Preparation and characterization of a low-phenylalanine whey hydrolysate using two-step enzymatic hydrolysis and macroporous resin adsorption

Abstract

A low-phenylalanine (Phe) diet is indispensable for phenylketonuria patients. The objectives of this study were to develop a two-step enzymatic method to effectively release Phe from whey protein, and then to prepare a low-Phe hydrolysate (LPH) by using adsorbent. Thermolysin (T) or Pancreatin (P) combined with Protease A2SD (A2) showed the degree of hydrolysis ranging from 42.62% to 45.43% and released more than 90% Phe from whey protein. The D101 macroporous resin column removed 98.38% Phe from TA2 hydrolysate (TA2H), compared to 64.50% of Phe removal by activated carbon. The protein content of LPH prepared by a magnified D101 resin column was 60.41 g/100 g hydrolysate and its Phe content was 1.38 ± 0.11 mg/g protein equivalent. After adsorption, the percentage of peptides below 600 Da significantly increased from 50.79% to 93.60%, while the intensity of bitterness and astringency measured by electronic-tongue also increased. However, aroma-active compounds such as Millard reaction and lipid oxidation products were reduced after absorption. The LPH prepared in our study could be a suitable protein substitute to make phenylketonuria food.