Effect Of Extrusion And Salt On The Quality Characteristics Of High Amylose Maize

High amylose maize is defined as the ration of amylose to the total starch > 50%, which posesses special physicochemical, nutritional and healthy properties due to its special amylose/amylopectin ratios, thus bringing great economic potential and social benefits to food and other industries. Regarding high amylose maize H3(Aa188XB1421-1), normal maize Shandan 609, waxy maize starch(Roquette, Italy), normal maize starch(Cargill, United States) and high amylose maize starch(Ingredion, UK) as experiment materials, this research studied the effect of extrusion treatment and salt on the quality characteristics of high amylose maize flour and maize starch with different amylose/amylopectin rations in order to provide theoretic guidance and related processing parameters for upper-stream the breeding of high amylose maize and down-stream food processing and exploitation of functional food. The thesis analyzed the effect of non-starch components on morphology and physicochemical properties of high amylose maize flour, the effect of extrusion treatment on morphology, physicochemical properties and functional profiles of high amylose maize flour and the effect of salt on physicochemical properties, rheological characteristics and saltiness perception of maize starch with different amylose/amylopectin rations respectively. The results are as following:1. SEM images showed that protein, lipid and other substances existed on the surface or embedded in the gap among starch granules. According to the DSC data, the T0, Tp and Tc of high amylose maize flour and starch were significantly higher than normal maize flour and starch. The enthalpy(?H) of high amylose maize flour and starch was lower than normal maize flour and starch. But the enthalpy(?H) of maize flour was greater than maize starch.Regarding RVA results, the through viscosity and peak viscosity of normal maize flour were lower than normal maize starch, while high amylose maize showed an opposite trend.The final viscosity, breakdown viscosity, setback viscosity of maize flour were greater than that of maize starch. However the solubility and swelling power of maize flour were higher than maize starch.2. The extrusion treatment raised the detectability of the protein, fiber, ash content and degree of gelatinization and the greater the DG value, the greater the disruption level of starch granules; The DSC results showed that the extrusion treatment made the structure of high amylose maize flour more stable, which needed more energy to destroy its structure; The RVA results exhibited that the extrusion treatment decreased the viscosity of maize flour; The XRD results displayed that the crystal type of normal maize flour and high amylose maize flour transformed from A-type and B-type into B+V type under extrusion treatment; The solubility and swelling power showed that the extrusion treatment increased the solubility of maize flour and make the swelling power going down with temperature growing; The digestion in vitro indicated that the extrusion treatment increased rapidly digested starch(RDS) content, decreased slowly digested starch(SDS) content of maize flour and rasied resistant starch(RS) content of normal maize flour while reduced RS content of high amylose maize flour. However, extruded high amylose flour still retained higher RS content of extruded normal maize flour.3. The swelling power results showed that salt inhibited the swelling process of starch granules and the higher salt content, the lower swelling power; The DSC results displayed that to destroy the crystal structure of starch granules needed more energy with amylose content and salt content increasing; The RVA results exhibited that the pasting curves moved toward the right direction when raising amylose content and salt content, indicating that the pasting process requested higher temperature and more time; The rheological testing showed that salt raised the gelatinization temperature of waxy maize starch and normal maize starch to prolonged the gelatinization process, the higher salt content, the stronger the inhibition effect; the storage modulus(G’), the loss modulus(G’’) and apparent viscosity of starch in 0.6% salt content were higher than that in 2.0% salt content; During frequency sweeping, the G’ and G’’ of normal maize starch were highest, while high amylose maize starch was lowest and the G’ and G’’ of starch in 0.6% salt content were greater than that in 2.0% salt content, but the G’’ of high amylose maize starch showed no change; The rheological behavior of normal maize starch and waxy maize starch exhibited liquid-like because of increasing tanδ while high amylose maize starch displayed solid-like due to decreasing tanδ; The sensory evaluation indicated that the saltiness perception and mouthfeel attributes of high amylose maize starch were best while waxy maize starch was poorest at 50 s-1 shear rate, 180 mPa.s and 0.6% salt content.