J.G. van Logtestijn

Bacteriological quality of broiler carcasses as affected by in-plant lactic acid decontamination

In an attempt to improve the bacteriological quality of broiler carcasses the bactericidal effect of treatments with 1% and 2% lactic acid was investigated. Bacterial colonisation was determined immediately after treatment, after the carcasses had been chilled and during storage at 0 degrees C. Examination included numbers of mesophilic aerobic and psychrotrophic aerobic colony-forming units (CFU), CFU of Enterobacteriaceae at 37 degrees C and CFU of Staphylococcus aureus. Immediately after treatment colonisation per gram skin was generally reduced by about 1 log. Initially 2% lactic acid was not found significantly more effective in reducing colony counts than 1%. However, treatment with 2% lactic acid suppressed post-decontamination colonisation with Enterobacteriaceae more effectively than 1% lactic acid, as determined after 15-18 days storage at about 0 degrees C. Lactic acid treatment was most effective when applied shortly before chilling. Successive treatment at three different stages during slaughtering did not increase reduction of colony counts. It is concluded that decontamination with 1-2% lactic acid at pH 2, when applied shortly before chilling, will markedly improve the bacterial safety and increase the refrigerated shelf life of broiler carcasses.

The transmission of campylobacter in piggeries; an epidemiological study

The campylobacter infection of 10 sows and their piglets was monitored. These pigs werekept on two multiplier farms. Rectal faeces samples were taken from the sows shortly beforelittering and at different intervals after littering. Swab samples of rectal content were taken fromsix piglets per sow at different intervals after birth. Nine sows were shown to be infected withcampylobacter before litter and all sows after litter, with an average colony count of 4·1in log N g–1 of faeces. Half of the piglets became infected withcampylobacter during the first week of life and 85%, after four weeks. Two genetic subtypingmethods (ERIC‐PCR and RFLP) were used to study the relationships between campylobacterisolates from sows and piglets. A large diversity of campylobacter subtypes was found.Nevertheless, piglets and their mothers often harboured campylobacter isolates with identicalgenetic subtyping profiles, suggesting that piglets become infected via their mothers. However,observed similarities in genetic subtyping profiles between campylobacters isolated on differentfarms made this difficult to prove.

Microbial and nutritional aspects of feeding fermented feed (poultry by‐products) to pigs

Broiler by-products (heads, feet, and viscera) mixed with 4% dextrose were pasteurized for 4 min at 90 degrees C core temperature, cooled to 20 degrees C, and fermented with Lactobacillus plantarum as starter culture. These fermented poultry by-products were fed to 12 individually housed fattening pigs as part (17.6% of the dry matter) of their fattening ration, the remainder composed of compound pig feed. Control pigs received a compound pig feed only. Both groups of pigs were fed restrictively on the basis of body weight. The technical results of the pigs fed the experimental diet showed a significantly improved feed:gain ratio (2.46 vs 2.57), a significantly higher carcass weight (86.1 vs 81.8 kg), a lower meat percentage (50.9 vs 52.5%) and an increased backfat thickness (21.5 vs 18.7%). The bacterial flora in the intestinal tract of the pigs fed the experimental diet differed significantly from the control animals. Decreased colony counts of mesophilic aerobic bacteria, Enterobacteriaceae, enterococci and lactobacilli were found in the rectal content and the prevalence of salmonella was lower. It is suggested that the improved feed:gain ratio and the reduced bacterial activity of the measured groups of bacteria is a result of 1) the higher energy content of the diet, and(or) 2) an assumed enhanced digestibility of nutritional components in the diet, and(or) 3) the lower incidence of diarrhea in the pigs fed with fermented poultry by-products. This resulted in a lower contamination level of enteropathogenic bacteria like, salmonella and Escherichia coli, in the gastro-intestinal tract of the pigs fed fermented poultry by-products.

