Microbial succession during ripening of Naples-type salami, a southern Italian fermented sausage

Studies were carried out on the microbiological and physico-chemical changes which occurred during the ripening of five batches of Naples-type salami, manufactured without starter cultures. Salami were sampled internally and externally, and the following microbial groups were studied: lactic acid bacteria, Micrococcaceae and yeasts. The results obtained indicated that lactobacilli constituted the predominant flora, both on the surface and in the interior of the pieces throughout the ripening period. Micrococcaceae and yeasts were also found in considerable number in both locations. Characterisation of 191 lactic isolates indicated that the salami microflora was dominated by homofermentative lactobacilli; approximately 63% of them could be identified as Lactobacillus sake; 40% showing the traits of a racemase negative variant of this species, once referred to Lactobacillus bavaricus. Yeast population mainly comprised Debaryomyces strains. All the colonies grown on mannitol salt and Kranep agar were catalase-positive cocci; novobiocin-resistant staphylococci were the only Micrococcaceae found. The API Staph identification system did not prove to be reliable: 82% of the isolates remained unidentified. To achieve improved characterisation, cluster analysis was subsequently performed on this group, corroborating the existence of a fairly homogeneous group representing an intermediate variety between Staphylococcus xylosus and Staphylococcus saprophyticus that was isolated during the whole ripening process.     

发酵香肠成熟过程中的生化变化

本文综合概述了有关发酵香肠在成熟过程中的一系列复杂生物化学变化及其影响因素,并提出今后有关发酵香肠的主要研究方向.     

Tyramine degradation by micrococci during ripening of fermented sausage

The ability of tyramine oxidase exhibiting strains of Micrococcus varians to degrade tyramine in vivo during sausage fermentation was investigated. Fermented sausage was produced with a tyramine forming strain of Lactobacillus curvatus which acquired a final tyramine concentration of 190ppm. The addition of either one of two strains of M. varians exhibiting a potential to oxidise tyramine decreased the amount of tyramine formed to 160 and 150ppm, respectively. No effect on growth of L. curvatus and pH development in the fermented sausage was observed when micrococci were present during a three weeks ripening period. Sausage fermentation was further carried out with a non-amine forming strain of L. sake and M. varians after addition of 100ppm tyramine to the raw material. The amount of tyramine in the end product was 60ppm, and during the first 10 days of ripening the decrease was faster on the outside of the sausage.     

Accelerated ripening of dry fermented sausage by addition of a Lactobacillus proteinase

Accelerated ripening of dry sausage was investigated by adding two different concentrations of proteinase isolated from Lactobacillus paracasei ssp. paracasei NCD0151 to sausage mixtures. Sausages with proteinase showed a greater pH decrease and a greater increase in lactic acid formation, water loss, protein degradation and peptide formation than control, no enzyme, sausages. Changes were most pronounced in the sausages containing 12 Ug^-1 proteinase. Addition of proteinase caused a specific increase in glutamate, serine and lysine content. Sensory evaluation after 14 days of ripening showed a significant increase in flavour intensity, maturity flavour, acidity, bitter taste and hardness in the proteinase-containing sausages. Addition of proteinase induced changes earlier in the fermentation and ripening period than in the control, thereby indicating an acceleration of maturation.     

Colour parameters of Turkish-type fermented sausage during fermentation and ripening

Colour parameters of Turkish-type fermented sausage during fermentation and ripening were evaluated. CIE x y, L^* a^* b^*, C^* h°, pigment nitrosation (NI) and pigment discoloration (RSI) were measured. Sausage processing had four stages consisting of first and second fermentation steps and then two consecutive ripening steps. Variations of colour parameters with processing indicated that Turkish-type fermented sausage processing might be divided into two well defined phases from the colour point of view. Optimum colour was obtained at the end of the first ripening step.     

Monitoring the bacterial population dynamics during the ripening of Galician chorizo,a traditional dry fermented Spanish sausage

The dynamics of the bacterial population throughout the ripening of Galician chorizo, a traditional dry fermented sausage produced in the north-west of Spain, were investigated by using classical and molecular approaches.     

