Chocolate milk is a well-known and popular product around the world. Except for a few products where a visible sedimentation is desired, chocolate milk is expected to be a homogeneous product without visible sedimentation and creaming. Most of the cocoa powder is insoluble in milk and water meaning that if no precautions are taken, the cocoa particles settle at the bottom and the text ‘shake before use’ will have to be written clearly on the packaging. This labelling has a negative impact on the consumer. Further, for long shelf-life products creaming occurs over time - a process which can also be delayed by taking appropriate action.
Forming the thixotropic system
Chocolate milk usually contains up to 2% cocoa powder. In order to make a homogeneous suspension of the cocoa particles in the milk, a three-dimensional network has to be formed. The cocoa particles are entrapped herein. When shear is applied to the chocolate milk the network is broken and the viscosity decreases. When the shear is removed the three-dimensional network is restored. It is a so-called thixotropic system.
The ingredients used to form this thixotropic system are generally mono- and diglycerides carrageenan and microcrystalline cellulose. Mono- and diglycerides further have an important function in preventing creaming in the product.
The effect of emulsifiers in chocolate milk
Mono-and diglycerides are emulsifiers produced by reaction of edible vegetable fats/oils and glycerol. The result is a molecule with a hydrophilic and a lipophilic part and consequently it is placed at the interface between the fat/protein and water. This happens during homogenisation and ageing of the chocolate milk. The mono- and diglycerides form complex with the whey proteins, making the fat globule membrane more resistant towards coalescence. Hence they reduce fat separation in the product. However, they also reduce the net charge of the fat globule membrane and thereby increase the flocculation of the fat globules forming a three-dimensional network, which increases the creaminess in the milk.
The effect of carrageenan in chocolate milk
Carrageenan is by far the most commonly used stabiliser in chocolate milk. Carrageenan is extracted from seaweed. In Europe carrageenans are divided in 2 groups, refined carrageenan (E-407) and semirefined carrageenan (E-407a). Both types are applicable in chocolate milk.
Carrageenans are further grouped in Kappa-, Lambda- and Iota carrageenan according to their chemical composition. It is especially Kappa carrageenan, which has found use in chocolate milk due to its ability to react with the milk proteins and form a three-dimensional network. The carrageenan forms a helix with negatively charged sulphate groups turning outwards. This helix interacts with the positively charged casein micelle. When carrageenan is used as stabiliser, the chocolate milk must be cooled down below 25°C before filling, or cooled down below 25°C during constant rotation if in can/in bottle sterilization is used. This is necessary for formation of the carrageenan network. Figure 2 shows how the network is formed in a carrageenan stabilized chocolate milk. Further storage of the chocolate milk should be below 30°C as the formed network breaks down at higher temperature.
The effect of the MCC/CMC complex
Microcrystalline cellulose (MCC), or rather a MCC/CMC complex, also finds application in chocolate milk, however, often in combination with carrageenan. MCC is derived from plant fibres from which the crystalline part of the cellulose is extracted. When in dispersion the MCC forms a three-dimensional network due to formation of hydrogen bonds.
Below 80°C a change in temperature only has limited effect on the functional properties of MCC, meaning that cooling and storage temperature is less critical when MCC is used. Consequently, MCC based products are recommended when cooling below 25°C is not applicable or if the storage temperature is higher than 30°C which is often the case in eg. South East Asia and the Middle East. MCC based products often gives more body and creaminess to the milk drink, which could be another reason for recommending a MCC based solution. Figure 3 below illustrates the network formation of MCC/CMC in which the cocoa particles are kept in suspension.
Finding the right stabiliser dosage
The dosage of the stabiliser is very crucial. Underdosing means sedimentation in the chocolate milk and overdosing results in heavy body and gelation. When working with carrageenan one has to be very careful as the margin between underdosing and overdosing is very narrow. The use of mono- and diglycerides together with carrageenan increases the dosage margin of carrageenan and at the same time reduces the amount of carrageenan needed for formation of a stable product. This is due to the fact that the mono- and diglycerides form a network between the fat globules and the whey proteins.
Further the dosage of the carrageenan depends on:
- The fat content of the milk. Higher fat demands less stabiliser
- The cocoa content. Higher dosage less stabiliser
- The heat treatment. Sterilization demands less stabiliser than UHT treatment which again demands less stabiliser than a pasteurised product
The dependence of stabiliser dosage to the heat treatment can be explained as follows:
During heating to sterilizing or UHT-temperatures the whey proteins denaturate and become less soluble. This causes further agglomeration of the proteins with the cocoa powder and fat. The extent of agglomeration depends on e.g. the type and time of heating, the homogenisation, the type and amount of cocoa powder and stabiliser, the milk quality including the protein quality and pH of the milk.
As MCC doesn’t react with the milk proteins in the same way as carrageenan the risk of separation due to overdosing is less. However overdosing results in heavy body and high viscosity.
The effect of the cocoa particles
The cocoa particles also strengthen the network formation, as casein is adsorbed to cocoa particles. This adsorption takes place almost immediately when milk and cocoa powder are mixed. The strength of the network is depending on the degree of alkalisation of the cocoa powder. Cocoa powder contains polyhydroxyphenols, which during alkalisation polymerise to tannins known for its protein binding properties. In general the heat stability of chocolate milk is lower than that of milk, however, the closer the pH of the cocoa powder is to the pH of the milk the less impact it has on the stability in the milk.
It is important to consider the particle size of the cocoa powder, as the formed network cannot keep too heavy particles. It is recommended that less than 0.5% of the particles are larger than 75 micrometer.
We are experts in emulsifiers and stabilisers for chocolate milk - and we like to share our knowledge
For many years, Palsgaard has supplied the dairy industry with high quality emulsifiers and stabilisers. In our well equipped application labs in Denmark, Singapore, Mexico, Russia and China we are working on creating the right blends for a given market, taking milk quality, recipe, process conditions as well as sensory preferences into consideration. Our equipment enables us to work with as well pasteurized, UHT-treated as sterilized products and to make shelf-life studies covering the entire shelf-life of the chocolate milk.
Our products for chocolate milk ensure uniform products with good creaminess and mouth feel and high storage stability. An example of a carrageenan based product for chocolate milk is Palsgaard® ChoMilk 150 composed of mono- and diglycerides, carrageenan and guar gum. Palsgaard® ChoMilk 150 results in a uniform chocolate milk with a pleasant creaminess and mouth-feel. If it is difficult to cool down the product below 25°C after the production or if the storage temperature of the product is above 30°C, Palsgaard® ChoMilk 173 is applicable. Palsgaard® ChoMilk 173 is declared MCC, mono- and diglycerides, carrageenan and CMC. This product is also applicable in chocolate milk drinks with low protein content either due to the protein content in the milk or due to dilution with water to form a chocolate milk drink.
All mentioned products result in a uniform product without visible creaming and sedimentation and with a pleasant creaminess and mouth feel. Palsgaard® ChoMilk 150 is an integrated product, meaning that by using the spray cooling technology the stabiliser is coated by the emulsifier.
Compared to a dry blended product an integrated product has several advantages:
- Free flowing properties
- Uniform product, no risk of deblending during storage and transportation of the emulsifier/stabiliser mixture
- No dust formation
- Addition to the milk without premixing with sugar
Due to its total composition, Palsgaard® ChoMilk 170 is a dry mixed product and the suspension of the product in the milk is facilitated by dry mixing the product with sugar before addition.
For further information on the abilities of Palsgaard’s emulsifier and stabiliser blends for chocolate milk, or if you would like to request a sample, please contact your local Palsgaard office.