Characteristics of lactobacilli isolated from dry fermented sausages

A study of the microflora of Spanish dry fermented sausages showed a similar pattern to that observed in other sausages during ripening. Lactic acid bacteria and organisms growing on Mannitol-salt-agar increased during the first five days, remaining at constant levels afterwards. From MRS agar, 368 strains were isolated and characterized. All Lactobacillus strains (343) could be separated into three groups according to their reactions in the API-50 L system. The biochemical characteristics of the Lactobacillus strains analyzed were those typical of isolates from sausages and other meat products. The extracellular and intracellular lipolytic activities of some strains of the three groups were also studied. It is concluded that lipolytic activity of lactobacilli is mainly directed against mono- and diglycerides and short-chain fatty acid triglycerides.     

Probiotics in fermented sausages

Probiotic foods receive market interest as health-promoting, functional foods. They have been introduced in a wide range of food industries. However, commercial application of probiotic microorganisms in fermented sausages is not common yet. There are both advantages and disadvantages connected to fermented meat matrices. They are adequate for the carriage of probiotic bacteria since they are usually not or only mildly heated and may promote the survival of probiotic bacteria in the gastrointestinal tract. In contrast, bacterial viability may be reduced due to the high content in curing salt and the low water activity and pH. Therefore, results are expected to be strain-dependent. Up till now, several approaches have been followed but most results are too preliminary to be able to evaluate the effect of probiotic fermented meats on human health. Candidate probiotic strains have been obtained through screening for technological requirements among bacteria that are naturally present in the meat or that originate from meat starter cultures. Alternatively, existing probiotic bacteria have been applied in meat products. Finally, the evaluation of the end-products needs to deal with both health effects and technological characteristics, for instance through human intervention studies and taste panels, respectively.     

Biogenic amines in dry fermented sausages: a review

Biogenic amines are compounds commonly present in living organisms in which they are responsible for many essential functions. They can be naturally present in many foods such as fruits and vegetables, meat, fish, chocolate and milk, but they can also be produced in high amounts by microorganisms through the activity of amino acid decarboxylases. Excessive consumption of these amines can be of health concern because their not equilibrate assumption in human organism can generate different degrees of diseases determined by their action on nervous, gastric and intestinal systems and blood pressure. High microbial counts, which characterise fermented foods, often unavoidably lead to considerable accumulation of biogenic amines, especially tyramine, 2-phenylethylamine, tryptamine, cadaverine, putrescine and histamine. However, great fluctuations of amine content are reported in the same type of product. These differences depend on many variables: the quali-quantitative composition of microbial microflora, the chemico-physical variables, the hygienic procedure adopted during production, and the availability of precursors. Dry fermented sausages are worldwide diffused fermented meat products that can be a source of biogenic amines. Even in the absence of specific rules and regulations regarding the presence of these compounds in sausages and other fermented products, an increasing attention is given to biogenic amines, especially in relation to the higher number of consumers with enhanced sensitivity to biogenic amines determined by the inhibition of the action of amino oxidases, the enzymes involved in the detoxification of these substances. The aim of this paper is to give an overview on the presence of these compounds in dry fermented sausages and to discuss the most important factors influencing their accumulation. These include process and implicit factors as well as the role of starter and nonstarter microflora growing in the different steps of sausage production. Moreover, the role of microorganisms with amino oxidase activity as starter cultures to control or reduce the accumulation of biogenic amines during ripening and storage of sausages is discussed.     

优质发酵香肠加工技术

发酵香肠加工伴随着极为复杂的微生物及理化过程,适宜微生物发酵剂的选择对发酵进程起到调控作用。然而在发酵香肠加工中,从原辅料选择到发酵、干燥和成熟等不同工序的控制比发酵剂的选择更为重要。本文择重于加工关键控制点,对优质西式发酵香肠加工技术作一较为系统的介绍。     

Accelerated ripening of dry fermented sausages

Research on accelerated ripening of dry fermented sausages started in the early 1990s. Fermented sausages manufacture is a very important part of meat industry in many countries and the acceleration of ripening would result in a reduction of the storage time and would increase the profit margin and the competitiveness of the end product. The different strategies that have been assayed with this purpose include ripening at elevated temperature, use of genetically modified starter bacteria, addition of enzymes and addition of slurry systems. Over the last decade, numerous studies have been carried out, especially on the addition of enzymes. The aim of this paper is to review and update the knowledge on this topic. The more recent approaches in this field, such as the use of microbial extracts, are also presented.     

