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.

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Green beans, corn, peas and asparagus, which were filled in 211 X 011 cans, were subjected to various heat treatments in order to determine the values or reaction kinetic parameters for the thermal destruction of organoleptic quality. Shortly after these treatments, samples were subjected to flavor panel evaluation. Frozen vegetables were used as control samples for the evaluation. Since there were significant heating and cooling lags, each thermal process was mathematically converted to an idealized process with no lag's in the temperature response of sample food. This conversion is based on the use of a mass average sterilizing value estimated from a temperature history curve determined at the center of a can of sample food. Organoleptic quality destruction curves were obtained by plotting the common logarithm of isothermal heating time at which the quality of treated samples became objectionably poor against temperature. From the slope of these curves, the z values were obtained. These values are 52°F for green beans, 57 for corn, and 51 for peas. The z value was not determinable for the thermal destruction of quality in asparagus because of its special response to heat treatments.

The thermal resistance of Salmonella senftenberg 775W, Salmonella muenster previously isolated from raw fluid milk, and two mixtures each consisting of ten Salmonella strains commonly isolated from human or non-human sources was tested. Cells were suspended in whole milk at a final concentration of 105 cells/ml. The inoculated milk was thermally processed at temperatures ranging from 60°C to 74°C using a pilot-scale plate pasteurizer unit. The mean and minimum residence time of milk in the holding tube of the pasteurizer was 17.6 and 16.2 s, respectively. The maximum temperature at which viable salmonellae were detected in the human (61.5°C) and non-human (64.5°C) mixtures was considerably lower than that obtained with S. senftenberg 775 W (67.5°C). S. muenster failed to show any milk-adapted response and could not be recovered at temperatures greater than 63.0°C. Treatment at 63°C produced a 4 log10 or greater reduction in the number of viable Salmonella including the heat resistant S. senftenberg 775 W, and a minimum 2 log10 decrease at 60°C. These findings warrant caution in the use of subpasteurizing temperatures for thermal processing of fluid milk.

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