Fate of gram-positive bacteria in reconditioned, pork-processing plant water

This study investigated the responses of Enterococcus faecium (ATCC 19433), Staphylococcus aureus (196E), and Listeria monocytogenes Scott A in water from a local meat-processing plant. Each bacterium was added to a starting count of 3 log10 CFU/ml and held from 5 to 28 degrees C. At intervals (0, 2, 7, 14, and 21 days), aliquots were plated on appropriate selective agars. In contrast to the gram-negative bacteria studied previously and which grew, the three gram-positive bacteria survived with some slight increase in number in only nonchlorinated, reconditioned water, either filtered (0.22 microm pore size) or nonfiltered. The presence of chlorine in either potable or reconditioned water contributed to the rapid decline in viable counts for all three bacteria. These results further emphasize the importance of residual chlorine in preventing the growth of these gram-positive bacteria in potable and reconditioned waters.     

Pig sire type and sex effects on carcass traits,meat quality and physicochemical and sensory characteristics of Serrano dry‐cured ham

This study demonstrates that improvements in animal line selection by breeding enterprises exert a strong effect on carcass traits, meat quality and sensory characteristics of Serrano dry‐cured ham. A total of 461 pigs from the offspring of a Duroc (DU) × Landrace (LD) sow mated with two DU boars and a DU × Large White (LW) boar from three breeding enterprises were evaluated. The two DU terminal sires were significantly different (P < 0.05) in carcass conformation, backfat thickness, ham and loin yields, raw ham traits, myoglobin concentration and total pigments formed during the curing process; in addition, the two lines provided different percentages of hams (54 vs 91%) with sufficient subcutaneous fat and weight to manufacture dry‐cured Serrano hams using a slow ripening process (11 months). The DU × LW sire had the best carcass and ham traits from an economic standpoint and obtained highest scores for sensory characteristics of Serrano ham evaluated by a trained panel test; furthermore, this line provided 84% of total hams suitable for manufacturing Serrano hams by a slow process. When the sex effect was analysed, carcass and ham traits of females were more favourable, but females presented a higher incidence of pale, soft and exudative (PSE) meat and a lower percentage of hams with sufficient subcutaneous fat and weight to produce Serrano hams using a slow ripening process (61% for females and 91% for castrates). On the other hand, castrates provided Serrano hams cured by a slow procedure with better organoleptic characteristics than females. Right and left hams were similar. Copyright © 2005 Society of Chemical Industry     

Quantitative investigation of the effects of chemical decontamination procedures on the microbiological status of broiler carcasses during processing

The effects of elevated chlorine concentrations (25 ppm) added to water in the final carcass washing equipment on total viable counts (TVCs 22 degrees C) and Escherichia coli and Enterobacteriaceae levels on poultry carcasses were investigated. Mean TVC counts on neck skin samples were significantly reduced when pre-evisceration and postwash samples were compared with log10 4.98 to 4.52 CFU/g recovered, respectively (P < or = 0.05). No significant reductions in TVC counts were observed in control samples at corresponding sampling points subjected to wash water containing 1 to 2 ppm chlorine. E. coli and Enterobacteriaceae counts were not significantly altered following final carcass washing in the processing plant. A second trial assessed the microbial decontamination capabilities of sodium triphosphate (TSP) on broiler carcasses. Neck skin samples from carcasses were obtained before final washing (control), following a 15-s dip in potable water and after dipping in a 10% TSP solution (pH 12) for 15 s. Reductions in E. coli and Enterobacteriaceae counts were all statistically significant for both water and TSP-treated samples when compared with corresponding controls (P < or = 0.01). The TSP treatment resulted in higher reductions of log10 1.95 and 1.86/g for E. coli and Enterobacteriaceae, respectively. In contrast, reductions of log10 0.37 and 0.3 l/g were observed for E. coli and Enterobacteriaceae counts when water-dipped carcasses were compared with corresponding controls. Significantly, Salmonella was not detected in any of the TSP-treated carcasses, while log10 1.92 and 1.04/g were found in control and water-dipped samples, respectively. Thermophilic Campylobacter counts were significantly lower in both treatment groups when compared with corresponding controlsresulting in log10 0.55 and 1.71/g reductions for water- and TSP-dipped carcasses, respectively (P < or = 0.01).     

