冷却肉生产中胴体减菌技术的研究进展

冷却肉生产中,胴体减菌技术是关键技术之一,它能降低胴体的初始菌数、延长产品的货架期、保证产品的安全.对冷却肉生产中胴体减菌技术的研究进展进行综述.以期为肉类加工企业控制产品初始菌数及肉类研究机构提供参考.     

EFFECT OF WASHING ON THE AMINO ACID COMPOSITION AND CONNECTIVE TISSUE CONTENT OF SEAL MEAT

Effects of washing on the amino acid composition and connective tissue content of mechanically separated seal meat (MSSM) was studied. Aqueous washing of MSSM resulted in a considerable decrease in histidine, and to a lesser extent, leucine, lysine, phenylalanine, taurine and valine content of the samples. However, the concentration of glycine, proline, hydroxyproline and hydroxylysine, and dominant components of connective tissues, was increased. Thus, the predicted PER values of washed meats decreased by up to 11.7%, and the content of connective tissues in the final product was increased by a factor of approximately four. The lipid and hemoprotein content of washed seal meat was decreased by 30% and 68%, respectively.     

改良培养条件对发酵酸奶中乳酸菌检测效果的影响研究

主要研究培养条件对发酵酸奶中乳酸菌检测效果的影响研究,通过在MC改良培养基中加入番茄汁、吐温-80和在培养基上覆盖琼脂的方法研究,改良乳酸菌检测效果.结果表明:在1000mL改良MC培养基中加入20 mL蕃茄汁、0.5 mL吐温-80,平板凝固后再覆盖一层琼脂,能使乳酸菌菌落变大和清晰易于准确计数.     

乳酸菌营养饮料稳定性的研究

探讨了蛋白酶酶解牛乳蛋白对发酵型乳酸菌饮料稳定性的影响。研究表明,加入0.0015%的胰蛋白酶,在42℃下发酵6h的酸乳,制作的乳酸菌饮料多肽和游离氨基酸的含量较高;当控制酸度在60°T,乳化稳定剂的添加量为0.5%,糖10%时,乳酸菌饮料的稳定性最佳,同时风味也较好。     

发酵肉制品中乳酸菌的分离鉴定及菌种性能的研究

从自然发酵肉制品中分离乳酸菌并对其进行生化试验鉴定,对得到的乳酸菌进行了耐盐、耐亚硝酸盐、产酸能力、生长曲线及抑菌试验。通过分离和鉴定得到5株乳酸菌,3株为乳酸杆菌,2株为乳酸球菌;它们对食盐、亚硝酸盐均具有较好的耐受性,在6％的NaCl、80kg／mg-150kg／mgNaNO2溶液中能生长;对蛋白质,脂肪无分解作用。乳酸杆菌和乳酸球菌对大肠杆菌均有抑制作用,且杆菌的抑制作用大于球菌;乳酸杆菌与乳酸球菌的生长曲线和产酸特性不同,杆菌比球菌生长快,pH值下降快,所需的发酵时间比球菌短。5株乳酸菌都可作为肉制品的发酵剂。     

THE ACTION OF NISIN ON BEER SPOILAGE LACTIC ACID BACTERIA

Within one minute of adding nisin to suspensions of Lactobacilli clumping of cells was observed. This happened with all the strains assayed, irrespective of their sensitivity or resistance to nisin. There was, however, no evidence of cell lysis. Two different assays for cell viability were used to show that the vast majority of cells of sensitive strains were killed within one minute of contact with nisin. The time needed to kill all the cells depended on the concentrations of both nisin and cells. One strain was more resistant and only 50–60% of the cells died within one minute of nisin addition . Using an ATP-bioluminescence assay it was shown that the addition of nisin to both Lactobacilli and Pediococci caused a rapid fall in intracellular ATP levels, which was reflected in a simultaneous appearance of ATP in the extracellular medium. Actively growing cells lost ATP more rapidly than did those in stationary phase. The amount of intracellular ATP lost was affected both by the concentration of nisin used and the sensitivity of the bacteria. It appears that an initial effect of nisin is to make the cell membrane ‘leaky’ as happens with many antibiotics, yeast killer factors (zymocins), colicins, and other gram-positive bacteriocins .     

