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previously made for Temple oranges (10), tangerines (9), and grapefruit (8), showing the relation of consumer approval to total solids and total acid were constructed for each variety of tangelo. These were obtained by connecting lines between values for total solids and total acid for each of the samples which rated 70 or more in the taste tests. From the nomographs thus drawn, base lines of minimum acceptability were established. The composite nomograph for Orlando, Thornton, Minneola, and Seminole tangelos is shown in figure 4. From this basic information, it was possible to set forth in tabular form the percent minimum total solids and the min
for practical standards (appendix table 19).
These standards were enacted by the Legislature of the State of Florida in 1957 at the request of the citrus industry (5). Should the consumer demand sweeter fruit, the standards could be easily adjusted by an increase in ratio requirements, or an increase in minimum solids, or both. Conversely, in order to allow more tart fruit to be shipped, the ratio requirements could be decreased, the minimum solids requirement decreased, or both.
Table 3 shows the relationship between total solids, total acid, solids-to-acid ratio, and palatability
Figure 4.—Base line of a composite nomograph showing the relation of total solids and total acid in 398 samples of Orlando, Thornton, Minneola, and Seminole tangelos rated as meeting consumer approval according to taste tests. Using this information, 5 picking periods for acceptable fruit were established, August 1 through October 31, November 1 through November 15, November 16 through November 30, December 1 through January 31, and February 1 through July 31. See table 19, Appendix.
Line A, entirely above the base line, is representative of fruit meeting consumer approval. Line B, crossing the base line, is representative of fruit not meeting consumer approval.
and Seminole tangelos rated "acceptable" in taste tests by scoring 70 or above
of the 398 samples rated as acceptable and used in construction of the nomograph. From this it can be seen that over 60 percent of the fruit had total solids ranging from 10.00 to 11.99 percent, total acid from 0.38 to 1.42 percent, and ratios from 7.80 to 29.29. Over 80 percent of the samples had total solids between 9.17 and 11.99 percent with the same ranges as above for total acid and ratios.
Of a total of 585 samples tested, 187 samples failed to pass the test for consumer approval. The data for these samples are given in table 4. Low palatability ratings were usually associated with low total solids content, high total acid content, and, in some cases, lack of juiciness and coarse texture of the flesh.
Total Solids, Total Acid, and Solidsto-Acid Ratios
The balance between total solids, which are principally sugars in
mature fruit, and total acid, is closely related to palatability. As with tangerines (9), the Orlando, Minneola, and Seminole tangelos increased in total solids rapidly and reached high levels of total solids. Thornton tangelos resembled grapefruit (8), in that they increased slowly in total solids content from an average of about 9 percent in October to about 10.5 percent in February (table 5, fig. 1). At the level of minimum acceptability the total solids were 9.8 percent for Orlando and Thornton tangelos, 11.0 percent for Minneolas, and 11.2 percent for Seminoles. Orlando, Thornton, and Minneola tangelos grown on Cleopatra rootstock were consistently higher in total solids than when grown on rough lemon rootstock.
Total acid decreased during the season, this decrease being fairly rapid up to maturity, and very slow thereafter (table 6, fig. 1).
Table 4.—Composition of 187 samples of Orlando, Thornton, Minneola, and Seminole tanyelos rated "unacceptable" in taste tests by scoring less than 70
There were consistent varietal differences in total acid content. At minimum acceptability, Orlando tangelos averaged 0.93, Thorntons 0.93, Minneolas 1.26, and Seminoles 1.38 percent acid, when all were grown on Cleopatra rootstock (fig. 1).
Table 6 —
Orlando tangelos grown on Cleopatra, sour orange, and Husk rootstock had a slightly higher total acid than those grown on rough lemon. The effect of rootstock on total acid was more variable for Minneola and Seminole tangelos (table 6).
Total acid: Seasonal changes in tangelos by variety and by kind of rootstock, 1952-56
to weight of total acid gives an indication both of maturity and consumer acceptability, and is a part of the Florida laws. At minimum maturity, Orlando, Thornton, Minneola, and Seminole tangelos on Cleopatra root stock had high solidsto-acid ratios, 10.20, 10.50, 9.90, and 8.10, respectively. The low ratio for Seminole was due primarily to the high acid content of this variety (table 7, fig. 1).
The kind of rootstock had little effect on the solids-to-acid ratio for Orlando, Thornton, or Seminole varieties. Minneola tangelos, in February, showed wider variation according to rootstock, with a low of 12.73 on rough lemon and a high of 18.49 on sweet orange (table 7).
The ascorbic acid content of the principal varieties of tangelos was about equal to that of the tangerine parent (9), and slightly lower than that normally found in the grapefruit parent (8). The concentration of ascorbic acid of the juice reaches a maximum in the early
fairly constant during the marketing season (table 8, fig. 3).
Of the different varieties on Cleopatra rootstock, Thornton tangelos had the highest average ascorbic acid concentration, and Minneola the lowest. Orlando and Seminole fruits were intermediate.
The ascorbic acid concentration varied less with rootstock than with variety, although Orlando tangelos on sour orange and Cleopatra rootstock averaged slightly higher in ascorbic acid than those on rough lemon or Rusk (table 8).
In active acidity, the tangelos resemble the tangerine parent (9), rather than the grapefruit (8). In October, when all varieties of fruit are immature, the pH values ranged from as low as 2.8 in Seminoles to 3.2 in Orlandos. By February, the pH values had increased, ranging from 3.3 in Seminoles to 3.9 in Orlando tangelos. Thus the active acidity, a measure of hydrogen ion concentration, decreased (pH values increased) steadily during the de
Table 7.—Ratio of total solids to total acid: Seasonal changes in tangelos by variety and by kind of rootstock, 1952-56
velopment of the fruit (table 9, fig. 3). It should be borne in mind that since pH units are logarithmic values, a change of one pH unit represents a tenfold change.
Weight of Fruit and Juice per Fruit
The changes in weight of fruit closely paralleled the increase in volume of juice per fruit (fig. 2). The average weight of fruit increased until maturity was reached. Thornton, Minneola, and Seminole tangelos showed greater rates of increase than the Orlando. Rootstock had only a very slight effect on weight of fruit as may be observed in the case of Orlando and Seminole tangelos (table 10).
During early stages of development the volume of juice increased rapidly, reached a maximum when the fruit was in prime condition, and decreased slowly as the fruit remained on the tree. The volume of juice per fruit was associated with variety (table 11, fig. 2). Minneola tangelos were the largest in size and averaged about 200 milliliters of juice per fruit. Seminole and Thornton tangelos were
intermediate as to size and volume of juice. Orlando tangelos were smaller and contained a lower amount of juice.
The percentage of fruit by weight that was juice and the milliliters of juice per 100 grams of fruit decreased very slightly throughout the season. Variety and rootstock had little influence on the amount of juice per fruit, and during the period of prime eating quality the juice averaged from about 58 to 61 percent of the.fruit (tables 12, 13, fig. 2).
Rind color was determined by matching samples of 25 fruit against the color standards shown in plate II. In October the tangelos were deep yellow-green in color. As the fruit matured the green pigment faded rather rapidly. The rinds of Minneola, Orlando, and Seminole tangelos progressed through yellow to yellow-orange and finally became deep red-orange in color. Of these varieties, Minneola had the deepest color. Thorntons remained yellow to yellow-orange at maturity and