乳酸菌青贮添加剂。本文主要阐述了在青贮中加入乳酸菌添加剂可以促进作物的发酵速度,并且改善家畜的生产性能。