We compared the firmness and force relaxation characteristics of tomato flesh harvested at six maturity stages and stored intact or as 7-mm slices for 0 to 20 days. Three measurements were made on outer pericarp and columella tissue. A 4-mm cylindrical probe provided more consistent firmness measurements (lower percent CV) than a 6.4-mm spherical probe at harvest, and distances of 3 mm were more consistent than 1 mm. Following loading, stress relaxation was recorded for 10 s. Stored tomato samples were tested only with the 4-mm cylindrical probe and distance of 3 mm. Firmness was taken as the maximum force (Fmax) in the loading portion, usually occurring at 3 mm. Fmax of freshly harvested tomatoes ranged from 15 to 2 N for mature green and red tomatoes, respectively. Fmax was closely correlated to area, slope, and force at first peak, i.e., all four parameters measured the same physical property, and was moderately correlated (R > 0.9) to forces at specific relaxation times. Tomatoes stored intact generally had lower CVs than that of those sliced before storage, although there was little difference in average firmness (Fmax) between the two at a given storage time. A three-parameter model was developed to fit the relaxation curves. There was little correlation between Fmax and the three relaxation characteristics (R = 0.6 to 0.0), i.e., the relaxation characteristcs measured different physical properties than did Fmax. The responses of the relaxation characteristcs over storage time were dependent on the initial maturity of the tomatoes, but their values usually differed significantly between tomatoes stored intact or sliced, with tomatoes sliced before storage generally having higher values.
Tianxia Wu and Judith A. Abbott
Nithiya Rattanapanone, Yuen Lee, Tianxia Wu and Alley E. Watada
The marketable period of fresh-cut `Tommy Atkins' and `Kent' mango cubes was 3 to 5 days at 10 °C and 5 to 8 days at 5 °C. The marketable period was extended by 1 to 2 days when cubes were held in a 4 kPa O2 + 10 kPa CO2 or 2 kPa O2 + 10 kPa CO2 (balance N2) atmospheres, depending on cultivar and temperature. Variations in texture (shear force), pH, and soluble solids were greater among cubes from different mango lots than among cubes held at different temperatures or atmospheres. Yeast count increased more with time than did the total mesophilic aerobic count, and the increase was less under controlled atmosphere (CA) than in air at 10 °C. The CA was beneficial in maintaining quality of the cubes; however, low temperature was more effective than CA.