E. Wiklund

Electrical stimulation of red deer (Cervus elaphus) carcasses: Effects on rate of pH-decline, meat tenderness, colour stability and water-holding capacity

A total of 14 female red deer were included in a study on the effects of low voltage carcass electrical stimulation on meat tenderness, colour stability and water-holding capacity. Carcasses were randomly allocated to either electrical stimulation treatment (ES; 90-95 V unipolar pulses, 7.5 ms duration, 15 Hz for a duration of 55 s) or no electrical stimulation (non-ES) (n=7 in each group). Temperature and pH decline was recorded in M.m. triceps brachii, longissimus dorsi et lumborum (at the last rib; LD) and biceps femoris, at intervals from 0.5 to 20 h post-mortem. At 24 h post-mortem, LD from the left side were excised, vacuum packaged and refrigerated at -1.5°C. Glycogen concentrations, measured at 30 min post-mortem, and ultimate pH did not differ between groups. Compared to controls, ES increased the rate of muscle pH decline and produced lower shear forces at 1 day, 1 week and 3 weeks post-mortem, but these differences disappeared by 6 and 12 weeks post-mortem. Sarcomere lengths at 24 h post-mortem were unchanged by ES. After 1 week of refrigerated storage, ES significantly reduced display life (hours of Minolta a* value ⩾ 12), but this difference disappeared at 3, 6 and 12 weeks of ageing. ES did not affect drip at any ageing time point. The present results demonstrate that the benefits of ES on tenderness are not permanent, and the procedure is not necessary for a long-term, chilled product. This study showed no detrimental effects of using electrical stimulation on meat colour stability or drip loss.

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.

Fatty acids, antioxidants and oxidation stability of processed reindeer meat.

The effect of hot smoking and drying on reindeer meat (M. semimembranosus) was investigated with regard to vitamin content, fatty acids (FA), lipid oxidation and lipolysis. In smoked and dried meat, free fatty acids were found to increase (P<0.001), whereas polar lipids, cholesterol and triacylglycerols decreased. Only slight changes in FA composition of the smoked meat were found but the composition of the dried meat differed significantly from both smoked and fresh meat. Fresh and smoked meat were found to have low values (0.11 μg/g dry matter (DM); 0.21 μg/g DM) of thiobarbituric acid reacting substances but dried meat had high values (8.33 μg/g DM; P<0.001). Retinol was found only in the fresh meat and the tocopherol content decreased significantly (P<0.001) as a result of the processing. We conclude that the smoking process slightly changed FA composition, lipid class composition and vitamin content, whereas drying resulted in major changes in all the analysed parameters.

Ultimate pH values in reindeer meat with particular regard to animal sex and age, muscle and transport distance

The distribution of ultimate pH values and the frequency of high pH values in three reindeer muscles (AL longissimus, M. biceps femoris and M. triceps brachii) from bulls, cows and calves after short and long distance transport were studied. About 3400 reindeer carcasses from 12 different herds were included in this study. The post mortem processes in reindeer meat seemed to develop very rapidly, and therefore an early measurement (approx. 15h post mortem) of ultimate pH can be done without electrical stimulation of the carcasses. In a comparison between muscles, M. triceps brachii had a higher ultimate pH value than M. longissimus and M. biceps femoris. Meat from reindeer calves had higher ultimate pH values than meat from adult animals, indicating that calves are more susceptible to stress than adult animals and hence deplete their energy stores more readily. Road transport by lorry did not cause any increase in ultimate pH values in bulls and calves. Reindeer cows, however, did have an increase in ultimate pH, while more borderline cases of DFD (5.80<pH<6.20) were observed when cows were transported over more than 500 km. The physical condition and energy balance of the animals before transport were suggested to determine their ability to tolerate transport stress.

