Sensory evaluation of breast fillets from argon‐stunned and electrically‐stimulated broiler carcases processed under commercial conditions

1. A comparison of eating quality of breast meat (pectoralis major) filleted at 2 h post‐mortem was made between broilers stunned with argon‐induced anoxia (less than 2% residual oxygen) and broilers which were electrically‐stunned and their carcases electrically‐stimulated under commercial conditions.

2. Fifty breast muscles were filleted from the carcases of argon stunned broilers at 2 h post‐mortem. Fifty breast muscles were also removed at the same time from the carcases of broilers which were electrically‐stunned and electrically‐stimulated. A ‘control’ group of broilers which were electrically‐stunned and electrically‐stimulated and processed under as similar conditions as possible were also filleted after overnight ageing in the air chiller.

3. Sensory analysis was performed using 10 trained panelists, who were asked to rate the fillets on a 1 to 8 hedonic scale for taste, texture, juiciness and overall liking.

4. The mean ranks for texture and overall liking differed between the groups. The mean ranks based on texture were the highest for control, intermediate for argon stunning and the lowest for electrical stimulation treatment group. The mean ranks based on overall liking were similar for the control and argon stunning groups, and their ranks were higher than that of electrical stimulation treatment group. The mean ranks for taste and juiciness did not differ significantly between the groups.

5. It is concluded that, in comparison with electrical stimulation of broiler carcases soon after plucking, stunning broilers with argon‐induced anoxia produced tender breast meat when filleted at 2 h postmortem.     

Effect of stunning method,carcase chilling temperature and filleting time on the texture of turkey breast meat

1. Three hundred and sixty turkeys comprising 16 week‐old stags (medium stags), 22 week‐old stags (large stags) or 52 week‐old hens (hens) were stunned with either argon‐induced anoxia, 30% carbon dioxide in argon with 2% residual oxygen (gas mixture) or electric current and the carcases were processed under commercial conditions. The carcases were chilled at either 16°C or 3°C using a commercial immersion chiller and the carcases were held in a cold room (3°C).

2. Breast muscles (pectoralis major) were filleted at either 2, 3, 5 or 18 h post‐mortem, and pH and muscle temperature were measured at the time of filleting for the medium and large stags. The breast fillets removed soon after killing were stored at 3°C until transported to the laboratory.

3. All the breast fillets were cooked to an internal muscle temperature of 85°C and their texture was measured instrumentally. The fillets were weighed before and after cooking to determine the proportional cooking loss.

4. The results showed that, for electrical stunning, the rate of pH fall soon after killing differed between the bird types, and it resulted in a variable texture in the breast meat when filleting was performed soon after killing. The medium stags had a relatively slower rate of pH fall and filleting them soon after killing resulted in tougher breast meat.

5. By contrast, in all the three bird types, gas stunning resulted in a rapid pH fall soon after killing and produced tender breast meat at all the filleting times tested.

6. The cooking loss was higher in the large stags than in the medium stags or hens.

7. Stunning turkeys by anoxia or 30% carbon dioxide in argon would enable filleting to be performed soon after killing, and produce less variable‐and more tender breast meat.     

Effect of early filleting on the texture of breast muscle of broilers stunned with argon‐induced anoxia

1. Eighty broilers were stunned in batches of 10 with less than 1 % oxygen (air displaced by argon) and their chilled breasts were filleted at 2, 3, 5 or 21 h (argon control) post‐mortem. Twenty broilers were electrically stunned and their breasts filleted at 21 h post‐mortem (electrical control).

2. Meat quality variables studied included pH of the pectoralis major muscle measured at 20 min post‐mortem and at filleting, and texture at 24 h post‐mortem.

3. Argon stunning resulted in a rapid early post‐mortem pH fall, but there was no indication of heat toughening in the breast muscles.

4. Filleting at 2 h post‐mortem, after argon stunning, resulted in 5% of the p. major muscles having greater than 4 kg yield force (slightly tough).

5. Although post‐mortem ageing of argon stunned broilers improved the texture of breast muscle, it is inferred that filleting at 2 h postmortem resulted in breast muscle with acceptable texture.     

Effect of stunning method and filleting time on sensory profile of turkey breast meat

1. Twenty four 22 week‐old large stags were stunned using one of two methods, argon‐induced anoxia (2% residual oxygen) or an electric current (150 mA per bird, 50 Hz). The birds were processed under commercial conditions and carcasses held at 3°C until the breast muscles were filleted at either 3 h after killing or after overnight maturation.

2. The meat samples were frozen at — 40° C and stored at — 20°C until they were thawed at 1°C and cooked at 85°C. They were subjected to sensory evaluation by 10 experienced assessors and instrumental texture measurements were made.

