Krystyna Palka

Changes in texture, cooking losses, and myofibrillar structure of bovine M. semitendinosus during heating.

Vacuum-packed slices of bovine semitendinosus (ST) muscle were retorted to internal temperatures of 50, 60, 70, 80, 90, 100, and 121°C. Changes in texture of the meat were evaluated by measurements of Texture Profile Analysis (TPA) parameters. Changes in microstructure were evaluated using a Scanning Electron Microscope (SEM) and measuring fibre diameter and sarcomere length. Cooking losses were also estimated. During heating the TPA parameters changed independently of each other. They reached a maxima at different endpoint temperatures of the meat and then decreased. A decrease in fibre diameter was observed in samples heated to 60 and 121°C. Sarcomere length decreased continuously in the range 50-121°C. Cooking losses increased with increased heating temperature. Relationships between changes in sarcomere length and cooking losses and between springiness and fibre diameter were found.

The influence of post-mortem ageing and roasting on the microstructure, texture and collagen solubility of bovine semitendinosus muscle.

Bovine semitendinosus (ST) muscles aged for 5 and 12 days at 4xa0°C were roasted at 170xa0°C to internal temperatures of 50, 60, 70, 80 and 90xa0°C. Microstructural changes in meat were evaluated using a scanning electron microscope (SEM). Texture profile analysis (TPA) and measurements of the shear force values of samples were conducted using a texture analyser. The cooking losses and quantity of total and soluble collagen were also estimated. The structure of intramuscular connective tissue and myofibrillar structure of meat after 5 days of ageing was very regular. In 12-day-aged samples fibrous and myofibrillar structures were less distinct, damages of endomysium tubes appeared and fibres of perimysium were swelled. Ageing of ST muscle for 12 days caused a two-fold increase in the quantity of soluble collagen and a two-fold decrease in the value of TPA parameters-hardness and chewiness, as compared to 5-day-aged samples. The decrease in fibre diameter and sarcomere length during roasting started at 60xa0°C in 5-day-aged meat and at 50xa0°C in 12-day-aged samples. The shear force values measured after roasting were lower for 12-day-aged meat than for 5-day-aged samples. The quantity of soluble collagen in roasted meat increased at an internal temperature of 80xa0°C. At a higher temperature of meat this variable depended on the degree of meat ageing. The cooking losses during roasting of meat were about 3% lower for 12-day-aged than for 5-day-aged samples. In the examined range of internal temperature of meat the cooking losses and the sarcomere length were negatively correlated.

Changes in intramuscular connective tissue and collagen solubility of bovine m. semitendinosus during retorting

Vacuum-packed slices of bovine m.semitendinosus (ST) muscle were retorted to internal temperatures of 50, 60, 70, 80, 90, 100 and 121°C. Changes in the microstructure of the endomysium and perimysium were evaluated using a scanning electron microscope (SEM). Changes in solubility of intramuscular collagen were also estimated. In samples heated to 50°C changes in intramuscular connective tissue were not seen. At 60°C granulation of the perimysium and sarcolemma was seen, and on longitudinal sections, as well as granulation, fibrous structures of perimysium were observed. At 70°C increased granulation was observed. In the range 80-121°C progressive compression of the meat structure was seen in the transverse sections. The percentage of soluble collagen in the meat changed little up to an internal temperature of 60°C, but at 70°C it almost doubled, and in the range 80-121°C drastically decreased.

Changes of myofibrillar and centrifugal drip proteins and shear force of psoas major and minor and semitendinosus muscles from calves, heifers and cows during post-mortem ageing

Changes in myofibrillar protein content and centrifugal drip proteins of psoas major and minor (PM) and semitendinosus (ST) muscles of calves, heifers and cows taken from carcasses on the 1st, 6th and 12th day of post-mortem cold storage were estimated. Washed myofibrils and centrifugal drip from muscles were analysed using SDS-PAGE 10 and 12% polyacrylamide gels. No significant changes were observed in content of contractile proteins, α-actinin and regulatory proteins (except for TN-T). There were no significant differences between muscles from investigated groups and between muscles aged in chilled conditions. The levels of titin T1 during ageing varied slightly. The 30 kDa-fraction appearance was fastest in calf, slower in heifer and slowest in cow muscles. More pronounced differences in the level of protein degradation with regards to muscle type, age of animals and time of storage were found in the centrifugal drip of meat. In the drip, the level of high molecular weight proteins was higher in muscles from young animals and in the muscles stored longer. The opposite was observed in case of 26-28 kDa proteins. Their amount in muscle drip decreased with increased storage time. The rate of proteolysis and release of cytoskeletal proteins during cold storage of muscles were related to change in shear values of roasted meat. The highest rate of protein degradation was observed in PM calf muscle and the lowest rate in ST cow muscle. The fastest tenderization process was registered in calves muscles and the slowest tenderization in cows.

Changes in structure of psoas major and minor and semitendinosus muscles of calves, heifers and cows during post-mortem ageing

Changes occurring during post-mortem ageing in structure of psoas major and minor (PM) and semitendinosus (ST) muscles of calves, heifers and cows were observed. Samples from muscles taken 3 h after slaughter and after 6 and 12 days of storage at the temperature of 4xa0°C were analysed using light and transmission electron microscopy. Three hours after slaughter muscle fibres were close to each other and sarcomeres showed normal structure of A- and I-bands, M-lines and Z-disks. The space between myofibrils and sarcolemma and also between single myofibrils in muscle fibres increased during storage. Structure of sarcomeres underwent continuous degradation, length of sarcomeres increased due to enlargement of I-bands accompanied by Z-disk degradation. During ageing structural changes in myofibrils took place faster, were more intensive in muscles of younger animals and were more extensive and faster in PM than in ST muscles.