Slaughter by‐products: Problems, preliminary research and possible solutions

The collection, storage, disposal and processing of slaughterhouse by-products is an important part of veterinary care in regions with intensive animal husbandry and meat production. Transmission of diseases and environmental pollution through an improper and/or incorrect handling of slaughterhouse by-products needs to be prevented. The use of animal by-products as feedstuff could be of economical benefit to slaughterhouses and could add nutritive value to animal feed. As a results of the centralisation and intensification of slaughtering, the amount of slaughter by-products produced at a single location is increasing. Until now, hardly any attention, in practice or in research, has been paid to the collection and disposal of these by-products. There are important socio-economic reasons to increase scientific knowledge about the handling of slaughter by-products. Several animal by-products were contaminated with Salmonella. We also showed that rapid breakdown of amino acids in poultry by-products occurs during storage at 20 degrees C. It is concluded that as far as safety, environmental care and nutritive value of animal by-products is concerned, diversification and separation of slaughter by-product collection, storage, disposal and processing is necessary. Measures at source, the slaughterline, and some technologies are suggested for future use.

Electrical stimulation during exsanguination: Effects on the prevalence of blood splash and on sensory quality characteristics in veal

Twenty-four veal calves were stunned with a captive bolt. Twelve calves were shackled by the left, the other twelve by the right hindleg. Approximately 1 min after sticking, six carcasses of each of these subgroups were stimulated electrically with equipment relying on a combined high (3000 V, 0·83 pulses s(-1), 1·5 ms duration) and low 35 V, 14 pulsess(-1)) voltage action. The remaining carcasses were left unharmed. At 24 h post-mortem hindquarters were boned to commercial primal cuts. Surrounding connective tissue and cut-up surfaces of primals as well as certain locations vulnerable for blood splash were further dissected. Neither electrical stimulation nor shackling by either of the hindlegs significantly affected the prevalence and severity of blood splash. Post-mortem factors promoting blood splash and possibly related to electrical stimulation and shackling are discussed. At 7 days post-mortem the sensory meat quality was assessed. In general, electrical stimulation did not significantly affect waterbinding and colour characteristics in longissimus (M. longissimus dorsi) and semimembranosus samples. Sarcomere lengths were similar in stimulated and control groups in longissimus but not in semimembranosus muscle. In both muscles shear force values were lower after electrical stimulation. In general, neither longissimus nor semimembranosus samples excised ipsilaterally from the shackled leg side exhibited differences in tenderness and sarcomere length. It is concluded that shackling by one leg or the other does not interfere with the tenderising effect of electrical stimulation.

Variation in post-mortem rate of glycolyis does not necessarily affect drip loss of non-stimulated veal

In this study the effect of the rate of post mortem pH fall on the water-holding capacity of meat from moderately chilled veal carcasses was investigated. Also the relationship between muscle protein denaturation and drip loss of veal was examined. Three groups of 10 Friesian Holstein male veal calves each were selected on the basis of their pH in M. longissimus thoracis et lumborum (LTL) at 3 hr post mortem (pH(3)): (1) fast pH-fall, pH(3) < 6.2; (2) intermediate pH-fall, 6.5 < pH(3) < 6.6; (3) slow pH-fall, pH(3) > 6.7. After 48 hr of chilling the LTL was excised from the carcass and sampled for determination of drip loss, filter paper wetness, sarcomere length, protein solubility and transmission value. Differences in pH(3) were not associated with differences in drip loss, filter paper wetness or differences in protein denaturation. It is suggested that at the relatively high veal carcass chilling rate the effect of rate of pH-fall on protein denaturation and thus on drip loss is negligible. Drip loss of veal was highly correlated with both solubility of sarcoplasmic (r = -0.67; p < 0.001) and total muscle protein (r = -0.54; p < 0.01) and with transmission values (r = 0.66; p < 0.001). These results indicate that protein denaturation measurements may be a good predictor for drip loss of veal.

