Using X-ray-computed Tomography to Nondestructively Determine Maturity of Green Tomatoes

Cross-sectional X-ray-computed tomography (X-ray CT) images through the equator of tomato fruit (Lycopersicon esculentum Mill., CV. Sunny) ranging in maturity from immature (Ml) to advanced mature green (M4) revealed localized dif- ferences in X-ray absorption related to the formation of locular gel during maturation of the fruit. While maturity stage was poorly correlated with average X-ray absorbance and standard deviation or with average fruit density and water content, significant relationships' existed between maturity stage "and the number of image pixels with absorbance values >10 (Ml vs. M2 vs. M3) or 20 (M3 vs. M4) Hounsfield units. Using discriminant analysis, a relationship was developed that correctly identified the ma- turity class of 77% of the fruit and placed 96% of the tomatoes into the correct or an adjacent class. Proper maturity at harvest is a critical fac- tor in determining the quality of tomato fruit picked green. The U.S. Standards for grades of fresh tomatoes, recognizing the relation- ship between maturity and the ability of the fruit to ripen properly, defines maturity using the internal indicators of gel formation in the locules and seed development (U.S. Dept.