Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.

Chickpea grain contains a high amount of starch and valuable protein. Many grain legumes (pulses) can be processed by pin milling and air classification with high separation efficiency. However, chickpea exhibits low separation efficiency because it has a relatively high fat content compared to other pulses. Therefore, the main goal of this research was to improve the starch-protein separation from chickpea flour in order to increase the economic value of chickpea grain.<p>The chemical composition of pin-milled chickpea flour was determined. The functional and physical properties of chickpea flour affecting starch-protein separation were determined. No chemical interactive force was detected between starch granules and protein particles. Therefore, a physical separation technique, i.e. applying centrifugal force in a hydrocyclone, was employed to separate starch granules from protein particles. <p>Using a hydrocyclone, centrifugal force was applied to chickpea flour particles. Chickpea flour was suspended in two different media, isopropyl alcohol or deionized water. In both media, high inlet pressure resulted in smaller geometric mean diameter of particles collected in the overflow and underflow. Isopropyl alcohol as a medium resulted in particles with smaller geometric mean diameter than did deionized water. Starch and protein separation efficiencies were higher at greater inlet pressures. The application of a double-pass hydrocyclone process increased the purity of starch in the underflow and of protein in the overflow, although this process reduced separation efficiencies. Starch granules and protein particles were separated at higher purities in deionized water than in isopropyl alcohol. Separation in deionized water resulted in higher starch separation efficiency and lower protein separation efficiency than did separation in isopropyl alcohol. This difference was due to the difference in density and viscosity of the two media. The higher viscosity of isopropyl alcohol reduced the likelihood of starch granules reaching the inner hydrocyclone wall. Thus, some starch granules were retained in the overflow instead of in the underflow. Additionally, the centrifugal force and drag force applied to the chickpea flour particles differed between the two different media. Hydrocyclone operation resulted in higher centrifugal force and lower drag force in deionized water than in isopropyl alcohol. Since the drag force in isopropyl alcohol was higher than that in deionized water, some small starch granules were diverted to the overflow which caused reduction of protein purity. <p>The use of pH 9.0 and defatting of chickpea flour improved both starch and protein separation efficiencies. Chickpea flour in deionized water at a feed concentration of 5% yielded a pumpable slurry which was delivered efficiently to the hydrocyclone at an inlet pressure of 827 kPa Fractionation of starch and protein from chickpea flour in deionized water using an integrated separation process resulted in starch and protein fractions containing 75.0 and 81.9% (d.b.) starch and protein, respectively. This process resulted in starch and protein separation efficiencies of 99.7 and 89.3%, respectively. <p>Experiments were also conducted to determine the physical and functional properties of chickpea flour and starch and protein fractions. Thermal conductivity, specific heat, and thermal diffusivity were determined and the polynomial linear models were fitted very well to experimental data. Internal and external friction properties of chickpea flour and starch and protein fractions were determined. Samples were subjected to uniaxial compression testing to determine force-time relationships. The samples particles underwent rearrangement rather than deformation during compression. The asymptotic modulus of samples was also computed, and it was linearly related to maximum compressive pressure. The functional properties of fractionated products were highly affected by the separation process. The water hydration capacity of starch fraction increased, whereas the emulsion capacity and foaming capacity of starch and protein fractions were reduced, compared to that of chickpea flour.

