Worldwide the food industry is under pressure to reduce caloric values of sweet bakery products such as cakes. In addition, there is a need to optimize baking processes so that both energy consumption and waste generation can be reduced. Irrespective of the product, understanding fundamental mechanisms behind the changes occurring during processing is key. This article presents tools to study the behavior of cake batters during baking, generating knowledge on batter stabilization mechanisms and foam-to-sponge conversions. Cake batter stability is generally favored by low air bubble velocity, small bubble diameter, and high batter viscosity. Unfortunately, temperature gradients during baking negatively affect each of these variables, resulting in coarser cake structure. Changes in these physicochemical variables were studied using dynamic viscosity and rheological techniques. Foam-to-sponge conversion is a key stage in which the transformation of liquid cake batter (foam) into the solid and aerated cake structure (sponge) takes place. Substantial viscosity changes occur during baking that are highly affected by ingredients such as flour type and sugar content. These factors were studied using various imaging techniques, such as photography and dynamic or static computerized tomography (CT) scanning. By combining physicochemical and imaging techniques, information on fundamental aspects of the system were obtained. Many different varieties of cakes are produced worldwide. Per country, desired product qualities differ, resulting in many different formulations and preparation methods. One traditional type is a pound cake, containing equal quantities by weight of flour, sugar, fat, and egg. This cake is popular for home baking but does not contain enough sugar to provide the long moldfree shelf life required for retail sale. Increasing the sugar level in a pound cake tends to cause structural collapse because of the inability of the flour to support the extra liquid required when sugar levels increase. Heat-treated and chlorinated flours provide solutions to this problem. In Europe, heat-treated flour is used to stabilize the structure when higher sugar and associated liquid levels are required. These cakes are known as highratio cakes because sugar is incorporated at a higher level than flour. Alternatively, there are sponge cakes, which do not contain added fats, and angel cakes, which are made with egg whites rather than whole eggs (4). These are just a small selection of the many cake types produced worldwide. While bread is a basic product that people consume on a daily basis, cake is an indulgent product that should be eaten in lower quantities. Despite its indulgent character, however, British consumers purchase on average 107 g of cakes and pastries per week (Weekly UK Household Consumption of Cakes, Buns, and Pastries, 2018/2109, available online at www.statista.com/ statistics/698176/weekly-uk-household-consumption-of-cakesbuns-and-pastries, accessed 6-02-2020, 2020). As a result, cake products are under pressure within the United Kingdom with respect to sugar reduction to reduce the caloric intake of U.K. consumers. In addition, the whole food supply chain faces increasing pressures as consumers and governments ask for reduced energy consumption and waste generation, while using sustainably sourced ingredients that preferably have a clean label. The desire for “free-from” products is creating additional challenges. Irrespective of the type of cake product, obtaining a fundamental understanding of the changes that occur during the baking process is key to creating an optimal product. During the cake baking process, all cake batters go through a “foam-to-sponge” conversion (7). A thermodynamically unstable foam-like cake batter converts itself to a solid and thermodynamically stable cake foam (1). This stable structure can be stored for a period of time and consumed at a later date. In this article, we outline the basic structural changes that take place during cake baking and demonstrate tools that can be used to increase our understanding of the changes and the effects of ingredients on these changes. The research tools described can be extrapolated to other food products and assist in development of more sustainable, yet indulgent, products.

The effect of replacing 5 and 10% of the flour in a biscuit formulation with two wheat fibres (of different lengths) and apple fibre (differences in morphology and proportion of soluble fraction) was studied. All the fibres decreased the flour pasting properties. The longer wheat fibre produced the greatest increase in the G′ and G″ viscoelastic moduli of the dough compared to the control (no fibres added). The biscuit texture properties were measured using the 3-point break test and cone penetrometry: wheat fibre biscuits were more resistant to breaking while apple fibre produced a crumbly biscuit. Sensory analysis by a trained panel showed minor changes in the apple fibre biscuits compared to the control and greater hardness in the wheat fibre biscuits.