The aim of this study was to evaluate the effect of growth intensity of 43 bulls with different growth intensity (< 900 and ≥ 900 g/day) on the microstructure of musculus longissimus lumborum. Commercial crosses of Polish Lowland black-and-white cows with Charolais and Limousin bulls were used in this study; within the particular genetic groups the hybrids had similar slaughter weight (447.6 and 517.2 kg) and age (526 and 606 days), respectively. The share of fibres with active tetrazole dehydragenase in the more intensively growing animals was smaller. For fibres with myofibrillar ATPase activity, the intensively growing animals produced higher standard deviation values than the other groups. Further analysis of the muscular tissue in this group revealed that out of the 24 muscles, 9 had giant fibres. In comparison with the less intensively growing animals, the muscles of the bulls that gained more than 900 g/day in weight were found to contain significantly less glycogen (P ≤ 0.01) and, consequently, the meat was less acidic. The difference of the pH ranged from 0.19 in the case of pH 24 (P ≤ 0.01) to 0.06 for pH 48 (P ≤ 0.01). It should be noted that the intensively growing animals were found to have a relatively high pH variability (SD = 0.69 and 0.49, respectively). The pH 24 and pH 48 values, as well as pH variability show that the meat of this group was dark, firm and dry. Daily body gain, beef, histological traits, meat faults

Materiał badawczy stanowiły 124 mieszańce uzyskane w wyniku krzyżowania krów rasy czarnobiałej, u których udział genów rasy holsztyńsko-fryzyjskiej nie przekraczał 25 %, z buhajami: rasy czarnobiałej (25 buhajów) i ras mięsnych (99 osobników).Celem badań było porównanie cech histologicznych i właściwości fizykochemicznych wołowiny w zależności od występowania włókien olbrzymich w mięśniach buhajów czarno-białych i mieszańców towarowych.Wykazano, że włókna olbrzymie występowały częściej w mięśniach mieszańców z rasami mięsnymi. Wśród mieszańców towarowych wykazano je w 42 % populacji, a w grupie buhajów rasy czarno-białej w 20 % populacji. Obecność włókien olbrzymich związana była z większą aktywnością ATP-azy miofibrylarnej, a transformacja włókien FTO w tych mięśniach skutkowała zwiększeniem udziału włókien FTG (54, 4 -58,5 %) i wzrostem: względnej powierzchni przekroju włókien o metabolizmie beztlenowym oraz indeksu beztlenowego AnF% (4,18 -5,47). Stwierdzono, że mięśnie zawierające włókna olbrzymie wykazywały częściej cechy odstępstw jakościowych: pH 48 większe niż 5,8, mniejszą jasność barwy oraz więk-szą zdolność utrzymywania wody.

Most scientific studies are dedicated to the possibility of preparing beef for consumption under industrial conditions. Few publications are devoted to the issue of collagen thermohydrolysis in conditions available to the consumer. This study has analyzed the effect of small values of water vapor pressure on major culinary indices and chemical components of the longissimus lumborum muscle obtained from bulls with different growth rates. The experiment involved 48 animals. On the basis of the gain during the fattening time, the animals were divided into a low growth intensity group, with a daily body weight gain of ≤900 g, and a high growth intensity group with a daily gain of >900 g/day. A part of the samples of the longissimus lumborum muscle (control) was thermally treated in a water bath at 75°C. Another part was heat treated in a pressure-pot at 150°C, at a pressure of 0.1 MPa. The next part of samples was subjected to the same temperature, but the pressure was 0.2 MPa. The obtained results indicate that the values of the studied indices were largely affected by thermal processing parameters rather than the animals' growth rate. The highest contents of total protein and water-soluble collagen were obtained in the case of a temperature of 150°C and the highest pressure (0.2 MPa). Water vapor with increased temperature and pressure also created favorable conditions for obtaining better meat tenderness and more favorable values of the water holding capacity. The latter characteristic appeared to be strongly connected with an increasing amount of water-soluble collagen, which was confirmed by relatively high values of the correlation coefficient between these characteristics. A strong positive correlation was also shown between thermal drip and the total collagen content in meat.