Cultivars, citrus

Feldman, A.W. and Hanks, R.W. (1968). Phenolic content in the roots and leaves of tolerant and susceptible citrus cultivars attacked by Rodopholus similis. 

Table G1.5.9 Peel-Oil Content of Various Florida Citrus Cultivars"... 

Table Gl.5.9 is a summary of the total available oil for various citrus cultivars. Table G1.5.10 is the aldehyde composition for orange and grapefruit oils.

Kesterson, J.W. and Braddock, R.J. 1975. Total peel oil content of the major Florida citrus cultivars. J. Food Sci. 40 931-933. 

Both directly and indirectly, flavonoid composition affects the quality of individual citrus cultivars and hybrids. Some cultivars, such as the sour orange, are directly affected by the presence of bitter neohesperidosides to the point they are unpalatable. The quality of other cultivars may be indirectly affected due to the presence of bitterness suppressing flavone neohesperidosides. Certain hybrids, such as the K early, also contain bitter flavanone glycosides at levels which reduce its acceptability. Therefore, the knowledge of the relative type and... 

Sonnen et al. (jl) observed the effect of root temperatures on the fruit color of two citrus cultivars. When comparisons were made with satsumas at 14°C and 30°C and with calamondins at 12°C and 25°C, there were higher amounts of carotenoids and better color in the peel from fruit grown at the lower root temperatures. 

The bright orange and yellow colors of citrus peel are due to the lipid soluble carotenoids. The more common ones in peel and juice are shown in Figure 1. Some of the first studies on citrus carotenoids were by the European workers, Zechmeister and Tuzson, in 1931 (26, 2 7, 28). They isolated p-carotene, cryptoxanthin, lutein, zeaxanthin, p-citraurin, and probably violaxanthin. In 1952, Natarajan and MacKinney (29) found phytofluene and a, p, and zeta carotenes. These studies were followed by those of Curl, who between 1953 and 1967 reported the presence of some 74 carotenoids in several citrus cultivars. 

The flavor of most citrus cultivars is complex, and compounding citrus flavors requires the blending of several components in specific proportions to obtain the unique flavor of each citrus cultivar (3). Studies on Sicilian mandarin oil suggest the distinct flavor and aroma of mandarins is mainly due to 2 compounds, thymol and methyl-N-methyl anthranilate (dimethyl anthranilate) but no evidence to support this claim has been presented (42). Thymol has been identified in Dancy tangerine peel oil, and both thymol and dimethyl anthranilate have been identified in Sicilian mandarin oil (3). The reported quantities of thymol in mandarin oil varied from 0.04-0.2% of the oil, whereas only one value (0.9%) was reported for dimethyl anthranilate. 

Yi, Z., Yu, Y., Liang, Y., andZengB. 2008. In-vitro antioxidant and antimicrobial activities of the extract of Pericarpium Citri Reticulatae of a new Citrus cultivar and its main flavo-noids , Foo(7. Sci. Tech., 47 597-603. 

Crop cultivar variation in trace element uptake had been observed with com, rice, barley, wheat, and cocoa (Adriano, 1986). Wheat and soybeans showed variety-based variation of P-Zn interaction. Crop varieties with a low capacity for uptake of Zn in soils were more vulnerable to Zn deficiency by P application. Crops sensitive to Zn deficiency included beans, potatoes, peaches, flax, com, rice, soybeans, and citrus (Adriano, 2001). 

Citrus is one of the long-standing horticultural and agricultural plant genera with a rich history from centuries of cultivation. As a result, there are many species and varieties (cultivars) within species, each with characteristic properties. These properties include vegetative growth pattern as well as fruit characters such as flavor, seediness, size, and appearance. 

There have been many survey studies of citrus flavonoids, yet by no means has an exhaustive analysis been performed for all species and cultivars. Surveys often are initiated by hydrolysis of tissue extracts and identification of the flavonoid aglycones present in the tissues. This provides a basis for subsequent identification of the glycosylated compounds present... 

F3H Citrus maxima cultivar Guanxi pomelo F3H mRNA GQ121373 Y N... 

DFR Citrus sinensis cultivar tarocco DFR gene DQ084723 Y [102] Y [102]... 

Citrus sinensis cultivar navel DFR gene DQ084722 Y [102] N... 

This is the major citrus fruit produced worldwide. Since this citrus type has been produced for over 2,000 years, there are a wide range of named cultivars. However, the major cultivars of commercial importance include Valencia, Pera, Navel, Hamlin and Shamouti. The sensory characteristics of juices from a few of these cultivars have been reported [19]. 

The desired citrus flavor is the result of volatile compounds in specific proportions. Citrus oils have unique composition profiles depending on the cultivar, the processing conditions, and the storage conditions. There have been more than 200 different compounds identified in citrus oils. However, the degree of unsaturation in monoterpenes leads to rapid oxidation and unstable compounds. The reactivity and volatility of citrus oils require strict quality control protocols. 

The processing of citrus oil is highly regulated. Processors must account for total available oil, recovered oil, and emitted oil. This is done primarily for environmental reasons, due to the reactive nature of terpenes. The total available oil varies depending on the cultivar. 

Figure 2. Effect of time of sampling and cultivar on the a/b color ratios of citrus peel. The a/b ratios are negative for green, approximate zero for yellow, and are positive for orange through red.

Very little is known regarding factors that affect the color of citrus juice. The author has used many combinations of temperature and ethylene with fruit of several cultivars. 

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