J. Agric. Food Chem. 43 : 2007-2011 (1995)

Functional Changes of Carboxymethyl Potato Starch by Conjugation with Whey Proteins

M. Hattori, W. Yang and K. Takahashi

Department ofApplied Biological Science,
Faculty of Agriculture,
Tokyo University of Agriculture and Technology
Tokyo 183, Japan

Potato starch granules and whey protein were conjugated with a covalent bond to improve the function of starch. Slightly carboxymethylated starch (CMS) was prepared and dispersed in a water-soluble carbodiimide (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide) solution. Whey protein isolate (WPI) was added and the reaction mixture was incubated at 24 degree C for 5 h, resulting in the formation of an acid-amide bond between CMS and WPI. WPI-CMS conjugate was recovered after thoroughly washing with a 0.9% NaCl solution and distilled water and then air-drying. The conjugation of WPI to the CMS granules was demonstrated by Coomassie Brilliant Blue (CBB)-staining, the WPI content of the conjugate being estimated to be about 6%. Conjugation markedly decreased the solubility and swelling of starch granules . DSC data revealed that the conjugate gelatinized at a higher temperature than CMS and ceased retrogradation. The digestibility of the conjugate with alpha-amylase and beta-amylase decreased as compared with CMS and native starch. The retinol binding activity of the conjugate was confirmed by fluorescence titration.