Changes in the Composition of Volatile Compounds during Aging of Dry-cured Sausages

The change in the composition of volatile components during aging and storage of dry-cured sausages containing a mixture of Lactobacillus plantarumand Staphylococcus carnosusas fermenting cultures was studied by high-performance capillary gas chromatography and gas chromatography-mass spectrometry. A total of 52 compounds were identified. It was found that sausage storage is accompanied by a significant increase in the concentration of flavoring aldehydes. The terpene concentration monotonically increases with sausage aging and storage.     

Fate of Escherichia coli O157:H7 as affected by pH or sodium chloride and in fermented, dry sausage.

The influence of pH adjusted with lactic acid or HCl or sodium chloride concentration on survival or growth of Escherichia coli O157:H7 in Trypticase soy broth (TSB) was determined. Studies also determined the fate of E. coli O157:H7 during the production and storage of fermented, dry sausage. The organism grew in TSB containing less than or equal to 6.5% NaCl or at a pH of 4.5 to 9.0, adjusted with HCl. When TSB was acidified with lactic acid, the organism grew at pH 4.6 but not at pH 4.5. A commercial sausage batter inoculated with 4.8 x 10(4) E. coli O157:H7 per g was fermented to pH 4.8 and dried until the moisture/protein ratio was less than or equal to 1.9:1. The sausage chubs were then vacuum packaged and stored at 4 degrees C for 2 months. The organism survived but did not grow during fermentation, drying, or subsequent storage at 4 degrees C and decreased by about 2 log10 CFU/g by the end of storage. These studies reveal the importance of using beef containing low populations or no E. coli O157:H7 in sausage batter, because when initially present at 10(4) CFU/g, this organism can survive fermentation, drying, and storage of fermented sausage regardless of whether an added starter culture was used.     

The microbial association of Greek taverna sausage stored at 4 and 10 degrees C in air, vacuum or 100% carbon dioxide, and its spoilage potential

Strains of the Lactobacillus sakei/curvatus group, mainly non-slime-producing Lact. sakei, dominated the microbial flora of industrially manufactured taverna sausage, a traditional Greek cooked meat, stored at 4 degrees C and 10 degrees C in air, vacuum and 100% CO2. Atypical, arginine-positive and melibiose-negative strains of this group were isolated. The isolation frequency of Lact. sakei/curvatus from sausages stored anaerobically was as high as 92-96%, while other meat spoilage organisms were practically absent. Conversely, in air-stored sausages, leuconostocs, mainly Leuconostoc mesenteroides ssp. mesenteroides, had a considerable presence (14-21%), whereas Brochothrix thermosphacta, pseudomonads and Micrococcaceae grew, but failed to increase above 10(5) cfu g(-1) in all samples during storage. Only yeasts were able to compete against LAB and reached almost 10(7) cfu g(-1) after 30 d of aerobic storage at 10 degrees C. The great dominance (> 10(8) cfu g(-1)) of LAB caused a progressive decrease of pH and an increase of the concentration of L-lactate, D-lactate and acetate in all sausage packs. The growth of LAB and its associated chemical changes were more pronounced at 10 degrees C than 4 degrees C. At both storage temperatures, L-lactate and acetate increased more rapidly and to a higher concentration aerobically, unlike D-lactate, which formed in higher amounts anaerobically. Storage in air was the worst packaging method, resulting in greening and unpleasant off-odours associated with the high acetate content of the sausages. Carbon dioxide had no significant effect on extending shelf-life. The factors affecting the natural selection of Lact. sakei/curvatus in taverna sausage are discussed. Moreover, it was attempted to correlate the metabolic activity of this group with the physicochemical changes and the spoilage phenomena occurring in taverna sausage under the different storage conditions.     

