Effect of THI on milk coagulation properties of Holstein-Friesian dairy cattle

ABSTRACT The objective of this study was to evaluate the effect of temperature-humidity index (THI) on the milk coagulation properties of Holstein-Friesian dairy cattle from northeast part of Italy. A total of 592 individual milk samples from six dairy herds were evaluated. The milk coagulation properties traits analysed were milk rennet coagulation time and curd firmness, as well as the fat, protein, and casein contents, pH, milk aptitude to coagulate (IAC), and the somatic cell count. The THI was determined during the periods of sample collection. The THI results showed that values of up to 75 did not significantly change the IAC values; however, when the THI values were above 75, the IAC decreased significantly. The control of THI can be used to guarantee appropriate milk coagulation properties

TEOR DE HIDROXIPROLINA EM PELES DE FRANGO SUBMETIDAS À TRATAMENTO TÉRMICO

Extraiu-se colágeno da pele de coxa e sobrecoxa de frangos de corte mediante processamento térmico, quantificando-o na pele crua, na pele cozida e no resíduo de cozimento sob a forma de hidroxiprolina. Pele resfriada, oriunda da coxa e sobrecoxa de frangos de corte, de lotes mistos, de aves abatidas com idade entre 47 e 49 dias e peso vivo entre 2500 e 2600 g foi utilizada para o cozimento sob temperatura constante de 97,1 ºC por 30, 60 e 120 minutos. Hidroxiprolina, proteína bruta e umidade foram determinadas quimicamente e os valores de colágeno obtidos por cálculo de conversão em relação a hidroxiprolina. A análise dos resultados evidenciou diferença entre os tratamentos. O cozimento exerceu efeito de solubilização da proteína estrutural da pele de frangos de corte, constatado pelos maiores teores de colágeno encontrados na pele cozida que na pele crua. O tempo ideal de cozimento para maior obtenção de proteína bruta no resíduo de cozimento foi de 60 minutos, devido a menor intensidade de desnaturação da proteína do resíduo. Os maiores teores de colágeno obtidos no resíduo de cozimento demonstram a sua característica hidrossolúvel, a viabilidade de sua extração e justifica esforços na recuperação e aplicação deste resíduo, minimizando o índice de dejetos no efluente. HIDROXIPROLIN CONTENT IN POULTRY SKIN SUBMITTED TO THERMAL TREATMENT Abstract The collagen of poultry skin was extracted by thermal processing, and quantified in raw, cooked and in the residues of cooking in the hidroxiprolin form. Frozen skin from thigh and over-thigh poultry, of mixed lots, of poultry 47 and 49 days old and weighting between 2500 and 2600 g was utilized for cooking at constant temperature of 97.1 ºC for 30, 60 and 120 min. Hydroxiprolin, raw protein and humidity levels were determined chemically and collagen concentrations were calculated in function of hydroxiprolin levels. Statistical analysis of data showed differences between treatments. The cooking exerced effect of solubilization of structural protein of poultry skin. The ideal period of cooking for collagen extraction from the cooking residue was 60 min since the highest levels of raw protein were obtained at this time. The high levels of collagen in the residue demonstrate the solubility of the protein, the feasibility of its extraction and justifies any efforts in order to minimize its loss in waste water

milk coagulation properties and methods of detection

ABSTRACT: One of the most crucial steps in cheesemaking is the coagulation process, and knowledge of the parameters involved in the clotting process plays an important technological role in the dairy industry. Milk of different ruminant species vary in terms of their coagulation capacities because they are influenced by the milk composition and mainly by the milk protein genetic variants. The milk coagulation capacity can be measured by means of mechanical and/or optical devices, such as Lactodynamographic Analysis and Near-Infrared and Mid-Infrared Spectroscopy