Browsing by discipline "Livsmedelsteknologi (kötteknologi )"

Genetic selection of broilers has produced heavier birds that grow faster, with consequent change in morphology and allometry (relative growth) of their body parts. Wooden Breast (WB) is a defect of the breast muscle that affects meat quality. Its cause is unknown, but heavy weight and/or rapid growth rate seem to be predetermining factors. The aim of this work was to study the differences in morphology and relative growth (allometry) between WB affected and unaffected birds. Random groups of a total of 350 male chickens of 5 hybrids were slaughtered at 7 different ages. Morphometric measurements of heart, liver, intestine, breast muscle, girth, coracoid, clavicle, keel and leg bones were analysed with a statistical software. Affected birds presented higher body weight, heavier, longer and thicker breasts and heavier livers than unaffected birds. On the other hand, unaffected birds presented longer legs, heavier intestines and hearts. Keel length, coracoid length and clavicle length did not present any difference between both groups. The comparison of allometric curves of affected and unaffected birds showed differences in almost all body parts, but the heart and liver. Clavicle was the only body part that presented a slower growth rate in unaffected birds, all the other body parts showed a higher growth rate. The relationship between breast thickness and clavicle, coracoid and keel lengths, had a great effect on the presentation of WB. Affected birds presented changes in morphology and growth, very similar to the ones caused by genetic selection. Genetic selection of broilers is very complex and dynamic and it may be possible that WB has several causes. It seems that one of them is the lack of support of the breast muscle, due to an impaired growth of its bone structure.

The literature review dealed with stunning of poultry. The effects of the stress induced by handling on the physiological and biochemical changes, and how they further affect the meat quality, were discussed. Suitability of different stunning methods for poultry was also reviewed. Methods for measuring the welfare of poultry before slaughtering and the meat quality were described, at the end of the literature review. The aim of the experimental work was to find out the influence of two different types of stunning gases, CO2 and N2, on turkey meat quality. An additional aim of the study was to examine how the chilling rate affects meat quality and also if there are any differences between the stunning methods concerning this. Furthermore, the most suitable gas stunning method for small-scale slaughterhouses, from a meat quality perspective, was hoped to be revealed by the results. Two-phase CO2-stunning was used as a control treatment. The turkeys were stunned using a gas stunning mask designed for the conditions of small-scale slaughterhouse. The post mortem metabolism was controlled with the rate of the pH fall as well as with the glycogen and lactate contents. Drip loss, cooking loss and tenderness were measured to predict the meat quality. The post mortem pH fall was significantly faster in the breast muscles of the nitrogen stunned turkeys than in the breast muscles of the turkeys stunned with other gases. Stunning with N2 could enable the fast chilling of the carcasses without the risk of cold shortening because the meat of the N2 stunned birds was not as tough as the meat of the CO2 stunned birds, when chilled at 0 °C. The pH fall of the CO2 stunned turkeys was similar to the birds stunned with the two-phase method. As a result, CO2 could be a good alternative for gas stunning. On the other hand, CO2 has been stated noxious for poultry to breath in high concentrations. In addition, there is a risk of cold induced toughening when using carbon dioxide if chilled rapidly.

A structural problem found in pork – so-called destructured meat - complicates the production of high quality meat products. Destructured meat resembles PSE meat, although it is relatively dry compared to the watery PSE meat. Muscle fiber bundles can be peeled off in strips from destructured meat. Structural problems can already be seen in raw meat as soft texture and light colour. In addition to light colour, the pH-value of destructured meat is lower and drip loss is higher than in normal meat. In a cooked meat product this problem is seen as dry spots which are light in colour and as broken slices. The objective of this study was to improve the quality of cooked meat products. It was examined whether the quality of cooked ham improved when destructured meat was removed from the raw material before preparation of the product. In addition, it was also examined whether the mincing rate of the meat with two different grinder plates (larger, 0-plate or smaller, 20-plate) influenced the appearance of the final product. The crucial method used for whole meat products was sensory analysis. The appearance of the final ham product made of normal meat was better than that made of destructured meat. The result was the same regardless of whether a 0-plate or a 20-plate was used. The structure of the product made of pork minced with 20-plate was, however, considered superior compared to the product made of pork minced with 0- plate. The use of destructured meat as raw material in fermented sausages was also investigated – whether destructured meat could be used without weakening the quality of the final product. The ripening of fermented sausages was followed by determining the aw-value, firmness and pH-value. The study showed that fermented sausage is an excellent product to be made from structurally flawed meat. It can be concluded that the visibility of structural problems in a final product can be decreased by selecting raw material combined with a grinder plate of small size.