An improvement of potato pulp protein hydrolyzation process by the combination of protease enzyme systems

The enzymatic hydrolysis of potato pulp (PP) was carried out by using four different enzymes, Alcalase (ALC), Novo Pro-D (NPD), Flavourzyme (FLA) and Corolase (COR) and eight combination of proteolytic enzyme systems in a 4 l batch reactor at 50 °C for 26 h without pH control. The endoprotease ALC and exopeptidase FLA were the most suitable for hydrolyzing the PP protein, whereas the endoprotease NPD and exopeptidase COR were presented a very low hydrolyzation activity for this protein type. An immediate hydrolyzation rate and the highest degree of hydrolysis (DH), 22%, was observed in the presence of FLA, whereas the lowest DH was obtained from NPD and COR. To improve the hydrolyzation process, the combination of an endoprotease, ALC or NPD and an exopeptidase, FLA is more efficient than using the individual proteases. The amount of FLA influenced the DH and the obtained end products. The highest DH 44% was obtained from the combination of 2% ALC + 5% FLA (w/w), while the lowest DH, 17%, was obtained from 2% NPD + 5% COR (w/w) system and 3% NPD + 4% COR (w/w) system, as well. The amino acid concentration in the enzymatic hydrolysates was significantly higher than that in the native potato pulp (NPP), especially aromatic amino acids (His, Phe, Trp and Tyr) and the sulfur-containing amino acid methionine (Met). For many free amino acids, the first four h after adding FLA seemed to be the most important period. The long time hydrolysis had a negative effect on the concentration of Asn and Gln. The highest amount of free amino acid Leu was produced: approximately 18% of the total amount of free amino acid (Σ faa) for each enzyme combination system. The highest amount of Σ faa, 306 mg/g protein, was obtained from the combination of 2% ALC + 5% FLA (w/w).