Date of Award
Doctor of Philosophy
Food Science and Technology
Mary Nelle Traylor
Ada Marie Campbell, Grayce E. Goertz, Jimmie Collins
Objective quality control standards for prepared food, held heated for varying periods of time were studied. Frozen Grade A whole stringless Peco and Slender White string green beans grown, blast frozen, and packaged in Tennessee were used.
Before cooking, 12 lb of each variety were randomly chosen, removed from the freezer and package, mixed together, then divided into seven 735 g portions. Portions were placed in seven half-size shallow stainless steel steam table inset pans marked with holding times of 0, 10, 20, 30, 40, 50, and 60 minutes.
All pans of green beans were steamed at one time for 30 minutes under 5 pounds of pressure in an upright stack steamer. Six of the pans then were placed in improvised steam tables and held for the specified time. Internal temperature of the beans was held above 140° F. The pan marked for zero holding time was covered and allowed to cool.
Five replications of objective measurements for Peco and Slender White beans were obtained for the seven holding periods with the Kollmorgen Color Eye for dominant wavelength, Munsell color, and Hunter a and b. Instron measurements were used to obtain "force," "shear peak area," and "work." Moisture content and pH of the beans also were determined.
A seven-member trained sensory panel evaluated both varieties of beans for texture, overall acceptability, and color for the first four replications. A consumer panel evaluated each green bean variety for overall acceptability during the fifth replication. Evaluation of consumer panel scores was by an analysis of contingency tables using chi-square values as test statistics to test no difference in preference of the two varieties. Orthogonal comparisons and analyses of variance of mean values for objective measurements and panel scores were performed.
The two varieties of beans were inherently different in color (P<0.01). Holding time affected the dominant wavelength and Munsell color, significantly (P<0.01). Panel scores for color and texture were affected significantly (P<0.01) by holding time. Instron measurements of "force" and "work" were affected significantly (P<0.05) by holding time. Both panel scores and objective measurements of dominant wavelength indicate a linear change in green bean color from green to yellow with holding time. Panelists discerned a steadily declining rate of firmness of the green beans as indicated by the linear component of the orthogonal comparison. "Force" and "work" components also were linear. Acceptability of the green beans by panelists had a cubic relationship with holding time. The acceptability scores were highest between 30 and 40 minutes' holding time, when the beans were noticeably but not maximally soft and yellow. Consumer panels did not discern a significant difference between varieties with regard to acceptability. Indications from the statistical analysis are that objective quality control standards could be a range of either Munsell colors or dominant wavelengths measured at 30 and 40 minutes of heated holding time as the lower and upper limits. Instron measurements for "force" and "work" at the same holding periods also could be objective measurements.
Brenner, Anna Mae, "Quality Control Standards for Cooked Frozen Green Beans Held Heated for Varying Holding Times. " PhD diss., University of Tennessee, 1975.