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1、Chapter 7 Starch processing 知识点知识点2 Starch propertiesStarch properties1.Gelatinization,Pasting and Gelation When starch is heated in waterHydrogen bonds break,allowing water to enter the granule and the granule swellsAmylose migrates out of the granuleH-bonding between water and amylopectin increase
2、sReduced free water changes the viscosity of the starch mixture,thickening it Gelatinization and PastingStarch gelatinisation is the collapse(disruption of molecular order)within the starch granule,manifested in irreversible changes in properties such as granular swelling,native crystalline melting,
3、loss of birefringence and starch solubilisation.Gelatinization and PastingPasting is the phenomenon following gelatinisation in the dissociation of starch.It involves granular swelling,exudation of molecular components from the granule;and eventually the total disruption of the granules.Gelation As
4、a starch paste cools,a gel is formed.Free amylose molecules lose energy as the temperature decreases and form hydrogen bonds.The bonds create a network that holds the swelled granules in place.Raw,uncooked starch granulesheated in waterSwelling is evidentNotice loss of amylose from the granulesGelatinization and pasting are complete Some granules have collapsed.Now we start to cool.GelationNotice areas of association.These arecalled junction zones.This picture is not yet complete as we havent accounted for the water in the system.waterwaterwaterwaterwaterwaterThis is a starch gel