Determination of physicochemical, microbiological and sensory properties of low protein yogurt substitution produced for phenylketonuria (PKU) patients

Phenylketonuria (PKU) is one of the most common congenital metabolic disorders. Treatment of phenylketonuria is a lifelong special diet program starting from the newborn period. The aim is to keep the phenylalanine level in the normal range by minimizing the amount of phenylalanine taken with food. The aim of this study is to produce an alternative product that can be consumed without any problem by phenylketonuria patients. Tranaz Dalia low protein milk substitutes, xanthan gum (1%), Nestle Nestergel yogurt builder gel (1.5%), starch (8%) andpectin (1.6%) were used. The milk produced from cow's milk is a control yoğurt. On days 1, 7, 14, 21 of the storage, pH, water holding capacity, rheological properties of the sedimentary phase, dry matter, Lactobacillus. delbrueckii ssp. bulgaricus and Streptococcus thermophilus number were analyzed. Crude protein, phenylalanine content, sensory analysis and color analysis were performed on the 1st day of storage. According to the results of the analysis, the pH values and water holding capacity of the low protein yogurt samples were decreased during storage. The amount of dry matter is significantly different (p <0.01) each other. The shear stress of xantham gamma, Nestle Nestergel, starch added samples were found close to each other. The shear stress of the pectin-added sample is higher than for them. L * value of the control sample and starch added sample, a * and b * values of pectin added sample were significantly higher than those of other samples (p <0.01). The amount of protein and phenylalanine was significantly higher in the pectin added sample than the other samples (p <0.01). In the microbiological analysis results Lb. delbrueckii ssp. bulgaricus, While bulgaricus numbers increased during storage, Streptococcus thermophilus numbers increased in pectin addition and decreased in other samples. In terms of general acceptability in sensory analysis, the most admired sample except the control sample was the sample added to Nestle Nestergel.