Fermentation of aerobically activated pig slaughterhouse sludge for animal feed purposes

Abstract Aerobically activated sludge from a pig slaughterhouse wastewater-treatment plant was mixed with 0.35 or 0.5% (wt/wt) dextrose, with 0.5% (wt/wt) dextrose and 0.05 or 0.2% (v/v) formic acid, or with 2.5% (wt/wt) molasses and 0.1% (v/v) formic acid, and was pasteurized at 95°C for 5 min. After cooling to approximately 20°C the sludge was inoculated with 10 6 –10 7 cfu Lactobacillus plantarum /g sludge. Fermentation was performed at 20°C for 21 days. When 0.05% (v/v) formic acid or less was added, the initial pH of the sludge was favourable for the germination and outgrowth of clostridia spores and resulted in amino acid breakdown. In the case of the addition of 0.2% (v/v) formic acid and 0.5% (wt/wt) dextrose the initial pH was below 4 and the number of lactobacilli did not substantially increase. No amino acid breakdown was observed. Concerning the safety of the fermented product, it was concluded that pasteurized activated sludge from a pig slaughterhouse can be effectively fermented into a stable product, suitable for animal feed purposes, with 2.5% (wt/wt) molasses, 0.1% (v/v) formic acid and L. plantarum as the inoculum.

Bacteriological quality assurance (BQA) of mechanically deboned meat (MDM).

Adequacy of bacteriological quality assurance during the commercial production of mechanically deboned meat (MDM) was assessed. Lax standards of hygiene during production were observed, resulting in high numbers of Staphylococcus aureus, viz. 10(4) to 10(5) cfu g(-1), and severe contamination with Enterobacteriaceae: 10(5) to 10(6) cfu g(-1). These data indicate that measures of hygiene observed during boning of carcasses and during collection, storage and transport of bones or poultry parts should be markedly tightened, while conditions of refrigerated storage of raw materials and MDM should be improved. Use of bones of poor sensory quality (discoloration, abnormal smell) generally resulted in MDM of inferior bacteriological quality. Phage typing, biotyping and assessment of enterotoxin production was carried out with 136 St. aureus cultures, isolates from mechanically deboned pork produced at one plant. Fifty-five per cent of the isolates was not typable, 28% was typable with human phages, 8% with bovine phages. The majority of the strains could not be explicitly assigned to any Meyer and/or Hájek and Marŝálek types. Applying the simplified system of Devriese to eighteen strains isolated in our investigation, ten were found to belong to the poultry ecovar, one to the bovine ecovar, while seven strains were non-host specific. None of the isolates produced enterotoxins A-E. Microbiological inspection of end products is recommended as part of an integrated quality assurance system. The following reference values for the final product (maximal colony counts to be expected under GMP conditions expressed as 95th percentile) were calculated: Pig MDM: log(10) mesophilic colony count 6·8 and log(10) cfu mesophilic Enterobacteriaceae g(-1) 4·8; Poultry MDM: log(10) mesophilic colony count 6·6 and log(10) cfu mesophilic Enterobacteriaceae g(-1) 4·7.

Tissue composition of mechanically deboned pork (MDP).

The tissue composition of the mechanically deboned pork produced by a discontinuous pressure system was investigated. By means of quantitative microscopy volume ratios (in terms of volume in volume fractions) of striated muscle, collagenous and elastic connective tissue, bone and cartilage in homogenized samples from eight different producers were determined. Crude protein, fat, calcium and the hard bone residue were determined chemically. In addition, we measured the size of the hard bone particles. The muscle/connective tissue ratio varied from 0·3 to 6·9. The hard bone residue, determined by means of the KOH-method, varied from 0·05 to 0·62%. 0·6% of the bone particles were larger than 3 mm. In addition to chemical analysis we regard quantitative microscopy for the determination of the tissue composition of mechanically deboned pork as imperative for quality control.