A Rapid and Accurate System for Scoring Tomato Fruit Cracking

Many studies have been conducted concerning the crack resistance of tomato fruits. Various means of measuring crack susceptibility of tomato fruits have been used. Iverson (3), Reynard (6), and Prashar and Lambeth (5) have used rating systems to evaluate cracking of tomato fruits. These systems were rapid and suitable for distinguishing between relatively large differences in crack resistance. Johannessen (4), Voisey and MacDonald (10), and Voisey and Lyall (9) have devised instruments to measure the mechanical strength of the tomato skin. Methods using these instruments are slow and the relationship between crack resistance of tomato fruits and the mechanical strength of the skin has not been definitely established. White and Whatley (11) have suggested the use of a map measure to measure the lengths of cracks in tomatoes and apples. This method is very accurate, but it is slow and limits the number of fruits that can be evaluated. Hepler (2) developed, and Thompson et al.(7) and Thompson (8) used the Illinois vacuum-immersion technique for testing the resistance of fruit cracking in tomatoes. It consists of placing in water fruits selected at incipient color, drawing a partial vacuum and holding the vacuum until bubbles are no longer emitted from the stem scar, then continuing the immersion for a certain period at normal pressure. The resulting cracks are measured with a map measure. This method has the advantage in that it can differentiate crack resistance among lines that appear resistant to cracking in the field. The conditions under which cracking occurs can be controlled by using this method, and a large part of the environmental effect upon cracking can be eliminated. This method is rapid as far as inducing cracking is concerned, but extremely time—consuming when it comes to measuring the induced cracks. This is especially true on lines where large amounts of cracking are induced on the fruit.