Transcript Colloid and surface phenomena aspects of Chocolate CE 457/527 Chin Kok Ooi

Colloid and surface phenomena
aspects of Chocolate
CE 457/527
Chin Kok Ooi
Teck Yu Sia
Anshu Verma
Shushan Munshi
Introduction
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Chocolates has a wide variety and found in
common places
Has to meet consumer need
Types of chocolates
Good for health
Marketing
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Designing chocolates
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Energy
Size
Price
Efficiency
Legal requirements
Advertisement
Components and Compositions
The
ingredients of chocolate
Cocoa,
cocoa butter, milk and sugar
Additional
ingredients
Lecithin(emulsifier)
agents
and flavoring
Cocoa and Cocoa butter
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Both are obtained from the seeds of
‘Theobroma Cocoa’.
‘Cocoa beans’ grow in pods.
Cocoa and Cocoa butter
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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
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Alkaloids
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Theobromine and caffeine
Theobromine – 3,7-dimethyl-xanthine
 Caffeine – 1,3,7-trimethyl-xanthine
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‘Cocoa red’– is formed during the drying
of the beans by the action of enzymes on
the glucosides.
Cocoa and Cocoa butter
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Special characteristics of cocoa butter:
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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
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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
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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
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Sucrose
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Combination of ‘glucose’ and ‘fructose’
Sugar bloom
Chocolate manufacturing process
Fermented and Dried Beans
Cleaning
Roasting
Breaking and Winnowing
Nib-Shell Mixtures
Nib
Shell
Germ Separation
Germ-free Nib
Milling
Cacoa-Mass
(Chocolate liquor)
Cocoa manufacture
Chocolate manufacture
Alkalization
Addition of Sugar, Flavor, Milk etc. and
Cocoa Butter
Removal of excess moisture
Mixing
Fat Pressing
Refining
Press Cake
Cocoa Butter
Conching
Breaking
Tempering
Grinding
Molding
Enrobing
Sifting
Cocoa Powder
Plain or Milk
Chocolate
Chocolate -coated
goods
Major function of these processes
1.
Fermenting and drying
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2.
Roasting
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3.
Critical for flavor development
Winnowing
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4.
Removal of adhering pulp
Removal of moisture
Removal of seed coat
Size selection of nibs
Milling
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Release of fat from cells
Major function of these processes
5. Cocoa manufacture
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Production of additional fat (cocoa butter)
6. Refining
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Grinding of sugar particles
7. Conching
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Reduction in viscosity
8. Tempering
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Pre-crystallization process
Chocolate flow properties
Chocolate exhibits non-Newtonian properties
For Newtonian fluid:   D
For Bingham fluid:       pl D
D
1
2
3
Different types of rheogram: (1) Newtonian;
(2) Bingham; (3) pseudoplastic
(e.g. chocolate)
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Steiner’s model for chocolate - adapted from
Casson’s model for printer’s ink
1  a 
DN 


1
1  a    2 K 0 .......................................................................(1)
K1
a  r / R................................................................................................................(2)
DN 
2
.........................................................................................................(3)
1 a2
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 =K02 = yield value according to Casson
(1  a) DN
b=2K0
(1  a) 
Casson rheogram according to OICC
Factors affecting the flow properties of
chocolate
Fat content:
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12
Casson plastic viscosity (Pa.s)
10
8
1
6
4
2
2
0
28
32
36
% fat
Influence of fat content on Casson parameters of two milk chocolates with 0.25% lecithin.(1) Fine chocolate with 5.7% particles >
20m; (2) moderaltely coarse chocolate with 16% particles > 20m.
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Lecithin and other emulsifiers: immediate
reduction in viscosity
Moisture content: increases viscosity
Particle size distribution:
80
70
3
Casson yield value (Pa)
Casson plastic viscosity (Pa.s)
4
1
2
2
1
60
50
1
40
30
2
20
10
0
0
0
10
20
30
%>20 m icrons
40
50
0
10
20
30
40
50
%>20 m icrons
Influence of fineness on Casson parameters of two milk chocolates with 0.25% lecithin. (1) 30% fat; (2) 32% fat
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Temper: increases viscosity
Thixotropy: decreases viscosity
Vibration: decreases viscosity
Temperature:
5
4
100
Casson yield value (Pa)
Casson plastic viscosity (Pa.s)
120
3
2
2
1
1
1
80
60
2
40
20
0
0
40
50
tem perature C
60
40
45
50
55
60
Tem perature C
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:
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ammonium phosphatides (YN)
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polyglycerol polyricinoleate (PGPR)
The chief function are:
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reduce viscosity
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Reduce thickening due to moisture and temperature
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Modify the setting behavior of fat phase
Flow characteristics of plain chocolate with added surface-active lipids
Addition
0.3% soy lecithin
0.3% YN
0.3% sucrose dipalmitite
0.3% PGPR
0.8% PGPR
Casson plastic
viscosity
(poise)
6.1
10.3
8.6
32.5
20.3
Casson yield
value
(dynes/cm2)
92
30
166
25
0
80
7
70
Casson yield value ( Pa)
Casson plastic viscosity (Pa.s)
8
6
5
4
3
1
2
2
1
60
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
50
40
1
30
20
2
10
0
0
0
0.2
0.4
0.6
0.8
1
% lecithin
0
0.2
0.4
0.6
0.8
1
% lecithin
10
Apparent viscosity (Pa.s)
8
4
6
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
3
4
1
2
2
0
0
0.2
0.4
% addition
0.6
0.8
Mechanism of viscosity reduction by
lecithin
1.
2.
3.
4.
5.
a monomolecular film is formed on the surface of the
non-fatty particles by surfactant molecules.
reduction in internal friction by promoting the coating of
sugar and cocoa solids by fatty medium.
increase in the amount of ‘free’ cocoa butter in the
dispersion medium by displacement from the surface of
solids.
prevention of agglomeration of sugar particles and cocoa
particles by break down of any lattice-type structure
between them.
absorption of moisture
Effect of lecithin on the stability of
emulsions
Lecithin molecule
at interface
between water and
oil
oil-inwater
waterin-oil
Oil
Types of emulsions
Creaming
Sedimentatio
n
Creaming of emulsions: four phases
Coalescence
Separatio
n
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 STORAGE
METHOD OF WRAPPING:
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MOLDED CHOCOLATE
BLOCKS.
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CHOCOLATE COUNTLINES.
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BOXED CHOCOLATE.
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TWRIST WRAPPING.
MATERIAL FOR PACKAGING:
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ALUMINUM FOIL.
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REGENERATED
CELLULOSE FILM (RCF).
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PLASTIC FILM.
MOLDED CHOCOLATE BLOCK
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Protection against dirt, moisture and taint.
It is more economical .
Wide surface for labeling.
CHOCOLATE COUNTLINES
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Normally wrap in “pillow pack”
By heavy-backed foil, waxed paper or
glassine.
Protection against moisture vapor and taint.
BOXED CHOCOLATE
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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
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In “double end fantail” form.
By aluminum foil, backed and unbacked plain
sliver, colored and printed film.
Protection against dirt and taint.
ALUMINUM FOIL
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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)
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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
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Three different forms: polyethylene,
polyvinyl chloride and polyester.
Available in film or coating purposes.
Protection against moisture, gas and
ultraviolet.