Air supply
Food and confectionery industry consultant Graham Godfrey considers the most important aspects of the various methods of aeration.
Aerating confectionery not only adds interest and novelty in terms of texture and flavour, but it also greatly increases apparent value, and of course air is about the cheapest ingredient available.
Aeration has a wide range of applications across the confectionery industry, and although only general principles will be discussed here, there are a considerable number of products that rely on highly adapted (and closely guarded) processes to give them their unique characteristics.
Clean air is the gas used in virtually all mechanical aeration systems. However, other gasses have been and are used in some specialist applications – particularly where fats are being aerated. Other gasses used include carbon dioxide and nitrogen.
Mechanical aeration
Most confectionery materials can be mechanically aerated in one way or another. The results can range from very high levels of aeration in products such as mallows to very low (but still significant) levels in products such as pulled sugar.
High levels of aeration generally need a proteinaceous material (gelatine, egg albumen, soya protein products, milk products) to form and stabilise the aeration and sufficient water present for that material to be active.
Gums and jellies
Gums and jellies are generally aerated by whipping air into the cooked mass under pressure using specialist equipment such as that supplied by companies including Asser Oakes and Haas.
High levels of aeration will produce soft, light products such as mallows and lower levels can be used to provide different texture and colour effects to gums and jellies.
Control of the degree of aeration is vital because it has such a big effect on product characteristics, weight and so on. Because most of these types of product are starch moulded, it is important that the foaming agent (which may also be the gelling agent) is stable and that its characteristics are predictable and controlled.
Materials that will rapidly reduce aeration (particularly oils and fats) need to be added at a point in the process when the aeration has been stabilised; even flavour carriers can cause problems. In addition, high temperatures at low moisture contents, which will denature the proteinaceous materials, should be avoided.
Once aerated, the mass needs to be handled carefully so that mechanical shear does not cause aeration to
be lost. It is therefore ideal to mix in ingredients such as flavours and colours before aeration as long as they do not interfere with aeration. This is because the aeration process increases the viscosity of the mass and makes even distribution of minor additions difficult.
Nougatines, caramels
Products such as nougatines and caramels generally have a lower moisture content, so the proteinaceous materials employed to give texture and body to the mass are less able to be active and form foams in the whole mass. The products are also too viscous for whipping and are vulnerable to excess shear, which can cause fat expression and crystallisation.
These products are generally aerated by adding a low density foam produced using one of the common whipping agents in a sugar syrup to the base nougatine or caramel mass and mixing it in with minimum shear to reduce the loss of air. This addition significantly alters the texture of the product, making it softer, lighter and easier to chew.
While most nougatines are aerated to some degree, aerated caramels and fudges are less common but can be interesting products. Because these masses are generally highly viscous even at elevated temperatures, mixing and forming them without reducing or eliminating the aeration can be difficult and may require some experimentation and compromise.
Care is also needed when adding scrap back to the mix as release agents used in sheeting and cutting systems can make aeration difficult.
Sugar
Because of the temperature involved, conventional foaming agents are not applicable to sugar products. Mechanical aeration in this case is generally achieved by ‘pulling’ the sugar mass – effectively stretching and folding it while it is in a plastic state. The degree of aeration achieved by this method is relatively low, but the effect in terms of textural and colour change can be significant. Perhaps the best known example of this type of aeration is seen in the colours and textures produced in traditional ‘rock’.
The recipe and moisture content need to be carefully controlled as pulling almost always causes a degree of crystallisation. If this is excessive, the product will break down and the residual glass phase, which will contain all the residual moisture, may have a water activity low enough to absorb moisture and become sticky.
Another method of sugar aeration is to inject and disperse carbon dioxide gas into a high temperature sugar mass under pressure and to cool and solidify it while still under pressure. This results in the individual bubbles retaining the pressure and therefore producing a unique sensation as the product breaks down in the mouth.
This product (often brightly coloured and sometimes referred to as ‘space dust’) is something of a novelty, but one that can produce exciting children’s products when incorporated into dry systems such as chocolate. Adding it to water-containing systems simply causes the product to soften and release the gas.
Chocolate
Because chocolate has such a unique structure, it is difficult to aerate and two different approaches have been used commercially. Both of these are technically difficult and what is more, well covered by patents, so this brief detail is really only for interest.
