Effects Of Particle Size On Quality And Protein Digestibility Of Soymilk

Recently, preparing soymilk with household soymilk maker is getting more and morepopular in China. But Okara increased gritty mouth feel of soymilk, which may also decreasethe digestibility of soymilk. The objective of this research was to analyze the effects ofparticle size on quality and protein digestibility of soymilk. Three soymilk makers, JoyoungFine-grinding (JY1), Joyoung Dry-bean (JY2), and Midea Dry-bean (MS) were used toprepare soymilk from raw and dehulled soybeans by "dry-bean" and "soaked bean" programrespectively. The relationship among particle size, soymilk quality and protein absorption ratewere analyzed. Then using dehulled soybean powder of different particle size as material andusing JY1make soymilk. The relationship between particle size and protein digestibility ofsoymilk made by household soymilk maker was analyzed. Then explore the relationshipbetween viscosity and mouth feel, stability of soymilk.The main results are as follows:(1)The materials were intact dry soybeans, intact soaked soybeans, dehulled drysoybeans and dehulled soaked soybeans. The average particle size D[4,3] of soymilk made byJY2was63.34μm,32.04μm,45.84μm and49.21μm. The D[4,3] of soymilk made by MS was40.14μm,31.29μm,47.73μm and41.33μm. The D[4,3] of soymilk made by JY1was35.35μm,20.42μm,34.43μm and29.98μm. The average particle size of soymilk D[4,3]wasJY2>MS>JY1. The Significant difference was showed in the particle size of soymilk made bythree soymilk makers. In the same processing conditions (soaked or unsoaked), the okara indehulled-bean soymilk was smaller than that of raw-bean soymilk significantly (P<0.05). Theaverage particle size of soaked-bean soymilk was smaller than dry-bean soymilk. The proteincontent, protein absorption and sensory score (except dehulled soybeans) of soaked-beansoymilk were also higher than dry-bean soymilk significantly. This indicated that smaller theparticle size was the higher quality of soymilk was.(2)The dehulled soybean powder of different particle size was obtained by grinder. Thegrinding time was20s,40s,60s and100s. The D[4,3] of it was238.99μm,120.09μm,130.89μm and85.88μm, respectively. The soybean powder (grinding time:0s) and finegrinding powder (D[4,3]67.39μm) were also used as materials. The particle size of soybean powder reduced significantly with the grinding time increasing. Using soybean powder (0s,20s,60s and100s) as material, soymilk of different particle size was obtained. The proteindigestibility of soymilk was49.82%,57.67%,63.34%,64.26%and64.50%. It indicated thatthe protein digestibility of soymilk increased when the particle size of soymilk reduced. Theprotein digestibility of soymilk didn't increase significantly when the particle size of soymilkdeclined to a certain value (112.20μm).(3) The dehulled soybean was ground (40s) and prepared with soymilk maker JY1.Adding xanthan gum (dosage:0.05%~0.25%) to the soymilk, the index of viscosity was2.30~31.57g·sec. When the index of viscosity of soymilk increased, people's sensitivity onparticle size decreased. But the stability of soymilk didn't increase. Adding xanthan gum(dosage:0.15%) to the soymilk of different particle size, people's sensitivity on particle sizedecreased when the particle size reduced to a certain value. The smaller the particle size was,the more stable the soymilk system was.The results suggested that decreasing in particle size of soymilk can make highutilization of raw materials. The soymilk was smoother and protein absorption was higher.The protein digestibility of soymilk didn't increase significantly when the particle size ofsoymilk declined to a certain value. Using dehulled soybean powder as material, we can makefull use of soybean. The soymilk contained less okara and was easily digested. It can providea theoretical basis for the development of special soybean powder for household soymilkmaker.