3. Only stunning method had significant effects on the sensory profile and instrumental texture. Breast meat from anoxia‐stunned turkeys was less firm on cutting, more tender and had a more powdery residue on eating than that from electrically‐stunned turkeys. The instrumental texture values confirmed that breast meat from anoxia‐stunned turkeys was more tender than that from the electrically‐stunned turkeys.

4. There was no significant correlation between the subjective tenderness rating and the instrumental texture value.

5. Principal components analysis showed that 59% of total variation was explained by the first two dimensions, the first being a contrast between turkeys that were tender and powdery and those that were firmer and fibrous. When values from individuals were plotted, this dimension was related to the differences between anoxia and electrical stunning, with anoxia‐stunned turkeys at the tender end of the first dimension.     

Effect of electrical and gaseous stunning on the carcase and meat quality of broilers

1. The aim of the experiment was to investigate the effect of gaseous stunning methods on the carcase and meat quality of broilers (dead weight 1.0 to 2.3 kg) in comparison with electrical stunning.

2. Two replicates of broilers (age 54 and 59 d respectively) were stunned in carbon dioxide, in argon or by electric current, and the carcases were plucked either by a mechanical plucker or by hand.

3. Carcase and meat quality were evaluated to determine the effect of these stunning treatments and plucking methods. The quality factors measured included pH at 20 min post‐mortem, ultimate pH, texture and colour of the pectoralis major muscle, and the incidence of carcase appearance defects, cooking loss, broken bones and bruises in the breast and leg muscles.

4. Stunning method had a significant effect on pH at 20 min, ultimate pH, texture and colour of breast meat. Plucking method had a significant effect on the cooking loss and texture.

5. Argon stunning resulted in fewer muscle haemorrhages, a more rapid early post‐mortem fall in pH and more tender breast meat than in the electrically stunned broilers; carbon dioxide stunned broilers had intermediate values for pH decline and meat tenderness but were not significantly different from argon stunning regarding muscle haemorrhages.

6. Appearance defects occurred to a similar extent in all the stunning methods and mechanical plucking resulted in 4 times as many defects compared with hand plucking; the incidence of broken bones was higher in mechanically plucked broilers than in hand plucked carcases.

7. Gaseous stunning of broilers produced relatively better quality carcases and meat than electrical stunning, and therefore may have commercial advantages.     

Effect of ventricular fibrillation at stunning and ineffective bleeding on carcase quality defects in broiler chickens

1. This experiment was concerned with whether ineffective bleeding could exacerbate the incidence of haemorrhagic conditions in broiler carcases, when ventricular fibrillation (VF) was induced at stunning.

2. Broiler chickens were electrically stunned with 81 mA per bird and then allocated to three treatments. About 67% experienced a VF at stunning and half of these birds were bled out before processing while the other half were processed without being bled out. The birds which did not experience a VF at stunning were bled out before being processed. The carcases were subjectively graded for haemorrhagic conditions.

3. Inducing a VF at stunning caused increases in the incidence of red wingtips and haemorrhaging at the humerus‐radius joint in the birds which were bled out. There were no other obvious effects of inducing a VF on carcase downgrading.

4. Failure to bleed the chickens which had a VF at stunning resulted in high incidences of red wingtips, red necks, haemorrhaging at the humerus‐radius joint and red sternal feather tracts. It was concluded that bleeding efficiency was important in influencing the expression of these characteristics when a VF occurred at stunning.     

Carcase and meat quality in broilers either killed with a gas mixture or stunned with an electric current under commercial processing conditions

1. Carcase and meat quality were evaluated under commercial conditions in 400 broilers either killed with a mixture of 30% carbon dioxide and 60% argon in air or stunned with a 50 Hz AC with clipped sine wave.

2. Compared with electrical stunning, killing broilers with the gas mixture eliminated or substantially reduced the prevalence of carcase and meat quality defects.

3. The results also showed that killing broilers with a mixture of 30% carbon dioxide and 60% argon would enable filleting (deboning) to be performed at 4 h post mortem without adversely affecting the cook loss or texture of breast meat.     

Flow routes of electric currents in domestic hens during pre‐slaughter stunning

1. For a bird to be adequately stunned, sufficient electric current needs to reach the brain in order to induce an epileptic seizure. Methods are presented for determining the percentage of the stunning current which reaches the brain.

2. A transverse section of the thorax was examined and tissues including epithelium, fat, muscle, liver, keelbone and heart, were tested for the percentage of current flowing through each tissue.

3. It was found that the proportion reaching the brain varied from bird to bird whereas, with the exception of a slight variation in the proportion reaching the heart, that flowing through the other tissues located in the thorax was similar in all the birds tested.

