| Black rice is a special type of cereal that has been cultivated for a long time in the gramineous plant.The black rice is black or dark brown,rich in nutrients,high in food and medicinal value.In addition to porridge,it can also produce various nutritious foods and wines.Known as the "black pearl" and "the king of the world".The most representative black rice in Yangxian County of Shaanxi Province has the reputation of "medicine rice","Gongmi" and "Shoumi" since ancient times.However,the black rice table is tightly cortexed and contains a large amount of substances such as cellulose and pectin which are not conducive to cooking and eating,which greatly hinders the development and utilization of black rice.In this paper,we explored the use of exogenous enzymes to digest black rice and improve the eating quality of black rice by pre-gelatinized.The exogenous enzyme mainly utilizes cellulase and pectinase to partially digest the cellulose and pectin in black rice skin,so that the black rice epidermis is softened,thereby shortening the cooking time of black rice and improving the quality of food;pre-gelatinization It is to improve the cooking time of black rice and improve the quality of food by improving the black rice epidermis and starch texture by soaking,cooking(pre-gelatinizing)and drying the black rice.The main conclusions are as follows:1?The black rice of Yangxian County was used as raw material,cellulase was exogenous enzyme,cellulose content and cooking time were the main indicators.The effects of enzymatic hydrolysis p H,temperature,time and enzyme dosage on enzymatic hydrolysis were investigated by single factor experiment.The effect of the enzymatic hydrolysis conditions was p H 5.2,temperature 45 ° C,enzymatic hydrolysis time 2 h,cellulase dosage 0.09 mg / m L;analysis of the p H of the enzymatic hydrolysis,temperature and enzyme dosage by response surface methodology The mutual influence,through the model correction,the optimal working conditions were p H 5.19,temperature 45 ° C,cellulase dosage 0.092 mg / m L.At this time,the residual cellulose content in black rice was 2.201%,and the required cooking time was 24 min.Compared with the untreated black rice,the cellulose content decreased by 24.36%,and the cooking time was shortened by 52.74%.2?Pectin enzymatic hydrolysis experiment: using Yangxian black rice as raw material,the main influencing factors of pectinase activity were investigated by single factor experiment,including enzymatic hydrolysis p H,temperature,time,and pectinase dosage to obtain the best working conditions.The p H was 5.2,the temperature was 50 °C,the enzymatic hydrolysis time was 2 h,and the pectinase dosage was 0.6 mg/m L.Then the response surface was used to analyze the interaction between p H,temperature and pectinase dosage,and the model was corrected.The optimal working conditions were p H 5.2,temperature 50 ° C,pectinase dosage 0.64 mg / m L,at this time the galacturonic acid content in black rice was 0.4873 g / kg,the required cooking time was 31 min,and not Compared with the treated black rice,the galacturonic acid increased by 23% and the cooking time was shortened by 54%.3?The black rice of Yangxian County was used as raw material,the pectinase was exogenous enzyme,the content of galacturonic acid and cooking time were the main indicators.The enzymatic hydrolysis of p H,temperature,time and enzyme dosage was investigated by single factor experiment.The effect of the effect was obtained,and the suitable enzymatic hydrolysis conditions were p H 5.2,temperature 50 °C,enzymatic hydrolysis time 2 h,pectinase dosage 0.6 mg/m L;the p H,temperature and pectinase dosage were analyzed by response surface.The interaction between the two,through the model correction,the optimal enzymatic conditions were p H 5.2,temperature 50 ° C,pectinase dosage 0.64 mg / m L,at this time the galacturonic acid content in black rice was 0.4873 g / kg The required cooking time was 31 min.Compared with untreated black rice,galacturonic acid increased by 23% and cooking time was shortened by 38%..4?For the soaking process of pre-gelatinized black rice,the effects of soaking method,soaking time on water absorption,expansion rate and sensory quality of black rice after soaking were investigated.The suitable soaking method was ultrasonic assisted soaking(ultrasound temperature was 25 °C).The best soaking time is 4h.At this time,the water absorption rate of black rice is 24%,the expansion rate is 331%,and the sensory score is 28 points(total score 30 points).5?The effect of cooking water ratio on cooking quality was investigated for the cooking process of pre-gelatinized black rice.The effects of soaking method and soaking time on cooking quality were also verified.Taking the cooking time,the sensory quality and texture characteristics of black rice after cooking as the indicators,the suitable cooking water ratio was 1:1.6,and further verified that the suitable soaking method was ultrasonic assisted soaking and soaking time was 4h.At this time,the cooking time was 21 min,which was shortened by 58%,and the sensory score was 95 points.6?For the drying process of pre-gelatinized black rice,hot air drying was carried out,and the drying effect of one temperature drying and two temperature drying was examined.Drying at a temperature for 40 ° C,60 ° C,80 ° C,100 ° C,120 ° C,140 ° C,drying target moisture content of 11-12%,drying time,drying rate,rehydration after drying Rate and sensory quality are evaluation indicators.The comprehensive evaluation showed that the pre-gelatinized black rice obtained by drying at a drying temperature of 80 ° C had the best quality,the required drying time was 60 min,the rehydration rate was 1.79,the sensory score was 90 minutes,and the pre-gelatinized black rice after drying.Good color,no waist and gran7?For the two-stage temperature drying process of pre-gelatinized black rice,the combination of two temperature ranges is 120°C+40°C,140°C+40°C,120°C+60°C,140°C+60°C,respectively.The drying time of the stage is 20 min,and the moisture content of the drying target is 11-12%.The total time required for drying,the drying rate,the rehydration rate after drying and the sensory quality are the evaluation indicators.The comprehensive evaluation showed that the pre-gelatinized black rice after combination drying at 120 °C+40 °C had the best quality,the required drying time was 50 min,the rehydration rate was 1.84,the sensory score was 94,and the black rice color was good after drying.Burst and granules.8?In order to investigate the drying characteristics of pre-gelatinized black rice,the low-field nuclear magnetic resonance technique was used to determine the moisture content of the black rice after gelatinization and the variation of the drying process.The results showed that most of the water in the black rice after gelatinization was bound water,and a small part was free water.The semi-bound water signal was not detected.In the drying process,the free water in the pre-gelatinized black rice was mainly evaporated in the early stage,and dried.After about 20 minutes,the free water evaporated completely,and the combined water began to accelerate evaporation.According to the characteristics of free water and combined water,the evaporation in the dry free water belongs to the surface vaporization control,and the black rice temperature is kept at the wet bulb temperature.In order to improve the drying efficiency,the drying at this stage can be dried at a high temperature.When evaporating the combined water,the water gradually diffuses from the inside of the rice to the surface,which belongs to the internal diffusion control,and the temperature of the rice will gradually increase.The drying at this stage should be carried out at a low temperature.This experiment proves from the drying theory that the pre-gelatinized black rice adopts two Section temperature drying is most suitable.9?The texture analysis and rheological properties of the pre-gelatinized black rice after drying were further verified to confirm the drying mode and drying temperature.The texture properties were evaluated by hardness and viscosity.The rheological properties were evaluated by peak viscosity and final viscosity.It was further verified that the drying effect was best after drying at a drying temperature of 80 °C.The drying temperature of two sections was 120 °C+40 °C.The best conclusion. |
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