Upload
patrick-bell
View
215
Download
1
Tags:
Embed Size (px)
Citation preview
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
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
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
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.