Navel orange fruit

Good quality navel oranges were purchased as the experimental material. The fruits had been distributed by Sunkist Growers, Inc. and were in excellent condition from a consumer s point of view. For the short duration of these tests, the oranges were kept in a polyethylene bag in an ordinary refrigerator. It was assumed that the fruits had received normal post-harvest treatments washing, waxing, and diphenyl inhibitor treatment. 

When 5-g-size navel oranges were fed with 44 x 10 cpm of acetate-2- 4C at the rate of 4.4 x 10 cpm per day for 10 consecutive days either by injection of the fruit or by application on the peel, no labeled XIV was detected in the fruit. Also, no 4C was incorporated into XIV when 5-g-size navel orange was similarly fed with 20 x 10 cpm of mevalonate-2--1-4C. When labeled acetate was fed to leaves adjacent to a 5-g-navel orange, radioactivity was incorporated into XIV in the fruit (12). These results suggest that limonoids are most likely not synthesized in the fruit tissues (12). However, they do not rule out the possibility that a precursor(s) of limonoids beyond acetate or meva-lonate is synthesized in leaves and translocated to fruit and there converted to limonoids. 

While most of the limonoids of Citrus have been isolated from seeds, several occur in detectable amounts in other parts of the fruit. Minor amounts of deacetylnomilin, nomilin, obacunone, de-acetylnomilinic acid and nomilinic acid were identified in extracts of navel orange peel (37). 17-Dehydrolimonoate A-ring lactone was isolated from peel and juice of navel oranges (38) and nomilin has been reported to occur in grapefruit juice and juice vesicles (39). The only Citrus limonoids known to be bitter are limonin, VI, XII, obacunoic acid and IX (3). 

Isoenzymes. Multiple forms of citrus PE were reported by Evans and McHale (AO) and Versteeg et al. (Al). PE was purified from West Indian limes and Navel oranges by fractionation of the whole fruit extracts with (NH. SO (AO-65%), adsorption and elution from Sephadex G-75 columns (AO). The PE active fractions were combined and concentrated before separation into two active PEs on the basis of their elution volume from a DEAE Sephadex A-50 column. Orange PEI (OPEI) and lime PEI (LPEI) had the same elution volume also OPEII and LPEII had the same elution volume. A higher concentration of NaCl was required at all pH values for optimum activity of OPEI and LPEI than of OPEII and LPEII. When the component parts of oranges were separately analyzed chromatographi-cally with DEAE-Sephadex A-50, OPEI was detected only in the peel, whereas OPEII was identified in juice sacs and section walls (AO). 

Several postharvest treatments to citrus fruits have been tested in an effort to improve the quality of the extracted juice. Bruemmer and Roe subjected citrus fruits to anaerobic conditions for periods of 20 to 32 hours at 32.2 to 43°C (228, 229). This treatment reduced the titratable acidity and increased the Brix-acid ratio by about 10%. The decrease in acidity was accompanied, however, by a 20-fold increase in ethanol (229). Since the soluble solids-acid ratio is a major criterion of citrus juice quality, this procedure, if perfected, could allow earlier harvesting of fruit and a more consistent supply of fruit during the processing season. Bitterness of products from navel oranges, lemons, and grapefruit is related to limonin content. A 3-hour treatment of fruit with 20 ul ethylene/1 of air lowered the limonin content, reduced bitterness, and the juice was judged more palatable than juice from untreated fruit (230). 

Before spraying oil on citrus crops, check with local Cooperative Extension Service agents for the best timing of sprays for your area and cultivars. On lemons, oils are usually applied in April and May for other citrus crops, oils are used in late summer or fall. (Navel oranges are very susceptible to damage from oil,. so do not spray them after September 1.) Avoid treating citrus trees while mature fruit is present, because fruit may drop or the color and quality may suffer. 