4. The variability in current reaching the brain and to some extent the heart may determine whether a bird is stunned, inadequately stunned or killed after having entered a water‐bath stunner.     

Yield and composition of raw and cooked meat of small white turkeys as influenced by dietary nutrient density and energy to protein ratio

1. Raw and cooked meat yields and the dry matter and fat contents of meat samples were determined on 144 carcases of Small White turkeys fed on diets that varied in nutrient density (ND) and energy to protein ratio (E:P).

2. High ND diets increased body weights, eviscerated carcase weights, relative carcase yields and carcase skin yield, but not breast or total meat yields.

3. Feeding a low ND diet to 6 weeks followed by diets with progressively increasing ND yielded performance and carcases with qualities comparable to feeding diets of constant medium or high ND; consequently cost savings could be made.

4. Increasing E:Ps reduced body weights, eviscerated carcase weights and carcase yields. Breast and total meat yields from male but not female carcases, and skin yield of female but not male carcases decreased with higher E:Ps.

5. The fat contents of breast and thigh meat samples increased with ND. The fat content of breast but not thigh meat decreased with higher E:P. Dry matter contents of meat samples did not vary consistently with changes in fat content.     

Ratification of broiler carcase condemnations in poultry meat inspection

1. In the years 1985 to 1989 decisions (approvals and condemnations) made by poultry meat inspectors were examined by the individual reinspection of 26,815 broiler carcases.

2. The extent of agreement between inspection and revision ranged between 83.2 and 86.2%.

3. Agreement between inspectors and revisors was higher for the category of approved birds than for the condemned category.

4. Differences in the criteria used to assess the birds were observed.

5. The conclusion was drawn that findings in meat inspection require further discussion to reach an agreed standard.     

Influence of various dietary protein levels on carcase composition in the male Japanese quail (Coturnix coturnix japonica)

1. The present study was conducted to determine the effect of various dietary protein concentrations on the carcase composition of male Japanese quail.

2. Six diets varying in protein from 160 to 300 g/kg and containing approximately 11–72 MJ/kg ME were fed for 5 weeks and analysed for dry matter, protein, fat and ash.

3. Treatments affected carcase weight, dry matter, protein, ether extract and ash

4. The water content of the carcases decreased with increasing dietary protein concentrations, while the carcase protein content increased with higher dietary protein. The carcases with the highest fat content were obtained from quail receiving the low protein diet.     

Broken bones in chickens: Effect of stunning and processing in broilers

1. Broilers and broiler carcases, sampled immediately before the stunner, at the end of the processing line and from a supermarket company, were physically dissected to determine the incidence of broken bones.

2. Over 95% of the frozen broilers from the supermarket company had broken bones and there were between 3 and 4 breaks per carcase. Only 3% of live birds had broken bones so most of the carcase damage must have been caused by processing.

3. The effect of 100, 200 and 300 V electrical stunning on the incidence of broken bones was investigated: increasing voltage resulted in an increase in the incidence of broken bones in the collar region.     

Microbiological survey of five poultry processing plants in the UK

1. Neck skin samples were taken from chickens and turkeys at all the main stages of processing to monitor changes in total viable count (TVC) and counts of coliforms and pseudomonads.

2. Processing reduced TVC by up to 100‐fold. Geometric mean counts after packaging were log₁₀ 4.4 to 5.3 CFU/g whilst corresponding counts of coliforms were 2.7 to 3.8 CFU/g.

3. Increases in mean TVC or coliforms as a result of either defeathering or evisceration did not exceed 0.6 log.

4. Pseudomonads represented only a minor fraction of the initial microflora of the bird and were often reduced by scalding to a figure which could not be detected by direct plating of samples; however, subsequent contamination resulted in means between log₁₀ 2.9 and 4.0 CFU/g for packaged carcases.

5. Although Staphylococcus aureus was readily isolated from defeathering equipment, mean counts from defeathered carcases were always below log₁₀ 3.0 CFU/g.     

Effect of electrical stunning current on the duration of insensibility in hens

1. Hens were subjected to electrical stunning at 85, 105 or 125 mA per bird. The time to recovery of physical behaviour was measured in those birds which did not experience a cardiac arrest at stunning.

2. On average the duration of apparent insensibility lasted between 53 and 59 s, and at 105 mA per bird it was as short as 22 s in the bird which showed the quickest recovery.

3. Increasing the stunning current had no effect on the duration of insensibility.     

Microbial status of chicken portions and portioning equipment

1. The sources and numbers of microbes contaminating poultry portions, which form an increasing proportion of poultry meat production were investigated. Total aerobic count at 30°C, pseudomonads, coliforms, enterococci and Staphylococcus aureus were enumerated.

