Studies On The Preparation Of Rice Milk Beverage And Its Stability

The rice germ and bran of brown rice are abundant in nutrients (vitamins and minerals) andhealth keeping factors. A remarkable amount of the nutriments were lost along with the removalof rice bran and germ during the rice milling process. About 10%～15% of rice kernels werebroken in the milling process. The nutrients of broken rice are similar to those of sound rice, butthe price of broken rice is only 1/3～1/2. A novel cereal-based health beverage, rice milk, wasdeveloped using the brown rice and broken rice as raw material in order to improve integratedutilization of rice and value adding of rice resource.The raw materials were roasted to produce pleasant flavor and taste. The effects of roastingwere studied respectively on the physicochemical properties of the brown rice and broken rice byscanning electro-microscopy (SEM), gelatinization degree determination, and Brabenderviscosity curve, and on the volatile flavor components by solid phase microextraction-gaschromatography-mass spectroscopy (SPME-GC-MS). Two new components, namely, pyrazineand furfural, were produced in the volatile flavor after roasting treatment. The brown rice mademore contribution to the flavor enhancement as compared with broken rice.Then the roasted raw materials were subjected to enzymatic treatment to obtain rice milk. Theenzymolysis reaction conditions were optimized from factorial and orthogonal experiments:temperature 80℃, time 50min, enzyme quantity 10U/g raw material, and pH 6.5. The glucose,maltose and other oligosaccharide concentrations of the supernatant were quantitated by HPLC.The percentage addition of non-dairy creamer and fructose-glucose syrup were decided upon, byorganoleptic evaluation, at 0.8% and 5%, relatively. Pyrazine was found to be the main flavoringredient by SPME-GC-MS.The stability of the rice milk was studied as affected by various factors. The formulation wasobtained to increase the rice milk stability by experiments with single and simultaneous use ofadditives: sodium caseinate 0.05%, sucrose ester 0.05%, and sodium alginate 0.05%. The effectsof pH, homogenization and sterilization conditions on the rice milk stability were also studied,and their optimum levels were determined: pH 6.5～7.0, homogenization in two steps at40MPa and 30MPa, and sterilization at 115℃ for 15min.