Utilization at high pH of starter cultures of lactobacilli for Spanish-style green olive fermentation

Inoculation at alkaline pH (above 9) of lye-treated green olives with starter cultures of Lactobacillus pentosus CECT 5138 was studied. Despite an initial loss of viability in the order of 1-2 log cycles on average, depending mainly on time of application, cultures grew and initiated an accelerated fermentation process. Inoculation reduced the population of Enterobacteriaceae, and thereby potential spoilage, and produced a quicker acidification of brines and decrease of pH, when compared with control uninoculated batches. Results obtained throughout three consecutive seasons demonstrated that utilization at high pH of starter cultures of lactobacilli is feasible, provided that the inoculum size takes into account the initial low survival.     

干发酵香肠中的生物胺

综述干发酵香肠中生物胺产生的条件,国外干发酵香肠中常见生物胺的种类及含量,与生物胺积累有关的微生物以及影响生物胺产生的理化因素,并提出了控制干发酵香肠中生物胺积累的措施。     

Technological characterization of a bacteriocin-producing Lactobacillus sakei and its use in fermented sausages production

The aim of this paper was the technological characterization of a Lactobacillus sakei strain, able to produce the bacteriocin sakacin P, that was originally isolated from naturally fermented sausages. Experiments were conducted in situ, using MRS-based medium, and in situ, when the strain was inoculated as starter culture in real sausage fermentation. The results obtained underlined that the strain was able to grow in conditions that are commonly used in the production line, and only lactose and high concentrations of NaCl (5% w/v) reduced the capability for bacteriocin production. When inoculated in sausages, the strain showed a good performance, being able to colonize rapidly the ecosystem. A high number of isolates, capable of producing sakacin P, were already isolated after the third day of fermentation, and persisted throughout the course of the fermentation. The inoculated strain also affected other microbial colonization trends; in fact the total bacterial count and fecal enterococci showed a rapid decrease at the end of the fermentation. Moreover, during sensory evaluation, the final sausage product received high scores for the parameters of tenderness and juiciness, with medium acidity and low rancidity. Lastly, the panelists preferred the sausages produced with the L. sakei characterized in this study when compared to a fermented sausage produced with a commercial starter.     

Quantifying nonthermal inactivation of Listeria monocytogenes in European fermented sausages using bacteriocinogenic lactic acid bacteria or their bacteriocins: a case study for risk assessment

Listeria monocytogenes NCTC10527 was examined with respect to its nonthermal inactivation kinetics in fermented sausages from four European countries: Serbia-Montenegro, Hungary, Croatia, and Bosnia-Herzegovina. The goal was to quantify the effect of fermentation and ripening conditions on L. monocytogenes with the simultaneous presence or absence of bacteriocin-producing lactic acid bacteria (i.e., Lactobacillus sakei). Different models were used to fit the experimental data and to calculate the kinetic parameters. The best model was chosen based on statistical comparisons. The Baranyi model was selected because it fitted the data better in most (73%) of the cases. The results from the challenge experiments and the subsequent statistical analysis indicated that relative to the control condition the addition of L. sakei strains reduced the time required for a 4-log reduction of L. monocytogenes (t(4D)). In contrast, the addition of the bacteriocins mesenterocin Y and sakacin P decreased the t(4D) values for only the Serbian product. A case study for risk assessment also was conducted. The data of initial population and t(4D) collected from all countries were described by a single distribution function. Storage temperature, packaging method, pH, and water activity of the final products were used to calculate the inactivation of L. monocytogenes that might occur during storage of the final product (U.S. Department of Agriculture Pathogen Modeling Program version 7.0). Simulation results indicated that the addition of L. sakei strains significantly decreased the simulated L. monocytogenes concentration of ready-to-eat fermented sausages at the time of consumption.     

Molecular, technological and safety characterization of Gram-positive catalase-positive cocci from slightly fermented sausages

