Studies On The Properties Of Starches And Proteins In Beans (small Red Bean, Large Red Bean And Scarlet Runner Bean)

Starches and proteins were extracted and separated from small red bean, large red bean and scarlet runner bean by wet milling method. Physicochemical properties of starches and proteins as well as the differences between them have been studied systemically.1. The three beans all have a higher content of starch and protein.The purity of samples of starch and protein is higher.2. Microscopic characteristics of the three starch granules have been studied in this paper. The results show that: (1) Starch granules of small red bean, large red bean and scarlet runner bean are pebble, oval or round shapes. The average granule size of small red bean, large red bean and scarlet runner bean are 34.8, 45.2 and 35.4μm with the ranges of particle size 13~80, 17~105 and 13~80μm, respectively. The average particle sizes of three starches are 34.8, 45.2 and 35.4μm, respectively. Polarization crosses of starches are of X-shape mostly. Starch granules of the three beans have smooth surface observed by SEM. The three starchs all belong to the A-type crystal structure and degree of crystallinities of small red bean, large red bean and scarlet runner bean are 50.9%, 37.1%, 40.2%, respectively. (2) The infrared absorption spectrum of the three starches all is similiar, which means they have the same characteristics of structure. (3) At about 80℃, solubility and swelling power of three starches increased dramatically. The order of the swell ability from better to worse is: large red bean starch> small red bean starch>scarlet runner bean starch. (4) The results of DSC show that: large red bean starch is the mostly easy to gelatinization, and scarlet runner bean is the most difficult. (5) The scanning spectrums of compound of starch with I2 of small red bean, large red bean and scarlet runner bean show that the chain structure of their amylose are longer than that of high amylose corn starch. Their amylose contents are 36.5%, 28.0% and 30.0%, respectively3. This paper studied paste and gel properties of the three starches. The results show that: (1) Pastes of the three starches are pseudoplastic liquid with a certain degree of thixotropy. The shear resistances of bean starch pastes are stronger. (2) The freeze-thaw stability of the three starch pastes is poor. The order of the retrogradation capacity from better to worse is: large red bean starch> small red bean starch >scarlet runner bean starch. The order of the transparency from better to worse is: scarlet runner bean starch> large red bean starch> small red bean. (3) The Brabender viscosity curves show that: large red bean starch is the mostly easy to gelatinization, and scarlet runner bean is the most difficult. The three starches all have better hot paste stability and cold paste stability. With the addition of NaOH, the begin temperature of three starches decreases, the peak viscosity increases substantially, but hot paste stability gets weak. With the addition ofcitric acid, the paste viscosity reduces significantly and hot paste stability becmmes worse, the cold paste is stable. (4) The texture analysis of large red bean starch gels show that: hardness, stickiness, chewiness are significantly increased with the concentration increase of large red bean starch. Ion couldn't influence the large red bean starch gel so much. Acid and alkali have a greater impact on the large red bean starch gel and make the rupture strength of large red bean starch gel increased Sucrose can enhance the rupture strength of large red bean starch gel, as well as increase its hardness, elasticity, viscosity and chewiness.4. This paper studied the characteristics of the three bean proteins, the results show that: (1) Proteins isolate of red beans have their isoelectric point between 4 and 4.5. The pI of scarlet runner bean proteins isolate is 4.5. (2) The protein isolate subunits of red beans are very similar. Red beans contain a lot of subunits with molecular weight between 43~66.2 kDa. The protein subunits of scarlet runner bean have smaller molecular weight, especially concentrated in the vicinity of 31 kDa. (3) The contents of essential amino acids in small red bean and large red bean are 26.72 %, 27.95 %, respectively, which are higher than that in scarlet runner bean (25.14 %). The amino acid composition and thermal property of small red bean and large red bean proteins isolate are similar.