Both methods deal with the same problem; because chocolate has so little liquid phase, it is extremely difficult to create reasonably sized bubbles by conventional means, so very small bubbles have to be made to grow.
In one approach the chocolate is aerated mechanically using a fairly conventional whisk system before moulding and setting under reduced pressure. This makes the tiny air bubbles grow to the size required.
Alternatively, the chocolate is aerated under pressure before moulding at atmospheric pressure. As the pressure is released, the entrapped bubbles grow.
Both methods of aeration result in some textural changes as well as a change in volume, and produce products that are interestingly different from solid moulded chocolate.
Other fat based systems
Other fat based substances such as praline (and also of course chocolate) can be aerated to a small degree using conventional mechanical whipping. Only a modest degree of aeration will be achieved, but this substantially lightens the texture and can greatly improve the eating quality of the product, making it smoother and less sweet. It may be necessary to use different fats and stabilisers to achieve good results and advice needs to be taken from specialist suppliers.
Chemical aeration
Chemical aeration – basically causing the decomposition of sodium bicarbonate within the mass to produce carbon dioxide – is only applicable to hard sugar products because of the temperature needed to decompose the bicarbonate and the need for rapid immobilisation of the mass to retain the expanded structure. The mass produced can be used in different ways – from careful forming and cutting into solid shapes for enrobing to granulating in different sized pieces for adding to chocolate bars.
The products that undergo this process tend to be very hygroscopic due in part at least to the presence of sugar and glucose breakdown products generated during the reactions. Consequently all handling and storage needs to be carried out at a low atmospheric relative humidity – below about 35 per cent.
Bicarbonate only aeration
If a high boil sugar mass at ex cooker temperature (about 145°C) is mixed with a relatively small amount of finely ground sodium bicarbonate dispersed in glucose syrup, the bicarbonate decomposes rapidly and the gas released creates a viscous, foaming mass. The breakdown products of the chemical reaction are alkaline and cause rapid caramelisation of the sugar itself, resulting in a golden brown colour and distinct caramel flavour in the mass.
This caramelisation reaction is rapid at the cooking temperature of the mass and the foamed product needs to be cooled quite fast in order to avoid the mass becoming charred (which is where the term cinder toffee probably originates).
The mass is generally spread into a thin sheet before rapid cooling and slightly warmed before cutting to reduce brittleness.
The addition of about 1g of bicarbonate per kg of sugar will give substantial aeration.
Because the mass rapidly increases in volume following the addition of the bicarbonate, care is needed when producing this type of product.
Acid/bicarbonate aeration
If a small amount of a suitable acid is added to the sugar boil before the bicarbonate suspension, it will neutralise the breakdown products of the bicarbonate and consequently there will be no caramelisation.
This allows the preparation of pale aerated masses that can be coloured and flavoured, for example green with mint flavour added to the material in which is dispersed.
Either as products enrobed in chocolate or added to chocolate as granules, these produce a range of interesting flavour and texture sensations, particularly when the aerated granule and its carrier
have different but complementary flavours.
The forming and cutting process is similar to the bicarbonate only process mentioned previously.
The addition of about 0.7g (citric) acid per kg of sugar will react with about 1g of bicarbonate per kg sugar to result in a pale aerated mass,
which requires the same precautions in terms of care during processing and handling.
Sugar free systems
This is a difficult area in which to make accurate predictions because of the variety of sugar free materials that are available.
Most sugar free materials produce lower viscosity masses than conventional sugar/glucose systems, and this will clearly have an effect on the ability to create and stabilise aeration.
There is also evidence that at least some sugar free materials react differently with gelling agents and as these are often the basis for aeration then some differences may be expected in the foaming performance of products such as gums, jellies and mallows based on sugar free recipes. The reason for this behaviour is not widely understood and is by no means universal.
Conclusion
Aerated confectionery is an exciting product category and aeration can be applied to many products, bringing excitement, new textures and increased apparent value. Some uses are well-established, while others are much newer and some doubtless remain to be discovered.
A particular advantage that aeration can bring is the lightening of texture, making a product less satiating
while enhancing flavour and general appeal. It is certainly a technique
that should be considered when
looking at new products and new ingredients.
very good literature on aerating inconfectionery