Physicochemical And Functional Properties Of Flours And Starches From Different Legumes

Legume is well known for its high nutrition and health care. Starch is the main carbohydrate in legume, and its properties directly impact on the development and utilization of legume. Therefore, it is necessary to study the physicochemical and functional properties of legume flour and its starch to provide theoretical basis and guidance on the exploitation and utilization of legume. In this paper, pinto bean, black eye bean, baby lima bean, lentil, chick pea, small red bean, red kidney bean, black bean, navy bean and mung bean had been selected as the specimens to systematically analyze the compositions, physicochemical and functional properties, in vitro digestibility and antioxidant activity of full legume flours, as well as particle properties, structural characteristics and the paste properties of legume starches. The main conclusions are as follows:The starch and protein content of legumes is high. Their essential amino acids are rich. And their amino acid compositions are consistent with the human body need. The nutritional value of protein in legumes is high. Physicochemical and functional properties of legumes are significantly different. With the increase of temperature, the water absorption index of legume flours increases, but their water solubility index decreases. Six kinds of legumes which belong to Phaseolus.L have higher water and oil absorption, emulsion activity and stability. Foaming capacity of legume flours tends to first increases, then decreases and then increases with rising concentration of flours. The physicochemical and functional properties of legume flours are affected by the content of starch, protein, crude fat and ash. The clustering of legume flours based on quality characteristics is in agreement with botanical classification. Quality characteristics of legume flours are mostly influenced by the plant origin.The content of slowly digestible starch and resistant starch in both uncooked and cooked legume flours is high. In vitro enzymatic digestion of legume flours shows a two-stage hydrolysis pattern. The starch hydrolysis rate and extent are greatly influenced by cooking.The total phenolic content of 10 kinds of legumes is 9.49~47.60 mg/g. All legumes have antioxidant capacity, and are able to scavenge DPPH·and·OH. Lentil has the highest content of total phenol, and the most capacities of total antioxidant, DPPH·scavenging and total reducing power. The total phenolic content is significantly correlated with color values. And the total antioxidant activity, DPPH·scavenging rate and total reducing power of different legume flours are significantly positively correlated with total phenolic content.Legume starch granules are commonly kidney shape. Most of legume starch granules size are 10~30μm. Molecular structure, digestibility, paste properties of legume starches are different among various legume starches. Most properties of legume starches are significantly different from that of corn and potato starch. Legume starches are composed of amylopectin, intermediate fraction and amylose. Their amylose content is about 32.00~45.35%. The weight-average molecular weight,radius of gyration and branch chain length distribution of amylopectin in legumes are significantly different. The branch chain length of red kidney bean and black bean starches is greater than the other starches. Affected by moisture content, growing environment and other conditions, x-ray diffraction pattern of all legume starches are A-type, and the range of crystallinity is between 19.73 and 29.00%. The solubility and swelling power of legume starches increases with the increase of temperature. Acid hydrolysis of legume starches shows a two-stage model. Their acid hydrolysis rates are much lower than that of potato and corn starch. Starch hydrolysis rate increases with the extension of time. Compared with uncooked starches, the hydrolysis rate of cooked starches speeds up obviously. The anti-digestibility of starches is not as good as legume flours. Starch pastes have good thermal stability and a greater degree of retrogradation. There are correlations among granular structure, molecular structure, starch digestibility and paste properties of legume starches.The relationship between components and functional properties and antioxidant activities of legume flours, and between molecular structure and physicochemical properties of starches has been studied in this study. Also, the relationship between the low digestibility of legume flours and their starches and the starch composition and molecular structure has been revealed. These results will provide the basic theory for developing and using of legume resources, and have an important role in guiding the deep processing of flours and their starches, and the development of functional foods.