Enrichment of Phospholipids by Enzymatic Hydrolysis and Membrane Filtration of Whey Protein Phospholipid Concentrate

Abstract

Whey protein phospholipid concentrate (WPPC) contains high amounts of phospholipids (PL) (16.4 ± 3.6 % PL as % lipid) but there is interest in further enriching the PL content for nutritional and functional applications. Enzymatic hydrolysis, in combination with microfiltration (MF), was explored for the pilot scale production of an enriched PL concentrate derived from WPPC. This was achieved by hydrolyzing proteins to facilitate passage of low molecular weight peptides through the MF membrane, while concentrating the fat and PL in the MF retentate. Bench top experiments were performed to select the proteolytic enzyme that resulted in the most extensive hydrolysis from among five different commercial proteases. SDS-PAGE analysis was performed to measure the extent of protein hydrolysis over a period of 4 h with samples drawn every 30 min. Alcalase enzyme was found to exhibit highest proteolytic activity at conditions of pH 8 and temperature of ⁓50°C. The intensity of major protein bands (milkfat globule membrane proteins, caseins, β-lactoglobulin) in WPPC decreased in SDS-PAGE profiles as hydrolysis progressed, along with the appearance of low molecular weight bands. Pilot scale MF production, coupled with diafiltration (DF), of the hydrolyzed sample yielded a final retentate with total PL content of 19.0 ± 3.0 % as % of final retentate in dry basis (db) with protein and fat contents at about 43.8 ± 0.4% (db) and 48.9 ± 1.2% (db), respectively. A two-fold increase in PL content (db) was therefore achieved through this process with an ~18% reduction in protein content. The MF permeate had minimal fat content indicating that there was no transmission of lipids or PL through the membrane during MF/DF process. Complete removal of proteins and peptides was not achieved by this process suggesting that either additional enzymes would be needed for further hydrolysis or possibly a more open MF membrane might be needed to remove more peptides and further increase the PL content.