Effect of fermentation, aging and thermal storage on total glycosides, phenol-free glycosides and volatile compounds of White Riesling (Vitis vinifera L.) wines

There is growing recognition of the significance of the products of glycoside hydrolysis to varietal wine aroma. White Riesling wines were produced from four strains of Saccharomyces cerevisiae. Wines underwent conventional aging or anaerobic thermal storage (20 days at 45°C) either 2 or 40 months post-fermentation to quantify influences on total glycosides, phenol-free glycosides and selected volatiles. Glycoside and free volatile concentrations were estimated by analysis of glycosyl-glucose and gas chromatography/mass spectrometry, respectively. Thermal storage of wines 2 months post-fermentation reduced the total glycosides by an average of 33% for all yeasts and increased the concentration of free benzyl alcohol while decreasing the concentration of free linalool and geraniol. Conventional aging for 40 months reduced the total and phenol-free glycosides equally among yeasts by an average of 60%, with phenol-free glycosides averaging 80% of the total. Thermal storage of aged wines reduced the total glycoside concentration by an additional 29%. The effect of thermal storage on selected volatile phenols, higher alcohols, esters, acids, terpenes, carbonyl compounds, C-13 norisoprenoids and six-carbon alcohols was variable depending upon the component. Received 29 September 1998/ Accepted in revised form 16 January 1999     

Fate of Listeria monocytogenes in tissues of experimentally infected cattle and in hard salami.

Muscle, organ, and lymphoid tissues of four Holstein cows experimentally inoculated (intravenously) with Listeria monocytogenes were examined 2, 6, or 54 days postinoculation for the presence of the organism by direct plating and cold enrichment procedures. L. monocytogenes was isolated from 66% of the tissues sampled; 38% of the isolations were attributed to the use of cold enrichment. Isolation of the organism from muscle tissue was possible only with animals inoculated 2 days before slaughter. The fate of L. monocytogenes during the manufacture and storage of fermented hard salami made from this meat also was determined. Three sausage treatments were evaluated: (i) uninoculated control sausage, (ii) "naturally" contaminated sausage (NC) made from meat of an experimentally inoculated cow, and (iii) sausage made from beef inoculated with a laboratory culture of L. monocytogenes (I). Initial Listeria levels in NC and I sausage were 10(3) CFU/g in trial 1 and 10(4) CFU/g in trial 2. Numbers of L. monocytogenes decreased by approximately 1 log10 CFU/g during fermentation and decreased further during drying and refrigerated storage. Small numbers (less than or equal to 20 CFU/g) of L. monocytogenes were present in I and NC sausage at the end of 12 weeks of refrigerated storage; recovery of these organisms generally depended on the use of an enrichment procedure. The results indicate that L. monocytogenes does not multiply during the fermentation and drying processes typical of hard salami manufacture but that survival may occur if the organism is initially present at greater than or equal to 10(3) CFU/g.     

Fate of Listeria monocytogenes in tissues of experimentally infected cattle and in hard salami

Muscle, organ, and lymphoid tissues of four Holstein cows experimentally inoculated (intravenously) with Listeria monocytogenes were examined 2, 6, or 54 days postinoculation for the presence of the organism by direct plating and cold enrichment procedures. L. monocytogenes was isolated from 66% of the tissues sampled; 38% of the isolations were attributed to the use of cold enrichment. Isolation of the organism from muscle tissue was possible only with animals inoculated 2 days before slaughter. The fate of L. monocytogenes during the manufacture and storage of fermented hard salami made from this meat also was determined. Three sausage treatments were evaluated: (i) uninoculated control sausage, (ii) "naturally" contaminated sausage (NC) made from meat of an experimentally inoculated cow, and (iii) sausage made from beef inoculated with a laboratory culture of L. monocytogenes (I). Initial Listeria levels in NC and I sausage were 10(3) CFU/g in trial 1 and 10(4) CFU/g in trial 2. Numbers of L. monocytogenes decreased by approximately 1 log10 CFU/g during fermentation and decreased further during drying and refrigerated storage. Small numbers (less than or equal to 20 CFU/g) of L. monocytogenes were present in I and NC sausage at the end of 12 weeks of refrigerated storage; recovery of these organisms generally depended on the use of an enrichment procedure. The results indicate that L. monocytogenes does not multiply during the fermentation and drying processes typical of hard salami manufacture but that survival may occur if the organism is initially present at greater than or equal to 10(3) CFU/g.     

