IDM | Ingredients globules and whey proteins, of reducing the amount of carrageenan required to form a stable product. But more on that in a moment. Another factor to be taken into account, of course, in determining the right dosage of carrageenan, is the variation that may occur in the composition of the milk, depending on the season. But there’s more still to the dosage decision. It also depends, for example, on: • The milk’s fat content, as more fat requires less stabilizing • The cocoa content, because more cocoa demands less stabilizer • The choice of heat treatment (Sterilisation requires less stabilizer than UHT, which in turn requires less than a pasteurised product) Network 2: The MCC/CMC complex To consumers, it may seem surprising that refined wood pulp has a contribution to make to keeping milk drink particles in their place. But microcrystalline cellulose (MCC), as it is officially known, or rather a MCC/CMC complex, is often used in combination with carrageenan. MCC is derived from plant fibres from which the crystalline part of the cellulose is extracted. In a dispersion, MCC forms hydrogen bonds, creating the second of our three-dimensional networks. As an added bonus, MCC-based products can also lend more body and creaminess to the drink. At temperatures below 80°C, MCC’s functional properties are largely unaffected by fluctuations, so cooling and storage temperatures become less critical. That makes MCC-based products a good choice where cooling below 25°C isn’t an option – or if the storage is likely to be at more than 30°C, as is often the case in South East Asia or the Middle East, for example. Figure 2 illustrates the network formation brought about by MCC/CMC, in which particles are suspended. Because MCC doesn’t react with the milk proteins in the same way as carrageenan, the risk of separation due to overdosing is less. That said, overdosing will result in heavy body and high viscosity. Network No. 3: The effect of carefully selected emulsifiers The emulsifiers used in enriched milk drinks are typically mono- and diglycerides produced by the reaction of edible vegetable fats or oils when combined with glycerol. The resulting molecule 40 · 10 2016 | international-dairy.com Figure 3: An emulsifier is a molecule with ambiphilic properties (part of the structure is hydrophilic and other moieties are lipophilic). In a multiphase system the emulsifier will adopt a favourable position with respect to energy. The emulsifier reduces surface tension between the phases (source: Palsgaard) (Figure 3) is composed of a hydrophilic and a lipophilic part, positioned at the interface between fat and protein on the one hand, and water on the other. These molecules are formed during homogenisation and ageing of the product. The mono and diglycerides form a complex with the whey proteins, making the fat globule membrane more resistant to coalescence, and reducing fat separation in the product at the same time. But that’s not all – these emulsifiers lower the net charge of the membrane, creating a three-dimensional network that acts to increase the creaminess of the milk – and the consumer’s sensory perception of a thick, luxurious product. Importantly, and perhaps somewhat counterintuitively, the emulsifiers also guard against creaming in the finished product. Network No. 4: Cocoa particles For chocolate milk drinks, the work performed by carregeenan, the MCC/CMC complex and emulsifiers to create a robust suspension is further assisted by the cocoa particles themselves. A typical recipe contains around 1-2% cocoa powder – meaning there’s no shortage of particles to distribute and hold in position. From the moment the milk and cocoa powder are mixed, casein is almost immediately adsorbed to the particles. The strength of this particular network-building effect depends on the degree of alkalisation of the cocoa powder. That’s because cocoa powder contains polyhydroxyphenols, which polymerise during alkalisation into tannins, known for their 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 suspension’s stability. It is important, too, to consider the particle size of the cocoa powder, as the network simply can’t support particles that are too heavy. In fact, Palsgaard recommends that less than 0.5% of the particles are larger than 75 micrometers. Of course, the advantages of this fourth network are lost on enriched milk products that don’t contain cocoa powder. Calcium-fortified, non-chocolate milks, for example, which face the task of suspending particles of calcium instead of cocoa, are similarly subject to unattractive settling, but lack the networking effect of their cocoa cousins. Yet the suspension challenge is no less important to address. For example, where sedimentation has occurred, the consumer may lose the fortifying benefits of the drink – and, at worst, ends up with a mouthful of solids and a distinctly chalky taste. The creation of a durable suspension in this type of milk drink can largely be achieved, for example, by combining a small-particle-size, solid-precipitated calcium source with the networks built by the combination of carrageenan, the MCC/CMC complex and gellan gum, together with the right choice of emulsifier. Gellan gum is a polysaccharide produced by fermentation that creates a gel structure in solutions, keeping the calcium particles in
IDM_10_2016
To see the actual publication please follow the link above