This unit operation is very critical to obtain desirable color and clarity. The
manufacturers have an arsenal of different operating conditions such as temperature
(hot or cold), pH and flow rates to achieve the desired product specifications.
The latest addition to the manufacturing of protein hydrolysates is to replace the
plate and frame filter press with that of the ultra filtration systems (Fig. 5).
The protein hydrolysate industry typically uses spiral wound ceramic or hollow
fiber membranes with a 10,000 Da molecular weight cut off. This is to remove
endotoxins as a lower amount of endotoxins is preferred for cell culture applications.
However, this could also potentially remove the peptides greater than 10,000 Da.
For this reason some manufacturers use 50,000 or greater molecular weight cut off
membranes but this may not guarantee the removal of endotoxins. Therefore, depending
on the end use, the manufacturer uses either 10,000 or higher molecular weight
cut off membranes. However, in a recent publication, the authors demonstrated that
endotoxin specification for cell culture may not be critical (Limke 2009).
After filtration the product is typically pasteurized or heat treated to kill/
reduce the microorganisms. The term pasteurization is misleading because in
most cases the temperatures used are way beyond standard legal pasteurization
temperatures. Some manufacturers tend to pasteurize the product multiple times.
Some manufacturers tend to pasteurize the product multiple times.