Effect of Tumbling and Tumbling Time on Quality and Microflora of Dry-Cured Hams

Thirty-two intact hams were utilized to study the effects of tumbling and tumbling time (1 hr continuous, 3 hr intermittent, 6 hr intermittent) on the quality and microflora of intact dry-cured hams. Tumbled hams had higher salt concentrations, lower moisture percentages, and showed more muscle separation and excessive surface drying. Sensory panel scores were similar for all treatments except that 3 hr intermittently tumbled hams had higher salt and lower overall satisfaction scores. Tumbling significantly accelerated salt and nitrite penetration during the Fust 2 wk of curing but had little subsequent effect. Tumbled hams generally had lower microbial counts; however, after aging all hams were of acceptable microbial quality.     

Effect of different levels of beef bacterial microflora on the growth and survival of Escherichia coli O157:H7 on beef carcass tissue

The influence of various levels of endogenous beef bacterial microflora on the growth and survival of Escherichia coli O157:H7 on bovine carcass surface tissue was investigated. Bacterial beef microflora inoculum was prepared by enriching and harvesting bacteria from prerigor lean bovine carcass tissue (BCT) and was inoculated onto UV-irradiated prerigor BCT at initial levels of 10(5), 10(4), 10(3), and <10(3) CFU/cm2. Additional control BCT was inoculated with sterile H2O. E. coli O157:H7 was inoculated onto all tissues at an initial level of 10(2) CFU/cm2. Following a 48-h incubation at 4 degrees C, BCT was incubated up to 14 days at 4 or 12 degrees C, either aerobically or vacuum packaged. Regardless of the microflora level, there was no substantial growth of E. coli O157:H7 on BCT during storage at 4 degrees C under either aerobic or vacuum-packaged conditions. Instead, viable cell numbers at 4 degrees C remained constant, with no reduction in numbers associated with the different beef microflora levels. E. coli O157:H7 grew on all BCT stored at 12 degrees C, regardless of microflora inoculation treatment, reaching higher populations on aerobic samples than on vacuum-packaged samples in 10 days. However, the presence of the beef microflora did appear to delay the onset of growth or slow the growth of the pathogen, and E. coli O157:H7 counts on BCT without added microflora were generally higher following 7 to 10 days of 12 degrees C storage than those counts on BCT inoculated with beef microflora. These data demonstrate the importance of temperature control during meat handling and storage to prevent the outgrowth of this pathogen and indicate that proper sanitation and processing practices that prevent and reduce contamination of carcasses with E. coli O157:H7 are essential, regardless of background microflora levels.     

Influence of crossbreed on the degradation of myofibrillar proteins and on the cathepsin B+L activity in dry cured hams

Enzymatic activity and proteolysis undergone by the proteins extracted from the Semimembranosus and Biceps femoris muscles using high ionic strength buffer were studied in raw hams and hams dry-cured for 11 months. The hams were taken from three different crosses of three breeding enterprises: cross A (75% Duroc-25% Landrace); cross B (50% Duroc-25% Landrace-25% Large White); and cross C (75% Duroc-25% Landrace). Higher cathepsin B+L activity levels were recorded in the Semimembranosus muscle than in the Biceps femoris muscle both in the raw hams and in the cured hams, residual enzymatic activity in the hams being 1% of the initial levels; significant differences were not found for the three crosses. The proteolysis index was higher for the Biceps femoris muscle, similar values being observed for all three crosses. The raw hams from cross A exhibited the highest relative density values for low molecular mass peptides and the lowest relative density values for high molecular mass peptides. After 11 months of curing, proteolysis levels were highest in the hams from cross B, which had the highest levels of 8, 9 and 22 kDa fragments (in the Semimembranosus muscle) and 25 and 9 kDa fragments (in the Biceps femoris muscle). This finding confirms that genetic factors have an influence on proteolysis.     

Characterization by Volatile Compounds of Microbial Deep Spoilage in Iberian Dry-Cured Ham

Abstract: In the present study, volatile compounds of spoiled dry-cured Iberian ham with deep spoilage or “bone taint” were analyzed and correlated with level of spoilage and the microorganisms detected. Volatile compounds extracted by a solid phase micro-extraction technique were assayed by gas chromatography/mass spectrometry. The spoiled hams were evaluated sensorially, and the correlations among volatile compounds, spoilage level, and microbial counts were studied. The spoiled hams had higher concentrations of hydrocarbons, alcohols, acids, esters, pyrazines, sulfur compounds, and other minor volatile compounds than unspoiled hams. The sensorial analysis showed that the spoilage level of hams correlated with several volatile compounds, most of them associated with Gram-positive catalase positive cocci and Enterobacteriaceae counts. Cyclic compounds such as cyclohexanone, some ethers, and pyrazines should be considered as indicators to monitor incipient microbial deep spoilage in the elaboration of this meat product.     

