Studies On The Pea Starch Modified By Citric Acid

Peas are cultivated in many regions of the world, field pea ranks fourth in terms of the world production of food legumes below soybeans, peanuts and dry beans. The total world dry pea production is more than 10,000,000 m.t.. However, due to the differences from cereal and potato starch in composition, structure, physical and chemical properties, such as higher amylose content and strong retrogradation, pea starch's utilization is limited. The modification of pea starch is required seriously.Citrate starch is a kind of resistant starch, which is resistant to enzyme digestion and increase the necessary dietary fiber of the body. So, it is widely used in bread, biscuits and other food products in order to improve the quality of food.In this thesis citrate pea starch (CPS) with good performance was synthesized based on the method of Klaushofer et al. with some modifications. The raw materials were pea starch and citric acid, NaOH was the catalyst. Use of the dry method could streamline operations, get high yield and avoid pollution.First, the optimal reaction conditions were confirmed through orthogonal test: Reaction temperature: 140oC, Reaction time: 7h, pH: 3.5, Citric/starch weight ratio: 2/5. And the influence of every single condition was also analysed. Then FT-IR, 13CNMR, SEM were used to study the structure of CPS. The viscosity, swelling power and TG were also measured. In the course of the experiment, rice starch was used as a contrast. The results showed that: The esterification was happened between citric acid and starch, the crystallinity declined. However, the microscopic appearance of most CPS granules were nearly the same as pea starch. Citrate starches did not swell and gelatinize during the pasting test process and starch granules with citrate substitution resist granular swelling. Starch thermal stability declined, because of the introduction of citric acid.In this thesis the application of CPS in the TPS was also studied. From SEM, TG, WVP et al., the material properties were measured. The results showed that: After adding CPS, the elongation at break and tensile stress of TPS were increased in certain conditions, and the WVP was decreased. The thermal stability of CPS/TPS was a little lower than TPS.