Hui+Qin's Weekly+Lecture+Summary

= **Lecture Summary** =

**Week 1- week 5**
**(Gums and stabilizers)** **FOOD HYDROCOLLOIDS= A RANGE OF POLYSACCHARIDES AND PROTEINS** **-GUMS', 'STABILIZERS'** __Functions:__ primary: Secondary:
 * Thickening agent
 * Gelling or texturizing agents
 * Stabilisation of emulsion
 * Suspension of particulates
 * Control of cystallisation
 * Encapsulation
 * Formation of film

use<2%, if> 2%=very viscous

structure of hydrocolloid polymer

__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 tree
 * extract from seed (Locust bean gum)
 * extract from seaweeds (carrageenan)
 * microbial gum (xanthan gum)
 * extract from tubers (konjac)
 * extract from plant parts (pectin)

**__Thermoreversible gelling agents__** *Gel formed on heating or cooling and the process is reversible eg: gelatin, agar, kappa-carrageenan, Iota-carrageenan, LM pectin, HPMC.

__Thermally irreversible gelling agents__
*heating will not form solution eg: alginate, starch, konjac, HM pectin.

__Pectin__

 * derived from peel of citrus fruits, apple pomace, sugar beet, sunflower heads.
 * types of pectin---High methoxyl pectin (HMP), 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.



- DE < 50% — two sub-groups: Conventional low methoxyl pectin (LMP) and Amidated low methoxyl pectin (ALMP) - Form gels in the presence of Ca2+, with a low solids content & wide pH range (1-7) [but soluble solids can be up to 85%] - LMP – less Ca2+ reactive than ALMP ⇒ used as a thickening agent in yoghurt fruit - ALMP – very Ca2+ reactive ⇒ assist gelation in low sugar fruit preparations, e.g. low-sugar jams & jellies
 * __Low methoxyl pectin (LMP)__ **

**__Guar Gum__**
 * a linear chain of mannose with single galactose units atteched as side chains
 * more highly substituted than LBG
 * more soluble and hydrate fully in cold water giving high viscosity
 * non gelling- for stabilizer and water binding


 * chemical structure of guar gum**

**__Carrageenan__**
 * kappa-Carrageenan
 * Lambda-Carrageenan (cannot form gel)
 * Iota-Carrageenan







> >