Modeling of Microbial Growth in Refrigerated Packaged Beef

The effects of gaseous permeability of the film and storage temperature (0° and 4°C) on the microflora of refrigerated beef were analyzed; total aerobic counts, anaerobic counts, Pseudomonas sp., Brochothrix thermosphacta, Lactobacillus sp., Enterobacteriaceae and yeasts were determined as functions of time. Storage periods to reach a total count of 10⁷ CFU/cm² were established for different conditions. Microbial growth was modeled by mathematical equations in terms of initial contamination, growth rate and length of the lag phase for each component of the mixed flora.     

Physicochemical changes throughout the ripening of dry cured hams with different salt content and processing conditions

Physicochemical characteristics of Semimembranosus and Biceps femoris muscles from 24 dry cured Iberian hams were analysed. The hams were salted with different amounts of salt (60 g kg^–1, HS, and 30 g kg^–1, LS, w/w) and then ripened at different temperatures (traditional processing, T, versus modified processing, M). The processing conditions did not significantly affect the moisture content and the chloride molality of Semimembranosus and Biceps femoris muscles (p>0.05) throughout ripening, although daily weight losses were significantly affected (p<0.01). The effect of the processing conditions on water activity was also rather limited as it was only significant at the drying stage. Colour a* values and chroma were significantly higher in Semimembranosus muscles from T hams than from M ones (p<0.01). Muscles from hams elaborated in a traditional system showed a higher number of tyrosine crystals than muscles from hams processed in a modified one, though only to a significant extent in Semimembranosus muscle (p<0.05). The salt concentration was higher in HS than in LS hams. HS hams showed higher weight losses in the salting and postsalting stages, owing to a more intense osmotic dehydration.     

Effect of Sodium Lactate on Microbial and Chemical Composition of Cooked Beef during Storage

Cooked, vacuum packaged beef top rounds injected with 0, 1, 2, 3 or 4% sodium lactate were stored up to 84 days at 0°C. Aerobic plate counts (APC), water activity, pH and lactic acid content were determined at 14-day intervals. Microbial distributions were characterized following 0.56 and 84 days storage. Increasing sodium lactate resulted in reduction in APC. Water activity was not affected by sodium lactate level. Decreases in pH were minimized at sodium lactate >3%. Initially, the microflora of roasts consisted primarily of Micrococcus and coagulase-negative Staphylococcus spp. After 84 days the microflora consisted primarily of hetero- and homofermentative Lactobacillus spp. No differences in APC, lactic acid content, pH or water activity occurred between top rounds with 3 and 4% sodium lactate. Cooked, refrigerated roast beef injected with up to 3 or 4% sodium lactate had microbial shelf-life up to 84 days.     

Poultry Processing Line Speeds as Related to Bacteriologic Profile of Broiler Carcasses

Aerobic plate counts, Enterobacteriaceae, E. coli counts; and Salmonella prevalence were determined on broiler carcasses obtained in a comtnercial slaughter establishment in Puerto Rico. Samples were obtained from three sites in the production process. Each site represented an end-point of a discrete segment of the slaughter process. Whole bird carcass rinses (300) were randomly collected over 4 days of production for several linespeeds. Samples were collected for birds processed at 70 birds/min (BPM), 80 BPM, 90 BPM, and three replications of samples at 100 BPM (June 1990 to May 1991). A total of 1,800 carcass rinses were analyzed. Mean bacterial counts and Salmonella prevalence did not change significantly with processing line speeds.     

Preslaughter resting and hot-fat trimming effects on the incidence of pale, soft and exudative (PSE) pork and ham processing characteristics

Effects of preslaughter rest (0, 1, 2 or 3 h) and hot-fat trimming (HFT, one side) on muscle quality characteristics of hams and loins were tested with 120 pigs. Center-cut loins from each carcass side were vacuum packaged and stored for 7 or 14 days at 2°C. Pigs not rested before slaughter had a skin temperature 3°C higher and ham muscle temperatures 1°C higher than pigs rested 1-3 h (P<0.05). Three hour muscle pH was highest if pigs were rested for 1 h. HFT significantly accelerated carcass chilling rate, but did not affect rate of muscle pH decline. After 14 days of aging, pigs not rested had lower sensory panel ratings for juiciness, tenderness, flavor and overall mouthfeel of loin chops than pigs rested 1 or 2 h. Percentage bound water of hams was highest (P<0.05) if pigs rested 1 or 2 h rather than a shorter or longer times. Pigs should be rested 1 h before slaughter and HFT carried out to allow more rapid carcass chilling and improve muscle quality.     

