What we know about milk, cream and chocolate
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For soft chocolate, the optimal composition is about 10% water and 30% fat.
For ice cream, the optimal composition is about 55% water and >32% fat.
Milk is an emulsion of butterfat globules within a water-based fluid.
Whipping cream contains 30-36% butterfat.
Butter contains at least 80% butterfat.
Milk chocolate contains cocoa solids, cocoa butter (or other fat), sugar, and milk powder (or condensed milk).
Butterfat is a triglyceride derived from myristic, palmitic, and oleic acids.
Cocoa butter is a triglyceride (fat) derived from stearic, palmitic, and oleic acids.
Whipping cream is an emulsion of butterfat in water.
Butter is an emulsion of water in butterfat.
In cocoa butter, there are six essential polymorphic forms.
Examples of food emulsifiers are egg yolk (lecithin), mustard, protein, and soy lecithin.
Average milk freezing point is –0.523°C.
Melting temperature of butter is 28-36 °C (butter is partially solidify at room temperature).
Melting temperature of chocolate: Type V 34 °C, Type VI 36 °C (body temperature 37 °C).
What is an Ice Cream
Ice cream is a smoothly textured semi-solid (frozen) foam that made from milk/cream, and often combined with fruits and flavours. In USA, it may have the following composition:
- at least 10% butterfat.
- 9 - 12% milk solids (not fat) contains: proteins (caseins and whey proteins) and carbohydrates (lactose) found in milk.
- 12 - 16 % glucose-based corn syrup sweeteners
- 0.2 - 0.5% stabilisers and emulsifiers
- 55% - 64% water (from the milk or other ingredients).
The mixture of these ingredients is stirred slowly while cooling, in order to incorporate air and to prevent large ice crystals from forming.
Gelato, Italian word for ice cream, derived from the Latin word "gelātus." (meaning frozen). In English, gelato is defined as a soft ice cream containing little or no air. By statute, gelato in Italy must have at least 3.5% butterfat, with no upper limit established.
In order to keep ice cream soft, we have to avoid ice crystals forming. There are tricks to do so:
In order to keep ice cream soft, we have to avoid ice crystals forming. There are tricks to do so:
- Emulsifying fat - sticks fat molecules in between water molecules.
- Sugar - the higher the concentration of sugar (syrup), the lower the freezing point.
- Air - a more aerated ice cream is easier to scoop, and has a fluffier, less dense texture.
- Others - alcohol, starch, protein (in egg and milk), and natural stabilizers like guar gum.
Melting the Chocolate
When melting chocolate, be careful not to allow excess steam to develop, which will interface with the surface of the chocolate, moistening it and increasing the viscosity. The addition of 3% or 4% by weight of water will turn chocolate into a very thick paste. Continuous to increase the amount of water, say above 20%, there is enough water to form continuous streams through the chocolate and so help it flow.
Milk fat has the same effect as cocoa butter on viscosity. Milk fat will slow down the setting rate of chocolate if it is added at temperature 40°C. The effect of an extra 1% of fat upon the viscosity depends upon the amount that is already present. Above a fat contents of 32% there is very little change in viscosity with any further additions. The effect of fat is proportionately much higher for the plastic viscosity then the yield value. The majority of the fat is wetting fat, which is partially tied to the particles surface. This free fat has a large effect on lubricating the flow when it takes place and so the plastic viscosity decreases dramatically. On the other hand, the yield value is more connected with the forces between the solid particles, which in turn are connected with the absolute distance between them.
Cream can be added to chocolate to form a soft mixture, known as ganache, that does not have any snap when broken and does not contract very much upon cooling. This is made by stirring the cream very rigorously as liquid chocolate is added to it. Because there are emulsifiers in both cream and chocolate, the chocolate viscosity is slightly less affected by the moisture.
Chocolate is almost half made up of very tiny sugar particles. Sugar particles are hydrophilic (attract water) but lipophilic (repel fat). Liquid chocolate flow because the sugar and the other solid particles are able to move past one another. In this case, the emulsifier coats the solid surface and forms a boundary layer between the two and is more a surface active agent than a emulsifier. The most common surface active agent used is lecithin which is a naturally occurring substance frequently obtained from soya. Addition of 0.1 - 0.3% soya lecithin are said to reduce the viscosity by more than 10 times their own weight of cocoa butter.
