Colloid and surface phenomena aspects of Chocolate

Chin Kok Ooi

Teck Yu Sia

Anshu Verma

Shushan Munshi

CE 457/527

Introduction

Chocolates has a wide variety and found in common places

Has to meet consumer need Types of chocolates Good for health

Marketing

Designing chocolates Energy Size Price Efficiency Legal requirements

Advertisement

Components and Compositions

The ingredients of chocolateCocoa, cocoa butter, milk and sugar

Additional ingredientsLecithin(emulsifier) and flavoring

agents

Cocoa and Cocoa butter Both are obtained from the seeds of

‘Theobroma Cocoa’. ‘Cocoa beans’ grow in pods.

Cocoa and Cocoa butter General compositions of cocoa bean

Composition Per cent Composition Per cent

Moisture 6.3- 8.5 Cocoa Red 2.5- 5.0

Fat 46.9- 52.1 Ash 2.9- 4.8

Albuminoids 11.6- 21.1 Astringent matters 7.2- 8.6

Cellulose 3.3- 6.6 Cane sugar  

Alkaloids 0.3- 0.5 Starch 8.7- 12.6

Cocoa and Cocoa butter Alkaloids

Theobromine and caffeine Theobromine – 3,7-dimethyl-xanthine Caffeine – 1,3,7-trimethyl-xanthine

‘Cocoa red’– is formed during the drying of the beans by the action of enzymes on the glucosides.

Cocoa and Cocoa butter Special characteristics of cocoa butter:

The melting point of cocoa butter is between 32°C and 36°C.

In spite of low melting point, cocoa butter is hard and brittle at normal room temperature.

Help to prevent ‘fat bloom’

Milk Compositions of cow milk

Component Content (% w/w)

Water 87.3

Proteins (caseins & whey proteins) 3.3

Fat 3.9

Lactose 4.6

Minerals 0.65

Others (vitamins, organic acids, etc) 0.32

Milk Compositions of lipids in milk

Component Content (% of total fat)

Triglycerides 96-99

Diglycerides 0.3-1.6

Monoglycerides 0.02-0.1

Free fatty acids 0.1-0.4

Phospholipids 0.2-1.0

Sterols 0.2-0.4

Cerebosides 0.01-0.07

Sugar Sucrose

Combination of ‘glucose’ and ‘fructose’ Sugar bloom

Chocolate manufacturing process

Chocolate -coated goods

Chocolate manufacture

Press Cake

Breaking

Grinding

Sifting

Cocoa Powder

Enrobing

Plain or Milk Chocolate

Fermented and Dried Beans

Cleaning

Roasting

Breaking and Winnowing

Nib ShellNib-Shell Mixtures

Germ Separation Germ-free Nib

Milling

Cacoa-Mass

(Chocolate liquor)Cocoa manufacture

Alkalization Addition of Sugar, Flavor, Milk etc. and Cocoa Butter

Removal of excess moisture Mixing

Fat Pressing

Cocoa Butter

Refining

Conching

Tempering

Molding

Major function of these processes1. Fermenting and drying

Removal of adhering pulp Removal of moisture

2. Roasting Critical for flavor development

3. Winnowing Removal of seed coat Size selection of nibs

4. Milling Release of fat from cells

Major function of these processes

5. Cocoa manufacture Production of additional fat (cocoa butter)

6. Refining Grinding of sugar particles

7. Conching Reduction in viscosity

8. Tempering Pre-crystallization process

Chocolate flow propertiesChocolate exhibits non-Newtonian properties

For Newtonian fluid:

For Bingham fluid:

1 2 3D

o

Different types of rheogram: (1) Newtonian; (2) Bingham; (3) pseudoplastic(e.g. chocolate)

D Dpl

Steiner’s model for chocolate - adapted from Casson’s model for printer’s ink

 

where r, R are the inner and outer radius of the cylinder respectively, is the angular velocity, DN is the shear rate at the inner cylinder.

 CA = (1/slope)2 = (1/K1)

2 = plastic viscosity according to Casson;

 CA = (b/2)2 =K0

2 = yield value according to Casson

)3.....(....................................................................................................1

2

)2..(............................................................................................................../

)1.(......................................................................211

1

2

01

aD

Rra

KaK

Da

N

N

b=2K0

NDa)1(

)1( a

Casson rheogram according to OICC

Factors affecting the flow properties of chocolate Fat content:

0

2

4

6

8

10

12

28 32 36

% fat

Cas

son

pla

stic

vis

cosi

ty (

Pa.

s)

1

2

0

20

40

60

80

100

28 32 36

% fat

1

2

Influence of fat content on Casson parameters of two milk chocolates with 0.25% lecithin.(1) Fine chocolate with 5.7% particles > 20m; (2) moderaltely coarse chocolate with 16% particles > 20m.

