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Seasonal Changes in Florida Tangelos

By Paul L. Harding, 'principal plant physiologist, Milliard B. Sunday, biological science technician, and Paul L. Davis, chemist, Biological Sciences Branch, Marketing Research Division, Agricultural Marketing Service 1

Summary

Seasonal changes and yearly variations for the principal commercial varietiesof tangelos (Citrus reticulata X C. paradisi) are presented. The varieties included are Orlando, Thornton, Minneola, and Seminole. Chemical constituents and physical characteristics were determined and the data correlated with palatability tests. These tests provided a basis for the establishment of standards of maturity at harvest for these varieties of tangelos. The test period was from October to February for the four crop years 1952-53 to 1955-56. The groves were chosen to represent typical plantings in Florida. The rootstocks included sour orange (Citrus Aurantium), Cleopatra tangerine (C.

1 Acknowledgment is made to Mr. J. B. Prevatt, Chairman of the Tangelo Maturity Committee, and to committee members R. H. Prine, William Franklin Ward, and Leo H. Wilson for their helpful suggestions and approval of the tangelo maturity "code," and to the following growers and shippers for generously providing fruit for the investigation: Charles E. Bradshaw, H. A. Bradwell, G. R. Brooks, W. C. Daniels, S. Carey Colley, the late H. J. Edsall, Colin English, E. Allen Haley, Jr., L. E. Jefferies, J. A. Kauffman, Don Kemp, Lake Region Packing Association, J. W. Moore, A. E. Pickard, W. R. Pollard, C. W. Rex, F. E. Roberts, T. Ralph Robinson, R. S. Salter, Byrum Shockley, Jason Smith, C. C. Thullberry, E. G. Todd, G. F. Ward, and C. W. Worn. Staff members who assisted in conducting the investigations were: Helen L. Dudak, Burton S. Floyd, Ernest E. Forrest, Jr., William H. Henry, Earl F. Nelson, G. Lee Roberts, Emily A. Ross, M. J. Soule, Jr., and T. A. Wheaton.

reticulata), rough lemon (C. Limon), sweet orange (C. sinensis), Rusk citrange (Poncirus trifoliata X C. sinensis), and sweet lemon (C. Limon).

The Orlando reached maturity first and Seminole last; Thornton and Minneola were intermediate. To insure good eating quality, a marketing standard was established having varying requirements through the season. A nomograph was devised for easy calculation of minimum market acceptability. This standard provides for a sliding scale of acceptability based on seasonal changes in solids and acids and in the solids-to-acid ratio. Early season fruit must have a minimum of 9 percent total solids and a minimum ratio of solids to acid of 10 to 1. As the season progresses the minimum total solids requirement decreases and the minimum total solids to total acid ratio increases. The quality and quantity of fruit reaching the consumer can easily be controlled by adjustment of this standard.

The weight of total soluble solids increased and the weight of total acid decreased during the marketing season. These factors, together with the resulting solids-to-acid ratio, were closely associated with the palatability ratings.

Ascorbic acid (vitamin C) concentration showed no marked tendency to fluctuate during the season. Active acidity gradually decreased as the tangelos ripened.

weight of the fruit increased during maturation and tended to level off or decrease slightly after prime eating quality was reached.

Degreening was associated with maturation and took place rapidly during the October to February period.

By the time the fruit reached the minimum standard of consumer acceptability the color of the flesh was yellow-orange to orange for Orlando, Minneola, and Seminole tangelos, and tannish yellow for Thornton. Flesh texture of all varieties was good at this time.

Variation associated with rootstock was not as pronounced as that associated with variety. For Orlando tangclos, total solids, total acid, and palatability ratings were higher in fruit from trees on Cleopatra rootstock than in fruit from trees on some of the others, such as rough lemon.

Yearly variations in fruit characteristics were associated with rainfall. Fruits produced during a relatively wet season were heavy and had a high volume of juice; the juice had low total solids and total acid. During a relatively dry season the fruits were relatively light and had a low volume of juice. However, the total solids, total acid, and solids-to-acid ratio were high.

The Orlando, Minneola, and Seminole tangelos resemble the tangerine parent in many respects, such as total solids content, ascorbic acid concentration, active acidity, and rind color. The Thornton tangelo resembles the grapefruit parent in total solids content, ascorbic acid concentration, and color of the rind.

Introduction

Tangelos (Citrus reticulata X C. paradisi) are grown in Florida and marketed as specialty fruits. They are important items in the gift box trade which comprises about three million pieces, but in recent years

on the carlot basis has become even more important. Within 29 years, 1928 to 1957, nearly 400,000 tangelo trees, enough for planting over 5,000 acres, were reported to the Florida State Plant Board inspector as having been moved from Florida nurseries to Florida destinations (14).2 During the 1957-58 season, about 250,000 packed 4/5-bushel boxes of tangelos were certified by the Florida Inspection Service (6).

Tangelos comprise a group of citrus fruits which are hybrids of the tangerine, or mandarin orange (Citrus reticulata), with either the grapefruit, or pummclo (C. paradisi and C. grandis) (21). The tangelos used in this investigation, however, were crosses of Citrus reticulata X C. paradisi. The name tangelo is a combination of the first syllable of tangerine and the last three letters of pummclo. The first crosses giving rise to this group of fruits were made by Swingle at Eustis, Fla., in 1897. Other crosses were made by Webber in 1898. Another series of crosses by Swingle, Robinson, and Savage (17) cover a period from 1908 to 1912. This plant breeding work was done principally at Eustis and Glen St. Mary, Fla., by scientists of the U.S. Department of Agriculture.

In this investigation the fruit development and compositional changes of the principal varieties ot tangelos were studied during marketing seasons 1952-53 to 195556. From the results, it has been possible to establish minimum maturity standards by correlating physical measurements and chemical constituents with palatability ratings of the fruit. Practical standards were set up on a sliding scale. For example, early in the season a minimum of 9 percent total solids and a minimum solids-to-acid ratio of 10 to 1 is required, while for late season fruit the requirements

2 Italic figures in parentheses refer to items in Literature Cited, page 25.

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