Huan+Jia's Weekly+Lecture+Summary

= What is Hydrocolloid? =
 * Food hydrocolloids is a range of polysaccharides and proteins, also known as 'water soluble gum', 'gum', 'stabilisers'.
 * Primary functions: Thickening agents, Gelling or texturizing agents.
 * Secondary functions: Stabilisation of emulsions, suspension of particulates, control of crystallisation, encapsulation, formation of film.
 * Usage levels < 2%



= Factors affect gum properties =
 * molecular weight
 * monosaccharide composition
 * type of chains
 * number of side chains
 * distribution of side chains

= Main classes of hydrocolloids =
 * derivatives from exudation or sap of trees (e.g. cellulose, gum arabic, gum karaya, gum ghatti, gum tragacanth)
 * extract from seed (e.g. guar gum, LBG, tara gum, tamarind gum)
 * extract from seaweeds (e.g. agar, carrageenan)
 * microbial gums (e.g. xanthan, dextrun,curdlan)
 * extract from tubers (e.g. konjac)
 * extract from plant parts (e.g. starch, pectin, cellulose)

Thermoreversible gelling agents

 * 1) gelatin
 * 2) agar
 * 3) kappa carrageenan
 * 4) iota carrageena
 * 5) low methoxy (LM) pectin
 * 6) gellan gum
 * 7) methyl cellulose and hydroxypropyl cellulose
 * 8) xanthan gum and locust bean gum or konjac mannan

Thermally irreversible gelling agents

 * 1) alginate
 * 2) high methoxyl (HM) pectin
 * 3) konjac mannan
 * 4) locust bean gum

= __Pectin__ =
 * derived from peel of citrus fruits, apple pomace, sugar beet, sunflower heads.
 * primarily in the form of protopectin
 * types of pectin---High methoxyl pectin (HMP), DE> 50% and Low methoxyl pectin (LMP), DE< 50%

- High methoxyl pectin (HMP)

 * DE---58% to 75%
 * to form gel, soluble solid content 55-85%, pH 2.8-3.8. (e.g. jam and jellies)
 * ultrarapid/rapid set (DE as high as 77)---used in jam with whole fruits, to ensure uniform distribution of fruits particles.
 * slow set (DE~58) ---used in very acid fruits such as blackcurrant to avoid premature gelation.

- Low methoxyl pectin (LMP)

 * two sub-groups---Conventional low methoxyl pectin (LMP) and Amidated low methoxyl pectin (ALMP).
 * form gels in presence of calcium ions, low soluble solid content, wide pH range (1-7). Soluble solid can up to 85%.
 * LMP - less calcium ion reactive than ALMP---used as thickening agent in yogurt fruits.
 * ALMP - very calcium ion reactive---used in low sugar fruits preparatuin (e.g. low-sugar jam and jellies).

= = = Carrageenan = - Carrageenan is a highly refined extract of seaweed from the rhodophyta family. - Chemically its composition is a long chain of galactose residues linked, resulting in a long chain of high molecular weight. - There are a few examples food applications for carrageenan:
 * a) Iota carrageenan** - It is extracted from //Eucheuma Spinosum// seaweed.
 * b) Lambda carrageenan** - It is extracted from //Gigartina//, //Iriadeae// and //Chondrus crispus// seaweed.
 * c) Kappa carrageenan -** It is a extracted from //Eucheuma cottonii// and from //Chondrus crispus// seaweed.
 * water dessert gels: used in gelation
 * chocolate milk: used in suspension and mouthfeel
 * ice cream: used in wheying off prevention and control meltdown



= = = = = = = = = Alginate =
 * derived from brown seaweed ( //Laminaria hyperborea//)
 * made up of blocks of D-mannuronic acid (M-blocks) and L-glucuronic acid (G-blocks)
 * can form gel in presence of calcium ion in cold water; the gels is thermo-irreversible
 * provide excellent stabilizing effects in frozen products. (e.g. ice-cream)
 * act as thickeners and stabilizers in beverages (e.g. dry mix fruit drinks)
 * propylene glycol alginate with emulsification property, used as stabilizer in emulsion (e.g. mayonnaise) [[image:images_(9).jpg width="225" height="188"]] [[image:images_(8).jpg width="275" height="266"]]

= Gum Arabic =
 * derived from //Acacia senegal// L
 * dissolve easily in hot/cold water
 * least viscous and most soluble of all hydrocollods-up to 55%solid concentration can be used
 * uses of gum arabic:
 * to retard sugar crystallization & to promote emulsification
 * encapsulation agent to encapsulate volatile flavour compounds
 * promoting stabilisation in beer foam
 * emulsifying agent and stabilizer in soft drinks

= Locust Bean Gum (LBG) = = = = = = = = = = Guar Gum = > ==
 * derived from seed of carob bean ( //Ceratonia siliqua//)
 * insoluble in cold water, must be heated to dissolve-max viscosity develop when heated to~95 degree celcius, then cooled
 * does not form gel by itself but form gel when combined with xanthan gum
 * primary functions: thickening, stabilization of emulsions, inhibition of syneresis
 * used in canned foods, sauces, desserts, ice-cream, processed meat
 * more highly substituted than LBG, more soluble, hydrates fully in cold water giving high viscosity
 * non-gelling---used as viscosity builder, stabilizer, water binder
 * =**very stable from pH 4-10** =

= Xanthan Gum =
 * produced from fermentation of CHO substrate with //Xanthomonas campestris//
 * completely soluble in cold water, produce high viscosity at low concentration[[image:foodingredients/20435_303663769104_303659739104_3179222_2511255_n.jpg align="right"]]


 * excellent stability to heat and pH
 * viscosity remain unchanged across temperature range (0-100 degree celcius), pH 1-13
 * used as a thickening, suspending and stabilizing agents.

= Cellulose Derivatives =
 * chemically modified cellulose
 * alkaline treatment converts cellulose into ether
 * examples---carboxymethylcellulose (CMC), hydroxypropylmethylcellulose (HPMC)
 * very clear solution, stable over pH 4-10
 * used as thickener, suspending and stabilizing agents. Modify flow characteristics.
 * used in fried foods---create a barrier to oil absorption, retard loss of moisture, improve adhesion of batter.

= Relative Ranking of Gum Properties =
 * 1) solution claity
 * 2) solubility at various temperature
 * 3) gelling vs thickening
 * 4) suspension ability
 * 5) "natural" vs "not natural"
 * 6) ability to tabilize protein at low pH
 * 7) acid stability
 * 8) relative cost per unit weight

= Gelatin =
 * high MW polypeptide derived from collagen by acid or alkali treatment
 * 2 types of gelatin:
 * Type A : derived from acid processed materials,primarily porkskin
 * type B : derived from alkaline or lime processed materials,primarily cattle or calf hides and ossein
 * rich in proline & hyroxyproline which contributes to the gelling ability of gelatin
 * used in gelled jelly, yogurt, fruit iuices, top quality ice-cream and frozen produts, gummy bears, etc

-functional properties

 * gel formation
 * water binding
 * texturizing
 * thickening
 * emulsion formation anfd stabilisation
 * foam formation and stabilisation
 * film formation
 * adhesion/cohesion
 * protective colloidal function