BIET: Thickening and Gelling Agents

Thickening

chains of proteins and starches bump and loosely entangle

Gelling

• water and other particles are prevented from moving at all

• form large web that traps water and other molecules

Thermoreversibility

some thickening and gelling agents can be melted and re-liquified after cooling and setting

polysaccharides

• starches + gums

• many sugars

Protein

large molecules composed of chains of amino acids

Starches contain what two molecules

1. Amylose

2. Amylopectin

Amylose

• (pastry cream)

• higher concentration in seed/cereal starch

• cloudy and firm when cooled

• gel tightens/weeps overtime

• not freezer stable

• thicker cold than hot

• has a starchy taste

Amylopectin

• (blueberry pie)

• Higher concentration in root starch

• clear when cooled

• thickens; doesn’t gel

• less likely to weep

• freezer stable

• same consistency hot and cold

• neutral in flavor

starch gelatin is ________ thermoreversible

NOT

How is gelatin activated?

• heated with a liquid

• granules of starch absorb water

• fully gels at 200 F

what two factors impact gellation?

1. type of starch

2. amount of tenderizers

modified food starch

• starches that have been treated by the manufacturer to contain desirable features

• stability against excessive heat

Gelatin ________ Thermoreversible

IS

What is gelatin?

purified collagen protein from bones, skin, and connective tissue of animals

describe the two different types of gelatin

type A: pork

Type B: Beef/fish

How does gelatin gel?

• temp drops, proteins tangle

• begins at 68 F

• 24 hours before fully gelled

• melts between 80-90 F

Why must you be careful of using gelatin with tropical fruits?

Some tropical fruits contain an enzyme called “protease” which breaks down the proteins

What must be done to tropical fruits prior to being added to gelatin?

they must be heated and cooled

Pectin

• not thermoreversible

• present in all fruits in varying percentages

• extracted from cell walls of fruits

Agar

• technically thermoreversible at 185 F

• Polysaccharide derived from seaweed

• “vegetable gelatin”

• 8x stronger than gelatin