Anyone who has ever made bread at home can appreciate the complexity of baking the loaf for the optimum size, color, flavor, crust formation, thickness, and other finished loaf properties. The oven provides much more that than just a golden color. The temperature must inactivate the yeast, give the gas cells a final "oven spring" for proper size and shape, inactivate enzymes, set the final structure so the bread doesn't collapse, and various other properties not normally thought about.

In the commercial baking process, the time and temperature relationships are very important for finished product quality and production efficiency. Information on conventional oven technology can be found in various text books and trade articles. These include direct and indirect fired, single and double lap, tunnel ovens, gas and electric, and various other combinations.

A number of years ago, several bakers tried, unsuccessfully, to adapt microwave tunnel ovens to the baking process. But as is commonly known, there is no surface heating and drying to produce the browning reaction. There may still be opportunities for using microwave energy for the advantage of faster "cooking" if combined with other heating technologies.

Impingement Ovens have been used for many years in meat processing as well as the standard for pizza cooking. These ovens use very intense, high velocity air impinging directly on the product and with a heat transfer equal to 5-25 times greater than natural convection. This technology offers gains in speed and reduced oven size, while maintaining proper surface color.

Dielectric heating is a newcomer in the commercial market. It is commonly referred to as "electronic post baking" and is most recently being used as a drying step, to achieve the critical final moisture content of cookies and crackers. The heat is the result of inter-molecular friction caused by exposure to a high-frequency source. The moisture in the product really becomes the heat source. Heat within is a function of the moisture content -- the higher the moisture, the faster the moisture is driven off.

A very new technology, still in the early stages of acceptance, uses an electrostatic phenomenon. A network of high voltage grids induces a "corona wind" above the product, and is said to have effects on the rate that starch gelatinizes and the heat transfer efficiency.

Hybrid Ovens are the current "buzz" words being used by oven developers today. Recognizing that various heat transfer systems all have different properties for different products, the current thinking is that if multiple technologies were linked together in a reduced-size, flexible system, one could have optimum baking with the greatest production flexibility.

Today's manufacturers are using Programmable Logic Controllers (PLCs) to in fact not only link multiple heat transfer technologies, but optimize conditions and allow for shorter, more flexible production runs. The concept of Bake-to-Order is similar to Just-in-Time. Maximum store freshness can be achieved if short production runs are tied to farthest-truck-out distribution systems. This approach allows the larger, regional wholesale bakery to have a closer quality match to in-store bakeries.

Hybrid oven technologies allow for this flexibility and versatility, but are still in the early development stages. Work continues to select the best combination of heating systems for the products being produced. A smaller, hybrid oven would allow for smaller plants, shorter product runs, and optimum quality. What has slowed the progress in this exciting new area is the general lack of basic information on the electrical properties of food and their relationship to heating properties.

For faster market penetration to occur, a new focus is required on the interdisciplinary problems involved. There are great opportunities in the whole process of cooking foods, not only here on earth, but in the space programs as well.