The microbial flora of smoked pork loin and frankfurter sausage stored in different gas atmospheres at 4 degrees C

The development of the microflora of smoked pork loin and frankfurter sausage was followed during storage in vacuum, N2 and CO2 atmospheres at 4 degrees C. The total aerobic count on the smoked pork loin reached 10(7) organisms/g after 37 d in vacuum, 43 d in N2 and 49 d in CO2. The corresponding value for the sausage was 77 d in vacuum, while the growth stopped at 6 x 10(40 organisms/g after 98 d in N2, and at 4 x 10(2) organisms/g after 48 d in CO2. The predominant organisms on the fresh products were Bacillus spp., coryneform bacteria, Flavobacterium spp. and Pseudomonas spp. At the end of the storage time the microflora on both products in the three gas atmospheres, consisted mainly of Lactobacillus spp. and two large groups of organisms that could not be identified as any described genus. Some of the unidentified strains could be classified as a Lactobacillus sp. after subsequent subculturing on laboratory media. The numbers of Lactobacillus spp. at the end of storage decreased in the order, CO2 greater than N2 greater than vacuum. Lactobacillus viridescens generally constituted a substantial part of the Lactobacillus flora (5-72%). On the sausages two large uniform groups of unidentifiable homofermentative Lactobacillus spp. were also found.     

Effect of nitrite,storage temperature and time onClostridium botulinum type A toxin formation in liver sausage

Summary The occurrence ofClostridium botulinum-type A toxin in inoculated, commercially processed Finnish liver sausages that were kept under different storage conditions was studied. Two levels of sodium nitrite addition, three different storage times and three temperatures were used. An addition of 100 mg of sodium nitrite per kg of sausage emulsion prevented toxin formation during a 2-week period. In an inoculated sausage without nitrite the toxin was not produced when stored at 15°C, but was formed at 20 and 25°C.     

Microbiology of Lebanon Bologna

Various aspects of the microbiology of the Lebanon bologna process were studied. Manufacture of Lebanon bologna appeared to be similar to that of summer sausage and other fermented sausages and consisted of a lactic acid fermentation by lactobacilli accompanied by the production of cured meat color from the reduction of nitrate by micrococci. The traditional process consists of aging coarse ground beef at 5 C for several days. Aging the beef for about 10 days was necessary to allow development of lactic acid bacteria; for successful fermentation, the concentration of lactic acid producers must be 10(4)/g or more. At least 3% NaCl was necessary to suppress the development of pseudomonads during the aging period; higher concentrations of salt suppress the development of the lactic acid-producing flora. During aging, in the presence of salt, the predominant flora developing on the meat consisted of catalase-positive, gram-positive rods and cocci; during fermentation at 35 C, the predominant flora became catalase-negative, gram-positive rods with characteristics of lactobacilli. Lebanon bologna could be made from frozen beef if the meat was thawed, salted, and aged. However, bolognas could not be made from unaged beef unless a lactic acid starter culture was used. The microflora of several commercial bolognas is reported also.     

The microbial flora of smoked pork loin and frankfurter sausage stored in different gas atmospheres at 4°C