Muscle glycogen levels and blood metabolites in reindeer (Rangifer tarandus tarandus L.) after transport and lairage

A total of 66 reindeer cows and calves were included in a study on the effects of supplementary feeding, transport and lairage on muscle glycogen content, ultimate pH and blood metabolite values. Thirty reindeer (10 not transported, 20 transported 800 km) received no supplementary feed (groups A-C), another 30 animals (10 not transported, 20 transported 1000 km) were given a supplementary reindeer feed mixture 2 months prior to slaughter (groups D-F) and six animals, which had been part of a feeding experiment, were fed for 5 months and slaughtered at the research unit. Glycogen determinations and pH measurements were made in m. longissimus, m. biceps femoris and m. triceps brachii. Blood samples were collected at slaughter and muscle samples were taken 30 min after slaughter. Ultimate pH was measured 30 hr post mortem. The glycogen content in the muscles of groups A-C was very low (100-200 mmol/kg). In groups D-G, the glycogen content was equivalent to normal beef muscle values (300-500 mmol/kg). The values of the blood metabolites urea and creatinine, both of which could indicate protein catabolism caused by stress, were significantly (p < 0.05) higher in animals not having received supplemental feed (groups A-C). Alkaline phosphatase values were significantly (p < 0.05) higher in supplemental fed animals (groups D-G), indicating that their nutritional status was good. Total protein values were significantly (p < 0.05) higher in groups A, D, E and F compared to the other groups. Lorry transport did not significantly (p > 0.05) reduce the muscle glycogen content. Lairage (groups C and F) showed no negative effect on the parameters examined. These results suggest that the animals physical condition and nutritional status have a considerable effect on their ability to tolerate various stress factors, such as lorry transport and lairage.

Proteolysis and tenderisation in reindeer (Rangifer tarandus tarandus L.) bull longissimus thoracis muscle of varying ultimate pH

Proteolysis and tenderisation in reindeer (Rangifer tarandus tarandus L.) M. Longissimus Thoracis were studied. Mm. Longissimus ( the part cut out between vertebrae thoracales 6-7 and vertebrae lumbales 5-6) from 12 reindeer bulls (age 1 1 2 years) were, after ultimate pH and temperature measurements, excised and then sampled at various times post mortem for determination of sarcomere length, Warner-Bratzler shear force, calpain and calpastatin activities, cathepsins B + L activities, active site titration of cystatin-like inhibitors, myofibrillar protein degradation, collagen content and heat solubility. Upon measurement of ultimate pH, the carcasses were divided into two pH groups; normal pH (5.65 ≤ pH ≤ 5.79) and high pH (pH ≥ 5.80). Temperature and pH fall were relatively rapid in all reindeer carcasses. Sarcomere lengths tended to be shorter in the carcasses of the high pH group. In the three carcasses with the highest ultimate pH values (6.11, 6.34 and 6.38), sarcomere lengths were around or below 40% of resting length (1.37μm, 1.25μm and 1.25μm, respectively) which is likely associated with the occurrence of heat shortening. Total collagen content was higher and heat solubility lower in the high pH group, which could have masked differences in tenderness. However, all reindeer longissimus muscle samples were found to be extremely tender regardless of ultimate pH. By 3 days post mortem Warner-Bratzler shear force values were varying between 2.1-4.9 kg cm(2). There was a significantly higher activity of μ-calpain in the high pH group at 1 day post mortem. No differences in shear force, myofibrillar protein degradation as observed by SDS-PAGE, m-calpain and calpastatin activities, calhepsins B+ L activities or the levels of cystatin-like inhibitors were found between the two pH groups.

Proteolytic enzyme and inhibitor levels in reindeer (Rangifer tarandus tarandus L.) vs. bovine longissimus muscle, as they relate to ageing rate and response