2. Samples which had undergone different degrees of portioning, from whole birds to individual retail portions of poultry meat, were collected at points along the portioning line. Equipment surfaces, utensils and hands/gloves of factory personnel were examined.

3. In general, microbial numbers on carcase sampling sites were related to ‘exposure factor’, that is, the length of time the site was exposed to potential contamination during processing and portioning.

4. When results for individual sampling sites were analysed separately, no significant differences were found between sites on whole birds and the corresponding half bird sample sites. Comparison of numbers on half birds and on portions revealed a more variable situation.

5. Sites touched by rubber gloves when carcases were hung on the automatic portioning lines had greater contamination than other sites.

6. Provided factory and operative hygiene standards are high, portioning does not significantly increase numbers of microorganisms.     

Effects of evisceration and storage temperature on changes in meat quality of traditional farm‐fresh Turkeys

1. Conditions affecting the keeping quality of traditional farm‐fresh turkeys were investigated.

2. Storage of uneviscerated Wrolstad turkeys at 4 °C for 10 days caused no statistically significant changes in meat flavour or texture.

3. During further storage at —2 °C, however, there was a slight but significant change in flavour, which became more marked with time in birds which had been eviscerated after the initial period at 4 °C.

4. Both eviscerated and uneviscerated birds became slightly tougher during storage.

5. Initial holding at 4 °C increased the numbers of psychrotrophic bacteria on the skin by about 10³ but subsequent changes at — 2 °C were slight for uneviscerated birds.

6. Eviscerated carcases had higher counts than uneviscerated birds after storage at — 2 °C and, although ‘off’ odours were not detected, spoilage appeared to be imminent at the end of the 20‐d period.     

Broken bones in domestic fowls: Effect of husbandry system and stunning method in end‐of‐lay hens

1. The effects of age at sexual maturity, age at culling, and stunning frequency and current on the incidence of broken bones were examined in end‐of‐lay hens. In addition comparisons were made between 4 different egg‐laying breeds, and between battery, perchery and free range husbandry systems.

2. High frequency stunning (1500 Hz) caused a reduction in the incidence of broken bones compared with 50 Hz.

3. Battery birds had a higher incidence of recently broken bones in comparison with perchery and free range birds. However, there were more old breaks in the perchery and free range systems than in the battery system.

4. Breed of bird, age at sexual maturity and age at culling had no effect on the incidence of broken bones.     

Traits influencing the hatching performance of Japanese quail eggs

1. Japanese quail eggs from moderately heavier sires showed superior fertility; while fertile eggs from moderately heavier dams hatched slightly better than the eggs from lighter dams.

2. Higher rates of fertility and hatchability of Japanese quail eggs were observed from parents of 10 to 19 weeks of age, with peak fertility and hatchability at 14 and 12 weeks of age, respectively.

3. Sex ratios of 1:2 to 1:5 gave comparable fertility and hatchability results.

4. The hatching performance of quail eggs from cage and deep litter reared breeders was comparable.

5. Fertility and hatchability were directly proportional to the egg weight.

6. Quail egg shell colour, tints and blotches were found to influence hatching performance.

7. Storing quail eggs at 16 ± 2°C and 75 ± 5% relative humidity for more than 4 d reduced hatchability.

8. Hatchability of eggs stored at room temperature was improved if they were sealed in polyethylene bags.

9. Provision of light during the first 14 d of incubation resulted in a photo‐acceleration of about 3.2 h.     

Metabolic and anatomical adaptations of light‐bodied chicks to intermittent feeding

1. Chicks of a light‐bodied strain were deprived of food on alternate days from 15 to 46 d of age.

2. Hyperphagia, amounting to twice the intake of control birds early in the experiment, occurred on the repletion day.

3. Final body weight attained 80% of that of the controls.

4. Body fat concentration decreased at first but returned to that of controls after 3 weeks.

5. A consistent hyperlipaemia was observed after food deprivation or restoration.

6. There was a marked increase in the digestive enzymes found in the small intestine, but not in the pancreas during the repletion day.

7. These responses may be considered as mechanisms to reduce the physiological manifestations of starvation.     

Effect of stunning current on downgrading in ducks

1. Ducks were given 85, 150 or 250 mA electrical stunning currents; the proportion experiencing a ventricular fibrillation at stunning and the incidence of downgrading conditions were determined.

2. The ducks were less susceptible to a ventricular fibrillation than chickens or turkeys, but a stunning current of 250 mA induced a ventricular fibrillation in 99% of the birds.

3. The incidence of reddening of the rear margin of the wing was lowest in the 85 mA current treatment. The incidence of the following conditions was not affected by stunning current: red pygostyles, red wingtips, wing haemorrhaging, engorgement of the wing veins, breast and leg muscle haemorrhaging, and broken furcula and coracoids.