The population of Gram-positive catalase-positive cocci from slightly fermented sausages was characterized at species and strain level by molecular techniques and some technological and hygienic aspects were also considered. Staphylococcus xylosus was the predominant species (80.8%) followed by Staphylococcus warneri (8.3%), Staphylococcus epidermidis (5.8%) Staphylococcus carnosus (4.6%), and Kocuria varians (0.4%). Proteolytic activity was observed in 23% of the isolates. The species with the highest percentage of proteolytic strains was S. warneri. Lipolytic activity was found in 45.8% of the isolates and S. xylosus was the species with the highest percentage of lipolytic isolates. Biogenic amine production was not widely distributed (only 14.6% of the isolates). Tyramine was the most intense amine produced, although by only 4.6% of the isolates. Phenylethylamine was more frequently detected (10.8% of isolates) but at lower levels. Some strains also produced putrescine (3.3%), cadaverine (2.9%), histamine (1.3%) and tryptamine (0.4%). All isolates were susceptible to linezolid and vancomicin and over 70% were resistant to penicillin G, ampicillin and sulphonamides. Most of the mecA+ strains (only 4.6% of isolates) also displayed resistance to multiple antibiotics. A reduced enterotoxigenic potential was found. Only 3.3% of isolates showed staphylococcal enterotoxins genes, all identified as entC gene. The combination of RAPD-PCR and plasmid profiling allowed the discrimination of 208 different profiles among the 240 Gram-positive catalase-positive cocci characterized, indicating a great genetic variability.     

Perceptual masking of boar taint in Swedish fermented sausages

Surgical castration of male piglets has traditionally been practiced to avoid development of boar taint in pork meat which can occur if entire male pigs are raised. Boar taint is commonly characterised as exhibiting the odour and flavour of urine and manure. This study involves sensory characterisation of the possibilities to mask boar taint in meat from entire male pigs by fermentation and smoking to maintain high sensory quality in meat products if castration is prohibited. Model and commercial type Swedish fermented sausage products based on low or high levels of boar tainted fat, three different starter cultures and two different levels of smoking were studied. In the model sausages, liquid smoke masked the perception of boar taint. In contrast, the smoking procedure of the commercial sausages was insufficient to totally mask the perception of boar taint. In both the model and commercial sausages, the aroma development from the starter cultures lowered the perception of boar taint but was insufficient for total perceptual masking. Due to the total masking effect of smoking in the model sausages, it was clear that smoke may present a potential solution to remove the perception of boar taint in fermented sausages if the smoking procedure is optimised.     

Optimization of exopolysaccharide yields in sourdoughs fermented by lactobacilli

In this study, the yields of exopolysaccharides (EPS) produced in situ during sourdough fermentations with Lactobacillus reuteri TMW 1.106 synthesizing glucan from sucrose were investigated under variation of the fermentation parameters dough yield (DY), pH, sucrose content and fermentation substrate. The obtained amounts of EPS after 1 day of fermentation were higher in softer (DY 500) than in firmer (DY 220) doughs. With the regulation of the pH to a constant value of 4.7, the optimum for EPS synthesis in liquid medium, the EPS production in dough also increased. The EPS yield could further be improved by additional sucrose fed-batch during fermentation. Fermentations with wheat flours, a rye-wheat mixture and rye bran with 10% sucrose as fermentation substrate showed, that the use of rye bran is a promising tool to get high dextran formation through L. reuteri even in the first 8 h of fermentation. Further, alternative production of oligosaccharides and organic acids from sucrose was investigated. Lactobacillus reuteri synthesized high amounts of acetic acid leading to low fermentation quotient values. In wheat doughs, the formation of maltooligosaccharides was observed. Confirmatory experiments with fructan producing Lactobacillus sanfranciscensis TMW 1.392 revealed the same trends with a few distinct differences, indicating that this approach is transferable to other EPS types and producers.     

适合于发酵香肠的发酵剂的研究及展望

发酵剂是影响发酵香肠质量的重要的因素之一,最初的应用只是为了更好的保存肉类.随着研究的深入,发酵剂还可以促使香肠形成特定的风味,改善香肠的营养品质,产生明显的抑菌作用.本文介绍了发酵香肠分类和发酵剂选用的标准,并对发酵剂的应用历史做了简要回顾;着重对发酵剂的应用特点做了描述,列出了各种发酵剂常用的种属以及对发酵香肠风味的特殊作用.进一步地,对发酵剂在抑制或减少香肠中常见的致病菌、腐败菌以及亚硝胺的作用做了总结,希望对提高发酵香肠的安全性方面起到一定的指导作用.最后,对发酵剂的应用前景作了展望.     

复合发酵香肠加工工艺与发酵特性研究

为研制肉蛋奶于一体、营养风味俱佳的新型复合发酵香肠,将猪肉、鸡肉、牛奶和鸡蛋的混合原料经植物乳杆菌L1和双歧杆菌L2综合发酵,研究其加工工艺,通过单因素试验探讨各因素对发酵特性的影响,得出理想的工艺和配方及各参数对发酵特性的影响规律:发酵时间延长,水分、PH值、亚硝酸盐逐渐降低,氨基酸和过氧化值逐渐增大;发酵温度升高,水分、pH值、亚硝酸盐降低幅度增大,氨基酸和过氧化值增加显著;菌种用量增大,水分、pH值、亚硝酸盐降低显著,氨基酸和过氧化值升高显著;菌种L1与L2最佳配比为2:1.     