The development of the microflora of smoked pork loin and frankfurter sausage was followed during storage in vacuum, N₂ and CO₂ atmospheres at 4°C. The total aerobic count on the smoked pork loin reached 10⁷ organisms/g after 37 d in vacuum, 43 d in N₂ and 49 d in CO₂. The corresponding value for the sausage was 77 d in vacuum, while the growth stopped at 6 times 10⁴ organisms/g after 98 d in N₂, and at 4 times 10² organisms/g after 48 d in CO².
The predominant organisms on the fresh products were Bacillus spp., coryneform bacteria, Flavobacterium spp. and Pseudomonas spp.
At the end of the storage time the microflora on both products in the three gas atmospheres, consisted mainly of Lactobacillus spp. and two large groups of organisms that could not be identified as any described genus. Some of the unidentified strains could be classified as a Lactobacillus sp. after subsequent subculturing on laboratory media.
The numbers of Lactobacillus spp. at the end of storage decreased in the order, CO₂ > N₂ > vacuum. Lactobacillus viridescens generally constituted a substantial part of the Lactobacillus flora (5–72%). On the sausages two large uniform groups of unidentifiable homofermentative Lactobacillus spp. were also found.     

Differences between spent hens of different genotype in performance,meat yield and suitability of the meat for sausage production

The valorization of spent hens via the food chain has some major limitations, which include low meat yield and tough meat. The latter issue can be overcome by producing convenience foods; the first may be alleviated by employing a genotype with higher meatiness. To quantitatively compare two common layer genotypes in production performance, meat yield and sausage quality, 2200 57 weeks old Institut de Sélection Animale (ISA) Warren and Dekalb White hens each were investigated during the last 60 days of egg laying. The hens were housed in an aviary system in 2×10 compartments (10 compartments/each genotype). Measurements included feed intake, laying performance, egg weight and feed conversion ratio as measured per compartment. BW was determined twice on 10 animals per compartment. Finally, two sub-groups of five hens per compartment were slaughtered, meat yield was recorded and bratwurst-type sausages were produced (n=20 per genotype). Fat proportion, cooking loss, connective tissue properties and Kramer shear energy were measured. After 1, 4, 7 and 10 months of frozen storage, oxidative stability (thiobarbituric acid reactive substances (TBARS)) and microbiological status were determined as shelf-life related criteria. ANOVA was performed considering genotype as the main effect. The ISA Warren hens were inferior in laying performance (−11%) and feed conversion ratio (+10%) compared with Dekalb White, but had the same feed intake. The ISA Warren had higher BW and carcass weight than the Dekalb White. Carcass yield was higher by 5.9%. There were 80 g (23%) more meat available for sausage production from ISA Warren compared with Dekalb White. Sausages prepared from meat of ISA Warren hens contained less fat than those from Dekalb White, but showed the same cooking loss. Although the collagen proportion of the sausages produced from ISA Warren was lower than from Dekalb White, collagen solubility was lower and shear energy was higher. During the 10 months of frozen storage, TBARS increased continuously, but not to an extent that would prevent its use as food. The sausages from the ISA Warren genotype had marginally higher TBARS levels during storage. Total colony counts decreased with storage time, with slightly lower values found in the non-spiced sausage material from the ISA Warren hens. In conclusion, when intending to use spent hens as food, ISA Warren are clearly superior to Dekalb White in meat and sausage yield. When processing the meat to sausages, the higher shear energy is probably advantageous.     

Model experiments to establish behaviour of Yersinia enterocolitica O:9 strains in various types of fresh dry sausage

In model experiments different kinds of raw sausages were inoculated with liquid cultures of virulent-plasmid-carrying clinical Yersinia (Y.) enterocolitica (e.) strains of the O:9 serotype, doses being between 10⁴ and 10⁵ cfu g^-1. The sausage samples were stored at 3–5° and 13–16°C. During the first 10 d of storage the Y.e. plate count was detected with Desoxycholate-Citrate-Lactose-Sucrose Agar every day, later on in addition to it with phosphate buffer-enrichment and with enrichment according to Schiemann (1982) in intervals of several days' duration. The pH and a _w values, the contents of salt and water were detected. The multitude of complexly acting factors and substances prevents obviously the proliferation of Y.e. in fresh dry sausages. Decay dynamics of Y.e. were found to be considerably affected by storage temperature. Cold storage, basically, had a conservation effect and thus delayed the dying process of model strains. Yersinia enterocolitica -contaminated fresh dry sausage may cause potential danger to consumers, because of relatively extended survival periods of the pathogen. Therefore, manufacturers are expected to observe most stringent hygienic rules of Good Manufacturing Practice.     

