Optimization of Enzyme Assisted Processes for Extracting and Hydrolysing Corn Proteins Aiming Phenylalanine Removal

Abstract

Two enzyme assisted processes were studied in this work, protein extraction and hydrolysis, aiming phenylalanine (Phe) removal from corn. For protein extraction, a protease of Bacillus liccheniformis was used and the effect of temperature (55 and 60°C) and time (1, 5, 15 and 24 h) was evaluated. For Phe removal, a pancreatin was used for hydrolyzing corn proteins and the activated carbon (AC) was the adsorbent support. In this case, the influence of several parameters was estimated, such as protein extract concentration, E:S ratio, use of freezedrying, protein: AC ratio and way of using AC. The efficiency of Phe removal was evaluated by second derivative spectrophotometry, measuring the Phe content in the corn flour as well as in the hydrolysates after AC treatment. The results showed that the time and the temperature influenced the protein extraction yield and the best results were obtained at 55°C, after 5 h, 15 h and 24 h of reaction, having reached an average extraction yield of 85.3%. The removal of Phe, changed from 68.63 to 97.55%, and its final concentration from 18.80 to 240.75 mg/100 g hydrolysate. The condition that produced the highest Phe removal was the one using a protein extract concentration = 1%, E:S = 1 or 2%, pH 9, temperature = 25°C, protein: C = 1:88.5, using three types of AC and freezedrying (hydrolysates H1 and H2). However, this condition presents some disadvantages such as the use of freezedrying, which highly raises the process cost, and a non-controlled and non-repeatable reaction. Among the samples with no freezedrying stage and more controllable reaction (H9 and H10), H10 is the best one, since it showed smaller Phe content (149.27 mg/100 g) using three types of AC, which is advantageous from the technical point of view. The reduction of the protein: AC ratio, for these two hydrolysates (H9 and H10) was not beneficial for Phe removal, leading to higher Phe content.