Light and airy
Consultant Bill Edwards discusses the methods used to produce aerated sugar confectionery.
Aeration is a process that dates back to the origins of sugar confectionery. There are various methods of producing an aerated sugar confectionery product. It can be whipped or air can be incorporated into it using a process of pulling and folding. Chemical aeration using either sodium bicarbonate or sodium bicarbonate and acid is also an option, although it is generally used only in high boiled products.
Modern confectionery plant is designed to produce product of a consistent quality while minimising costs such as labour and energy. In any food plant, ease of cleaning is also very important, as is the availability of a cleaning in place (CIP) system.
Another important consideration is whether the production process should be batch or continuous. Batch plants usually have the advantage of flexibility but cannot achieve the throughput of a continuous plant. Thus batch plant tends to suit the smaller operator while continuous plant is more suitable for the larger producer. Continuous plants also tend to be ordered as part of a system rather than just as a mixer.
While un-aerated sugar confectionery such as jellies, gums or high boilings have a density of about 1.3g/cm3 to 1.5g/cm3, highly aerated products such as marshmallows have a density of about 0.2g/cm3. This illustrates how aeration makes ingredients go further.
Of course, it is not sufficient simply to incorporate vast amounts of gas into a product. Unless it has the right properties, the resulting foam will collapse. Soft, highly expanded foams usually depend on a foaming agent, which is typically egg white, although other ingredients have been used either on their own or in combination with egg white. Enzyme modified soy proteins have also been used with some success.
An ingredient that has recently become available as an egg white substitute is potato protein. This all natural vegetable product is acceptable to all religious denominations, as well as to vegetarians and vegans.
If a foaming agent is used, a typical method for producing marshmallow would involve boiling up the sugar and glucose to the necessary solids and then adding a solution of the foaming agent. Some systems dose the whipping agent into the product. One of the issues that can arise when there is a choice of whipping agent is tolerance to oils and fats in the product. While egg white is tolerant of oils and fats, some egg white substitutes are not. The minimal oil and fat content of some flavours can also cause problems.
While air is effectively an ingredient in aerated products, it is not listed on the label. The simplest systems incorporate ambient air, while more sophisticated systems can incorporate air, carbon dioxide, nitrogen or a mixture of gases. In all cases the gas has to be clean and of food grade.
In gum and jelly products, the degree of aeration is normally lower than in marshmallow, but they are still aerated by whipping. Gelatine has the advantage that it acts both as a whipping agent and a gelling agent.
In higher solids products such as caramels or nougatines, the product will not whip, so a typical method would be to gently mix in a pre-whipped foam made from a suitable whipping agent in a sugar and glucose syrup.
The final class of product, which includes traditional British seaside rock, is made using pulled sugar, which has been folded to incorporate air. In these products air bubbles are stabilised because the cold mass is in the glassy state. Some traditional products are made by pulling the sugar mass on a hook in the ceiling.
The simplest whipping machine is an open batch machine with a whisk, which is now generally used only by small scale artisan confectioners. Its only advantage is flexibility, while disadvantages include irregularity of the foam structure and therefore the density. The machine uses ambient air.
Using a batch machine is labour intensive in terms of loading, unloading and cleaning and the rate of production is slow. Closed batch pressure beaters still produce irregular structure and density as well as being labour intensive, but they are faster.
Continuous pressure beating systems avoid all the disadvantages of the preceding systems. They produce a product with a consistent structure. The air or other gas is clean and is not ambient. The system is closed, hygienic and easily controlled.
One of the brand names that many in the industry will associate with mixers is Asser Oakes. Its latest mixer incorporates a continuous high shear mixing head with three components: a rear stator, a rotor and a front stator.
The precision-machined intermeshing teeth of the rotor and stator provide an enhanced mixing action. The mixing head can act as a complete mixing and aeration system to produce aerated products with a uniform cell structure and a controlled specific gravity.
The mixer head consists of a radial disc where the product and aeration gas are fed proportionally under pressure to the centre of the rear stator in which they are gently blended. The mixing action then gently increases to a maximum at the periphery of the rotor before decreasing to ensure that the product leaves the head in a uniform and stress free condition.
The head incorporates a water jacket that removes any heat generated by shear heating. The machine has a flushed double mechanical head on the drive shaft sealing system to comply with modern hydraulic standards. Similarly the mixing head is designed to be compatible with CIP systems.
Other standard features include: a servo controlled variable drive speed rotor drive; back pressure regulator and gauge; air flow meter and full air system; mixing head high pressure alarm and cut out; low air pressure alarm; and a full mechanical head sealing system. The design of the mixing head ensures a rigid construction by minimising overhang.
The heart of the Haas Mondomix continuous aeration system is a mixing head comprising a stator and rotor each of which is fitted with square pins. At the inlet of the mixing head, the gas and the liquid phase are homogenised under controlled pressure.
The product texture and consistency are controlled by the mixing action, the system pressure, the rate of flow and the ratio between the gas and liquid phases as well as by the temperature. The machine is extremely versatile because these variables can be controlled.
Another leading supplier of aeration equipment is Chocotech, which would normally supply a complete plant to make a product. Its equipment for making aerated products includes a system for making the whipping agent solution. This system is designed so that the mixing tank has a large opening and support for a sack to make loading easier and ensure that no product ends up on the floor and provides intense mixing and short mixing.
Chocotech also produces a modern batch whipping system called Turbowhip, which consists of two parts, the first being a thermo siphon cooker that uses a steam coil to heat the sugar mass. The cooker can be operated at atmospheric pressure or under vacuum and has sufficient head room to prevent any foam from being sucked into the vacuum pump.
In the second chamber the cooked and vacuum treated mass drops into the whipping agent. The pressure applied to the tank then whips the product to a consistent fine pored foam. The system has been designed to minimise labour requirements.
The Chocotech continuous pressure beater is called Tornado. Depending on the product density required, this machine can deliver a maximum throughput of 2000kg per hour. At the heart of the machine is the aerating head, which consists of a rotor and stator for tempering. Meshing and shearing fingers blend the aerating gas intensively into the mass.
As well as the aerating head there is a small pre-rotor and a pre-stator. The solution of whipping agent is metered into the pre-stator where a pre-foam is generated. A homogeneous blend is produced by metering in the basic mass with the pre-foam at the most suitable point. Thus, a durable fine pored product is produced.
Other producers of aeration equipment include Hosokawa Bepex, Neofood, a German company that offers a very innovative machine and Beijing Yinrich, a Chinese company that provides continuous aeration machines.
The technology used in aerating sugar confectionery has moved on considerably since the only options were open whipping machines or hand folding the product.
Now a range of equipment is available from a number of manufacturers to meet the varying needs of the modern confectioner.