COMPARISON OF 2 METHODS USED TO DETERMINE APPARENT HEAT-TRANSFER COEFFICIENT FOR POUCHES PASTEURIZED IN A COMBINATION OVEN

Apparent heat transfer coefficients between pouch and heating medium i n a combination oven on Vario-steaming mode were determined by compari ng the experimental and simulated temperature histories and by the lea st square and optimization methods. Temperature histories and related P-70 values from experiments and simulation were compared One stage ap proximation of the heating process resulted in large mean square-roote d deviations (MSRDs) in simulated temperature histories, 2.6 +/- 0.4 d egrees C and 2.8 +/- 0.4 degrees C, and also large errors in predicted mean P-70, -21.5% and -11.3%, using h values determined by the least square and optimization methods, respectively. According to heat trans fer mechanisms the heating process was divided into two stages, i.e. a ir and mixture of steam and air heating. MSRDs were reduced to 0.6 +/- 0.3 degrees C for both methods and errors in predicted mean P-70 were reduced to 4.3% and 3.0% for the least square and optimization method s respectively. The differences in h values, MSRDs and mean P-70 produ ced by the two methods became negligible. (C) 1996 Academic Press Limi ted.