| Qianjiang kidney bean(Phaseolus vulgaris L.) is a featured crop in Qianjiang district, southeast Chongqing, China. The plant is commercially exploited due to its pleasant sensory characteristics and plentiful nutrients, but corrsponding study is not enough. In this study, Qianjiang kidney bean was used as experimental material. The contents of major nutritional components and minerals, and carbohydrate composition of Qianjiang kidney bean were analyzed. Starch is the main chemical component of Qianjiang kidney bean, and its property affects the process of Qianjiang kidney bean and quality of kidney bean production. Physicochemical properties of kidney bean starch were studied roundly, which provided basic food chemistry data for Qianjiang kidney bean starch and further processing of Qianjiang kidney bean. Meanwhile, kidney bean starches were produced noodles, and process parameters of Qianjiang kidney bean noodles were studied. Finally, sensory quality, cooking quality and texture properties of kidney bean noodles and mung bean noodles were comparatively analyzed. The main results were exhibited as follows:(1)Study on elementary composition and digestion characteristics of Qianjiang kidney bean starchThe results of kidney bean macronutrient showed that Qianjiang kidney beans contained moisture 13.33±0.23%, ash 3.44±0.02%, protein 24.54±0.23%, crude fat1.44±0.02% and carbohydrate 57.25%. So Qianjiang kidney bean had the characteristics of high content of carbohydrate, medium content of protein as well as low content of fat.The results of kidney bean micronutrient, minerals showed that the contents of macroelement Na, Mg, K and Ca in Qianjiang kidney bean were 16.54±1.22 mg/100 g,100.02±3.46 mg/100 g, 1029.41±32.06 mg/100 g and 8.60±0.72 mg/100 g, respectively,and the contents of microelement Fe, Zn, Cu and Mn were 8.32±0.23 mg/100 g,3.79±0.35 mg/100 g, 0.93±0.04 mg/100 g and 1.00±0.06 mg/100 g, respectively. Highcontent of potassium and magnesium as well as low content of sodium were observed.Further study of kidney bean carbohydrate composition found that kidney bean carbohydrate was mainly composed of starch, reducing sugar and crude fibre, and the contents of these were 48.16±0.59%, 1.56±0.03% and 3.59±0.11%, respectively, which occupied 93.12 percentage of total carbohydrate. Starch was the main component of carbohydrate, which occupied 84.12 percentage of total carbohydrate. Through analysis of the contents of amylose and amylopectin in kidney bean, it was found that the contents of Amylose and amylopectin were 18.54±0.20 g/100 g and 29.62±0.40 g/100 g.Dietary amylose and amylopectin ratio was 0.63±0.01, so kidney bean has high content of amylose. The contents of rapidly digestible starch, slowly digestible starch and resistant starch were 39.76±0.88%, 35.01±0.41% and 25.23±0.56%, respectively. GI1 and GI2 of kidney bean starch were 85.24±1.05 and 91.68±1.99, greater than 70, so it was belong to high-glycemic index. GI1 and GI2 of kidney bean full flour were65.08±0.50 and 69.34±0.91, less than 70, so it was belong to moderate glycemic index food and suitable for diabetics. The reason GI of kidney bean full flour lower than kidney bean starch was that kidney bean contains protein, fiber, tannins, phytic acid and fat, then these ingredients affected starch hydrolysis rate. Glycemic index in vitro of kidney bean was similar with mixed beans, such as broad bean, chickpea, as well as spotted cowpea.(2)Study on Qianjiang kidney bean propertiesStudies on particle characteristics of Qianjiang kidney bean starch found the granule size of kidney bean starch is different. The shape of larger particles was ovoid and kidney-shaped, but the small particles are round ball. The size of starch particles were roughly within 5~50μm. The birefringence was obvious and showed black cross-shape. Intersection was located in the center position. Kidney bean starch structure of X-ray diffraction was A type. Infrared absorption spectra showed that the kidney bean starch molecules contain primary and secondary alcoholic hydroxyl group of α-D-pyranoid ring which is the structure characteristics of the original starch molecules.The solubility and degree of swelling of kidney bean starch related to temperature,increased with increasing temperature, but the kidney bean starch was a kind of constrained swelling starch. The transmittance rate was 10.3%, reduced with the gradual extension of storage time. Supernatant fluid volume ratio was 75.0% after 2 h, increasedwith the standing time prolonged. Starch paste retrogradation feature was good, easy to aging. The solid-liquid separated during the first thaw cycle and the syneresis rate was41.90%. The freeze-thaw stability was poor. The Brabender viscosity curve showed that the pasting temperature of kidney bean starch was at a high level, could reach up to89.6℃, with a good thermal stability and cold stability.Studies on rheological characteristics of Qianjiang kidney bean starch showed that apparent viscosity of kidney bean starch fell sharply with the increase of shear rate, then flatten out gradually. The curve bulged to origin. This phenomenon was more obvious with the increasing of starch concentration. Gelatinized kidney bean starch was pseudoplastic fluid with shear-thinning property. The thixotropy of Kidney bean starch was obvious. Storage modulus G’ and loss modulus G’ increased slowly with the increasing angular frequency, and they also increased with the increasing concentration of starch pastes. Storage modulus G’ was signally greater than loss modulus G’’. The curves of storage modulus G’ and curves of loss modulus G’ did not cross each other within the limits of frequency sweeping. Kidney bean starch gel was weak gel.(3)Qianjiang kidney bean applied on noodles productionThere are many main factors of the process of Qianjiang kidney bean starch noodles, such as water concentration, paste concentration, water temperature, holding temperature during making the starch flours and aging time, freezing temperature,freezing time during the freezing process. Through the analysis of dough thixotropic curves found that each thixotropy curve had an obvious hysteresis loop. In accordance with the area of hysteresis loop and the practical production, the best optimal production technology was determined: 40% water concentration, 4% starch paste concentration,50℃water temperature and 50℃ holding temperature. By orthogonal experimental method to study the effect of aging time, freezing temperature and freezing time on the quality of noodles, and the results showed that the freezing temperature was the most critical factor, followed by aging time. The rational freezing process showed: aging 6 h at 4℃, and freezing for 6 h at-2℃。Qianjiang kidney bean noodles and mung bean noodles were produced according to optimal process, and the sensory quality, cooking quality and texture properties of kidney bean noodles and mung bean noodles were comparatively analyzed. The results of sensory quality showed that kidney bean noodles were bright and transparent and had good toughness, good taste, high hardness and low smoothness. Sensory evaluationscore of kidney bean noodles was less than mung bean noodles. The results of cooking experiment showed that broken bar and cooking loss rate of kidney bean noodles were0.67±0.58 root and 1.94±0.20%, respectively. It meant kidney bean noodles had the characteristics of low solubility, low cooking loss, strong boiling fastness and no burnt soup. So the cooking quality of kidney bean noodles was good, which was similar to mung bean noodles, but better than sweet potato noodles and corn noodles. The results of texture properties showed that the hardness, elasticity, shear deformation of kidney bean noodles were 24.00±2.00 g, 0.34±0.02 mm and 0.38±0.03, respectively. All of these were higher than mung bean noodles. People like noodles with moderately hardness and good toughness. So it does not mean toughness is the higher the better. Toughness of kidney bean noodles was too high and smoothness was too low compared to mung bean noodles, so its acceptability was inferior to mung bean noodles but better than sweet potato noodles and corn noodles. |
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