With the cumulative gas production technique (Theodorou et al., 1994), the amount of gas released as an end-product of substrate fermentation is measured at regular time intervals, as a measure of the kinetics of fermentation. CO2 is released both directly as a result of the fermentation and indirectly from the bicarbonate buffer in the medium (Beuvink and Spoelstra, 1992). This method was first described for the evaluation of fibrous materials. However, little work has been reported describing the use of cumulative gas production to evaluate concentrates. Soluble fermentable components are rapidly fermented after incubation, while the insoluble ones need to be hydrated and colonized by micro-organisms before they can be degraded (Van Milgen et al., 1993). The varying composition of substrates is one of the reasons for the different rates of gas production seen as these processes are taking place. Concentrates can differ greatly in their composition and therefore in their fermentation characteristics. Here, we describe our first trial with four individual concentrate ingredients, and mixtures of them, to determine whether the parameters from the individual ingredients can be used to predict the fermentation characteristics of the mixed foods.