A near-perfect natural health food, a raw whole orange embodies abundant nutrient and phytochemical diversity in a package you can open yourself Rich in fiber (include the white pith) and vitamin C, a juicy, delicious whole orange makes for an easy way to get the main superfruit signatures—fiber, antioxidant A-C-E vitamins, carotenoids, and polyphenols. Just one small navel orange equals one fruit serving. 

Flowers of Morita navel oranges were treated with brassinolide solution at anthesis. Fruit set of trees treated with 0.1 and 0.01 ppm brassinolide increased by ca. 5 and 2.5 times respectively, when surveyed 50 days after treatment. At harvest there were no differences in quality between treated and untreated fruits. Since brassinolide-treated squash segments only showed slight changes in hormone content, brassinolide may have a direct action on stimulating fruit set without marked changes in the levels of other endogenous phytohormones. 

Citrus cultivation in Japan accounts for 60% of the total fruit production. Nearly 70% of the citrus production is of satsuma mandarin. Navel oranges show poor fruit set in the south western coastal areas of Japan, because of cool conditions and, for this reason, are sometimes grown in glasshouses or under plastic. 

Recently brassinolide was found to retard the abscission of leaf explants of Calamondin (6). Thus, the present experiments were also included to observe the effects of brassinolide on the fruit set of Morita navel oranges (Citrus sinensis), a cultivar derived from Washington navel. 

IAA inhibited leaf abortion of Coleus when given at a high concentration (10). Although brassinolide was found to increase the IAA level in squash segments, such a slight increase may not cause much effect on fruit abortion in navel orange. 

The relative effectiveness of a bioregulatory agent on inhibition of cyclizatlon and on stimulation of net carotenoid synthesis leads to variations in the carotenoid response pattern. When fully mature navel oranges are treated postharvest by vacuum infiltration for ten minutes with 2,000 ppm of MPTA, the carotenoid pigment pattern in the flavedo of the peel is quite similar to that observed In the endocarp with the acyclic lycopene as the main pigment as shown in Table I. The control fruits were vacuum infiltrated with water. 

Navel orange worm Dried fruit beetle Rice moth Codling moth Oasis dates moth Tropical warehouse moth... 

Limonoid UDP-D>glucose transferase Limonin bitterness is a problem in juices extracted from early-season to mid-season winter fruit, but not a problem in juice extracted from the late season fruit. As the fruit ripens, the concentration of limonoate A-ring lactone (2) decreases (23,24). This natural limonin debittering process has been known for over a century, but the mechanism of this metabolism was not understood until the recent discovery that limonoid glucosides are present in mature fruit tissues and seeds. We observed that in navel orange the initial... 

During storage in air, there is a decrease in the volatiles produced in various fruits, after the first volatile induction caused by the treatment. Norman (1977) showed that Navel oranges produced large amounts of AA, methanol, ethanol and ethyl acetate when stored under N2 for 2-5 days but after removal to air, there was a gradual decrease in the production of volatiles. Progressive reduction in volatiles with increasing time at 20 °C may be a result of volatilization and/or further metabolism (Cossins 1978 De Pooler et al. 1983, 1987 Mattheis et al. 1991). 

Limonin bitterness is especially acute in juice obtained from short maturation time fruits such as navel oranges. Juices obtained from most of the other citrus crops, such as Valencia oranges, usually do not have the limonin bitterness problem, as the concentration of limonin has decreased sufficiently by the time the processing season starts. Juices from navel oranges, particularly early- to mid-season fruits, can contain over 30 ppm of limonin, which is well above the bitterness detection threshold of 6 ppm. Grapefruit also has significant levels of limonin, which vary from 10 ppm in the early season to 1 ppm or less in the late season. 

A number of other processes have become commonplace in the manufacture of fruit juices. For example, if oranges of the varieties Navel or Navellina are processed the juice becomes unpleasantly bitter because of the biochemical development of a glycoside, limonin. This substance can be partially or totally removed by the use of appropriate ion-exchange resins to yield a juice of acceptable taste. 

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