| The aim of this study was to reduce off-flavor of soy protein (SP) by removing protein-bound volatile compounds and phospholipids (PL). This was achieved via formation of inclusion complexes between protein-bound substrates and food grade beta-cyclodextrin (betaCD). First, by performing model study, it was shown up to 94% of SP-bound 2-nonanone could be removed with 6 mM betaCD at pH 8.0. Secondly, using a spread monolayer technique, it was determined that betaCD can form inclusion complexes with soy PL and remove up to 30-50% of those complexes from the air-water interface (hydrophobic phase) depending on the polarity of PL headgroup.;When a SP solution (50 mg/mL), with SP-bound PL content of 3.1 mg/g SP, was treated with betaCD (10 mM) alone, up to 21-36% PL could be removed. Further gains in extraction of PL were made by sonicating SP at 50 °C for 5 min with an energy input of 65 W, treating with enzyme phospholipase A2 (121 units/g SP) at 37 °C for180 min and equilibrating with 10 mM betaCD for one hour. betaCD-lipid complexes were separated from treated SP either by isoelectric precipitation or by a combination of ultrafiltration (UF) and batch diafiltration (DF). In the former case, PL content was reduced to 0.07 mg/g SP as compared to 0.4 mg/g SP in the latter case. Treated SP prepared via OF and DF method was spray dried and stored either at -20 °C or at 40 °C for 90 days. SPME analysis indicated that treatment caused significant reduction (p<0.05) in SP-bound volatile compounds in both fresh and storage SP. A quantitative descriptive analysis done on fresh and storage samples did not yield significant differences (p>0.05) in terms of sensory attributes. This was attributed to oxidation of residual PL in SP during storage. Functionality of SP was not affected by betaCD and PLA2 treatment. In fact, improvement in gelling properties and emulsification properties of treated SP were observed. Overall, the results of this study indicate that betaCD has a potential for use in off-flavor reduction of SP without adversely affecting protein functionality. |
