Effect of drying and proline addition on aroma volatile compounds of acid-hydrolysed rice bran protein concentrate

Rice bran protein concentrate (RBPc) was hydrolysed by 0.5N aqueous HCl at 95°C for 12h. The liquid hydrolysate obtained was prepared as hydrolysate powder by spray drying. Aroma volatile compounds in liquid hydrolysate and its hydrolysate powder were tentatively identified by GC-MS. Furfural and vanillin were found in both hydrolysates with high concentration, and vanillin showed the highest odour activity value. Hexanal was present in only liquid hydrolysate. Concentrations of carboxylic acids and heterocyclic compounds, especially 2-methoxy-6-methylpyrazine, increased after drying. Amino acid composition of the hydrolysate powder showed high aspartic acid and glutamic acid. Aroma volatile compounds of hydrolysate powder prepared by the addition of proline at pH 6.0 (Pro6.0-H) and pH 7.5 (Pro7.5-H) before drying were investigated. Furaneol was found only in Pro6.0-H, but it was not detected in Pro7.5-H and hydrolysate powder without proline addition. Pro7.5-H had higher furfural and vanillin concentrations than Pro6.0-H.