Polymorphism

Polymorphic forms are solid phases of the same chemical composition that differ among themselves in crystalline structure, but yield identical liquid phases upon melting.

Crystal Stability

Monotropic - one stable crystal form and one meta stable regardless of temperature change

Enantiotropic - each from has a definite temperature range of stability

Triglycerides are monotropic

Stearic Acid

Oleic Acid

Trilaurin

Triglycerides

Polymorphic Forms

a forms upon cooling from the melt

Upon further cooling b forms form

Heating a to its melting temperature yields b' forms

Crystal Forms

Crystal Properties

Characteristics

Alpha Crystals

Beta prime Crystals

Beta Crystals

b Fats

Some fats tend to spontaneously form b crystals:

Soybean Peanut Corn Safflower

Olive Coconut Lard Cocoa Butter

b' Fats

Fats the crystallize in the b' form include:

Cottonseed Palm Rapeseed milkfat tallow Modified lard

Triple Chain Length

Double Chain Length

Shortenings

Incorporation of air, plasticity, consistency and solid-liquid ratio are important characteristics of shortenings that depend, in part, on polymorphism.

b' Crystals - large amounts of small air cells- Yields whiter, creamier product that is tender and has a smooth texture

b Crystals - small amounts of large air cells - Yields large clustered crystals with a waxy or grainy texture

Enrobing

Cocoa Butter - 80% composed of disaturated triglycerides

SOS = 20%

POS = 55%

POP = 5%

POS determines the texture of cocoa butter

POS:

Alpha form 17° C

Beta Prime 27° C

Beta 35.5°C

Beta prime gives small crystal structure which leads to bloom

Lard

Natural lard mostly OPS (64%) tends to form beta crystals and is poor at air incorporation.

Randomized lard is less ordered and it is harder to form beta crystals. Beta prime incorporates more air.