THE DETECTION OF LACTIC ACID BACTERIA

An examination of lactic acid bacteria involved in beer spoilage has demonstrated that many Pediococci and Lactobacilli are capable of growth on glucose media but incapable of growth on sucrose within 6 days. Some Lactobacilli are incapable of utilizing glucose for growth and are also unable to grow on media based on sucrose. All Lactobacilli studied which could not utilize glucose could utilize maltose. The results presented suggest that the use of a detection medium incorporating both glucose and maltose will result in increased ability to detect lactic acid bacteria.     

EFFECT OF LACTIC ACID FERMENTATION OF CASSAVA ON FUNCTIONAL AND SENSORY CHARACTERISTICS OF FUFU FLOUR

The effects of lactic acid fermentation of cassava on the functional and sensory characteristic of fufu flour were investigated. Two strains of Lactobacillus plantarum were used as starter cultures for the fermentation of cassava to fufu for 96   h. The resultant wet fufu samples were dried at 65C in a cabinet dryer for 48   h, and were analyzed for functional and sensory characteristics.
Fermentation reduced the water-binding capacity of the fufu flour from 176.6% to between 118 and 125%. The pasting characteristics of the traditional and starter culture-fermented fufu flour samples were not significantly different from that of the unfermented cassava flour. When subjected to sensory evaluation, the traditional and starter culture-fermented cassava fufu flour were not significantly different in terms of color, odor and texture, but the cassava fufu flour produced, using starter culture SL19, had the highest overall acceptability ( P <  0.05).

PRACTICAL APPLICATIONS

Traditionally, processing of cassava to fufu is usually carried out by using the old stock from a previous fermentation to initiate the fermentation of a new batch. This old method usually results in fufu that has a strong odor that may not be acceptable to some consumers. The use of starter culture like Lactobacillus plantarum will reduce the strong odor of fufu ; this will increase its acceptability by consumers and ensure the overall quality. Also, the functional properties of fufu are not affected. The development of lactobacilli strains could help in optimizing the traditional processes, therefore increasing the economic returns.     

MICROBIAL CHANGES ON FRESHLY SLAUGHTERED PORK CARCASSES DUE TO "HOT" LACTIC ACID DECONTAMINATION

We studied the microbial changes on fresh (still warm) pork carcasses immediately after electrostatic spraying of lactic acid solutions and during chilled storage. Lactic acid decontamination (LAD) included electrostatic spraying of hot (55C) solutions of 1% lactic acid for 90 s and 2%- and 5% lactic acid for 30 and 90 s. The treatments increased the carcass surface temperature from 22C to about 32–43C. The bactericidal activity of lactic acid killed mainly Gram-negative bacteria. Reductions in "total" psychrotrophic Gram-negative and Entero-bacteriaceae counts were found reliable indicators for the efficacy of LAD. Hot 2–5% LAD treatments achieved overall reductions in Gram-negative psychrotrophs ranging from 0.8 to more than 1.4 log₁₀ cfu per cm². Overall reductions in mesophilic Enterobacteriaceae counts ranged from approximately 1.2 to more than 1.8 log₁₀ cfu per cm². Treatments with 1% lactic acid achieved marginal 0.5–0.6 overall log₁₀ reductions in these groups of organisms. Bactericidal effects after LAD occurred during a lag period of whose duration increased with the lactic acid concentration of the spray solution. The lag lasted less than 1 day on 1% LAD, 2 days on 2% LAD and 4 days on 5% LAD meat. During these lags the meat surface pH rose from pH 2.7 to 3.2 immediately after LAD to pH 4.8 to 5.2. During aerobic chilled storage after LAD the growth of Gram-negative psychrotrophs was controlled only temporarily. These organisms became the dominant group of organisms. The practical utility of electrostatic spraying of fresh pork carcasses with hot 1–5% LAD to improve the keeping quality is questionable .     

FUNDAMENTALS AND PERSPECTIVES FOR THE USE OF BACTERIOCINS PRODUCED BY LACTIC ACID BACTERIA IN MEAT PRODUCTS

Bacteriocins of lactic acid bacteria (LAB) are proteinaceous compounds that may present antimicrobial activity towards important foodborne pathogens and spoilage-related microflora. Due to these properties, bacteriocin-producing strains or purified bacteriocins have a great potential of use in biologically based food preservation systems. Despite the growing number of articles describing the isolation of bacteriocinogenic strains, genetic determinants for production, as well as the purification and biochemical characterization of these inhibitory substances, there are only limited reports of successful application of bacteriocins to meats.

