A water content sensor for baked products

The water content of baked products such as bread, cake and biscuits, affect the texture, colour, keeping qualities and consumer acceptance. Currently, moisture content is controlled by ensuring a uniform set of ingredients, mixing and baking, but inevitably variation arises from, for example, variation in ingredient characteristics, position within ovens and ambient temperature and relative humidity. A water content sensor that can measure on-line moisture after baking and adjust oven temperature distribution or just the mean oven temperature, will lead to more consistent products. This paper outlines requirements of a sensor for on-line measurement of moisture content, describes a sensor concept that meets these requirements, and then presents the results from experimental work that determined typical permittivity values of bread, one of the target baked products.