A repeat national survey of muscle pH values in commercial pig carcasses

Measurements of pH values at 45 min post-slaughter (pH₁) in m. longissimus were taken in a total of 5598 commercial bacon weight carcasses. pH values at 24 h post-slaughter (pH₂) were taken on a further 5598 carcasses. The overall mean pH₁ was 6.39 with 15.1% of values less than 6.0. The overall mean pH₂ was 5.64, none of the values recorded were greater than 6.5. This survey shows a small increase over the 1983 study in the incidence of potentially Pale Soft and Exudative (PSE) carcasses. It found no evidence of a Dark, Firm and Dry (DFD) problem related to high ultimate pH.     

A survey of pH values at the surface of beef and lamb carcasses,stored in a chiller

The surface pH values of lamb and beef carcasses stored at 5 ºC have been measured over a 5-day period. In both types of animal, muscle surfaces were at or near their minimum pH at 3 days, when the overall mean was pH 6.4. In the subsequent 2 days some sites showed no change in pH, while at others a small drop or a rise occurred. Rises in pH tended to be more common and greater on the beef. In lamb, intact muscle surfaces varied only from pH 6.3 to 6.6 at 3 days, while beef muscles varied widely, from pH 5.8 to 7.1. Muscle surfaces cut during dressing fell much more rapidly in pH, particularly in beef. Fatty sites fell from near pH 8.0 to near pH 7.0. The pH of beef surfaces chilled to -3 ºC fell more rapidly to lower final values than those at 5 ºC. At 5 ºC there was little multiplication of bacteria on fat surfaces, whereas on muscle they grew moderately, irrespective of pH.     

An investigation of ultimate pH in the muscles of commercial beef carcasses

Ultimate pH values were recorded in the carcasses of steers and heifers at a beef slaughtering plant over a period of 3 years. The incidence of carcasses with a pH_u ≥ 6·0 in the LD—a value usually associated with ‘dark-cutting’ in beef—was 3·2%. A pronounced seasonal effect was observed with the incidence rising from 1·2% for the period February to August to 5·2% for the period September to January, inclusive. An examination of thirteen muscles showed that increases in pH_u above normal values occurred most frequently in the LD and four large muscles of the hindquarter and were much less frequently observed in the eight other hind- and forequarter muscles examined. In the carcasses of young bulls, also slaughtered under commercial conditions, high pH_u values were predominantly associated with the same muscles as in steers and heifers. However, when experimental cattle were given adrenaline to induced high pH_u values, this treatment resulted in a general increase in pH_u in all the muscles examined. The different pattern of pH_u elevation in the adrenaline-treated and commercial carcasses suggests different physiological mechanisms in the two cases.     

A national survey of the microbiological quality of beef carcasses and frozen boneless beef in Australia

The third national baseline microbiological survey of Australian beef carcasses and frozen boneless beef was conducted in 2004. Carcasses (n=1155) sampled at 27 slaughter establishments had a mean aerobic plate count (at 25 degrees C) of 1.3 log CFU/cm2. Escherichia coli was isolated from 8.0% of the cacasses, with a mean count of -0.8 log CFU/cm2 for positive samples. On samples from 24 boning (fabrication) plants (n=1082), the mean aerobic plate count for frozen boneless beef was 1.3 log CFU/g, and the mean count for the 1.8% of samples with detectable E. coli was 1.5 log CFU/g. E. coli O157: H7 was isolated from 1 of 1,143 carcasses and from 0 of 1082 boneless samples. Salmonella was isolated from 0 of 1155 carcasses and from 1 of 1082 samples of boneless product. No Campylobacter spp. were isolated from carcasses or boneless beef. Coagulase-positive staphylococci were isolated from 28.7% of beef carcasses and 20.3% of boneless beef samples, and positive samples had a mean count of 0.3 log CFU/cm2 and 0.8 log CFU/g, respectively.     

A national survey of the weight loss in pig carcasses between slaughter and 24 hours post mortem

A national survey was carried out in Great Britain in 1978/79 to determine the weight loss occurring in pig carcasses between slaughter and 24 hours post mortem. A total of 20,600 carcasses were measured over a 12-month period, the sample covering forty-eight slaughtering plants and the main market weights of pig. At 24 hours post mortem, the overall mean weight loss was estimated to be 2·27% of the hot weight. The figure differed little between market weights or between times of the year, but there were important differences between slaughtering plants.     

