Starch plants

Starch granule in plant cell

Cassava starch Canna starch Mung bean starch

Barley & Wheat starches; large A granules:  m (disk shape) small B granules: < 10  m (spherical/irregular shape)

Starch granule structure Semi-crystalline structure -Amorphous phase (gel phase) -Crystalline phase (15-45%) The granule structure is due to amylopectin, and based on a super helical structure in which the double helices wind around each other

Growth Ring

Granule structure

Cluster

A-, B-, and C- chain of amylopectin A-chain : those that are linked to the rest of the molecule only through their reducing ends B-chain : those that are linked to the rest of the molecule through their reducing ends but, in addition, are branched at a C-6 position in one or more of their glucose residues C-chain : is the one that bears the reducing end group

Amylopectin Helix Hybrid amylose/amylopectin helix V-amylose helix Free lipid Free amylose 15 nm 6 nm 4 nm

Composition of raw materials Starch VS Flour

Composition of Starch Major components: starch Amylose (15-30 %) Amylopectin (70-85%) Minor components: Lipids ( %) Protein ( %) Phosphorus ( %, ppm)

Composition of Starch

Amylose Starch Molecules

Amylopectin

180/16 2

Reducin g end

Amylose -linear polymer containing 500-5,000 glucose units -extent of branching varies from 5-20 per molecule -forms inclusion complex with iodine and various organic compounds (butanol, fatty acids, phenol, surfactants, hydrocarbon,..) -Molecular size: potato, tapioca > maize, wheat -content: maize, wheat> potato, tapioca

Chain length (glucose unit) Number of helix turns color 122None Brown Red Purple >459Blue

Amylopectin -highly branched structure -branch chain length: DP units. (aver. DP 22-28) -the glucose units with an alpha-1,6 linkage are the branching points and make up about 5% of the total glucose units -branches of amylopectin are arranged in a cluster -cluster; alternating regions of ordered tightly packed parallel glucan chains and less ordered regions composed mainly of branch points -OH groups tend to attract each other (H-bond) and thus preventing the dissolution of starch granules in cold water -MW of amylopectin is about 1000 times of MW of amylose

Minor Components -tuber (potato) and root (tapioca) starches contain a small percentage of lipids (≈ 0.1%) -common cereal starches (maize, wheat, rice, sorghum) contain % lipid) -Fatty acid substances in cereal starches are predominantly free fatty acids (palmitic, linoleic, oleic in maize starch)/phospholipids (in wheat starch) -have a tendency to become rancid on storage 1. Lipids

Tend to reduce the swelling and solubilization of cereal granules -lipids form complex with amylose > 125  C are required to disrupt the organized native amylose-lipid complex structure in cereal starch granules

2. Proteins -Tuber and root starches contain ≈ 0.1% proteins -Cereal starches (maize, wheat) contain ≈ % proteins -have a tendency to foam 3. Phosphorus -in cereal starches; mainly present as phospholipids -tapioca starch contain a low amount of phosphorus compounds. -Potato starch contains as appreciate amount of chemically bound phosphate groups (at C-6 of amylopectin, 1 phosphate group per glucose units).

B-type pattern is typical to tuber and root starches (Hoover, 2001) and is characterized by a small peak at 5.6 , only one peak at 17  and a doublet at 22  and 24 . Mung bean and cassava starch, displayed A–type pattern (a doublet at 17  and 18  and a single peak at 23  ). Even cassava is a root starch, but has been shown A-type (or C A -type in some reports)

Amylopectin double-helical chains can either form the more open hydrated Type B hexagonal crystallites or the denser Type A crystallites, with staggered monoclinic packing, dependent on the plant source of the granules. Type A is found in most cereals with Type B being found in some tubers and high amylose cereal starches.

Starch Properties Swelling and Gelatinization Native starches are insoluble in water (below gelatinization temp.) due to H-bond In cold water “limited reversible swelling”

Swelling and Gelatinization “irreversible loss of the crystallites in the granules, all molecules in granule are accessible to water and will swell irreversibly” Gelatinization Conditions: -Heat and excess water -dissolve in solvents; alkali. DMSO, CaCl 2 at 25  C

Semi-crystalline native granule Swollen amorphous granule Heat Heat + Shear Gelatinization Pasting Cooling Short term storage Amylose retrogradation (gelation) Crystallization of amylose-lipid complex long term storage Amylopectin retrogradation Starch Conversion

Heating starch in water; sequence of events 1.Swelling begins in the least organized, amorphous, intercrystallite regions 2.As this phase swell, it exerts a tension on the neighboring crystallites and tend to distort them 3.Further heating leads to uncoiling/dissociation of double helical regions and break-up of crystallite structure. Liberated amylopectin chains become hydrate, excerting increased stress on the remaining crystallites. 4.Smaller, linear amylose molecules diffuse out of the swollen granule 5.Further heating and hydration weaken the granule and a sol results

2. ลักษณะของเจลแป้ง ก่อนขึ้นรูปฟิล์ม รูปที่ 1.8 ลักษณะเม็ดแป้ง พุทธรักษากินได้พันธุ์ไทยม่วง

รูปที่ 1.9 ลักษณะของเจลแป้งเมื่อให้ความร้อนที่ 80 0 C นาน 5( ซ้าย ), 20( กลาง ) และ 60( ขวา ) นาที รูปที่ 1.10 ลักษณะของเจลแป้งเมื่อให้ความร้อนที่ C นาน 5( ซ้าย ), 20( กลาง ) และ 60( ขวา ) นาที

Heating of starch

Molecular solubilization of starch starches cooked at 95  C for one hour may still contain highly swollen, hydrated starch aggregates. True solubilization of all starch substance occur normally at  C Tuber, root and waxy starches can be cooked to a completely dissolved state at about 100  C Maize starch required about 125  C amylomaize starch about 150  C

Viscosity rise at the pasting peak is due to; 1.Loss of water from the continuous phase to the inside of starch granules 2.Migration of amylose or other solubles from the granules into the continuous phase 3.Increasing size of the starch granules as they occupy more and more volume in the liquid phase

Behavior of amylose in solution (retrogradation)

Factors affecting the retrogradation of starch amylose/amylopectin ratio amylose/amylopectin size and structure starch concentration temperature other components (lipids)

Maize starch pastes and solutions retrograde ralatively quickly -high amylose (28%) -small molecular size of amylose -high lipid (0.8%) amylose-lipid complex reduces hydration capacity Potato starch has low tendency to retrograde -low amylose (21%) -high MW of amylose -low lipid (0.1%)

Stabilization Preventing retrogradation (esterification/etherification)