| Soymilk is a traditional dietary drink in China,which is rich in nutrients such as protein,tocopherol and soybean isoflavones,and is very popular among consumers.In recent years,with the transformation of social and economic development and the improvement of consumption concept,the disadvantageous factors,such as the waste water and soybean dregs produced in the traditional soymilk processing process,as well as the beany flavor and anti-nutritional factors of soymilk,have hindered the further expansion and development of soymilk industry under the new situation.In this thesis,aiming at the defects of traditional soymilk processing technology,the modern food processing theory was used to establish a new processing technology of soymilk without dregs production,which was based on soybean roasting → colloid grinding pulping → blending,and the key control technology was optimized and adjusted to develop a kind of whole nutrient soymilk with low beany flavor and good stability.The main contents and findings of this study are as follows:Based on the contents of protein,reducing sugar,fat,volatile flavor and sensory quality of roasted soybean and soymilk,the roasting process of soybean was optimized.The results showed that roasting reduced the contents of compounds causing beany flavor such as hexaldehyde and hexanol,and increased the contents of volatiles with burnt aroma such as pyrazines and furans.According to sensory evaluation,the optimal roasting condition of soybean was 160 °C for 10 min.Study on the colloid stability of soymilk.By using soybean protein isolate(SPI)as emulsifier,the effects of SPI concentration,pH and NaCl concentration on the colloid stability of soymilk were studied.With the increase of SPI concentration,particle size and flocculation degree of fat decreased,emulsification activity and emulsification stability increased,droplet Zeta potential and soymilk viscosity increased.Soymilk had good stability when pH was above 7,and there was no separation of fat phase after 10 days of storage.Fat floating can be effectively inhibited by the addition of 0.1% NaCl in soymilk.The optimal blending condition of whole nutrient soymilk was SPI concentration 2%(w/v),pH value 7 and NaCl concentration 0.1%(w/v).Study on the effects of sterilization technology on the active components and antioxidant capacity of soymilk.Soymilks were treated with pasteurization,high temperature steam sterilization,ultra-high pressure sterilization and ultrasonic sterilization,the results showed that pasteurization and high temperature steam sterilization reduced the contents of total phenols and total flavones in soymilk,and they also promoted the conversion of glucoside isoflavones to aglycone isoflavones.Ultrasonic sterilization significantly increased the contents of total phenols and flavonoids in soymilk,whereas ultra-high pressure sterilization has no significant effects on the contents of total phenols and flavonoids.High temperature steam sterilization effectively inactivated trypsin inhibitor and urease,and their activity losses were more than 90%.Thermal sterilization reduced,but ultrasonic sterilization increased the antioxidant capacity of soymilk.The colloid stability of soymilk was weak after thermal sterilization but strong after ultrasonic sterilization.The soymilk processing technology developed in this study has no water pollution to the environment,and the soymilk products have thin beany flavor,strong aroma,low nutrient loss and good stability.The results of this research can provide theoretical basis for the study on product innovation,flavor development and quality improvement of soymilk. |
