Measurement of tomato quality

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Van Teeling, Cornelis Gerald
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Twelve tomato varieties were harvested at two maturities and stored at two temperatures and comapred in quality at the table-ripe stage. Quality factors evaluated were juice color, surface color, firmness, pH, acidity, soluble solids, protopectin content and toal pectin content. Varieties differed significantly for all the quality factors. Total pectin and protopectin content was not affected by temperature of ripening or maturity at harvest while firmness was affected by both. A method for determining tomato firmness by the Allo-Kramer Shear Press was developed. Firmness was measured with a 7/16 in. diameter round-end probe on the mid-equatorial line of the tomato. Firmness was recorded as peak force and work area. The Shear Press results correlated at P = 0.01 to protopectin content, but not with total pectin content. A comparison was made to a smaller 1/8 in. diameter round-end probe. The results using the small probe had a higher correlation coefficient to protopectin content than the larger probe, but the peak force measurement of the small probe was essentially equal to the large probe work area. Firmness and alcohol-insoluble solids correlated significantly (r = 0.36).