Owen Fennema: Food Chemist Extraordinaire.

Periodically someone comes into a field and forces a change in direction, a paradigm shift. Owen Fennema was such a person in food science and technology. When he started his academic career, curricula in food science and technology had courses describing how to process plant produce and animal tissue into safer food with an extended shelf life. The "why" was often overlooked. Owen changed all that. He participated in and greatly contributed to a paradigm shift in teaching food science by editing one of the most important textbook series in food science and technology. In addition, his research on water and ice as they impacted the chemical, physical, and biological characteristics of plant and animal tissues extended the bounds of knowledge. He did the same for edible bilayers with research done in his laboratory. Who was this man, and how could he have such impact? Hopefully, this review provides some insights into Owen Fennema, Renaissance man.

Effects of temperature and time on mutagen formation in pan-fried hamburger.

Mutagenic activity generated in hamburger during pan-frying is dependent upon both temperature and time, with temperature appearing to be the more important variable. Uniformly prepared frozen hamburger pattie (115 g; 19% fat) were fried under carefully controlled conditions at 143 degrees C, 191 degrees C and 210 degrees C. Mutagenic activity assayed with the Ames test was not detected in uncooked hamburger, and in hamburger fried at 143 degrees C mutagenic activity remained low at all times studied (4--20 min). In contrast, frying at 191 degrees C or 210 degrees C for up to 10 min resulted in the generation of considerably higher levels of mutagenic activity. Mutagenic activity in fried hamburgers sold at selected restaurants ranged from very low to moderately high. Evidence is also presented for mutagenic inhibitory activity in uncooked and fried hamburger. Mutagenic inhibitory activity decreased mutagenesis mediated by liver S-9 from normal rats but not from Aroclor 1254-treated rats.

Effect of microwave heating in cook/chill food service system. Energy balance for heating beef loaf.

In the microwave-heating subsystem of the simulated cook/chill food service, 100-gm. portions of precooked beef loaf were heated 80 sec. (2,450 mHz; 237 V.; 3,003 W. input power; 1,407 W. output power) to a mean internal end temperature of 82 +/- 9 degrees C. Mean input power to the microwave oven during heating, controlled by a transformer, was 240 kJ. per 80 sec. Fifty-three percent of the input power to the microwave oven was used to operate the oven. Of the 47 percent output power available to heat the beef loaf, 12 percent of the total input power was estimated to heat beef loaf, 17 percent was estimated to evaporate water from beef loaf, and 18 percent was attributed to miscellaneous energy losses.

Fouling of Heat Transfer Surfaces by Solutions of Egg Albumin.

A major problem which can be encountered when biological fluids are heated is the deposition of components from the fluid on the heating surface. This results in loss of efficiency in the heat transfer process and usually contributes to requirements for more severe cleaning regimes to return the surface to the original clean condition. Since proteins have been implicated as a major source of the problem in heat exchanger fouling, we studied the effect of process and fluid variables on deposition from protein solutions. An electrically heated stainless steel surface was exposed to egg albumin solutions flowing at a variety of temperatures, fluid flow rates, and concentrations. The system for studying the rate of burn-on is unique and has been described elsewhere. The surface temperatures of the stainless steel surface could be monitored and controlled to any desired temperature. Results of the study indicated: (a) fouling rate increased with an increase in protein concentration, (b) increasing the fluid flow rate did not have a significant effect on rate of fouling, (c) increasing the temperature difference increased fouling rate, and (d) surface finish did not influence fouling.

Effect of microwave radiation on inactivation of Clostridium sporogenes (PA 3679) spores.

Three techniques for studying effects of microwave radiation on microorganisms were introduced. Spores of Clostridium sporogenes (PA 3679) were chosen as a test organism because the kinetic parameters for thermal inactivation are well known and because of the importance of the genus Clostridium to the food industry. For the first technique, a specially designed kinetics vessel was used to compare inactivation rates of microwave-heated and conventionally heated spores at steady-state temperatures of 90, 100, and 110 degrees C. Rates were found to be similar at the 95% confidence level. The second and third techniques were designed to study the effect of relatively high power microwave exposure at sublethal temperatures. In the second approach, the suspension was continuously cooled via direct contact with a copper cooling coil in a well-mixed vessel, outside the microwave oven. The suspension was pumped through a Teflon loop in the oven, where it continuously absorbed approximately 400 W of microwave power. Inactivation occurred in both irradiated and unirradiated samples. It was suspected that copper ions entered the suspension from the copper coil and were toxic to the spores. The fact that the results were similar, however, implied the absence of nonthermal microwave effects. In the third approach, the copper coil was replaced with a silicone tubing loop in a microwave transparent vessel. The suspension was continuously irradiated at 150 W of microwave power. No detectable inactivation occurred. Results indicated that the effect of microwave energy on viability of spores was indistinguishable from the effect of conventional heating.