what is the main function of gums? what are other functions?
main function: to increase viscosity
others
- water retention
- thickening and gelling
- texture
- emulsion stabilizer
- protective colloids
- clarifying agents
- foam stabilizers
- prevention of formation of ice crystals
how can natural gums be derived?
from tree exudates/extracts, seeds, roots or seaweed extracts
what gums are produced from tree exudates or extracts?
- arabic
- gum tragacanth and karaya
what gums are produced from seeds or roots?
- locust bean gum
- guar gum
what gums are produced from seaweed extracts?
- agar
- alginates
- carrageenan
- furcellaran
what gums are produced from bacterial fermentation?
- xanthan
- gellan
describe main properties of arabic gum
- good emulsifier and stabilizer
- v soluble in water
- p newtonian rheological behavior
- good water retention
- good film forming properties
what are types of non-newtonian suspensions?
where is each of them found?
- pseudoplastic: emulsions
- thixotropy: high fatty food pdts
- dilatant: candy compounds
- rheopexy
what is the equation for viscosity, in respect to shear?
viscosity = shear stress / shear rate
what are main functions of arabic gum?
- texturizer in sugar and polyols
- film former avoiding fat, water, gas migration
- anticrystallizing hydrocolloid
- binder for sugar and polyols compressed pdts
- emulsifier for oil in water emulsion
- stabilizer for colloidal systems
describe gum tragacanth structurally
- slightly acidic salt with:
1. insoluble bassorin
2. water soluble tragacanthin (Arabinogalactan)
what are main properties of tragacanth gum?
- hi bifunctional emulsifier
- psudoplastic suspension
- good water retention
- high thermal stability
- acid stable and resistant
- good film forming properties
- unusually stable to microbial attack
- compatible w/ most gums except arabic gum
what gum is tragacanth gum now compatible with?
arabic gum
what are main technical functionalities of tragacanth gum?
- water binding agent
- bifunctional emulsifier
- bodying agent
- creamy mouthfeel
- adhesive
- suspending agent
- thickener
describe the structure of locust bean gum (LBG)
polysaccharide composed of galactose and mannose units (galactomannan)
higher ratio of mannose to galactose than guar gum
compare and contrast locust bean gum (LBG) to guar gum
LBG has higher ratio of mannose to galactose
the two gums interact synergistically b/c they have slightly different properties
describe gelling properties of LBG
- can’t gel by itself
- imparts elasticity to agar and kappa carrageenan gels
- forms a gel when mixed with xanthan gum
compare how LGB effects calcium alginate gels
- LGB has opposite effect on properties of calcium alginate gels
- elasticity is reduced with little change in break strength
describe stability of LGB
- stable to acid
- unstable to retorting and freezing
describe the structure of guar gum
polysaccharide made of galactose and mannose (galactomannan)
describe the thixotropic properties of guar gum in high vs low concentrations
high concentrations: very thixxotropic
low concentrations: les thixotropic
compare solubility and emulsification abilities of guar gum to LBG
guar is more soluble and a better emulsifier
is guar gum affected by ionic conc or pH?
no, b/c it is non-ionic
but it will degrade at pH extremes and temps
compare the viscosity properties of guar gum with xanthan or LBG
guar is synergistic with xanthan and LBG
but viscosity is more when either one is used alone
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