Effects of Boning Time, Mechanical Tenderization and Partial Replacement of Sodium Chloride on the Quality and Microflora of Boneless Dry-Cured Ham

SEVENTY-TWO HAMS were utilized to study the effects of KCl replacement level (100:0, 70:30, 50:50 ratios of NaCl and KCl), boning time and mechanical tenderization on the quality and microflora of boneless dry-cured hams. Boning time had no effect on palatability or final yield. Hotboned hames had higher levels of residual nitrite and slightly higher microbial counts. Mechanical tenderization improved tenderness and microbial quality. However, tenderized hams had lower flavor preference and overall satisfaction scores. The replacement of NaCl with KCl at a level of 30% had no effect on palatability or microbial quality. NaCl replacement at a level of 50% severely decreased palatability and increased microbial numbers.     

The effects on product of a hot water pasteurizing treatment applied routinely in a commercial beef carcass dressing process

The effects of a pasteurizing treatment on the microbiological condition and the appearance of carcasses, routine in a commercial carcass dressing process, were examined. Beef carcass sides were pasteurized with water at 85°C. During 2-h periods, all sides from the dressing process were treated for 8, 9, 10, 11 or 12 s. During each period, microbiological samples were obtained by swabbing five randomly selected sides before and five others after the treatment, with a single sample being obtained from 25 treated and 25 untreated sides from each treatment time. All treatments similarly reduced the log mean numbers of total aerobic counts by about 1 log unit, but the reductions in the log total numbers of coliforms orEscherichia coli recovered from 25 samples increased with increasing treatment time, to >2 log units with treatment times of 11 or 12 s. Cooling of the sides did not obviously reduce the numbers of total aerobic bacteria on beef sides, but there were small reductions in the numbers of coliforms and E. coli on both treated and untreated sides. After cooling, sides treated routinely for 10 s yielded total aerobic counts at log mean numbers of about 2 log cfu cm⁻², and coliforms and E. coli at log total numbers of <2 and <1 log cfu 2500 cm⁻², respectively. After the carcass breaking process, loin primal cuts and manufacturing beef from such sides yielded total aerobic counts at log mean numbers of about 3 and about 4 log cfu cm⁻², respectively; coliform counts at log total numbers of about 3 and about 4 log cfu 2500 cm⁻², respectively; and E. coli counts at log total numbers >2 log cfu 2500 cm⁻²; which indicated that product was contaminated from improperly cleaned equipment during the carcass breaking process. When sides treated for 10 s with water that had previously been used to treat 120 or more sides were compared after cooling with untreated sides from the same carcasses, the appearances of treated sides were judged to be less desirable than those of the untreated sides because of the less desirable appearance of the fat tissue on the treated sides. However, the mean differences between untreated and treated sides for overall appearance and the appearance of fat tissue were only 0·45 and 0·46 assessment units, respectively, for assessments on a seven-point scale. The small adverse effect of the pasteurizing treatment on the appearance of beef carcass sides apparently did not affect the value of the meat. Thus, the data indicated that, in commercial practice, pasteurizing treatment times should be set by reference to reductions in numbers of E. coli rather than of total aerobic counts, to assure the maximum possible reduction in the number of enteric pathogens; that protein suspended in the circulating water of pasteurizing equipment will accumulate to levels that affect the appearance of carcass fat, unless the water is changed at appropriate intervals or actions are taken to remove the protein from the water or carcass surfaces; and that pasteurizing of carcasses alone is inadequate for assuring the safety of meat when recontamination of product with enteric organisms occurs during the carcass-breaking process.     

Bioassay Analysis of Dry-Cured Ham Processed to Affect Trichinella spiralis

Effects of curing time and temperature to destroy Trichinella spiralis in dry-cured hams were evaluated. Five muscle groups from small, medium and large, short-cure hams and large, bag-cure hams were subjected to a digestion technique to determine the number of spiralis larvae. Trichinae in small hams held at 10°C for 90 days, in medium hams at 23.9 and 32.2°C for 35 and 11 days, and in large hams at 10 and 23.9°C for 90 and 35 days, respectively, were rendered non-infective. Medium hams contained a number of trichinae after 90 days at 10°C. Bag-cure hams aged at 23.9°C for 35 days were free of trichinae. Results could indicate insufficient aging time at 10°C for medium hams and the need for reviewing current USDA-FSIS regulations for the destruction of T. spiralis.     