The curing agent sodium nitrite,used in the production of fermented sausages,is less inhibiting to the bacteriocin-producing meat starter culture Lactobacillus curvatus LTH 1174 under anaerobic conditions

Curvacin A is a listericidal bacteriocin produced by Lactobacillus curvatus LTH 1174, a strain isolated from fermented sausage. The response of this strain to an added curing agent (sodium nitrite) in terms of cell growth and bacteriocin production was investigated in vitro by laboratory fermentations with modified MRS broth. The strain was highly sensitive to nitrite; even a concentration of 10 ppm of curing agent inhibited its growth and both volumetric and specific bacteriocin production. A meat simulation medium containing 5 ppm of sodium nitrite was tested to investigate the influence of the gas phase on the growth and bacteriocin production of L. curvatus LTH 1174. Aerating the culture during growth had no effect on biomass formation, but the oxidative stress caused a higher level of specific bacteriocin production and led to a metabolic shift toward acetic acid production. Anaerobic conditions, on the other hand, led to an increased biomass concentration and less growth inhibition. Also, higher maximum volumetric bacteriocin activities and a higher level of specific bacteriocin production were obtained in the presence of sodium nitrite than in fermentations under aerobic conditions or standard conditions of air supply. These results indicate that the inhibitory effect of the curing agent is at least partially masked under anaerobic conditions.     

Fate of Listeria monocytogenes in processed meat products during refrigerated storage.

The fate of Listeria monocytogenes during refrigerated storage was determined on several processed meat products, including ham, bologna, wieners, sliced chicken, sliced turkey, fermented semidried sausage, bratwurst, and cooked roast beef. The meats were surface inoculated with a five-strain mixture of less than or equal to 200 or ca. 10(5) L. monocytogenes cells per package, vacuum packaged, and stored at 4.4 degrees C. Survival or growth of listeriae was determined for up to 12 weeks of storage or until the product was spoiled. The organism survived but did not grow on summer sausage, grew only slightly on cooked roast beef, grew well on some wiener products but not on others, grew well (10(3) to 10(5) CFU/g increase within 4 weeks) on ham, bologna, and bratwurst, and grew exceptionally well (10(3) to 10(5) CFU/g increase within 4 weeks) on sliced chicken and turkey. The rate of growth depended largely upon the type of product and the pH of the product. Growth was most prolific on processed poultry products. The organism generally grew well on meats near or above pH 6 and poorly or not at all on products near or below pH 5. These results indicate the importance of preventing postprocessing contamination of L. monocytogenes in a variety of ready-to-eat meat products.     

Fate of Listeria monocytogenes in processed meat products during refrigerated storage

The fate of Listeria monocytogenes during refrigerated storage was determined on several processed meat products, including ham, bologna, wieners, sliced chicken, sliced turkey, fermented semidried sausage, bratwurst, and cooked roast beef. The meats were surface inoculated with a five-strain mixture of less than or equal to 200 or ca. 10(5) L. monocytogenes cells per package, vacuum packaged, and stored at 4.4 degrees C. Survival or growth of listeriae was determined for up to 12 weeks of storage or until the product was spoiled. The organism survived but did not grow on summer sausage, grew only slightly on cooked roast beef, grew well on some wiener products but not on others, grew well (10(3) to 10(5) CFU/g increase within 4 weeks) on ham, bologna, and bratwurst, and grew exceptionally well (10(3) to 10(5) CFU/g increase within 4 weeks) on sliced chicken and turkey. The rate of growth depended largely upon the type of product and the pH of the product. Growth was most prolific on processed poultry products. The organism generally grew well on meats near or above pH 6 and poorly or not at all on products near or below pH 5. These results indicate the importance of preventing postprocessing contamination of L. monocytogenes in a variety of ready-to-eat meat products.     

