Research with high fat samples has given us the following understandings:
Some samples with fats that have low melting point triacylglycerides or emulsifiers may encounter fat migration during hydrolysis.
To improve fat retention, increase the level of diatomaceous earth (DE) to sample ratio. A ratio of up to 7:1 can be used by reducing the amount of sample and increasing the amount of DE. No more than 1.5g of DE and sample should be placed in each bag.
The increased volume of DE inside the bags will limit the number of samples processed in the Hydrolysis chamber to ten.
Reducing the hydrolysis temperature and time may also improve fat retention.
If, after increasing the DE-to-sample ratio, fat continues to migrate from the bag then a crude fat extraction prior to the hydrolysis may be necessary. By running a crude fat extraction first, the readily available fats are removed before the hydrolysis, but are accounted for. The challenge with this technique is the additional time the process takes.
Fat migration can be detected by placing a blank bag next to suspect samples. Place blank bags next to high fat samples in the holder, and perform the hydrolysis. If a blank bag looses more than 0.0025g of weight during the extraction, this is an indication of fat loss from the neighboring high fat sample during the hydrolysis. Blank bags should always contain at least 0.5g of DE.