Zou xiurong: the preparation process condition optimization of rice milk beverage.
The preparation process of rice pulp was optimized, and the quality raw materials were provided for the processing of fermented rice milk beverage. The three important processes of rice pulp preparation were studied by single factor experiment: rice roasting, rice pulp liquefaction and saccharification technology, and orthogonal test was used to optimize the liquefaction and saccharification process. The results show that the optimal baking conditions of 180 ℃ baking 15 min; Liquefaction of the optimal process conditions for the temperature of 80 ℃, high temperature resistant alpha amylase content of 30 U/g liquefaction under the condition of 140 min. Saccharification process conditions of the optimal temperature 60 ℃, saccharifying enzyme and enzyme amount is 300 U/g saccharification under the condition of 6 h. On this condition, can get the light fragrance of rice milk, rice DE value of 99.86%, soluble solids content (soluble solid content, TSS) was 9.4%.
Lactobacillus fermented rice milk beverage is the main raw material of rice, supplemented by milk powder, sucrose, fruit and vegetable juice, etc., inoculated lactobacillus and prepared into a nutritious and unique probiotics drink. The fermentation technology and nutritional characteristics of fermented rice milk beverage were studied by many scholars at home and abroad. Fu Liang , yellow-bright infusion over , , Zou Xiurong  on the various influence factors of rice milk fermentation such as strain, ratio of material to water, fermentation time, fermentation temperature, accessories add factors were studied and process optimization. GHOSH K et al. [5-6] studied the changes of bacteria and nutrients in the fermentation of traditional rice fermented beverages in India. Zhu lijie  studied the fermentation characteristics of lactic acid bacteria in germinated brown rice. SHORI  on milk beverage and the beverage respectively in the matrix effect on probiotics activity during storage were studied, the results show that different substrate material impact on the number of lactic acid bacteria living bacterium during storage is different.
RATHORE et al.  studied the effects of raw material composition on the fermentation parameters, and the results showed that the matrix of grain raw materials significantly affected the functional and sensory properties of grain fermented beverages. The main component of rice is starch, and its content varies from 67.72% to 73.48%. However, the lactic acid bacteria used in fermented rice milk were mainly composed of monosaccharides and disaccharides as carbon sources, and the starch could not be directly used. In addition, when starch is heated, the viscosity of the medium will increase significantly and inhibit the growth of microorganisms .
Accordingly in order to make the lactic acid bacteria can effectively using the carbohydrates in the rice, the rice milk production liquefaction and saccharification process, can be used to make the rice starch by the amylase hydrolysis into dextrin and maltose, then through saccharifying enzyme saccharification to glucose, provide fast using carbon source for growth of lactic acid bacteria, promote the growth of lactic acid bacteria; In addition, the rice aroma of baked rice helps to preserve the special aroma of rice.
Therefore, the preparation of rice milk directly affects the growth and sensory quality of lactic acid bacteria. In this paper, the preparation process of rice milk three important working procedure: baking, liquefaction and saccharification, discusses the influence of the baking time and temperature on rice quality, time, temperature, and the influence of enzyme quantity of liquefaction and saccharification process, optimizing the best craft parameter, provides the high quality raw materials for the development of the fermented rice milk matrix.
1 materials and methods
1.1 raw materials and reagents.
Japonica rice, market; High - temperature resistant - amylase (40 000 U/g), jiangsu ruiyang biotechnology co., LTD. Glycosylase (100 000 U/mL), jiangsu ruiyang biotechnology co., LTD. The reagents of 3, 5-dinitrosalicylic acid, NaOH, glucose, and glycerol were all analyzed.
1.2 instruments and equipment.
Colloid mill (jm80-1a), wenzhou colloid mill; All-purpose grinder (dfy-500), zhejiang wenling forest machinery co., LTD. Electric drying oven (101ab-2), Shanghai shenguang instrument co., LTD. Thermostatic water bath (hh-s28s), jintan earth automation instrument factory; Hand-held refractometer (NDJ-1), Shanghai yueping scientific instrument co., LTD. Electronic analytical balance (BS210S) : Beijing sidolis balance co., LTD. Electronic balance (T500), changshu shuangjie test instrument factory; Spectrophotometer (721G), Shanghai jingke instrument co., LTD.