Chickpea grain contains a high amount of starch and valuable protein. Many grain legumes (pulses) can be processed by pin milling and air classification with high separation efficiency. However, chickpea exhibits low separation efficiency because it has a relatively high fat content compared to other pulses. Therefore, the main goal of this research was to improve the starch-protein separation from chickpea flour in order to increase the economic value of chickpea grain.<p>The chemical composition of pin-milled chickpea flour was determined. The functional and physical properties of chickpea flour affecting starch-protein separation were determined. No chemical interactive force was detected between starch granules and protein particles. Therefore, a physical separation technique, i.e. applying centrifugal force in a hydrocyclone, was employed to separate starch granules from protein particles. <p>Using a hydrocyclone, centrifugal force was applied to chickpea flour particles. Chickpea flour was suspended in two different media, isopropyl alcohol or deionized water. In both media, high inlet pressure resulted in smaller geometric mean diameter of particles collected in the overflow and underflow. Isopropyl alcohol as a medium resulted in particles with smaller geometric mean diameter than did deionized water. Starch and protein separation efficiencies were higher at greater inlet pressures. The application of a double-pass hydrocyclone process increased the purity of starch in the underflow and of protein in the overflow, although this process reduced separation efficiencies. Starch granules and protein particles were separated at higher purities in deionized water than in isopropyl alcohol. Separation in deionized water resulted in higher starch separation efficiency and lower protein separation efficiency than did separation in isopropyl alcohol. This difference was due to the difference in density and viscosity of the two media. The higher viscosity of isopropyl alcohol reduced the likelihood of starch granules reaching the inner hydrocyclone wall. Thus, some starch granules were retained in the overflow instead of in the underflow. Additionally, the centrifugal force and drag force applied to the chickpea flour particles differed between the two different media. Hydrocyclone operation resulted in higher centrifugal force and lower drag force in deionized water than in isopropyl alcohol. Since the drag force in isopropyl alcohol was higher than that in deionized water, some small starch granules were diverted to the overflow which caused reduction of protein purity. <p>The use of pH 9.0 and defatting of chickpea flour improved both starch and protein separation efficiencies. Chickpea flour in deionized water at a feed concentration of 5% yielded a pumpable slurry which was delivered efficiently to the hydrocyclone at an inlet pressure of 827 kPa Fractionation of starch and protein from chickpea flour in deionized water using an integrated separation process resulted in starch and protein fractions containing 75.0 and 81.9% (d.b.) starch and protein, respectively. This process resulted in starch and protein separation efficiencies of 99.7 and 89.3%, respectively. <p>Experiments were also conducted to determine the physical and functional properties of chickpea flour and starch and protein fractions. Thermal conductivity, specific heat, and thermal diffusivity were determined and the polynomial linear models were fitted very well to experimental data. Internal and external friction properties of chickpea flour and starch and protein fractions were determined. Samples were subjected to uniaxial compression testing to determine force-time relationships. The samples particles underwent rearrangement rather than deformation during compression. The asymptotic modulus of samples was also computed, and it was linearly related to maximum compressive pressure. The functional properties of fractionated products were highly affected by the separation process. The water hydration capacity of starch fraction increased, whereas the emulsion capacity and foaming capacity of starch and protein fractions were reduced, compared to that of chickpea flour.

Regular starches contain two principal types of glucan polymers: amylopectin and amylose. The structure of amylopectin is characterized according to the unit chain length profile and the nature of the branching pattern, which determine the alignment of glucan chains during biosynthesis. The organization of glucan chains in amylopectin and their impact on the structure of starch are still open to debate. The location of amylose and its exact contribution to the assembly of crystalline lamellae in regular and high-amylose starch granules also remain unknown. The primary focus of this thesis is the organization and flexibility of glucan chains in crystalline lamellae. The organization and flexibility of glucan chains in native, annealed (ANN), and heat-moisture treated (HMT) normal, waxy, hylon V, hylon VII, and hylon VIII corn starches were examined. This study has shown for the first time that increased amounts of apparent amylose in B-type starches hinder the polymorphic transition (from B to A+B) during HMT. The research has also demonstrated that an iodine-glucan complex transformed the B-type polymorphic pattern of hylon starches into a V-type pattern. The differential scanning calorimetry (DSC) results showed that ANN- and HMT-induced changes were most pronounced in hylon starches. These findings suggest that the glucan tie chains influences the assembly of crystalline lamellae in high-amylose starches. The relationship between the internal unit chain composition of amylopectin, and the thermal properties and annealing of starches from four different structural types of amylopectin was investigated by DSC. The onset gelatinization temperature (To) correlated negatively with the number of building blocks in clusters (NBbl) and positively with the inter-block chain length (IB-CL). The enthalpy of gelatinization (∆H) correlated positively with the external chain length of amylopectin. Annealing results showed that starches with a short IB-CL were most susceptible to ANN, as evidenced by a greater increase in the To and Tm. The increase in enthalpy was greater in starches with long external chains and IB-CLs. These data suggest that the internal organization of glucan chains in amylopectin determines the alignment of chains within the crystalline lamellae and thereby the thermal properties and annealing of the starch granules.