Eight reindeer bulls (age 1.5 years) and six Friesian bulls (age 1.5 years) were included in the study for comparison of tenderness. The reindeer were slaughtered at a commercial reindeer slaughter plant in northern Sweden and the Friesian bulls at a commercial slaughter plant in The Netherlands. Samples for determination of calpain/calpastatin activity were taken from the M. longtssimus (LO) within 1 h post mortem (p.m.), and at various times p.m. pH and temperature were registered in LO; ultimate pH values were measured at 24 h p.m. for beef and at 35 h p.m. for reindeer. At day 1 p.m., samples of LO from both carcass sides were excised, divided in two parts, vacuum packaged and stored at 0-2 °C. One part of each muscle was randomly sampled at 1, 3, 7 and 14 days p.m. for determination of shear force, proteolytic enzyme activity, myofibrillar protein degradation, collagen content and heat solubility. pH and temperature fall was faster in reindeer than in beef. Collagen content in reindeer muscle was found to be low but collagen was 4 times less soluble as compared with beef. Reindeer LO was found to be extremely tender, at 3 days p.m. shear force values were only 2-3 kg/cm2 (8-12 kg/cm2 for beef LO). In reindeer meat, the jJ.-calpain levels dropped to about 55% within 3 days. Troponin T and 30 kDa values were not related to changes in tenderness in reindeer meat. Cathepsin activities in reindeer were up to ten times higher than in beef. As in beef, cathepsin B+L levels in reindeer increased during storage, which is probably associated with a decrease in cystatin-like inhibitor levels.

Pre-slaughter handling of reindeer-effects on meat quality.

The centralization of the slaughter industry has created one of the biggest problems for beef quality, namely dark-cutting or DFD. After studying the various handling routines and their effects on meat quality, it was found possible, by applying simple and clearcut rules, to minimize the DFD frequency in beef. We then started to scrutinize the slaughter procedure for reindeer, as we realized that new directives in Sweden would lead to centralization of the slaughter industry. Before the new directives were introduced we obtained sufficient funding to set up a four-year research project dealing with old and new slaughter handling procedures for reindeer and their effects on meat quality. The overall objective was to devise simple and effective rules for the handling of slaughter reindeer in order to avoid meat quality deterioration. Various preslaughter handling routines for reindeer, such as gathering and herding, selection, feeding, road transport and lairage, imply stressful events which can affect glycogen stores in muscle and hence meat quality. During a 3 day helicopter drive (20 km/day), we found no negative effects on glycogen stores or ultimate pH values. Lorry transport of reindeer over various distances (0 up to 1000 km) did not cause any increase in ultimate pH values in bulls and calves, though cows did show a slight increase in pH. A 2-day pre-slaughter waiting period at a slaughterhouse, where the reindeer were fed hay and water, caused no deleterious effects on muscle glycogen content or pH. Sorting out reindeer by use of the traditional lasso technique, however, seems to be the only handling procedure so far studied causing considerable physical and mental stress leading to muscle glycogen depletion and dark-cutting. The effects of various handling procedures are very much dependent on the physical condition of the animals. From our studies we can conclude that feeding has a major influence on physical condition, muscle glycogen content and hence meat quality.

Sensory meat quality, ultimate pH values, blood metabolites and carcass parametersin reindeer (Rangifer tarandus tarandus L.) fed various diets

This investigation was made to study and compare the effects of different diets on sensory meat quality and ultimate pH values in reindeer muscles and to relate stress-induced blood metabolites and carcass parameters to the meat quality traits measured. Altogether 23 female reindeer calves were included in the study. During an adaptation period, all reindeer were allowed free access to a mimicked natural diet containing 80% lichens (lichen diet). On January 28, 8 reindeer (group Cjan) were slaughtered. Five reindeer (group C.Mar) were allowed continuous free access to the lichen diet throughout the experiment. During 8 days, the other reindeer (groups PL and PS) were given the lichen diet, half of the amount offered to the control group, and were then starved for one day. Thereafter, these reindeer were fed 80% commercial reindeer feed (pellets) and either 20% lichens (group PL), or 20% silage (group PS) for 5 weeks. After this, all animals were slaughtered. The average carcass weight and dressing percentage in the group fed commercial reindeer feed and lichens (PL) were higher than in group CMar- Fat registrations were generally higher in groups PL and PS than in the groups Cj2n and CMar- Ultimate pH values in M. triceps brachii and M. longissimus were significantly lower in the group CMST than in PL. The levels of all blood metabolites (urea, ASAT and Cortisol) were generally higher in groups PL and PS than in groups Cja„ and CMEF- NO significant differences were found in any of sensory attributes of the meat (monitored according to ISO standards). The present study shows that muscle and fat depots in reindeer can be improved by feeding a diet based on reindeer pellets but suggests that a feeding period of 35 days might be too short to affect the sensory properties of reindeer meat.

