No abstract

Frozen asparagus, green beans, and green peas were properly defrosted and packed in 211 x 011 cans together with city water. The prepared samples were then heat processed at 175-300°Ffor OS-20 min. The tristimulus values of puree prepared from heat processed vegetables were determined by using a color difference meter. The ratio -a/b was used to determine the values of reaction kinetic parameters, D and z, for the discoloration of the vegetables since this ratio was closely related to the visual color of green vegetables. A D value was estimated from the slope of a linear portion of a curve. This curve was obtained by plotting the common logs of -a/b against isothermal heating times. A z value was determined from the slope of a thermal death time curve, which was obtained by plotting log, ,, D against temperature. The z values for the discoloration of asparagus, green beans and green peas were found to be equal to 7.5 CF), 70 and 71, respectively. Apparent activated energies for changes in visual green color, which was represented with -a/b, were estimated by assuming first order reaction kinetics. These energies for asparagus, green beans, and green peas were respectively equal to 18,080 (Cal/mole), 19,800 and 15,200.

A computerized procedure was developed for estimating the variability of process lethality when there were variations in all independent, thermal process parameters of conduction heating food packages. This was accomplished through the combined application of a Monte Carlo procedure and a reliable mathematical method for thermal process evaluation. By examining published information, statistical variations in physical and reaction kinetic parameters were represented by gamma distributions and others by normal distributions. The coefficients of variations in sterilizing values were estimated from temperature data collected by processing 211 x 300 and 307 x 409 cans of spaghetti in tomato sauce (60 cans each). They agreed well with those computed by the developed computerized procedure.

A new procedure was developed to determine the specific heat of food products by using a calorimeter which was prepared through the proper modification of a household vacuum jar. Since there was no direct contact between food and heat exchange medium in the calorimeter, the evaluation of heat of solution for dissolvable chemical entities in the food was eliminated and also this new method is readily applicable to food whose temperature is higher than 100°C. The reproducibility and reliability of the developed procedure were carefully examined by using several materials whose specific heat values were well documented. This procedure was utilized to determine specific heat values of four cookies, wheat flour and one fresh produce. The agreement between the experimental and literature values was found to be excellent. The standard deviations of replicated experiments were less than 2%.