Channel catfish (Ictalurus punctatus) muscle protein isolate performance processed under different acid and alkali pH values

Abstract: Channel catfish (Ictalurus punctatus) muscle was subjected to 6 protein extraction and precipitation techniques using acid solubilization (pH 2.0, 2.5, and 3.0) or alkaline solubilization (pH 10.5, 11.0, 11.5) followed by precipitation at pH 5.5. The catfish protein isolate was compared with ground defatted white muscle. Alkali‐processed catfish showed increased gel rigidity, gel strength, and gel flexibility compared to acid‐processed catfish, which exhibited inconsistent functional performance, increasing and decreasing gel rigidity, gel strength, and gel flexibility. The gel rigidity (G′) at pH 3.0 in the absence of salt had the highest G′ of the acid treatments and was not significantly different from the alkaline‐treated catfish muscle (P > 0.05). However in the presence of added salt pH treatment it had the lowest G′ and was different from alkaline treatments (P < 0.05) during break force testing. These results show that pH‐shift processing of channel catfish muscle provides highly functional isolates with a potentially broad range of applications. This range of applications is possible due to the modification of the textural properties of catfish muscle protein produced using different acidic or alkaline pH solubility treatments.     

Survival and growth of Clostridium perfringens in commercial no-nitrate-or-nitrite-added (natural and organic) frankfurters, hams, and bacon

The popularity of "preservative-free" foods among consumers has stimulated rapid growth of processed meats manufactured without sodium nitrite. The objective of this study was to quantify the potential for Clostridium perfringens growth in commercially available processed meats manufactured without the direct addition of nitrite or nitrate. Commercial brands of naturally cured, no-nitrate-or-nitrite-added frankfurters (10 samples), hams (7 samples), and bacon (9 samples) were obtained from retail stores and challenged with a three-strain inoculation (5 log CFU/g) of C. perfringens. Reduced inhibition (P < 0.05) was observed in seven brands of frankfurters, six brands of hams, and four brands of bacon when compared with each respective sodium nitrite-added control. In naturally cured and truly uncured commercial frankfurters, growth over time was approximately 4.7 log, while conventionally cured frankfurters exhibited growth at 1.7 log. Naturally cured ham and bacon products exhibited growth at 4.8 and 3.4 log, respectively, while their conventionally cured counterparts exhibited growth at 2.6 and 2.3 log, respectively. These products also demonstrated variation in growth response. The results indicate that commercially available natural/organic naturally cured meats have more potential for growth of this pathogen than do conventionally cured products. Natural and organic processed meats may require additional protective measures in order to consistently provide the level of safety from bacterial pathogens achieved by conventionally cured meat products, and which is expected by consumers.     

Fatty acid composition of M. longissimus lumborum, ultimate muscle pH values and carcass parameters in reindeer (Rangifer tarandus tarandus L) grazed on natural pasture or fed a commercial feed mixture

The effects of feeding regimen on the fatty acid composition of M. longissimus, ultimate pH values in three muscles (Mm. longissimus, triceps brachii and biceps femoris) and carcass quality were studied in15 reindeer bulls. Nine animals came from natural pasture and six had been fed a pelleted commercial feed mixture for two months prior to slaughter. The pellet fed reindeer had significantly better carcass grading scores (EUROP conformation), higher trim fat content, more intramuscular fat and lower ultimate pH values in all three muscles than the group from pasture. The polar and neutral lipid fatty acid composition of the meat was analysed separately. Meat from pasture fed reindeer showed a high content of the fatty acid 18:3 n-3 in the polar lipid fraction. In the same lipid fraction, the fatty acid 18:2 n-6 was dominant in meat from the pellet fed animals. Similar differences in the neutral lipid fraction were found when comparing fatty acid composition between treatment groups, however the abundance of these fatty acids was much less. The present results confirm previous findings that reindeer fed typical pelleted commercial feed mixtures generally have an improved nutritional status.     

VanA-type vancomycin-resistant enterococci (VRE) remain prevalent in poultry carcasses 3 years after avoparcin was banned

Avoparcin was used as a growth promoting feed additive in Norwegian broiler and turkey production from 1986 until it was banned in 1995, when an association between vancomycin-resistant enterococci (VRE) and avoparcin use became apparent. A recent study regarding faecal samples documented a continuing high prevalence of VRE among Norwegian poultry 3 years after avoparcin was banned. In the present study, carcasses of broilers and turkeys from farms where avoparcin had previously been in use and carcasses of layer chickens from farms where avoparcin had never been used were examined for the presence of VRE. One carcass from each of 150 different farms was included. By a direct plating method, VRE were isolated from 30 of 100 samples of broilers and turkeys, but not from any samples of layer chickens. When an enrichment step was included, VRE were isolated from a total of 81 of the 100 samples of broilers and turkeys and from nine of the 50 samples of layer chickens. All VRE isolated were highly resistant to vancomycin (MIC > or = 256 microg/ml) and possessed the vanA gene. These results correspond to the prevalence of VRE recently documented in faecal samples from Norwegian poultry. The present study reveals a high prevalence of VRE in broiler and turkey carcasses. Consequently, consumers are exposed to VRE when handling raw poultry meat, although the public health significance of such exposure is unclear.     