Glycolytic potential and ultimate muscle pH values in red deer (Cervus elaphus) and fallow deer (Dama dama)

The ultimate pH value of meat (measured at approx. 24 hours post slaughter) gives information about the technological quality, i.e. shelf life, colour, water-holding properties and tenderness and is a direct consequence of muscle glycogen (energy) levels at slaughter. It may therefore also indicate whether or not the animal has been exposed to stressful energy depleting events prior to slaughter. In the present study, 141 animals (130 red deer (Cervus elaphus) and 11 fallow deer (Dama dama) were included to investigate the relationship between ultimate pH and residual glycogen concentration in red deer and fallow deer M. longissimus. In addition, the muscle glycogen content and ultimate pH values in three red deer muscles (Mm. triceps brachii, longissimus and biceps femoris) were studied. M. triceps brachii had higher ultimate pH and lower glycogen content compared with the other two studied muscles. The frequency of intermediate DFD (5.8≤ pH<6.2) was 5.4% in red deer M. longissimus, compared with 9.1% in fallow deer, while the frequency of DFD (pH≥ 6.2) was much lower in red deer (3.8%) than in fallow deer (54.5%). A curvilinear relationship between ultimate pH and total glucose concentration (glycogen and glucose) 30 min post slaughter in red deer and fallow deer M. longissimus was found. The relationship between muscle pH and lactic acid concentration however, was indicated to be linear. A significant variation in total glucose concentration at ultimate pH below 5.80 was observed, including values in the range from 18 to 123 mmol/kg wet tissue. It was concluded that further studies are needed to further explore the relationship between muscle glycogen content and technological and sensory quality attributes of meat from different deer species. Abstract in Swedish / Sammanfattning: Kottets pH-varde (matt ca 24 timmar efter slakt) har stor betydelse for den teknologiska kvaliteten som t. ex. hallbarhet, farg, vattenhallande formaga och morhet. Glykogenforradet (energinivan) i djurens muskulatur vid slakt ar helt avgorande for kottets slutliga pH-varde. Darfor kan pH-vardet ocksa indikera om hanteringen av slaktdjur varit skonsam eller om stora mangder muskelenergi har forbrukats vid stress. I var undersokning ingick 141 hjortar (130 kronhjortar (Cervus elaphus) och 11 dovhjortar (Dama dama) for att studera sambandet mellan kottets pH-varde och glykogeninnehallet i M. longissimus. Glykogeninnehall och pH-varden i 3 muskler fran kronhjort (Mm. triceps brachii, longissimus och biceps femoris) undersoktes ocksa. M. triceps brachii hade hogre pH-varde och lagre glykogeninnehall jamfort med de tva andra musklerna. Det var inte sa stor skillnad i frekvensen av intermediar DFD (pH-varden mellan 5,8 og 6,2) mellan de tva hjortarterna (5,4% for kronhjort och 9,1% for dovhjort), daremot var frekvensen av DFD (pH-varden over 6,2) mycket lag hos kronhjort (3,8%) jamfort med dovhjort (54,5%). Det fanns ett kurvlinjart samband mellan slutligt pH-varde i kottet och total glukoskoncentration (glykogen + glukos) matt i M. longissimus 30 min efter slakt for bade kron- och dovhjort. Ett linjart samband mellan pH-varde och koncentration av mjolksyra i M. longissimus kunde ocksa visas. Vi fann en mycket stor varitation i glukoskoncentration (18−123 mmol/kg vatvikt) nar kottets pH-vardet var 5,8 eller lagre. Det behovs fler undersokningar for att vidare klargora sambanden mellan glykogeninnehall i muskulaturen och teknologisk och sensorisk kvalitet i olika typer av hjortkott.