Controlling processes in food technology by simplifying the canonical form of fitted response surfaces

Second-order response surfaces are often fitted to the results of designed experiments, and the canonical form of such surfaces can greatly help both in interpreting the results and in deciding what action to take on the process under study. A mixing process on pastry dough is described in which it is desired to simplify the canonical form to make the control of the process more economical, by basing it on only two of the three factors. We give examples where a simplification is possible with minimal loss of accuracy and where it can be seriously misleading, and we outline the features of the response surface that lead to these two situations. A method of improving the simplification by recalculating the constrained canonical axis is proposed. These methods ensure that the mixing process can be controlled by using only two factors without seriously lowering the quality of the pastry.