采后预冷处理和贮藏温度对台湾绿竹笋鲜笋老化的影响

研究采后预冷处理和贮藏温度对台湾绿竹笋鲜笋老化的影响。结果表明,采后预冷处理和贮藏温度对台湾绿竹笋的老化速度、保鲜期和失重率有显著影响。采后预冷处理抑制鲜笋的老化,降低其老化率,延长保鲜期。(5±0.5) ℃恒温箱贮藏下,鲜笋的老化率、失重率低于(30±0.5) ℃恒温箱贮藏,贮藏期则相反。贮藏3、6、9、12 d,(5±0.5) ℃恒温贮藏下的鲜笋失重率均低于1%;(30±0.5) ℃恒温贮藏下,鲜笋失重率分别为26.32%、38.10%、48.04%、55.23%。     

The influence of starter cultures on the formation of volatile compounds in dry smoked sausages

The differences between the composition of volatile substances in two specimens of dry smoked sausages produced using a standard and experimental (a mixture of propionic acid bacteria and bifidobacteria) cultures were studied by capillary gas chromatography. It was found that the experimental starter culture intensified the flavor-formation processes as compared with the standard culture. The experimental specimen had richer qualitative and quantitative compositions and displayed more intensive aroma and flavor. The contents of lactones and volatile terpenoids in the experimental specimen were much higher than in the control. The organoleptic characteristics of experimental dry smoked sausage specimen were considerably better.     

The Role of Trehalose and Glycogen in the Survival of Aging Saccharomyces cerevisiae Cells

The role of the storage carbohydrates trehalose and glycogen in the survival of aging Saccharomyces cerevisiae cells was studied. Culture aging for one week did not reduce cell viability. During this period, the cells accumulated the storage carbohydrates and showed increased activity of the glycolytic enzymes hexokinase and phosphofructokinase. However, further aging led to a drastic drop in cell viability and to a decrease in the cellular content of trehalose and glycogen and in the activity of hexokinase and phosphofructokinase. The possible reasons for these changes are discussed.     

Role of trehalose and glycogen in the survival of aging Saccharomyces cerevisiae cells

The role of the storage carbohydrates trehalose and glycogen in the survival of aging Saccharomyces cerevisiae cells was studied. Culture aging for one week did not reduce cell viability. During this period, the cells accumulated the storage carbohydrates and raised the activity of the glycolytic enzymes hexokinase and phosphofructokinase. However, further aging led to a drastic drop in cell viability and to a decrease in the cellular content of trehalose and glycogen and in the activity of hexokinase and phosphofructokinase. The possible reasons for these changes are discussed.     

The Curing Agent Sodium Nitrite, Used in the Production of Fermented Sausages, Is Less Inhibiting to the Bacteriocin-Producing Meat Starter Culture Lactobacillus curvatus LTH 1174 under Anaerobic Conditions

Curvacin A is a listericidal bacteriocin produced by Lactobacillus curvatus LTH 1174, a strain isolated from fermented sausage. The response of this strain to an added curing agent (sodium nitrite) in terms of cell growth and bacteriocin production was investigated in vitro by laboratory fermentations with modified MRS broth. The strain was highly sensitive to nitrite; even a concentration of 10 ppm of curing agent inhibited its growth and both volumetric and specific bacteriocin production. A meat simulation medium containing 5 ppm of sodium nitrite was tested to investigate the influence of the gas phase on the growth and bacteriocin production of L. curvatus LTH 1174. Aerating the culture during growth had no effect on biomass formation, but the oxidative stress caused a higher level of specific bacteriocin production and led to a metabolic shift toward acetic acid production. Anaerobic conditions, on the other hand, led to an increased biomass concentration and less growth inhibition. Also, higher maximum volumetric bacteriocin activities and a higher level of specific bacteriocin production were obtained in the presence of sodium nitrite than in fermentations under aerobic conditions or standard conditions of air supply. These results indicate that the inhibitory effect of the curing agent is at least partially masked under anaerobic conditions.