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.     

EFFECT OF CURING INGREDIENTS, SKINNING, AND BONING ON YIELD, QUALITY, AND MICROFLORA OR COUNTRY HAMS

Green hams were left intact, partially skinned, fully skinned, and fully skinned and boned. They were dry-cured with or without nitrate and aged 3 months. The presence of nitrate had no effect on the variables studies. Percent moisture loss and accompanying weight loss increased with each further removal of protective fat and skin. Percent residual salt was in proportion to weight loss. Residual nitrite was low for all groups Color and aroma scores were similar for all groups. General appearance scores, however, were lowest for the drier boneless group. Shear values were greatest while organoleptic flavor and over-all satisfaction scores were lowest in the boneless group. Tenderness scores were similar for the skinless and boneless group but both were lower than for the intact or partially skinned groups. In general, microbial counts were highest for surface samples from completely skinned fresh hams and lowest for partially skinned fresh hams. Higher counts were obtained for core samples from boneless fresh hams than for intact hams. Aerobic (26° and 37°C), lactobacilli, enterococci. streptococci. yeast and mold surface, and core counts tended to decrease during the manufacture of aged dry-cured hams. No trends in counts due to ham group or cure treatment were observed during the manufacturing process. At the end of the aging period none of the hams contained bacteria of public health significance. Aged dry-cured hams of acceptable microbial quality can be manufactured using intact, partially skinned, skinned or boneless fresh hams without potassium nitrate as part of the cure mixture.     

Decontamination of carcasses by vacuum-hot water cleaning and steam pasteurizing during routine operations at a beef packing plant

The microbiological effects of three operations for cleaning areas on dressed beef carcasses with vacuuming equipment which also applies hot water to the carcass, and of an operation for pasteurizing beef carcass sides with steam, were assessed. All four operations were routine in a commercial carcass dressing process. For each operation, swab samples were obtained from randomly selected carcasses, with a single sample being collected from each carcass, from a site selected at random from those affected by the operation. For the cleaning operations, 25 samples were obtained before and 25 after each operation. For the pasteurizing operation, 50 samples were obtained before and 50 after the operation. In addition, 50 samples were obtained from beef sides after the carcass cooling process which followed the pasteurizing operation. Total aerobic counts, coliforms and Escherichia coli from each sample were enumerated. The cleaning operations generally reduced the log mean numbers of bacteria on treated areas by ≤ 0.5 and had no discernible effect on the overall microbiological condition of the carcasses emerging from the process. The pasteurizing operation reduced the log mean numbers of total aerobic bacteria on carcasses by about 1, and the log mean numbers of coliforms and E. coli by > 2. The cooling process had no affect on the total counts, but further reduced the log mean numbers of coliforms and E. coli, apparently by about 1, to give beef sides from which E. coli were not recovered.     

Indigenous Yeast Microflora on Arkansas White Riesling (Vitis vinifera) Grapes and in Model Must Systems

The indigenous yeast microflora on Arkansas-grown White Riesling (Vitis vinifera) grapes and in model musts were examined during fermentation of sulfite-treated (0, 25, 50, or 100 mg/L total SO₂) musts held at two temperatures 113°C and 21°CL The yeast microflora were examined with time ?13°C musts were sampled it 5, 10, and 20 days; 21°C musts were sampled at 2, 4, and 8 days. A two log cycle increase in yeast counts occurred during fermentation, with little difference in counts due to sulfite treatments. Of 70 isolates, the main genera were Cryptococcus, Hanseniaspora, Pichia, Saccharomycopsis, Trichosporon, Zygosaccharomyces, Rhodotorula, Candida, Metschnikowia, and Succharomyces. All isolates recovered showed lipolytic activity on Spirit Blue Agar.     

Pre-freezing Hams Affects Lipolysis during Dry-curing

An initial freezing/thawing treatment of raw hams prior to dry-curing was compared to the standard process (refrigerated hams) by assaying free fatty acid generation and carbonyl index in both biceps femoris muscle and adipose tissues throughout curing. More intense lipolysis occurred between 0 and 5 mo for muscle, and 0 and 10 mo for adipose tissue. Lipid oxidation in adipose tissue was higher than in muscle. No significant differences (p<0.05) were observed in lipolysis between refrigerated and frozen/thawed hams at the end of the process. Ham sensory evaluation after 15 mo showed that initial freezing/thawing treatment did not affect final sensory quality except for a more salty taste.