TECHNOLOGY OF CEREALS Temperoture, C recently been found that is resistant to enzyme attack. Known as resistant starch, it behaves as Peak viscosity back viscos dietary fibre and is most abundant in autoclaved Setback amylomaize starch suspensions(Berry, 1988) setback Starch damage(see Chs 6 and 8) Granule damage of a pa properties of starch in some ways similar to gelatinization. Defining the exact type of damage is difficult and this accounts for the continued use of the general term. The essential characteris tics associated with damaged starch are somewhat Brabender arm Sogang. characteristics recorded oy the similar to gelatinized granules but there are differences also. Thus mechanical damage results the starch. Finally the paste is cooled to 30oC 1, increased capacity to absorb water, from and the increase in consistency is called set-back (Fig.3.9) 0.5-fold starch dry mass when intact to 3-4fold when damaged (gelatinized granules absorb as much as 20-fold) Retrogradation (see also Ch 8) ncreased susceptibility to amylolysis; Suspensions of gelatinized granules containing 3. loss of organized structure manifested as loss more than 3% starch form a viscous or semi-solid of X-ray pattern, birefringence, differential starch paste which, on cooling, sets to a gel. Three scanning calorimetry gelatinization endotherm dimensional gel networks are formed from the 4. reduced paste viscosidisoiaized granules amylose-containing starches by a mechanism 5. increased solubility, leading to leaching of known as 'entanglement. The relatively long amylose molecules that escape from the swollen amylose is preferentially leached( Craig and granules into the continuous phase become er angled at a concentration of 1-1. 5% in water. At a molecular level the disorganization of On cooling the entangled molecules lose transla- granules appears to be accompanied by fragmenta- tional motion, and the water is trapped in the tion of amylopectin molecules during damage network. Crystallites begin to form eventually at whereas gelatinization achieves loss of organization junction zones in the swollen discontinuous phase, without either polymer being reduced in size causing the gel slowly to increase in rigidity of wheat flour is important as it affects the amount Controlling starch damage level during milling (Osman, 1967). When starch gels are held for prolonged periods, retrogradation sets in. As of water needed to make a dough of the required applied to starch this means a return from a consistency( see ch 7)(Evers and Stevens, 1985) soluble, aggregated or crystalline condition Retrogradation is due largely to crystallization of Cell walls amylose, which is much more rapid than that The older literature describes the components of amylopectin. It is responsible for hardening of of cereal grain cell walls as pentosans and hemi- cooked rice and shrinkage and syneresis of starch celluloses. Pentosans are defined earlier in this gels and possibly firming of bread. Although chapter, but hemicelluloses are more difficult to regarded as crystalline, retrograded gels are define and indeed the term is even now only used susceptible to amylolysis, however a fraction has loosely Hemicelluloses were originally assumed62 TECHNOLOGY OF CEREALS Temperature, "C recently been found that is resistant to enzyme SVSU I Porta I Hold I cool attack. Known as resistant starch, it behaves as dietary fibre and is most abundant in autoclaved amylomaize starch suspensions (Berry, 1988). 30 55 95 ~ 95 53 Setback viscosity, C Peak viscosity 0 v) > c - Starch damage (see Chs 6 and 8) x f 4J Granule damage of a particular type alters the properties of starch in some ways similar to gelatinization. Defining the exact type of damage is difficult and this accounts for the continued use of the general term. The essential characteris￾tics associated with damaged starch are somewhat similar to gelatinized granules, but there are differences also. Thus mechanical damage results in: 1. increased capacity to absorb water, from 0.5-fold starch dry mass when intact to 34fold when damaged (gelatinized granules absorb as much as 20-fold); E a 2 40 60 90 Time (mid FIG 3.9 Chart showing characteristics recorded by the Brabender Amylograph. the starch. Finally the paste is cooled to 30°C and the increase in consistency is called set-back. (Fig. 3.9) Retrogradation (see also Ch. 8) 2. increased susceptibility to amylolysis; 3. loss of organized structure manifested as loss Suspensions of gelatinized granules containing of X-ray pattern, birefringence, differential more than 3% starch form a viscous or semi-solid scanning calorimetry gelatinization endotherm; starch paste which, on cooling, sets to a gel. Three 4. reduced paste viscosity; dimensional gel networks are formed from the 5. increased solubility, leading to leaching of amylose-containing starches by a mechanism mainly amylopectin. (In gelatinized granules, known as 'entanglement'. The relatively long amylose is preferentially leached (Craig and Stark, 1984).) amylose molecules that escape from the swollen granules into the continuous phase become en￾tangled at a concentration of 1-1.5% in water. At a molecular level the disorganization of On cooling the entangled molecules lose transla- granules appears to be accompanied by fragmenta￾tional motion, and the water is trapped in the tion of amylopectin molecules during damage network. Crystallites begin to form eventually at whereas gelatinization achieves loss of organization junction zones in the swollen discontinuous phase, without either polymer being reduced in size. causing the gel slowly to increase in rigidity Controlling starch damage level during milling (Osman, 1967). When starch gels are held for of wheat flour is important as it affects the amount prolonged periods, retrogradation sets in. As of water needed to make a dough of the required applied to starch this means a return from a consistency (see Ch. 7) (Evers and Stevens, 1985). solvated, dispersed, amorphous state to an Cell walls insoluble, aggregated or crystalline condition. Retrogradation is due largely to crystallization of amylose, which is much more rapid than that The older literature describes the components of amylopectin. It is responsible for hardening of of cereal grain cell walls as pentosans and hemi￾cooked rice and shrinkage and syneresis of starch celluloses. Pentosans are defined earlier in this gels and possibly firming of bread. Although chapter, but hemicelluloses are more difficult to regarded as crystalline, retrograded gels are define and indeed the term is even now only used susceptible to amylolysis, however a fraction has loosely. Hemicelluloses were originally assumed