Humidity change and its effects on baking in an electrically heated air jet impingement oven

A high temperature humidity sensor was used to monitor the absolute humidity inside an electrically heated conveyorized, food service-scale, two-zone, air-jet impingement tunnel oven as commonly used by pizza chain restaurants. The oven was first operated empty, then loaded with dummy loads consisting of pans of water in perlite while baking layer cakes, and finally when baking cakes with added dummy loads. Temperature and loading affected humidity, and humidity affected final product quality. High humidity lightened cake crust color, increased volume, and raised the final moisture content of the cake. There was no significant effect of humidity on the heat transfer coefficient as determined by a standardized metal target plate. In this study, one pan of perlite approximated three pans of cake. Adding perlite dummy loads was shown to be a useful technique to quantitatively measure and to demonstrate the effect of humidity during baking. It is also a convenient way to accelerate oven load-testing without producing and discarding a large number of samples. (C) 2002 Elsevier Science Ltd. All rights reserved.