- While breast milk is considered the best nourishment for newborns, they have a lowered ability to digest the fat rich liquid due to decreased lipase secretion for the first few months after birth. To offset this, breast milk itself contains Bile Salt-Stimulated Lipase (BSSL) which significantly heightens fat digestion ability. Pre-term infants (<37 weeks gestation age) are often fed donor breast milk, which is treated through Holder pasteurization by nonprofit milk banks to ensure microbiological safety. Due to the fact that Holder inactivates up to 95% of BSSL, two alternative techniques also proven to eliminate harmful breast milk pathogens were assessed for their ability to retain BSSL: high pressure processing (HPP) and gamma cell irradiation (IR). After treatment of breast milk samples with either Holder (62.5°C, 30 min), HPP (550 MPa, 5 mins), or IR (2.5 Mrads), BSSL activity was determined using a spectrometric assay and compared to raw untreated milk. IR treatment was shown to retain 32% of BSSL activity while HPP was shown to retain 84%, suggesting HPP could be an effective alternative to Holder pasteurization.