Hi ladies, I found some info for you about having extra lipase enzyme:

A few mothers find that their refrigerated or frozen milk begins to smell or taste soapy, sour, or even rancid soon after it's stored, even though all storage guidelines have been followed closely. These mothers have an excess of the enzyme lipase in their milk, which begins to break down the milk fat soon after the milk is expressed. The lipase enzyme stays active even when the milk is frozen.

Once the milk becomes sour or rancid smelling/tasting, there is no known way to salvage it. However, newly expressed milk can be stored by heating the milk to a scald to inactivate the lipase and stop the process of fat digestion. Scald the milk as soon after expression as possible.

To scald milk:

Heat milk to about 180 F (82 C), or until you see little bubbles around the edge of the pan (not to a full, rolling boil).
Quickly cool and store the milk.
Scalding the milk will destroy some of the antiinfective properties of the milk and may lower some nutrient levels, but this is not likely to be an issue unless all of the milk that baby is receiving has been heat-treated.

It also says that as long as your milk still smells normal after you thaw it, then it is generally safe for a baby to drink. The spoilt milk has a very distinctive smell similar to when cows milk spoils.