Development of a new type of flour with reduced phenylalanine content for phenylketonuria patients

Phenylalanine-restricted diet is the basis of the treatment for phenylketonuria (PKU) disease which is a disease of hereditary disorder of protein metabolism. However, a lifelong diet therapy is difficult for patients to apply and symptoms of disease appear when dietary therapy is not applied. Therefore production of foods with reduced and/or removed phenylalanine content is known to have an important role in the diet of the patients. In literature review, the studies like oral application of phenylalanine ammonium lyase enzyme to patients with PKU were found. However, no research has been seen on the staple and whole food production by phenylalanine ammonium lyase enzyme application with reduced phenylalanine content for patients with PKU. In this study, the release of the hydrolysable phenylalanine amino acid by in vitro hydrolysis of proteins in wheat flour, one of the main staple foods, with digestive enzymes and application of corn seedlings extract containing phenylalanine ammonium lyase enzyme in order to reduce the content of free phenylalanine and then drying of obtained product to prepare a type of flour with reduced phenylalanine content for PKU patients were aimed. As a first step of the study, protein content of wheat flour was subjected to in vitro hydrolysis with digestive. Corn seedlings were cultivated and harvested on 7th day of germination, on which the maximum phenylalanine ammonium lyase enzyme activity (6.09 µmol/h.g) was determined, in order to reduce free phenylalanine amino acid content which was increased about 15 fold by in vitro hydrolysis. It was determined that the extract obtained from corn seedlings had a significant reducing effect (49.78%) on the content of free phenylalanine. After in vitro digestion and phenylalanine ammonium lyase enzyme application, the obtained aqueous food material was dried and subjected to size reduction. Thus a flour production with the reduced phenylalanine content was obtained for PKU patients. The water holding capacity was determined as 1.13 g water/g dried flour, water solubility value as 7.39 g/g, water absorption index as 1.02 g/100 g, moisture content as 11.35%, water activity as 0.41, pH as 5.99, titration acidity as 0.248%, total protein as 11.54%, enzyme resistant starch content as 0.58%, L*, a*, b* as 71.62, -4.37, 20.92, bulk density as 1.03 g/mL for the obtained flour and, these values were compared with values of wheat flour. The biscuit production was also carried out using the flour with reduced phenylalanine content and the obtained product was well accepted by sensory panelists. KEYWORDS: In vitro digestion, Phenylalanine, Phenylketonuria, Phenylalanine ammonia lyase.