I see this complaint from moms every so often, too. It seems that all of us only have the info gleaned from Lawrence's book, regarding lipase activity and lipid breakdown. I'd like to appeal to folks with the smarts and necessary education to help me think about this issue. As you know, I did some time as a dairy(wo)man. If you have off-flavors in cows or goats there are in-depth analysis in dairy texts of why this is. For instance, in dairy cows, lack of vitamins A & E is said to increase incidence of mastitis (or sub-clinical mastitis) and is cause of "cardboardy" or sour tasting milk. (Thus, these vitamins are given to cows as a supplement when such off flavors occur). Acid flavors are said to result from bacterial growth that occurs when raw milk is not cooled quickly. (The active bacteria for this is usually Streptococcus lactis.) There are many definitions of off-flavors in dairy milk. The flavor described by lipid breakdown is noted in dairy texts as "a rancid flavor closely associated with bitter flavor; but, unlike the common bitter flavor, it has an odor resembling spoiled nutmeats." There are flavors described as malty, oxidized, metallic, tallowy, cowy, barny, unclean. Anyone who wants a crash course can read the materials for judging dairy products at www.aac.msstate.edu/pubs/pub1423.htm. The information on milk is informative. How much of what goes on in cow's milk might be happening with human milk? Especially with expressed human milk, which has only in recent history become popular in such quantities. With the development of pump technology, and the sheer numbers of women who avail themselves of this technology now, I think we need to look at this issue more critically. I think that babies are much less critical of flavors than we humans are when sipping bovine milk; my sense is that bf babies enjoy the wide range of flavors in their mother's milk. However, adult humans might be judging human milk by dairy standards. If the baby refuses the EBM the adults will be quick to blame the flavor; or wonder if the flavor/aroma means the milk is rancid. And when/how does it get rancid when handling seems within normal guidelines? Our discussions have been narrow in scope compared to those in dairy circles. Is there anyone on Lactnet who can address this issue, to help us identify where we can apply dairy standards to human EBM? Margery Wilson, IBCLC