Bovine serum albumin (BSA) was employed as a model protein emulsifier to conjugate with aldohexose (D-glucose (Glc) or D-allose (All)) and sugar fatty acid ester (6-O-octanoyl-D-glucose (GlcC8)) through the Maillard reaction. It was found during the reaction that rate of decrease of free amino groups in BSA was almost the same for the BSA-sugar mixtures whereas browning and protein aggregation developed in the following order: Glc < All < GlcC8. It was thought that the rate of degradation of the Amadori compound could have been influenced by the OH-group stereochemistry at the C3 position of aldohexose, while denaturation of BSA by GlcC8 enhanced the browning and protein aggregation. To understand the emulsifying ability of the BSA-sugar conjugates, hexadecane-water interfacial tension and the oil droplet size of emulsions prepared by homogenizing hexadecane and aqueous solution of the conjugates were examined. BSA-GlcC8 showed greater improvement in interfacial and emulsifying activity than did BSA-Glc and -All. However, no improvement in emulsion stability was observed for any of the BSA-sugar conjugates, suggesting the weakness of the film formed at the oil droplet interface.

The present work suggests that RBPH might be potently employed as a natural antioxidant in both bulk oil and emulsion models.

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The diesterification of D-psicose (the C-3 epimer of D-fructose) with fatty acid vinyl esters of selected acyl chain lengths (C 8 , C 10 , and C 12 ) was successfully carried out using Candida antarctica lipase (Novozym 435) at 45°C for 24 h to give the 1,6-diacyl-D-psicofuranoses with a high regioselectivity in good yields (83-90%). These diesters of D-psicose have hydrophilic-lipophilic balance (HLB) values (6.5-8.2) similar to HLB values of monoglyceride compounds which constitute the largest single type of emulsifiers employed by the food industry. Ability of the D-psicose diesters to stabilize oil-in-water emulsions and the weight-averaged oil-droplet diameter in the emulsions was evaluated in this study. Emulsion stability of oil droplets stabilized by D-psicose dicaprylate (0.3%, w/v in oil phase) was comparable to D-fructose dicaprylate (0.2%, w/v). It was further confirmed that the D-psicose diesters exhibited an emulsification activity depending on the chain length of fatty acid; D-psicose dicaprate showed better emulsion stability than the other diesters.