This paper presents a critical review of the methods available for screening of bacteriocin-producing LAB strains from meats and also discusses the proposed mechanisms of action for LAB bacteriocins. Additionally, an overview of the Brazilian experience in the application of LAB bacteriocins to meats and meat products is given.     

FUNDAMENTALS AND PERSPECTIVES FOR THE USE OF BACTERIOCINS PRODUCED BY LACTIC ACID BACTERIA IN MEAT PRODUCTS

Bacteriocins of lactic acid bacteria (LAB) are proteinaceous compounds that may present antimicrobial activity towards important foodborne pathogens and spoilage-related microflora. Due to these properties, bacteriocin-producing strains or purified bacteriocins have a great potential of use in biologically based food preservation systems. Despite the growing number of articles describing the isolation of bacteriocinogenic strains, genetic determinants for production, as well as the purification and biochemical characterization of these inhibitory substances, there are only limited reports of successful application of bacteriocins to meats.

This paper presents a critical review of the methods available for screening of bacteriocin-producing LAB strains from meats and also discusses the proposed mechanisms of action for LAB bacteriocins. Additionally, an overview of the Brazilian experience in the application of LAB bacteriocins to meats and meat products is given.     

THE EFFECTIVENESS OF CARCASS DECONTAMINATION SYSTEMS FOR CONTROLLING THE PRESENCE OF PATHOGENS ON THE SURFACES OF MEAT ANIMAL CARCASSES1

The effectiveness of decontamination systems for controlling the presence of pathogens and spoilage organisms on carcasses is discussed. Research using organic acids and water (hot or cold) demonstrates the general effectiveness of such treatments in lowering the aerobic plate counts (APC) on carcasses by 1–3 log₁₀ cfu per unit area. Chlorine has been found to be relatively ineffective for use in animal carcass spray washers. An example of direct application of the bacteriocin nisin to inoculated tissue in a spray washer is discussed. Reductions attributable to nisin were 2–2.5 log₁₀ cfu per unit area higher than those reported for various organic acids or water. Areas for further research are highlighted along with the potential use of newer technologies to elucidate attachment and detachment mechanisms of bacteria to meat animal carcasses.     

乳酸发酵鲜菇汁技术研究

以鲜菇汁为原料，经乳酸发酵而制成鲜菇汁发酵饮料，通过对接种量、发酵时间、乳粉量、糖酸比进行试验．从而确定最佳工艺参数为：接种量3％，乳粉量5％，发酵时间3．75h，蔗糖12％，柠檬酸0．04％。     

INFLUENCE OF LACTIC ACID AND MODIFIED ATMOSPHERE ON THERMAL DESTRUCTION OF LISTERIA MONOCYTOGENES IN CRAWFISH TAIL MEAT HOMOGENATE1

Precooked homogenized crawfish tail meat was inoculated with Listeria monocytogenes, treated with lactic acid, and packaged in various atmospheres for D value determinations at 60C. D₆₀ values using 0.0, 0.5, 0.75, and 1.0% lactic acid (LA) treated meat were 4.68, 4.41, 3.46, and 2.49 min, respectively. LA increased sensitivity of L. monocytogenes to heat but this was not solely due to a reduction of pH. Sensory analyses of odor, color, taste, and texture of uninoculated whole crawfish tail meat demonstrated no significant differences (P > 0.05) between LA treated samples and controls. D₆₀ values for the bacterium in crawfish tail meat homogenate packed in air, O₂, CO₂, or N₂ were 10.58, 9.22, 11.68, or 12.97 min, respectively, which were not significantly different (P > 0.05). When 1% LA was added, significant decreases (P < 0.05) in D₆₀ values were observed in each packaging atmosphere. Similar (P > 0.05) D₆₀ values for crawfish tail meat treated with 1% LA and packed in air, O₂, CO₂, or N₂ were 3.44, 3.88, 3.48, or 3.08, respectively. These results show that heat treatments of 60C were lethal to L. monocytogenes in packaged crawfish tail meat homogenate regardless of package atmosphere. Additionally, LA increased the lethality of heat to the bacterium in all tested package atmospheres.