Fat (3.9%) Protein (3.3%) Lactose (5.0%) Minerals (0.7%) …€¦ ·  · 2014-09-113.091 Introduction to solid M. J. Cima state chemistry Figure 1. A scanning electron micrograph

3.091 Introduction to solid state chemistry M. J. Cima

Constituents of Milk

• Fat (3.9%) • Protein (3.3%) • Lactose (5.0%) • Minerals (0.7%) • Water (87.1%)

Ice Cream Contents

• Whole milk

• Skim milk

• Cream

• Frozen cream

• Butter

• Egg

• Butter oil

• Condensed milk

• Dried milk

• Sugar

• Stabilizer

• Emulsifier

• Flavorings

• Water

• Air

3.091 Introduction to solid state chemistry M. J. Cima

3.091 Introduction to solid state chemistry M. J. Cima

Ice nucleation

Blade rotation

3.091 Introduction to solid state chemistry M. J. Cima

3.091 Introduction to solid state chemistry M. J. Cima

Figure 1. A scanning electron micrograph of ice cream (courtesy of M Kirkland, Unilever R&D Colworth). The scale bar is 100 µm. Ice crystals, air bubbles and sugar solution are marked. The fat droplets are too small to be seen at this magnification.

Microstructure of Ice Cream

3.091 Introduction to solid state chemistry M. J. Cima

Figure 5. Ice crystals recrystallizing (courtesy of M Izzard, Unilever R&D Colworth). (a) Ice crystals at -10 .C. (b) warmed up to -7 .C: the smallest crystals melt. (c) Then cooled back down to -10 .C: the ice reforms on the surviving crystals, which become larger.

(a) (b) (c)

Coarsening of Ice Crystals

3.091 Introduction to solid state chemistry

M. J. Cima

Theobroma cacao

Chocolate is made from the

seeds of the tree

Theobroma cacao.

Theobroma is Greek for

'food of the gods'. The

ancient Aztecs venerated

the cacao tree and used its

beans as a form of

currency. They saw the tree

as a source of strength and

wealth and assigned their

god Quetzalcoatl its

guardian

80% of cells in the bean store protein and fat to

nurture the germinated seedling

The rest contain defensive chemicals.

Purple dots contain astringent phenolic

compounds and bitter agents such as

theobromine

bean

pulp

antioxidants

3.091 Introduction to solid state chemistry

M. J. Cima

Food of the Gods

Known to Olmec, Maya, and Aztec cultures

Used as currency

Frothed by pouring from vessel to vessel or by whisking

whisk Native Americans Preparing and Cooking Cocoa.

Ogibe's "America," 1671

3.091 Introduction to solid state chemistry

M. J. Cima

Fermentation of pulp

heap

box • Mixed fermentation of the pulp

• Seed is effected as cells are lysed allowing phenols

to reacts with protein and oxygen

• Digestive enzymes convert storage proteins into

amino acids and simple sugars which are much

more reactive

• pH goes from 6.45 to 4.5 in 120 hrs

• Acetic acid from 0 to 1.36%

• Lactic acid from 0.005 to 0.12%

• Oxidative browning

Conversion of carbohydrates to

alcohol or acid

3.091 Introduction to solid state chemistry

M. J. Cima

Drying

Water content reduced to 5 - 8%

Composition of dried fermented beans

Water 5%

Cacao butter 54%

Protein and amino acids 12%

Starch 6%

Fiber 11%

Sugars 1%

Phenolic compounds 6%

Minerals 3%

Theobromine 1.2%

Caffeine 0.2%

3.091 Introduction to solid state chemistry

M. J. Cima

Roasting (non enzymatic browning)

arginine

3.091 Introduction to solid state chemistry M. J. Cima

55% cocoa butter

8-24% cocoa

butter

Van Houten

(Dutch)

extracted cocoa

butter in 1825

Rudolphe Lindt

(Swiss) started

adding extra

cocoa butter

during chocolate

manufacture in

the 1880s

3.091 Introduction to solid state chemistry M. J. Cima

Compositions of chocolate

3.091 Introduction to solid state chemistry

M. J. Cima

Conching • Large heavy roller in open container

kneads, blends, and grinds the mixture.

• Can take several days

High water content turns chocolate to a

thick paste. Emulsion starves oil phase

of surfactant and extracts sugar

3.091 Introduction to solid state chemistry

M. J. Cima

Conching and rheology • Four different types

of equipment used

(different shear

histories)

• No change in sugar

or liquor particle size

noted

• Addition of lecithin

(surfactant) has

dramatic affect on

viscosity

• Conching primarily

removes water and

acid as well as

dispersing particles

3.091 Introduction to solid state chemistry

M. J. Cima

Lecithin

A mixture of phosphatidylcholines

3.091 Introduction to solid state chemistry M. J. Cima

Fatty acid Structure

oleic acid CH3(CH2)7CH=CH(CH2)7COOH

myristic acid CH3(CH2)12COOH

palmitic acid CH3(CH2)14COOH

stearic acid CH3(CH2)16COOH

lauric acid CH3(CH2)10COOH

butyric acid CH3CH2CH2COOH

caproic acid CH3(CH2)4COOH

capric acid CH3(CH2)8COOH

caprylic acid CH3(CH2)6COOH

linoleic acid CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH

linolenic acid CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH

Fatty acids

3.091 Introduction to solid state chemistry M. J. Cima

Triglycerides

3.091 Introduction to solid state chemistry M. J. Cima

3.091 Introduction to solid state chemistry M. J. Cima

β-form

3.091 Introduction to solid state chemistry M. J. Cima

β-trimyristin or -MMM

3.091 Introduction to solid state chemistry M. J. Cima

CLC β’ structure

3.091 Introduction to solid state chemistry

M. J. Cima

Stability and properties of the polymorphs

Relatively high plasticity

Not nucleated from the melt.

Only known to form from solid state phase

transformation

Provides correct

melting range and

great “snap”

3.091 Introduction to solid state chemistry M. J. Cima

Solidification and form selection

Melt temperature

Solidification temperature

New form created

3.091 Introduction to solid state chemistry

M. J. Cima

Homogeneous nucleation and polymorphs

3.091 Introduction to solid state chemistry M. J. Cima

Composition and crystallization conditions

3.091 Introduction to solid state chemistry M. J. Cima

Bloom and poor tempering

3.091 Introduction to solid state chemistry

M. J. Cima

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