(Ref: The Science of Chocolate, P.77
http://books.google.com.hk/books?id=miv82VGPL9cC&pg=PA77&lpg=PA77&dq=chocolate+attract+water&source=bl&ots=J2Ie_Al2eE&sig=mqmws11NP982uQ3xW5xjykuIDFk&hl=en&sa=X&ei=ENn4UM3fDKnAiQfH_oCQAg&redir_esc=y#v=onepage&q=chocolate%20attract%20water&f=false)
Experiments
Values used:
Milk chocolate weigh to volume conversion: 100g = 140.83 ml
Milk chocolate: cocoa solid 26%, milk solid 28%, total fat 29.6%
Cream: butterfat 35%
When melting chocolate, be careful not to allow excess steam to develop, which will interface with the surface of the chocolate, moistening it and increasing the viscosity. The addition of 3% or 4% by weight of water will turn chocolate into a very thick paste. Continuous to increase the amount of water, say above 20%, there is enough water to form continuous streams through the chocolate and so help it flow.
Milk fat has the same effect as cocoa butter on viscosity. Milk fat will slow down the setting rate of chocolate if it is added at temperature 40°C. The effect of an extra 1% of fat upon the viscosity depends upon the amount that is already present. Above a fat contents of 32% there is very little change in viscosity with any further additions. The effect of fat is proportionately much higher for the plastic viscosity then the yield value. The majority of the fat is wetting fat, which is partially tied to the particles surface. This free fat has a large effect on lubricating the flow when it takes place and so the plastic viscosity decreases dramatically. On the other hand, the yield value is more connected with the forces between the solid particles, which in turn are connected with the absolute distance between them.
Chocolate is almost half made up of very tiny sugar particles. Sugar particles are hydrophilic (attract water) but lipophilic (repel fat). Liquid chocolate flow because the sugar and the other solid particles are able to move past one another. In this case, the emulsifier coats the solid surface and forms a boundary layer between the two and is more a surface active agent than a emulsifier. The most common surface active agent used is lecithin which is a naturally occurring substance frequently obtained from soya. Addition of 0.1 - 0.3% soya lecithin are said to reduce the viscosity by more than 10 times their own weight of cocoa butter.
(Ref: The Science of Chocolate, P.77
http://books.google.com.hk/books?id=miv82VGPL9cC&pg=PA77&lpg=PA77&dq=chocolate+attract+water&source=bl&ots=J2Ie_Al2eE&sig=mqmws11NP982uQ3xW5xjykuIDFk&hl=en&sa=X&ei=ENn4UM3fDKnAiQfH_oCQAg&redir_esc=y#v=onepage&q=chocolate%20attract%20water&f=false)
Experiments
Values used:
Milk chocolate weigh to volume conversion: 100g = 140.83 ml
Milk chocolate: cocoa solid 26%, milk solid 28%, total fat 29.6%
Cream: butterfat 35%
| Cream, ml | Chocolate, g | Butter, g | Refrigerator | Form | Water | Cocoa Solid | Total Fat |
| 10 | 16 | 10-14 °C | thick paste | 19.43% | 18.23% | 31.21% | |
| 20 | 21 | 10-14 °C | thick paste | 26.35% | 15.46% | 31.79% | |
| 40 | 21 | 5 | < 10 °C | icecream (soft) | 37.50% | 11.00% | 32.72% |
| 50 | 21 | freezer | icecream (hard) | 40.96% | 9.61% | 33.00% | |
| 60 | 21 | 5 | freezer | icecream (hard) | 43.65% | 8.54% | 33.23% |
| Planned Next | |||||||
| 30 | 100 | 10-14 °C | soft chocolate | 11.41% | 21.43% | 30.55% | |
| 400 | 50 | freezer | icecream (hard) | 55.27% | 3.89% | 34.19% |
Next:
For soft chocolate, the optimal composition is about 10% water and 30% fat.
For ice cream, the optimal composition is about 55% water and >32% fat.
