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Fermentation capability of bulk milk under usual conditions
BOUŠKOVÁ, Lucie
The evaluation of changes during fermentation of heat-modified milk in connection with different fermentation temperatures was main goal of this thesis. Titrable acidity, active acidity and growth dynamics of bacteria strains - Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus were observed during fermentation process.
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Possibilites of improving the quality of beef by ageing
BENEŠ, Karel
Internal and external factors affect the quality of meat, however ageing affects final product. Main objective of this work was to determine the effects of ageing on selected physical factors (pH, colour, water holding capacity and texture shear force) which affect meat quality from consumer and further meat processing perspective. Measuring of those factors was performed in periodical time sequences (one day post-mortem and 14 days of ageing) and factors of raw and heat-modified meat were measured. There were two hundred and fifty-eight samples from Czech pied cattle used in research. Musculus longissimus lumborum et thoracis (sirloin) was analyzed. Statistically high shear force difference (P=0.001) was identified at heat-modified and aged samples (decrease from 22.574 kg to 14.885 kg). Decrease of shear force during ageing of raw meat samples was observed at normal pH (pH < 5.8) beef ? from 6.403 kg to 5.982 kg. Correlations between pH and water holding capacity was found at samples which undergone ageing (r = 0.879 ***) and also at one day post-mortem samples (r = 0.872 ***). Middle correlation was observed between colour and pH at all colour parameters ? L* (r = -0.479 ***), a* (r = -0.478 ***) and b* (r = -0.581 ***). Water holding capacity and pH have influence on shear force of raw beef and also heat-modified beef; this was confirmed by correlation analysis. Lightness (L*) and water holding capacity affect heat-modified samples texture which was confirmed with multi-regression linear analysis (R2 = 0.565). As shown above the influence of meat ageing on quality parameters is high and properly aged meat from young bulls has better texture values. If the aged beef will be sold regularly it could be expected that consumer demand will increase especially due to remove the inconsistency of the quality of beef.
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PSE-Defect - Quality Impact During 48 Hours After Slaughtering
PUDIVÍTR, Aleš
Comparison of pig?s stunning (by electricity or CO2) at slaughterhouse and monitoring the occurrence of quality variance PSE during 48 hours post mortem was main goal of this work. Basic indicators such as pH1, drip loss of water and meat colour (lightness) were determined to assess PSE. In addition to these indicators have been also evaluated values of pH24 and pH48. The result of those indicators is that during stunning by CO2 gas value of pH1 was higher by 0,3 degree (P < 0,001), value of pH24 was higher by 0,243 (P < 0,001) and average drip loss of water was lower by 2,16 % (P < 0,001). Changes in other evaluated indicators were statistically non-significant. Occurrence of quality variance which tends to PSE (PSEi) and PSE was evaluated at slaughterhouse which is using electricity for stunning as higher by 7,843 % at PSEi and 1,961 % at PSE based on value of pH1. As higher was evaluated also drip loss of water by 23,810 % at PSEi respectively 4,762% at PSE. Difference between occurring of PSEi and PSE based on meat colour was not observed. The highest correlation dependence was found between pH1 and drip loss of water (r = 0,586, R2 = 34,315 %).
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