Characterization of Micrococcaceae isolated from dry fermented sausage

One hundred Micrococcaceae strains were isolated from two types of naturally fermented dry sausages at four different stages of the ripening process in order to select the most suitable strains according to their technological characteristics including antimicrobial activity against foodborne pathogens. Identification of the isolates revealed that 91% belonged to genus Staphylococcus, whereas 5% were identified as Kocuria varians, 2% asArthrobacter agilis and 2% as Dermacoccus nishinomiyaensis. The species most often isolated was S. saprophyticus (22%), followed by S. carnosus (20%) and S. xylosus (10%). The isolated strains of S. xylosus (10 isolates), S. carnosus (20 isolates) and K. varians (five isolates) were further characterized. A large majority of the above strains was able to grow in the presence of 10% and 15% NaCl, to reduce nitrates at 18°C and to hydrolyse casein. The majority of the strains of S. xylosus produced acetoin and 30% of them hydrolysed tributyrin. All S. xylosus strains and a large majority of S. carnosus and K. varians strains exhibited an anti-listerial activity against three Listeria monocytogenes strains.The enzymatic potential of the strains was evaluated using the API ZYM system. S. xylosus strains exhibited high β -galactosidase and esterase–lipase activities, whereas S. carnosus strains indicated strong cysteine aminopeptidase and acid phosphatase activities and K. varians indicated very weak activities of the enzymes tested. A rapid characterization of the above strains according to their enzymatic pattern could be achieved in order to follow the strains selected as starter cultures during sausage fermentation. The contribution of the selected strains to a possible inhibition ofL. monocytogenes in situ on fermented meats would be of considerable interest to enhance the hygienic quality of these products.     

Characterization of proteolysis during the ripening of semi-dry fermented sausages

The respective contribution of indigenous enzymes and enzymes from starter bacteria to proteolysis in fermented sausages were determined by comparing the proteolytic changes occurring in sausages resulting from the presence of a proteolytic strain of Staphylococcus carnosus, i.e. S. carnosus MC 1 to the proteolytic changes occurring in control sausages containing glucono-δ-lactone (GDL) and an antibiotic mixture. Proteolysis was quantified by assaying for non-protein nitrogen (NPN) and free amino acids. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and reversed phase high performance liquid chromatography (RP-HPLC) were used to qualitatively assess the proteolytic changes in the sarcoplasmic and myofibrillar proteins as ripening progressed. The concentration of NPN and free amino acids increased in both sausages initially, but subsequently decreased towards the end of ripening in sausages inoculated with the starter culture. SDS-PAGE showed a similar pattern of proteolysis of sarcoplasmic proteins in both sausages, while of the two sausage types; the S. carnosus MC 1 inoculated sausages exhibited the most intense degradation of myofibrillar proteins, especially myosin and actin. RP-HPLC profiles of 2% trichloroacetic acid (TCA)-soluble peptides for the two sausage types were similar, with the production of numerous hydrophilic peptides. N-Terminal amino acid sequence analysis and sequence homology with proteins of known primary structure showed that six of the TCA-soluble peptides were released from the sarcoplasmic (myoglobin and creatine kinase) and myofibrillar (troponin-I, troponin-T and myosin light chain-2) proteins. In addition, the initial degradation of sarcoplasmic proteins was due to the activity of indigenous proteinases, while both indigenous and bacterial enzymes contributed to the initial degradation of myofibrillar proteins. Furthermore, indigenous enzymes were responsible for the release of TCA-soluble peptides, which, were further hydrolysed by bacterial enzymes.     

Effects of addition of carrot dietary fibre on the ripening process of a dry fermented sausage (sobrassada)

Four formulations of a dry fermented sausage, known as sobrassada, containing different percentages of carrot dietary fibre (DF) [3% (S3), 6% (S6), 9% (S9) and 12% (S12) (w/w)] were analyzed for various physico-chemical and microbiological parameters and sensory attributes. The ripening process was monitored throughout storage. The pH of DF-supplemented sobrassadas was critically affected during ripening by the amount of DF incorporated, the values for sobrassada samples containing over 3% of DF suggested that the fermentation process in these samples was not successful. In addition, textural parameters, such as hardness and compression work, were significantly affected by the addition of over 3% of DF. The lipolytic process, one of the major biochemical events, was only affected when relatively large percentages of DF concentrate were incorporated. Thus, S3 and S6 samples exhibited similar free fatty acid profiles to the control throughout ripening.     