Lecithin and other emulsifiers: immediate reduction in viscosity

Moisture content: increases viscosity Particle size distribution:

0

1

2

3

4

0 10 20 30 40 50

%>20 microns

Cas

son

pla

stic

vis

cosi

ty (

Pa.

s)

1

2

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50

%>20 microns

Cas

son

yie

ld v

alu

e (P

a)1

2

Influence of fineness on Casson parameters of two milk chocolates with 0.25% lecithin. (1) 30% fat; (2) 32% fat

Temper: increases viscosity Thixotropy: decreases viscosity Vibration: decreases viscosity Temperature:

0

1

2

3

4

5

40 50 60

temperature C

Cas

son

pla

stic

vis

cosi

ty (

Pa.

s)

2

1

0

20

40

60

80

100

120

40 45 50 55 60

Temperature C

Casso

n y

ield

valu

e (

Pa)

1

2

Influence of temperature on Casson parameters of two milk chocolates. (1) 34% fat, without lecithin; (2) 30% fat, 0.15% lecithin

Surface- active substances in chocolate

manufacturing Lecithin is the chief surfactant used

The other surfactants are: ammonium phosphatides (YN) polyglycerol polyricinoleate (PGPR)

The chief function are: reduce viscosity Reduce thickening due to moisture and temperature Modify the setting behavior of fat phase

Flow characteristics of plain chocolate with added surface-active lipids

Addition

Casson plastic viscosity(poise)

Casson yield value (dynes/cm2)

0.3% soy lecithin0.3% YN0.3% sucrose dipalmitite0.3% PGPR0.8% PGPR

6.110.38.632.520.3

9230166250

0

1

2

3

4

5

6

7

8

0 0.2 0.4 0.6 0.8 1

% lecithin

Cas

son

pla

stic

vis

cosi

ty (

Pa.

s)

1

2

0

10

20

30

40

50

60

70

80

0 0.2 0.4 0.6 0.8 1

% lecithin

Cas

son

yie

ld v

alu

e (

Pa)

1

2

Influence of soya lecithin addition on Casson parameters of two dark chocolates. (1) 33.5% fat, 1.1% water; (2) 39.5% fat, 0.8% water

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8

% addition

Ap

par

ent

visc

osi

ty (

Pa.

s)

4

3

2

1

Viscosity reduction of dark chocolate by soya lecithin and by synthetic active

lipids . Apparent viscosity determined at shear rate 15 s-1 and 50oC; initial apparent viscosity before addition: 19.5 Pa s or 195 poises. (1) Soya lecithin; (2) phospholipid YN; (3) sucrose dipalmitate; (4) polyglyceryl polyricinoleate, PGPR

Mechanism of viscosity reduction by lecithin

1. a monomolecular film is formed on the surface of the non-fatty particles by surfactant molecules.

2. reduction in internal friction by promoting the coating of sugar and cocoa solids by fatty medium.

3. increase in the amount of ‘free’ cocoa butter in the dispersion medium by displacement from the surface of solids.

4. prevention of agglomeration of sugar particles and cocoa particles by break down of any lattice-type structure between them.

5. absorption of moisture

Effect of lecithin on the stability of emulsions

Lecithin molecule at interface between water and oil

oil-in-water

water-in-oil

Types of emulsionsTypes of emulsions Oil

Creaming Sedimentation

Coalescence Separation

Creaming of emulsions: four phases

Chocolate – an emulsion of hydrophilic sugar and lipophilic cocoa particles in a continuous fat medium

Molecular structure of main phospholipids found in lecithin

Phospholipid structure at the interface of an emulsion

PACKAGING AND STORAGEMETHOD OF WRAPPING:

MOLDED CHOCOLATE BLOCKS.

CHOCOLATE COUNTLINES.

BOXED CHOCOLATE.

TWRIST WRAPPING.

MATERIAL FOR PACKAGING:

ALUMINUM FOIL.

REGENERATED CELLULOSE FILM (RCF).

PLASTIC FILM.

MOLDED CHOCOLATE BLOCK

Protection against dirt, moisture and taint. It is more economical . Wide surface for labeling.

CHOCOLATE COUNTLINES

Normally wrap in “pillow pack” By heavy-backed foil, waxed paper or

glassine. Protection against moisture vapor and taint.

BOXED CHOCOLATE

Usually, a thin layer of greaseproof film includes at the inner fitment.

It prevents crushing of sweetness and cushioning.

Protect against handling dirt.

TWRIST WRAPPING

In “double end fantail” form. By aluminum foil, backed and unbacked plain

sliver, colored and printed film. Protection against dirt and taint.

ALUMINUM FOIL

Best barrier for water vapor and gas transmission.

Thickness range from 7-12 m for pure aluminum.

Combination with special alloy for extra strength.

Thickness range 7-8 m.

REGENERATED CELLULOSE FLIM (RCF)

Packaging in flexible form. Usually coated or giving other treatments. Protection against moisture vapor and taint. PVDC for extra protection such as

electrostatics. An advantage for tear strip product.

PLASTIC FILM

Three different forms: polyethylene, polyvinyl chloride and polyester.

Available in film or coating purposes. Protection against moisture, gas and

ultraviolet.