Starch

the predominant food reserve in plants provides dietary calories to humans used in foods for thickening, binding and gelling sources include cereal grains and roots

vary in size and shape based on their origin contain two polysaccharides: amylose and amylopectin

makes up 15-30% of the granule dense, long and largely unbranched long chain of d-glucose connected by alpha 1-4 linkages

makes up 70-85% of the granule d-glucose residues with an alpha 1-4 linkage branched with alpha 1-6 linkages chains form helices through hydrogen bonding which clump to form crystallites which line up to form crystalline (structured) and amorphous regions (unstructured) giving the appearance of growth rings easily digested

Maltese cross

• must be heated in excess water which leads to irreversible changes in the ordered structure of the starch granule, it swells causing a loss of biofringence • the crystalline melts causing the helixes to unwind • amylose leaches out leading to starch solubilisation which increases viscosity • the amylose gels on cooling

heating flour coats granules which separates them starch swells gradually boiling disintegrates granules retrogradation upon calling allows amylose to assemble into a network dextrinisation shortens chains giving a thinner sauce

Dextrinization is the process involving the browning of starch foods when subjected to dry heat. It is defined as the breakdown of starch into dextrins (disaccharides) and it is a non-enzymatic browning and chemical change which is easily digested as partial breakdown is complete

corn starch - cooks to a clear, translucent gel rice starch - soft, translucent gel potato starch - stringy transluscent solution

reduces water access proteins compete with starch for limited water limited granule expansion

granules swell bulging cells separate

water evaporates and fat enters when cooked at high temperatures dextrinisation occurs and forms a crust, colour, texture, flavour starch granules do not swell due to lack of water

• starches that have not been chemically processed • have a desirable functionality • e.g. maize starch

waxy maize, rice, tapioca

instant, preheated with water to gelatinise to a specific point then rapidly dried to make a powder

they produce a consistent product

it is an enzyme in salvia that breaks down food in the mouth stomach pH and more amylase (which is released during pancreatic stimulation) further break down glucans in the small intestine

disaccharide enzymes

acid modified cross linked stabilised

• 25% of all food starch • strengthens structre • resistant to pH and shear • slow to gelatinise • e.g. canned fruit pie fillings

found in plant cell walls, component of dietary fibre, chains bound via hydrogen bonding, provide strength

brown seaweed, thickener

thickener found in fruit, used in jam

no-only energy and protein