Two important chemicals and an essential mineral (phytonutrients) for human health and well-being are ascorbic acid, 5-methyl-tetrahydrofolic acid (folic acid) and potassium. The influence of cultivar, fruit size, soil type and year on these compounds in [Cucumis melo L. (Inodorous Group)] was determined. Fully mature (abscised) commercial size fruit: 4, 5, 6, 8, and 9 (fruit/0.031 m3 shipping box) from three commercial cultivars: Mega Brew, Morning Ice, and TAM Dew Improved (TDI); and one experimental hybrid `TDI' × `Green Ice' were grown on both clay loam and sandy loam soils. Total ascorbic acid and folic acid content increased with an increase in fruit size up to a maximum (size 6 or 5), then decreased with further fruit size increase. Total ascorbic acid and folic acid content for most fruit sizes were higher when grown on clay loam versus sandy loam soils. The experimental hybrid compared to the commercial cultivars contained generally higher total ascorbic acid levels and significantly higher folic acid levels regardless of fruit size or soil type. Free ascorbic acid and dehydroascorbic acid contents were generally higher from clay loam versus sandy loam soils and in the experimental line versus the commercial cultivars. However, free ascorbic acid content was high in small fruit and remained unchanged with an increase in fruit size until size 6 or 5 then significantly decreased; while dehydroascorbic acid content linearly increased with an increase in fruit size. Potassium content averaged 1.7 mg·g-1 fresh weight for each line and did not significantly differ due to fruit size, but did for soil type and year. Analyses of variance for the phytonutrients assayed demonstrated that cultivar (genetics) always was very highly significant (P = 0.001), whereas, soil and year (environment) were not.
Gene E. Lester and Michael A. Grusak
Commercially grown honeydew fruit (Cucumis melo Inodorus group) and netted cantaloupe fruit (C. melo Reticulatus group) in low-humidity regions of the U.S. are typically field packed, eliminating the possibility for postharvest chelated-calcium dip treatments to extend fruit shelf life. In this study, calcium treatments were applied to orange-flesh honeydew fruit commercially grown in 2001 and 2002 in Sacramento Valley, Calif. and orange-fleshed netted cantaloupe fruit commercially grown in 2002 in Imperial Valley, Calif., and Rio Grande Valley, Texas. Aminoacid-chelated calcium and mannitol-complexed calcium compounds were applied to field-grown plants at the rate of 2.3 L·ha-1 (1 qt/acre) at 0, 1, 2, or 4 total applications during growth of honeydew and cantaloupe fruit. Applications were A) at female flowering, B) within 15 days (cantaloupe) or 20 days (honeydew) after flowering, C) within 30 days (cantaloupe) or 40 days (honeydew) after female flowering, and/or D) within 3 to 5 days before abscission. One application equaled (A) or (D), two applications equaled (A + B) or (C + D) and four applications equaled (A + B + C + D). Evaluations of fully abscised fruit were exterior and interior firmness, marketability, calcium concentrations, interior soluble solids concentration (sugars), and consumer preference (taste) following harvest and up to 3 weeks commercial/retail storage. Cantaloupe fruit at both locations did not appear to benefit from preharvest plant applications of calcium when compared to fruit from plants treated with water. Honeydew fruit, however, did and the benefit was observed both years. Honeydew fruit that received four preharvest plant applications of calcium, regardless of source, were generally superior in firmness, marketability, and had a higher calcium concentration than fruit from plants receiving water or one or two applications of calcium. Fruit sugars and taste were not affected by preharvest plant applications of calcium.
Gene E. Lester and Michael A. Grusak
Commercially grown honey dew fruit [Cucumis melo (Inodorus group)] typically are harvested before abscission because fruit cut unripe have a longer storage life than fully ripe fruit. However, because fully ripe fruit contain higher concentrations of soluble solids (predominantly as sugars), an attribute that increases their preference among consumers, methods are being explored to extend the storage life of fully ripe fruit. In this study, fully abscised honey dew fruit were evaluated for tissue attributes and consumer preference following postharvest dipping in either chelated or nonchelated calcium (Ca) solutions. Calcium sources were an amino acid-chelated Ca, ethylene-diamine tetraacetic acid (EDTA)-chelated Ca, or calcium chloride (CaCl2), with each provided at three different rates. Fruit were evaluated at harvest, and after 14 or 22 days commercial storage. Evaluations were peel surface changes (color and disorders), hypodermal-mesocarp tissue Ca concentration, flesh firmness, soluble solids concentration, and consumer preference of the edible flesh. Peel color became yellowed and lighter during storage for all fruit, with higher Ca rates resulting in more intensely yellowed fruit. Hypodermal-mesocarp tissue Ca concentration was 0.90 mg·g-1 of fresh weight (900 ppm) at harvest, and declined in all fruit by 22 days storage. Peel disorders (disease and spotting) were none to slight for all fruit by 14 days storage, but by 22 days storage disease incidence ranged from none to severe, depending on the Ca source and rate. Fruit firmness declined in all fruit throughout storage, with the smallest declines measured in fruit treated with the amino acid-chelated Ca. Soluble solids concentration of fully ripe fruit was 12.3% at harvest, and showed either no decline or slight declines with storage among the treatments. Consumer preference was highest for freshly harvested fruit, but fruit were desirable even after 22 days storage across all treatments. Postharvest application of Ca at ≤0.16 m Ca in an amino acid-chelated form, versus EDTA-chelated Ca or CaCl2, slowed honey dew melon senescence so that after 22 days of commercial and retail storage the fruit were of high marketable quality, and there was no detrimental effect on consumer preference for the edible flesh.