1.3 preparation process of rice pulp.
Bake rice - crushing - weighing and water ratio (1:9) - 30 ℃ for 2 h - colloid slow slurry 3 min to 70 ℃ water bath gelatinization 30 min, high temperature resistant alpha amylase liquefaction and saccharification enzyme saccharifying enzyme to boil 5 min destroy - filter - rice milk
1.4 test method
1.4.1 optimization of rice baking conditions.
Take 100.0 g rice raw material and distribute it evenly in stainless steel tray, then place the tray in the drying oven. Baking temperature set at 140, 160, 170, 180, 200 ℃, bake for 5, 10, 15, 20, 25 min to test and sensory evaluation was carried out on the rice after baking, determine the best baking time and temperature.
1.4.2 optimization of process conditions of rice pulp liquefaction.
(1) the effect of liquefaction temperature on the solution effect of rice slurry: the fixed liquefaction time was 80 min, the enzyme amount was 10 U/g rice flour, and the pH value was 6.0. Take 500 mL after pasting rice milk, respectively, in 75, 80, 85, 90, 95 ℃ under the condition of liquefaction, the determination of DE value and the soluble solids content (soluble solid content, TSS), liquefaction, and the effects of temperature on the enzyme solution.
(2) the influence on the effect of liquefaction time of rice milk enzyme solution: fixed liquefaction temperature 85 ℃, with enzyme amount 10 U/g rice flour, pH value of 6.0. After 500 mL gelatinization, the rice pulp was liquefied 20, 40, 60, 80, 100, 120, 140 and 160 min respectively, and the value of DE and TSS were measured, and the effect of liquefaction time on enzymatic hydrolysis was compared.
(3) effect of liquefaction and enzyme concentration on the solution effect of the rice plasma enzyme: fixed liquefaction temperature 85, time 80 min, pH value of 6.0. Take 500 mL after pasting rice milk add 5, 10, 15, 20, 25, 30, 35 U/g rice resistance to high temperature of alpha amylase, DE value and TSS, compared with enzyme amount of rice milk enzyme solution effect.
(4) rice milk liquefied orthogonal test: according to the results of single factor experiment, the liquefaction temperature, liquefaction time, plus enzyme amount for factors, using L9 (33) orthogonal test, the optimum liquefaction process conditions.
1.4.3 optimization of the process conditions of rice slurry saccharification.
(1) influence of saccharification temperature on the solution effect of rice slurry: 3 h, 200 U/g rice noodle with fixed saccharification time, and 4.2 pH value. Take the rice milk after liquefaction in 50, 55, 60, 65, 65 ℃ under the condition of saccharification, DE value and TSS, saccharification temperature on the enzyme solution effect.
(2) fixed saccharification temperature of 65 ℃, with enzyme amount 200 U/g rice flour, pH value of 4.2. The effects of the saccharification time on the enzymatic hydrolysis were determined by the determination of DE and TSS, respectively, after the liquefaction of the rice pulp, respectively, 1, 3, 5, 7, 9 h.
(3) enzyme saccharification and rice milk enzymolysis effect: fixed saccharification time 7 h, the temperature of 65 ℃, pH value of 4.2. After the liquefaction of the rice pulp was made, the amount of the enzyme was 100, 150, 200, 250, 300, 350 U/g rice flour, and the value of DE and TSS were measured, and the effect of the enzyme amount on the enzymatic hydrolysis was compared.
(4) rice milk saccharification orthogonal test: according to the results of single factor experiment, saccharification temperature, saccharification time, plus enzyme amount for factors, using L9 (33) orthogonal test, the best saccharification technology conditions were determined.
1.5 index measurement
1.5.1 sensory grading of rice roasting.
To Browning happens after baked rice fermented rice milk can give special rice flavor, colour and lustre of baking form also have an impact on the color and luster of the finished product, with color and aroma rice baked sensory scoring criteria for grading project (see table 1). A group of six students with a food professional background graded the color and odor of the roasted rice according to the grading criteria and scored the final score.