A baseline survey of the microbiological quality of chicken portions and carcasses at retail in two Australian states (2005 to 2006)

Raw poultry products were purchased from the retail market place in two Australian states, New South Wales (n = 549) and South Australia (n = 310). The products sampled on a proportional volume basis were chicken portions with the skin off or skin on, in bulk or tray packs, and whole carcasses. They were collected from butcher shops, supermarkets, and specialty stores from urban areas during the winter (2005) and summer (2006) months. The samples were analyzed to determine the prevalence and concentration of Escherichia coli, Salmonella, and Campylobacter spp. in addition to total viable counts. Salmonella was found in 47.7 and 35.5% of retail chicken samples (35.3 and 21.9% were the less virulent Salmonella Sofia), at mean counts of -1.42 and -1.6 log MPN/cm2 in New South Wales and South Australia, respectively. Campylobacter was found in 87.8 and 93.2% of samples at mean counts of 0.87 and 0.78 log CFU/cm2, respectively. In both states in both seasons, the mean total viable count was 5 log CFU/cm2. On whole birds, E. coli was detected in all winter samples and on 92.9 and 85.7% of summer samples in New South Wales and South Australia, respectively; the log of the geometric mean per square centimeter was 0.5 in winter and slightly lower in summer. On chicken portions, E. coli was detected in around 90% of winter samples in both states, and in summer on 75.1 and 59.6% of samples in New South Wales and South Australia, respectively. The log of the geometric mean CFU per square centimeter for E. coli was 0.75 and 0.91 in winter, and 0.66 and 0.5 in summer in New South Wales and South Australia, respectively.     

A survey of water activity and pH values in fresh pasta packed under modified atmosphere manufactured in Argentina and Uruguay

The water activity (a(w)) and pH values of commercially available filled fresh pasta and gnocchi packed under modified atmosphere and manufactured in Argentina and Uruguay were examined. The retail survey included 58 samples (several brands) of filled pasta and 11 samples of gnocchi. Fillings consisted of different combinations of cheese (various types), beef, ricotta, ham, chicken, and spinach. The survey revealed that the a(w) values of the 58 samples of filled pasta ranged from 0.916 to 0.973, and their pH values ranged from 5.2 to 7.0. The a(w) of gnocchi was consistently higher and ranged from 0.936 to 0.983, with pH values from 4.8 to 6.4. Some samples of filled pasta and most gnocchi samples were found to have a(w) and pH values that would support growth of spores of Clostridium botulinum, if present, under conditions of temperature abuse (i.e., 30 degrees C).     

The effect of sex, breed and initial carcass pH on the quality of cure in bacon

The relationship between the pH₄₅ measured in the M. longissimus dorsi and the subsequent appearance of Wiltshire style bacon was examined in 110 pig carcasses. Except for extremely PSE and DFD carcasses, which produced bacon of poor appearance, there was an inverse relationship between pH₄₅ and the quality of appearance of bacon. There were no differences between hogs and gilts for either pH or bacon quality. The appearance of bacon was slightly better in breeds with lower mean pH₄₅ values but the differences were not significant.     

A note on the muscle, fat and bone contents of Portuguese light lamb carcasses

A total of 72 lambs weighing between 10.1-13.0 kg (category C of the European Union grading for light lambs) from the Bragan?ano, Campani?o, Merino Branco, Merino Preto e Serra da Estrela breeds were studied. These breeds represent 66.8% of the Portuguese sheep population. Evaluations were made at the same subcutaneous fat contents in the carcass (88.5 g kg(-1)). Small, significant (p < 0.05) differences in the range of muscle and bone contents were found; the ranges being 30 and 25 g kg(-1), respectively. These variations led to significant diferences in the muscle:bone ratios, the highest value being 3.30 and the lowest 2.73. Significant differences were also found in the content of higher-priced joints (leg + chump, loin + ribs and anterior ribs) and in the proportion of kkcf (9 g kg(-1)). No significant differences were found in the content of total fat [subcutaneous, intermuscular and kidney knob and channel fat (kkcf)] and in the muscle: total fat ratios.     

The effects of mixing,transport and duration of lairage on carcass characteristics in commercial bacon weight pigs

On arrival at the factory commercial crossbred pigs were subjected to various treatments: (i) penned in producer lots; (ii) mixed with pigs from another producer and (iii) mixed and subjected to an additional transport of 1-1.5h duration. Groups of pigs were killed on the day of arrival or after overnight lairage. Carcass parameters including pH₁ (pH 45 min post mortem) and pH_u (pH 20 h post mortem) values of the Longissimus dorsi (LD) and adductor muscles were taken post mortem. Mixing and transport had no statistically significant effect on any of the carcass parameters measured, although overnight lairage resulted in significant decreases in hot carcass weight, killing-out percentage and liver weight. The incidence of carcasses classified as pale soft and exudative [PSE (muscles with a pH₁ of 5.9 or less)] or dark firm dry [DFD (muscles with a pH_u of 6.2 or greater)] was high after both normal and overnight lairage. pH₁ and pH_u values of the LD and adductor muscles were not significantly affected by mixing or transport. Statistically significant differences in the incidence of DFD between treatment groups were observed. In general the incidence of DFD increased more after overnight lairage in pigs penned in producer lots, than in pigs penned in mixed producer lots.