Dietary supplements for phenylketonuria: removing Phe by activated carbon

Abstract

Purpose This paper aims at testing several conditions using activated carbon for removing phenylalanine (Phe) from protein hydrolysates, in order to prepare dietary supplements for phenylketonurics, based on skim milk. Design/methodology/approach Six hydrolysates from skim milk were prepared, using a protease from Aspergillus oryzae (AO), isolated or in association with papain (PA). Some parameters were tested for removing Phe, such as amount of activated carbon, temperature and stirring time. The second derivative spectrophotometry was used to evaluate the efficiency of Phe removal. Findings The best condition for removing Phe was achieved using an activated carbon: casein ratio of 118 (in g), a stirring time of 30 min, at a temperature of 25°C, which produced 96 to 99 per cent of Phe removal. Among the hydrolytic conditions employed, the association of AO and PA (1 hour, 1 per cent and 4 hours, 2 per cent, respectively) led to the lowest absolute value for the final Phe concentration (0.060 × 10 −4 mg/100 mg of protein). Original/value Since we know, there is no formula for PKU on the market based on skim milk hydrolysed proteins. Isolated casein, the main milk protein, is the choice in most cases. This is a factor that may be taken in consideration especially in developing countries, where milk proteins are imported and, consequently, are much more expensive than skim milk.