What is non-protein nitrogen?
This is a normal part of milk. The non-protein nitrogen (NPN) fraction iscomposed of urea and other low molecular weight nitrogen containingcompounds such as creatine and creatinine. About 50% of the NPN in milk isurea, and variation in NPN is attributed primarily to variation in ureacontent. Non-protein nitrogen has little nutritional value and does notcontribute to cheese yield. Therefore, it does not have the same economicvalue as "true" milk protein to either the processor or the consumer.
牛奶中的NPN主要是尿素和其它低分子的含氮化合物，如肌酸和肌酸酐。尿素約占奶中NPN的50%。奶中NPN約為0.12-0.25%
How much of the crude protein is NPN?
The amount of NPN in milk varies naturally, just like any other milkcomponent. On average, NPN represents approximately 6% of the totalnitrogen. On absolute basis, NPN accounts for about 0.19% of the"protein" in a crude protein value, but may range at the extremesbetween 0.12-0.25%.
Are there differences in NPN between farms? Betweenbreeds?
Milk NPN levels are influenced primarily by farm management and feedingpractices. Feeding practices account for much of the variation in NPNobserved between farms, regions and seasons. Any differences in NPNbetween breeds will be small compared to the effects of diet.作者: 牛郎阿飛 時(shí)間: 2010-5-30 18:49
可以看看這個(gè)作者: majiangtao 時(shí)間: 2010-5-31 09:59
謝謝了，老外的東西不過(guò)如此啊