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Departments of Dairy Science and Agricultural Engineering, University of Wisconsin, Madison 53706
ABSTRACT
Protein in freshly extracted alfalfa juice was coagulated by heat at 60 or 80°C for 30, 60, 120, 240, or 480 s, then freeze dried. Nitrogen content was higher while solubility, nonprotein nitrogen, and ash content were less at a coagulation temperature of 80°C compared to 60°C. Acid detergent fiber, acid detergent insoluble nitrogen, and pepsin insoluble nitrogen remained unchanged. Both essential and nonessential amino acid concentrations were higher for alfalfa protein concentrate coagulated at 80°C.
Degradability of alfalfa protein concentrate was estimated by in situ procedures with polyester bags suspended in the rumen of lactating cows for up to 48 h. Residual dry matter (%) after .5, 24, or 48-h incubation in the rumen were 73, 36, and 12 for alfalfa protein coagulated at 60°C and 85, 52, and 18 for alfalfa protein coagulated at 80°C. Residual nitrogen percents were 89, 44, 15, and 95, 56, 20 according to the same sequence. Rate of nitrogen disappearance (% h–1) was 3.7 and 3.2 for alfalfa protein coagulated at 60 and 80°C. Duration of heat at coagulation tended to affect nitrogen disappearance when incubation time in the rumen was prolonged. The correlation coefficient between residual nitrogen and dry matter of alfalfa protein concentrate was .98.
1 Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison; Hatch Projects 6003 and 5026; and National Science Foundation Grant Number AIR 75-13078. Contribution of Plant Juice Protein Team.
2 Department of Dairy Science.
3 Department of Agricultural Engineering.
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