The effect of post-mortem ageing and heating on water retention in bovine muscles

The muscles semitendinosus (ST) and psoas major (PM) were removed from chilled young bull carcasses 24h after slaughter and stored at 4°C. At the 1st, 6th and 12th day of post-mortem ageing the chemical composition (moisture, fat, protein, collagen) and contents of free, immobilized and unfreezable water in the muscles were estimated. The muscle steaks were boiled at 100°C, roasted at 170°C or fried at 160°C to an internal temperature of 75°C, and the amounts of total, free, immobilized, and unfreezable water in heated muscles were evaluated. The unfreezable water was estimated by DSC. In the raw muscles immobilized water constituted 74-75%, free water 16.6-17.6% and unfreezable water 7-8% of the total water. Independent of time of ageing, PM muscle contained significantly more free water than ST muscle. During post-mortem ageing, changes in free, immobilized and unfreezable water in muscles were not significant. The level of free water was highest in boiled and least in fried meat, however the amount of immobilized water was highest in fried and lowest in boiled meat. The amount of unfreezable water in muscles heated after 12 days of post-mortem ageing decreased.

Physico‐chemical, biochemical and microbiological changes of Kumpia wieprzowa during ripening

Purpose – The purpose of this paper is to estimate physico‐chemical, biochemical and microbiological changes during the three‐month ripening of the Polish traditional raw smoked fermented meat product Kumpia wieprzowa, produced from pork shoulder without fore‐shank.Design/methodology/approach – After one, two and three months, the pH, aw, chemical composition, the content of nitrogen – total and soluble – as well as the profile of aromatic compounds and microflora, were evaluated.Findings – During ripening, the water content decreased from 62.7 percent to 47.5 percent, while the protein and fat amount increased from 20.8 percent to 25.0 percent and from 9.7 percent to 16.3 percent, respectively; the aw decreased from 0.95 to 0.88 and pH from 5.80 to 5.35. The proteolytic changes, measured by free amine groups and Nsoluble content, as well as the quantity of free fatty acids and percentage of most of the volatile compounds increased, particularly during the first two months of ripening. The total number of...

20. The Effect of Muscle Type and Time of Storage on Myofibrillar Protein Proportion in Beef

Abstract Tenderness is usually associated with the proteolysis occurring in muscles. However, most of the studies concentrate on one muscle only. The aim of this study was to describe the changes in myofibrillar protein percentage proportions during the ageing of 8 bovine muscles. Investigations were conducted on the muscles from different parts of the carcass, from the forequarter: m. pectoralis profundus, m. infraspinatus, m. triceps brachii, m. serratus ventralis, and from the hindquarter: m. biceps femoris, m. semimembranosus, m. semitendinosus and m. longissimus dorsi (thoracis et lumborum). The effect of muscle type was significant for all parameters except for percentage proportions of titin (3000÷3700 kDa), MHC (205 kDa) and protein fractions between <205÷42> kDa. Differences between the muscles varied depending on the analysed proteins and the time of storage. A significant effect of ageing time for titin, nebulin (approx. 800 kDa), proteins of molecular weight of 38 kDa, proteins smaller than 42 kDa and in the range of 3000÷205 kDa, 205÷42 kDa and 38÷20 kDa was observed. The decrease of percentage proportions of titin, nebulin and proteins in the range of 3000÷205 kDa and an increase of protein bands in the range of 38÷20 kDa and proteins below 42 kDa was also observed. During the storage period of beef from the 2nd to the 14th day, the progress of myofibrillar proteolysis was different in each muscle. The changes of tenderness were not related to shear force values. It is probable that the changes in other constituents of meat might influence the tenderness more than those in myofibrillar proteins.

Variable effect of steam injection level on beef muscles: semitendinosus and biceps femoris cooked in convection-steam oven.

BACKGROUNDnCombi ovens are used very often in restaurants to heat up food. According to the producers the equipment allows to cook meat portions which are more tender and flavoursome comparing to conventional cooking techniques.nnnMETHODSnBeef steaks from muscles semitendinosus and biceps femoris were cooked in convection-steam oven at three humidity levels: 10, 60 and 100%. Chemical composition, including total and insoluble collagen content and cook losses were analysed along with the texture and colour parameters.nnnRESULTSnM. biceps femoris was the hardest and the most chewy at 100% steam saturation level and hardness measured for m. semitendinosus was the lowest at 10% of vapour injection. Changing the steam conditions in the oven chamber did not affect the detectable colour differences of m. biceps femoris, but it was significant for m. semitendinosus. Applying 100% steam saturation caused higher cook losses and the increase of insoluble collagen fractions in both analysed muscles.nnnCONCLUSIONSnThe results are beneficial for caterers using steam-convection ovens in terms of providing evidence that the heating conditions should be applied individually depending on the muscle used. The tenderness of m. semitendinosus muscle cooked at 10% steam saturation level was comparable to the tenderness obtained for the same muscle aged for 10 days and cooked with 100% steam saturation. Steaks from m. biceps femoris muscle should be cooked with maximum 60% saturation level to obtain higher tenderness.