Navel oranges

The citrus and cereal crop groups can be represented by any crop within that group (below), with the exception of Unshu orange for citrus, and rice, corn and buckwheat for cereals. Data from Chinese orange can cover grapefruit, navel orange, etc., and wheat and barley can cover oat and rye. 

Fig. 4.7.7 A portable NMR system for measuring freeze damage in Navel oranges. The Halbach magnet is shown above the completed system with two Navel oranges for comparison. The complete system has the battery powered spectrometer electronics housed in a metal box and the system is run by a portable computer.

Table IX. Surface Residues of Parathion on Navel Oranges at Harvest...

Type Formulation Technical Grade DDT/100 Gal., Lb. Navel oranges P.P.M. , DDT Valencia oranges Eureka lemons... 

Table VI. Harvest Residues of Parathion in Mature Navel Oranges...

Figure 2. Transmission-Wave-Length Curves for Dyed Benzene Extractives from Peel of Parathion-Treated Navel Oranges...

Because of continued interest in the in situ degradation products of both DDT and parathion, preliminary spectrophotometric evidences, which are also indicative of structural alterations and/or changes in composition, have been secured with extracts of navel oranges previously treated with standard formulations of these compounds. 

Thompson, C. R., and G. Kats. Effects of ambient concentrations of peroxyacetyl nitrate on navel orange trees. Environ. Sci. Technol. 9 35-38, 1975. 

Thompson, C. R. Effects of air pollutants on lemons and navel oranges. Calif. Agric. 22(9) 2-3, 1968. 

The 4-coumarate CoA ligase (4CL EC 6.2.1.12) enzyme activates 4-coumaric acid, caffeic acid, ferrulic acid, and (in some cases) sinapic acid by the formation of CoA esters that serve as branch-point metabolites between the phenylpropanoid pathway and the synthesis of secondary metabolites [46, 47]. The reaction has an absolute requirement for Mg " and ATP as cofactors. Multiple isozymes are present in all plants where it has been studied, some of which have variable substrate specificities consistent with a potential role in controlling accumulation of secondary metabolite end-products. Examination of a navel orange EST database (CitEST) for flavonoid biosynthetic genes resulted in the identification of 10 tentative consensus sequences that potentially represent a multi-enzyme family [29]. Eurther biochemical characterization will be necessary to establish whether these genes have 4CL activity and, if so, whether preferential substrate usage is observed. 

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. 

Table VII. Limonoid Distribution in Desert Navel Orange Tissue3...

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). 

Purification. Orange PE was isolated initially from Navel orange flavedo by extraction with a borate-acetate buffer at pH 8.2 and then precipitation from the extract with (NH, SO ... 

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). 

Hasegawa et al. (56) dj ected the enzymic conversion of 19-deoxylimonoic acid 3-methyl C ester to the 17-dehydro derivative by albedo tissue slices of Navel oranges. They isolated the product and identified it by TLC as the reaction product formed when the substrate was dehydrogenated by limonoate dehydrogenase (EC 1.1.1)... 

Recently, a nonspecific enzyme capable of degrading the precursor was extracted from Navel orange albedo (63). Nicol and Chandler (63) used a proximate assay for the degrading enzyme that is, the substrate was not identified except as a limonin precursor. The crude extracts from albedo contained degradation activity that was concentrated by 40 to 60% saturation with (NH J SO. Instability of the enzyme prevented further purification. 

Emerson, 0. H. The bitter principle in Navel oranges. Food Tech, 19A9, 3, 2A8-250. 

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