请教NPN的来源问题

majiangtao

那位高人了解牛奶中NPN的来源

sxdy168

找本NRC看看

茅十八

感觉你问的问题有点问题，我想你大概是想问奶牛饲料中的NPN

majiangtao

以后出去别说你是搞奶牛的

majiangtao 于 2010-5-25 08:11 补充以下内容

我说的就是牛奶中的NPN

ytcykw

你说的是牛奶尿素氮吧，来源于血液中的尿素

lmstdd

楼上的是答案！

majiangtao

不是的
你说的是BUN

southlaker

回复 1# majiangtao

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。尿素约占奶中NPN的50%。奶中NPN约为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.

牛郎阿飞

可以看看这个

majiangtao

谢谢了，老外的东西不过如此啊