New formulations for healthier dry fermented sausages: a review

An excessive intake of meat products, particularly dry fermented sausages, is not recommended from a health point of view, at least for some population groups, due to their high level of sodium and animal fat. Many efforts of the meat industry are focused on the development of new products with better nutritional properties than traditional ones. KCl, CaCl₂, and/or calcium ascorbate, among others, have been assessed as partial substitutes of NaCl, giving products with acceptable sensory quality, smaller amounts of sodium and being sometimes a significant source of potassium or calcium. In relation to fat, recent research has focused on the use of different types of fibres and vegetable oils as partial substitutes of pork backfat. The use of fibres results in low-fat and low-energy products. The use of vegetable oils results in products with healthier fatty acid profiles. Aspects related to improving sensory properties and control of oxidation should be taken into account in future research.     

Proteolysis in dry fermented sausages: The effect of selected exogenous proteases

The effect of three commercial proteases (pronase E from Streptomyces griseus, aspartyl proteinase from Aspergillus oryzae and papain) on protein breakdown and the sensory characteristics of dry fermented sausages was investigated. Water soluble, non-protein, 5% phosphotungstic acid soluble, 5% sulphosalicylic acid soluble and total volatile basic nitrogen contents increased during fermentation, stabilizing later until the end of ripening (26th day). Nitrogen values were always greater in the aspartyl proteinase added batch in comparison with the other protease added batches. Total free amino acid changes showed a similar pattern to those observed for the 5% sulphosalicylic acid soluble nitrogen. The electrophoretic studies demonstrated that proteolysis of high molecular weight myofibrillar and sarcoplasmic proteins was more prominent in protease added batches. It was especially intensive in papain one. The dominant amino acids at the end of ripening were similar in all batches. Tyramine and histamine increased throughout ripening. No significant differences in sensory properties were found between control and pronase E and papain added batches, but they were significantly different (p < 0.01) from the sausages containing aspartyl proteinase, due to an excessive softening. The effect of exogenous enzyme addition on the flavour potentiation of dry fermented sausage is discussed.     

Fructooligosaccharides as a fat replacer in fermented cooked sausages

Fermented cooked sausages with a 50% reduction in pork back fat and addition of 0%, 3%, 6% or 9% of fructooligosaccharides (FOS) were produced and studied during manufacturing and storage. Their production was monitored by physicochemical (pH, water activity, weight loss, proximate composition, colour and texture profiles) and microbiological analysis (aerobic mesophiles, lactic acid bacteria, and total and faecal coliforms). During storage, it was evaluated the sensory properties, stability to lipid oxidation and microbiological safety. The final fat content of the control was 27.54%. F0, F3, F6 and F9 treatments had final fat contents of 17.63%, 17.55%, 17.91% and 17.59%, respectively, representing an approximately 40% reduction in the fat content. The simple reduction in pork back fat without fat substitute adversely affected the technological and sensory properties of the fermented cooked sausages, but the addition of FOS suppressed the defects caused by the fat reduction. The content of FOS did not changed during storage, indicating that this functional prebiotic compound can be used for developing of reduced fat fermented meat products.     

鲶鱼发酵香肠的研制

为了获得质量、口感较好的鲶鱼发酵香肠,通过发酵剂适应性试验,选择用戊糖片球菌,植物乳杆菌和木糖葡萄球菌按1:1:1比例混合生产鲶鱼发酵香肠,在接种量、温度、相对湿度单因素试验的基础上结合正交实验,通过感官评价,确定鲶鱼发酵香肠的最佳生产工艺。试验结果表明:鲶鱼发酵香肠的最佳生产工艺为:三种菌的接种量为106cfu/g,发酵温度为25℃,发酵相对湿度为90%。     

山梨糖醇与八角茴香复配在发酵香肠中的应用

研究了山梨糖醇与八角茴香复配对发酵香肠品质的影响。对比了添加山梨糖醇、八角茴香复配的香肠与普通香肠的水分含量、水分活度、核磁成像、菌落总数及感官评定。结果表明:复配香肠具有高水分含量、低水分活度、菌落总数较低的特点,核磁成像显示复配香肠具有良好的保水性和抑菌性,感官评分明显高于普通香肠。山梨糖醇与八角茴香复配作为复合型添加剂应用在发酵香肠中具有较好的作用。