Author
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WU, TIANXIA - NANJING AG UNIV, CHINA |
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Abbott, Judith |
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Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/24/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Firmness is an important aspect of the quality of fresh tomatoes. Its measurement is important in postharvest studies to develop procedures for preparation and handling of fresh-cut tomato slices. Cutting fruits induces the wound hormone ethylene which affects many metabolic processes in the tissue. Although there is considerable literature on the firmness measurement of intact tomatoes, little has been published on measuring cut tissues. This study was conducted to determine how cutting affects the textural changes in tomato tissue during storage and to determine the effects of initial ripeness on such changes. We found that strength or firmness, elastic properties, changed little over storage for tomatoes of a given initial ripeness, whether stored intact or as slices. However, viscoelastic behavior differed between intact and sliced tomatoes. This finding indicates that measurement of simple elastic properties may be inadequate and that research is needed to determine the impact of viscoelastic changes on sensory quality and functional behavior of fresh-cut tomato slices. This information should benefit postharvest physiologists and food scientists involved in the evaluation of tomatoes, particularly for fresh-cut slices. Technical Abstract: Firmness and force relaxation characteristics were compared for tomato flesh harvested at six ripeness stages and stored intact or as slices for 0 to 20 days. Measurements were made of outer pericarp and columellar tissue. Following loading, stress relaxation was recorded for 10 s. A 4-mm cylindrical probe provided more consistent firmness measurements than a 6.4-mm spherical probe at harvest, and distances of 3 mm provided more consistent results than 1 mm. Fmax (maximum force) was closely correlated to area, slope, and yield force; i.e., all measured elastic behavior. Tomatoes stored intact generally had lower variances than those sliced before storage, although there was little difference in average Fmax between sliced and intact tomatoes at a given storage time and initial ripeness. The model Y = 1 A ln(1+t) B t/(C+t) was developed to fit the relaxation curves. There was little correlation between Fmax and the relaxation parameters (A, B, and C), i.e., the relaxation parameters measured viscoelastic behavior. The responses of the relaxation parameters over storage time depended on initial ripeness, but values usually differed significantly between tomatoes stored intact or sliced, with tomatoes sliced before storage generally having higher values. |
