linoleic-acid and alpha-chymotrypsin

β-Lactoglobulin (BLG) is a member of lipocalin family, proteins with ability to bind small hydrophobic ligands, such as retinol, vitamins and fatty acids. Moreover, BLG is susceptible to protease action producing a wide range of polypeptides depending on the hydrolysis degree (HD). In the present work, the effect of limited enzymatic hydrolysis on fatty acid binding properties of BLG was studied. Linoleic acid (LA) was used as a model fatty acid. Limited enzymatic hydrolysis was performed using α-chymotrypsin immobilised on agarose microparticles. BLG hydrolysates were produced at HD: 1%, 3% and 5%. In order to determine the influence of HD on BLG molecular weight SDS-PAGE was used. BLG structural modification and LA binding properties were monitored by means of fluorescence spectroscopic techniques. The increase in HD produced: (i) a BLG degradation and a molecular weight distribution of BLG hydrolysates and (ii) an increased exposition of buried hydrophobic residues, however it was observed a decrease in surface hydrophobicity possibly due to a deterioration of hydrophobic protein domains. It was observed that enzymatic hydrolysis treatment produced a decrease in BLG ability for binding LA. It was concluded that limited enzymatic hydrolysis could deteriorate the specific site on BLG structure necessary for binding LA.

Topics: Chymotrypsin; Hydrolysis; Hydrophobic and Hydrophilic Interactions; Lactoglobulins; Linoleic Acid; Protein Binding; Spectrometry, Fluorescence

To utilize soy protein isolate (SPI) more widely, a convenient and effective method for deodorizing it is required. This paper reports a new deodorizing method using various types of solid adsorbents made of polystyrene, polymethacrylate, and zeolite, as well as charcoal. Treatment of the SPI solution with them decreased the hexanal content in the solution, whereas the content of linoleic acid was not much decreased. A brominated polystyrene adsorbent (SEPABEADS SP207) and a zeolite adsorbent (HSZ-360HUD) removed hexanal most effectively, although 30-40% of the total hexanal remained. A model experiment showed that their hexanal adsorption capacity was much higher than the hexanal content in the SPI solution and that an excess amount of hexanal added to the SPI solution was mostly removed by them. These results suggest that hexanal in the SPI solution can be classified into two types. Hexanal of type I may be free or bound weakly on the surface of proteins and is removable by the adsorbents, whereas hexanal of type II may be bound tightly inside proteins and is unremovable by the adsorbents. Despite the considerable amount of hexanal remaining in the SPI solution even in the most successful cases, the SPI solution was well deodorized as shown by the sensory test. Accordingly, type I hexanal may be closely related to the soybean odor. Removal of hexanal by the adsorbents was not much improved by alpha-chymotryptic digestion of SPI. Type II hexanal might be in similar states even in the chymotryptic digests.

Topics: Adsorption; Aldehydes; Charcoal; Chemical Phenomena; Chemistry, Physical; Chymotrypsin; Linoleic Acid; Odorants; Polymethacrylic Acids; Polystyrenes; Soybean Proteins; Zeolites