Proteolysis in Painho de Portalegre dry fermented sausage in relation to ripening time and salt content

The effect of salt addition (3% and 6% in the final product) on the shelf-life related physicochemical characteristics and proteolysis profile during the ripening period of a Portuguese dry fermented sausage "Painho de Portalegre", were evaluated. The product with 6% salt concentration had low a(w) and pH values at most ripening periods evaluated, due to the influence of NaCl on the water binding capacity of the protein structure and to the low ammonia accumulation, respectively. Similar changes were observed for total basic volatile nitrogen (TBVN), free amino acid nitrogen (FAAN) and non-protein nitrogen (NPN) fractions in both products. After a clear increase during the first days of the processing phase, all the initial rates slowed down with some fluctuation in FAAN and NPN. In relation to small peptides and free amino acid accumulation, the major differences between the tested formulations were mainly observed on distinct profiles rather than on overall concentrations.     

Characterization of yeasts involved in the ripening of Pecorino Crotonese cheese

The aims of this work were to identify and characterize for some important technological properties the yeast species present throughout the ripening process of Pecorino Crotonese, a traditional cheese produced in a well defined area of Southern Italy. In particular, the strain technological properties considered include fermentation/assimilation of galactose and lactose, assimilation of lactate and citrate in the presence of different NaCl concentrations, hydrolysis of butter fat, skim milk, gelatine and casein, production of brown pigments in cheese agar and ability to produce biogenic amines. High yeast levels were recorded in cheese samples already after 5 h of brining (about 5 log cfu/g) and these concentration remained constant during ripening. The yeast isolates belonged to restrict number of yeast species. While Kluyveromyces lactis and Saccharomyces cerevisiae were isolated prevalently in the first stages of Pecorino Crotonese production, Yarrowia lipolytica and Debaryomyces hansenii dominated during the later stages of maturation. Otherwise, the latter two were very NaCl resistant species. In fact, D. hansenii strains conserved the ability to assimilate lactose and galactose in the presence of 10% NaCl, while almost all the strains of Y. lipolytica isolated assimilated citrate and lactate up to 7.5% NaCl. Y. lipolytica isolates evidenced also the highest proteolytic and lipolytic activities and the capability to catabolize tyrosine producing brown pigment. In addition they resulted in the highest aminobiogenic potential decarboxylating ornithine, phenylalanine, tyrosine and lysine. However, they were not able to produce histamine, biogenic amine produced by three strains of D. hansenii.     

Biogenic amine content in dry fermented sausages as influenced by a producer,spice mix,starter culture,sausage diameter and time of ripening

Sixteen types of dry fermented sausages were commercially produced as combinations of two producers (designated K and R), two starter cultures (Pediococcus pentosaceus, C; Lactobacillus curvatus + Staphylococcus carnosus, F), two spicing mixtures (H; P) and two casing diameters (4.5 cm, T; 7 cm, W), and were sampled at days zero, 14, 28 (end of ripening), 49, 70, 91 and 112 (samples were stored at 15 °C and relative humidity of 70% between days 28 and 112). Tyramine and putrescine content (Y, mg kg⁻¹) increased (P < 0.01) with increasing time of ripening/storage (X, days): Y = 52.0 + 5.19X − 0.0275X² (R² = 0.60) and Y = 37.0 + 3.45X − 0.0192X² (R² = 0.23), respectively. Smaller diameter (T), spice mix containing red pepper (P) and starter culture C decreased (P < 0.05) both tyramine and putrescine content in the sausages as compared to the W, H and F counterparts, respectively; content of both amines was lower (P < 0.05) in the K-sausages than in the R-sausages. Tyramine content in the sausages at the time interval 28 days of ripening + 21 days of storage was in the range from 170 (KHCU sausage combination) to 382 (RHFS) mg kg⁻¹.     

