Evaluation of Bitterness in Enzymatic Hydrolysates of Soy Protein Isolate by Taste Dilution Analysis

Abstract

Although enzymatic hydrolysates of soy protein isolate (SPI) have physiological functionality, partially hydrolyzed SPI exhibits bitter taste depending on proteases and degree of hydrolysis (DH). To determine proteolysis conditions for SPI, it is important to evaluate bitterness during enzymatic hydrolysis. Taste dilution analysis (TDA) has been developed for the screening technique of taste-active compounds in foods. The objectives of the present study were to evaluate bitterness of enzyme-hydrolyzed SPI by TDA and to compare bitterness of SPI hydrolysates with respect to kinds of proteases and DH. SPI was hydrolyzed at 50 degrees C and pH 6.8 to 7.1 to obtain various DH with commercial proteases (flavourzyme, alcalase, neutrase, protamex, papain, and bromelain) at E/S ratios of 0.5%, 1%, and 2%. The DH of enzymatic hydrolysates was measured by trinitrobenzenesulfonic acid method. The bitterness of enzymatic hydrolysates was evaluated by TDA, which is based on threshold detection in serially diluted samples. Taste dilution (TD) factor was defined as the dilution at which a taste difference between the diluted sample and 2 blanks could be detected. As DH increased, the bitterness increased for all proteases evaluated. Alcalase showed the highest TD factor at the same DH, followed by neutrase. Flavourzyme showed the lowest TD factor at the entire DH ranges. At the DH of 10%, TD factor of hydrolysate by flavourzyme was 0 whereas those by protamex and alcalase were 4 and 16, respectively. These results suggest that TDA could be applied for the alternative of bitterness evaluation to the hedonic scale sensory evaluation.

BITTERNESS AND PHYSICHOCHEMICAL PROPERTIES OF ANGELWING CLAM (Pholas orientalis) HYDROLYSATE

“…This result was also supported by Seo et al [17] where the small amount of S/E% at 0.5 % bromelain used could gave a bitter taste to soy protein hydrolysate. According to Imelda [18] samples showed hydrolysis with different proteases had varying level of bitterness, where alcalase and protamex showed high level of bitterness within 1500 to 2000 ppm caffeine.…”

Bromelain: an overview of industrial application and purification strategies

“…Partial hydrolyzation of soy protein isolate (SPI) by bromelain showed lower (TD) factors of 4 and 16 in 10 and 15 % DH, respectively, compared to alcalase and neutrase. This phenomenon could be due to the remaining nonpolar amino acid residues at the C-terminus of the peptide after bromelain hydrolyzes the hydrophobic amino acid residues (Seo et al 2008). Cheung and Li-Chan (2014) found that after 8 h of hydrolysis, shrimp hydrolysate by bromelain demonstrated less bitter and high umami taste in the instrumental taste sensing system rather than alcalase and protamex hydrolysate.…”

“…Low temperature is favorable to avoid denaturation during precipitation. To recover the protein of interest, additional steps such as centrifugation and dialysis are needed to remove contaminant proteins (Janson 2011). Shian et al (2005, for example, successfully precipitated 1 l of homogenate pineapple juice at 55 % of ammonium sulfate.…”

A Systematic Approach to Comparison of the Cost Efficiency of Endopeptidases to Hydrolyze Atlantic Salmon (Salmo salar) By-Products

“…However, this causes additional processing cost and increases the level of salt in the fi nal hydrolysate. In addition, the comparison of proteases is most frequently conducted based on equal mass to substrate ratio and reaction time (16)(17)(18). However, this will give diff erent fi nal DH and protein recovery levels of the hydrolysates.…”