Late Father Christmases or early Easter Bunnies? Bettina Wolf Division of Food Sciences 1
The Science of Chocolate Physical properties of chocolate How to make good chocolate? Why does chocolate usually melt in my mouth and not my hand? Why does chocolate feel smooth in your mouth? Chocolate bloom Q&A session 2
How to make good chocolate? Inspect your wrapper for the ingredients. Which are the major ingredients? Cocoa beans, sugar, cocoa butter, non-gmo soy lecithin 3
Theobroma cacao 10 o N & 10 o S of the Equator largest producing countries: Côte d'ivoire, Ghana and Indonesia. Cacao pod 4
Cacao beans inside the xx 5
From cocoa to chocolate Cocoa cultivation From the bean to liquor From liquor to powder From liquor to chocolate 6
Images taken from the Barry Callebaut WebPages. Cocoa cultivation harvest shipping fermentation drying 7
Images taken from the Barry Callebaut WebPages. From the bean to liquor cleaning and quick drying roasting cocoa liquor chocolate ingredient further processing into cocoa powder and cocoa butter grinding 8
Images taken from the Barry Callebaut WebPages. From liquor to chocolate Types of chocolate cocoa liquor cocoa butter sugar cocoa liquor cocoa butter sugar milk powder cocoa butter sugar milk powder 9
Types of milk chocolate Added as preprocessed combined ingredient cocoa liquor cocoa butter sugar milk powder Added as separate ingredient Crumb Dry mix 10
Chocolate process Dry mix Cocoa butter Emulsifier Raw materials Mixing Refining Conching Tempering Moulding Sugar Milk powder Cocoa mass Cocoa butter Structure Development of Flavour 11
Why does chocolate usually melt in my mouth and not in my hand? - Experiment 1 - Which chocolate melts first in your mouth? 12
Different types of chocolate melt at different temperatures. Why? We need to look at the concept of phases. 13
Water 14
Melting component in chocolate cocoa butter butter olive oil lard 15
mostly Triacylglycerols (TAGs) 16
Fatty acids straight kinks affects packing thus melting temperature of TAGs Linoleic acid 17
The answer: Milk chocolate contains milk fat which melts at lower temperatures than the fats in cocoa butter. 18
Ready for another experiment? Experiment 2: Why does chocolate feel smooth in your mouth? 19
Possible reasons Solid particles milled to different sizes papillae Diameter of papillae: 50 100 microns Grittiness threshold: 25 microns Chemical composition 20
Chocolate microstructure Suspension = solid dispersed in liquid Solids (dispersed phase) Sugar Liquid (continuous phase) Cocoa solids Milk powder 30 μm molten fat 30wt% 21
Demonstration Finding: Sugar and cocoa solids dislike oil! Science speak: these ingredients are hydrophilic and thus do not disperse well in oil (hydrophobic). How can we make chocolate then? 22
Emulsifier Likes water and oil amphiphilic molecule therefore allows to combine water and oil. 23
Emulsifiers used in chocolate Lecithin (E322) Contains phospholipids Isolated from egg yolk or from soy beans (chemical or mechanical extraction. PGPR (E476) Polyglycerol Polyricinoleate Emulsifier made from castor beans phosphatidylcholine 24
Emulsifier action in chocolate Cocoa butter Sugar (Figure not to scale) 25
Chocolate process Dry mix Cocoa butter Emulsifier Raw materials Mixing Refining Conching Tempering Moulding Sugar Milk powder Cocoa mass Cocoa butter Structure Development of Flavour 26
Conching addition of remaining fat & emulsifier low fat (dry, plastic) conching liquid conching Dry-paste phase during filling Liquid phase towards the end of conching Plastic phase intense mechanical treatment 27
Learning from exp. 2 These amphiphilic molecules coat the hydrophilic cocoa solids and sugar with a hydrophobic layer, and make the chocolate feel smooth in your mouth. 28
Another observation of physical nature on chocolate untempered bloom tempered 29
Fat bloom v sugar bloom 30
Sugar and cocoa butter are crystalline in chocolate Solution/melt Crystallisation solid Slows molecules Ultimately forces them into ordered structures Different patterns of ordered structures 31
Polymorphism Cocoa butter has 6 polymorphs FORM MELTING POINT(C) SYSTEMATIC NAME COMMENTS I 17.3 β' 3 (sub-α) Not important II 23.3 α -2 Not important III 25.5 β' 2-2 Not important IV 27.5 β' 1-2 Untempered V 33.8 β 2-3 Tempered VI 36.2 β 1-3 Associated with bloom 32
So, grey appearing chocolate is NOT mouldy, it has simply re-crystallised. 33
Physical sciences of chocolate Melting and how it is affected by fat composition Emulsifiers and how they help to make chocolate smooth Polymorphism and chocolate bloom 34
Thank you for your attention & participation Q/s? 35
Please donate your chocolate wrappers! Needed as props for the February OUTREACH talk. Thank you. Bettina