Lipolysis, proteolysis and formation of volatile components during ripening of a fermented sausage with Pediococcus pentosaceus and Staphylococcus xylosus as starter cultures

Bacterial growth, formation of acids, lipolysis, proteolysis, fat oxidation, formation of volatile compounds and flavour characteristics were followed during ripening and storage of a fermented sausage. The starter culture used was composed of Pediococcus pentosaceus and Staphylococcus xylosus. The number of Pediococcus sp. increased by 1.5 log cfu/g during the first day of processing and remained constant at this level for 3 weeks. The corresponding initial increase in the numbers of Staphylococcus sp., 0.4 log cfu/g, was followed by a rapid decrease in the viable numbers. Lactic acid, mainly d-lactic acid, and acetic acid were formed during ripening. The triglycerides were hydrolysed to 1,2-diglycerides and free fatty acids at the beginning of ripening, followed by the formation of 1,3-diglycerides and monoglycerides, indicating lipolytic activity. Moreover, the nonprotein nitrogen increased during ripening as a result of the proteolytic activity. Most of the changes with respect to pH, formation of d-lactic acid, acetic acid, peroxides and flavour development occurred during the initial 3 days of ripening, when growth of Pediococcus sp. and Staphylococcus sp. occurred. Lipolysis as well as proteolysis continued after this initial period. The volatile compounds identified belonged to several chemical families, viz. aliphatic and aromatic hydrocarbons, aldehydes, ketones, alcohols, phenols, carboxylic acids, esters, nitrogen compounds, sulphur compounds, chloride compounds, terpenes and furans. Many of the volatile compounds probably originated from smoke and seasoning (onion/garlic and pepper), while others were a result of the activities of muscle enzymes and bacteria.     

Inhibition of Escherichia coli O157:H7 in ripening dry fermented sausage by ground yellow mustard

Compounds generated by the enzymatic hydrolysis of glucosinolates naturally present in mustard powder are potently bactericidal against Escherichia coli O157:H7. Because E. coli O157:H7 can survive the dry fermented sausage manufacturing process, 2, 4, and 6% (wt/wt) nondeheated (hot) mustard powder or 6% (wt/wt) deheated (cold) mustard powder were added to dry sausage batter inoculated with E. coli O157:H7 at about 7 log CFU/g to evaluate the antimicrobial effectiveness of the powders. Reductions in E. coli O157:H7 populations, changes in pH and water activity (aw), effects on starter culture (Pediococcus pentosaceus and Staphylococcus carnosus) populations, and effects of mustard powder on sausage texture (shear) were monitored during ripening. Nondeheated mustard powder at 2, 4, and 6% in dry sausage (0.90 aw) resulted in significant reductions in E. coli O157:H7 (P < 0.05) of 3.4, 4.4, and 6.9 log CFU/g, respectively, within 30 days of drying. During fermentation and drying, mustard powder did not affect P. pentosaceus and S. carnosus activity in any of the treatments. Extension of drying to 36 and 48 days reduced E. coli O157:H7 by >5 log CFU/g in the 4 and 2% mustard powder treatments, respectively. The 6% deheated mustard powder treatment provided the most rapid reductions of E. coli O157:H7 (yielding <0.20 log CFU/g after 24 days) by an unknown mechanism and was the least detrimental (P < 0.05) to sausage texture.     

微生物在发酵风干肠中的应用

传统发酵风干肠的生产是依赖自然发酵过程完成的。采用人工接种发酵剂开展发酵肠的研究与应用,对风干肠独特风味的形成起决定性的作用,使发酵肠的生产得到了极大的推进。     

Digestibility of collagenous fermented sausage in man

The digestibility of the protein of a fermented collagenous sausage was studied in three patients with ileostomies with small bowel resections. The patients were given four ordinary meals each day with a total protein content of about 64g, half of which was derived from collagen. Pigskins from 6-month old scalded pigs were used as the collagen source. A fermented sausage, based on meat, was used as a reference and the patients with ileostomies served as their own controls. Urine was collected from two patients. The true nitrogen digestibilities were found to be 71-79 % for the collagenous diets and 69-85 % for the reference diets. Hydroxyproline digestibilities (apparent and true) for the collagenous diet periods were similar: 70-82 %. This indicated that collagen was digested to the same extent as other proteins. Amino acid patterns of ileal excreta distinctly differed for each of the two periods, further confirming that all the protein was not absorbed. Elevated excretion of hydroxyproline in the urine after ingestion of the collagenous sausage was found, mainly as peptide bound hydroxyproline, but accounted for about only 2% of the ingested hydroxyproline. It was concluded that collagenous fermented sausage is as digestible as a reference sausage based on meat even without prior heat treatment.