The role of the baking process in the formation of wafer structure
Ramana Sundara, Nestle Product Technology Centre, UK
This research study is based on two precepts: firstly, wafer is foam, a cellular solid of dried gelatinised starch containing gas cells. Secondly, wafer texture is a result of competition between the developing gas phase and the increasing viscosity of the continuous solid phase due to gelatinisation of starch during the early stages of baking. Solid to gas ratio (relative density) and gas cell distribution are major factors in determining wafer texture.
Methodology was therefore influenced by how to create and measure foams. A series of baking experiments were designed to give a competitive advantage to either the gas or solid phase. Baking was interrupted at intervals and changes in the gas and gel phases of batter measured with time. Samples from baking trials were characterised using microscopy, mechanical analysis and density measurements.
The architecture of flat wafer shows gas bubbles dispersed in a dried gelatinised starch (solid) phase. The texture of brittle foam is determined by its structure – the relative amounts of gas to solid phase, bubble size and, shape and distribution. This work shows that this applies equally to wafer as it does to any other material foam. When viscosity of gelatinising starch dominates, it limits the growth of gas cells resulting in thicker cell walls and therefore a harder structure. When gassing dominates, it encourages the gas cell growth thereby resulting in thinner cell walls and weaker structure. Wafer texture can be influenced by manipulation of heat delivery to the batter; an alternative way of delaying or advancing the gelatinisation of starch by varying plate distance, plate temperature, surface area and/or delayed closure.
Creation and control of wafer texture is critical to the development of this strategic area of Nestlé’s confectionery business. The simple model proposed in this study shows how a wide range of wafer textures can be created using existing ingredients and assets.
Emailramana.sundara@rdyo.nestle.com
