though water and SMS changed biscuit dough rheology by different mechanisms.
used for the incorporation of air to create a foam structure and, along with added water, to dissolve the large quantities of sugar that are used in the recipe. The mixture may be acidified to improve the stability of the albumen proteins in the egg white.
Macaroon products are based on ground almond nuts; here water is required to wet the mixture rather than truly hydrate it and to dis-solve the added sugar. As with meringue products, the level of sugar is very high and the resulting strength of the sucrose solution may lead to recrystallisation in the baked product. Some recrystallisation may be desirable because this confers a ‘crunchy’ texture to the final product (see Chapter 5).
Fillings
A wide range of fillings may be used with bakery products. In all cases water plays a significant role in dissolving materials and contributes to a generally soft eating texture. Water may come directly from added recipe water or through the addition of other water-containing ingredi-ents, such as dairy cream or fruits. In all cases a most important issue is the retention of water within the filling and prevention of its loss or migration to some other component in the composite product. Water retention in the filling is controlled by adjusting its water activity and through the use of stabilisers. There are a wide range of stabilisers which may be used for the purpose of preparing creams and fillings, each of which has its own special properties and range of uses. In some cases more than one stabiliser may be added to a filling. Stabilisers which might be used include sugar, sodium alginate, sodium carboxymethyl-cellulose, carrageen and gelatine. The stabilising mechanism is different with each of the materials but in all cases involves the ‘binding’ of the water present in the filling to prevent its loss from the matrix. In fruit fillings the stabiliser also has to cope with a low pH because of the acidic nature of fruits. Control of water activity in fillings and mois-ture migration in composite products are discussed in more detail in Chapter 7.
Toppings and icings
All the common toppings that are used with bakery products contain high levels of added sugars. The main role of the water in the formu-lation is to dissolve the sugars and to disperse and suspend some of the other ingredients. The strength of the sugar solution in the topping has a major impact on its sensory qualities and its behaviour during storage. In many cases the topping has undissolved sucrose present and is therefore hygroscopic, which leads to particular problems with
moisture absorption from the atmosphere and migration between com-ponents (see Chapter 7).
A common form of icing for use as a bakery topping is called ‘fon-dant’ in the baking industry. Essentially, fondant is a suspension of sugar crystals in a sugar syrup. It is made by heating a water–sucrose mixture (1:3 parts by weight) until it boils, and then beating the solution as it cools. Other sugars may be present, e.g. glucose. The resulting prod-uct requires re-heating before it can be used; after being applied to the finished product it has a soft, plastic texture with a slight crust, and is very sweet. Other forms of icing may be based on unheated mixtures of sugar and sugar syrups (water icing), or with the addition of egg whites (royal icing).
Sugar-based pastes or soft roll icings are often used for the dec-oration of cakes and the manufacture of surface decdec-orations, such as flowers. This product has become a popular alternative to water icings and fondants because it is easy to work with. These pastes contain water as an added ingredient as well as the potential contri-bution from water-containing ingredients such as egg white and glu-cose syrups. Commonly a starch-based compound or other suitable sta-biliser, e.g. gum tragacanth, will be present to aid water retention in the paste.
A form of meringue may be used as a topping, for example, in the production of lemon-meringue pie. In this form the meringue will be soft eating in contrast to the crisp eating meringue discussed above.
A boiled form of meringue is often used as a topping. In this case the egg whites are whisked to a stiff foam and a sugar–water mix is boiled (around 115◦C) before being poured onto the egg whites and being fur-ther whisked to maintain a light foam. This topping may be browned on the surface to give the product its characteristic appearance.
Marshmallow
These products are similar to meringues in that they are often based on egg white and sugar but with the addition of a suitable gelling agent, e.g.
gelatin or modified starch. Unlike meringue, however, marshmallow products are usually soft eating. Both the sugar and the gelling agent act to hold the water within the matrix of the marshmallow.
Jams and jellies
The various forms of jams and jellies used in the bakery are based on mixtures of fruit and sugars, with some form of stabilising agent, com-monly pectin. The water needed to dissolve the sugars that are present may come from the fruit alone or through the addition of extra water
in the formulation. As with marshmallow, the combination of sugars and stabiliser acts to keep the water held within the product matrix. The stabilising agent will need to be the one which can work at the lower pHs which are typical of jams and jellies.
Conclusions
Even when gluten formation is not desirable in bakery products, water plays a major role in the formation of their structures. In products that contain relatively high levels of sugar, the formation of a sugar solution in the aqueous phase is important so that the right conditions for the necessary starch gelatinisation processes are set up or initiated. Higher levels of fat also characterise many types of cakes, biscuits, cookies and pastries, with the fat contributing to the inhibition of gluten formation and also conferring soft and tender eating qualities.