Harold E. Nordby

Fatty acid profiles of citrus juice and seed lipids

Abstract Fatty acids from the juice and seeds of six citrus varieties were quantitatively determined for the region C12–C26. The total number of juice acids observed ranged from eighty-one (Key limes) to one hundred and two (Eureka lemons) and the total number of seed acids ranged from sixty-two (Valencia oranges) to sixty-eight (Key limes and Eureka lemons). Thirty-eight different iso and twenty-six anteiso acids were observed for the first time in edible plant material in concentrations ranging from less than 0·001 per cent to greater than 1 per cent. These single branched acids were verified by comparison of retention times with standards and by their characteristic mass spectrographic fragmentation patterns.

Fatty acid composition of sterol esters from Citrus sinensis, C. paradisi, C. limon aurantifolia and C. limettioides sacs

The fatty acid compositions of sterol esters from 4 citrus species, viz, orange. grapefruit, lemon and lime, were determined by GLC. Each species possessed its own intrinsic fatty acid pattern which could be used to differentiate it from the other species. In most cases varieties within a species had fatty acid patterns which could be used for varietal differentiation. In all citrus tested except Columbia lime, the major acid was linoleic acid; this acid varied from 10 to 56% of the total acid content. The ratios of 16/16:1 were distinct for each citrus species. The C22-C29 fatty acids were prevalent in citrus sterol esters ranging from 6·5% for some orange and grapefruit varieties to over 41% for two lime varieties. In all varieties C24 was the most prominent of these longer chain fatty acids. Argentation TLC indicated that these longer chain fatty acids primarily were esterified to dimethyl sterols. ft*|One of the laboratories of the Southern Region, Agricultural Research Service, U.S. Department of Agriculture.

An evaluation of recent gas-liquid chromatographic liquid phases for resolution of acetylated plant sterols

Abstract The relative retentions of twelve acetylated plant sterols were determined on fourteen gas-liquid chromatographic liquid phases. These phases were rated according to their ability to resolve three “critical sterol pairs”. The modified Carbowax, SP-1000 2 adequately resolved all three pairs in thirty minutes at 240°.

Fatty acid profiles of orange and tangor juice sac lipids.

Abstract Fatty acids from the juice sacs of four orange varieties from early season harvest, one variety from mid- and one variety from late season, and two tangors were quantitatively determined and it was found that the five major fatty acids, viz. palmitic, palmitoleic, oleic, linoleic and linolenic, comprised more than 92 per cent of all acids. There appeared to be no correlation between the major fatty acids and the harvest season of the various orange varieties. The two tangors were distinctly different from the oranges in both their major and minor fatty acid profiles. A theory is proposed for the occurrence of specific iso- and anteiso-branched acids in citrus.

Comparative citrus fatty acid profiles of triglycerides, monogalactosyl diglycerides, steryl esters and esterified steryl glucosides

Vesicular lipids from six orange and two tangor varieties were extracted, purified and separated by chromatography into triglycerides, monogalactosyl diglycerides, steryl esters and esterified steryl glucosides. Methyl esters of the fatty acids found in these four lipids were prepared and analyzed by gas liquid chromatography. Each of the eight citrus varieties gave a series of four profiles which could be distinguished from the others. The Temple tangor has four profiles all showing a large percentage of linolenic acid. In all varieties steryl esters and to a lesser extent esterified steryl glucosides contain relatively large concentrations of 22∶0 to 26∶0 saturated acids. The profiles differ markedly from the patterns found for these four lipids in other higher plants studied.

Distribution of free and conjugated sterols in orange and tangor juice sacs

Comparative studies of the sterol composition of four sterol fractions, vis., free sterols, sterol esters, sterol glucosides and esterified sterol glucosides, were conducted on the juice sacs of six varieties of oranges and two tangor varieties. The sterols quantified in each fraction were β-sitosterol, campesterol, stigmasterol, cholesterol, 24-ethylidene cholesterol, brassicasterol and 24-methylene cholesterol. Each variety showed its own intrinsic composition for these sterols in the four sterol fractions.

Fatty acids of triglycerides from Citrus juice sacs

Abstract The fatty acid composition of trigylcerides from oranges, grapefruit, lemons and limes, was determined by GLC. Each species possessed its own intrinsic fatty acid pattern which might be used to differentiate it from the other species. The five major acids in all species were palmitic, palmitoleic, oleic, linoleic and linolenic. Collectively these acids comprised greater than 92% of the total acid content. Lemons were distinguished from all other species by their higher 16/16:1 ratios while grapefruit showed the highest total percentage of 16 and 16:1 acids. Lemons and limes contained higher percentages of branched-chain acids than oranges and grapefruit.

Effects of cold hardening on acyl lipids of citrus tissue

Abstract Cold hardened and unhardened 8- or 16-month-old citrus plants were examined for differences in fatty acid (FA) content. Unhardened leaves from 8-month-old Valencia scion budded on sour orange rootstock had 29% less FAs than leaves from seedling sour orange. After cold hardening triacylglycerol (TAG) FAs increased 4-fold in Valencia on sour orange and 6-fold in sour orange seedling. The percentage of FAs associated with TAGs for unhardened-hardened 16-month-old Valencia on sour orange tissues were: upper leaves 7–20, lower leaves 6–17, bark 6–9, and roots 57–73%. Cold hardening increased the amount of TAG FAs of 16-month-old Valencia on sour orange in upper leaves by 226% and in lower leaves by 173%. Concentrations of linoleic acid increased by 479% in upper leaves and by 303% in lower leaves. Quantities of lionolenic acid in monogalactosyl diacylglycerols declined by 27% in upper leaves and by 20% in lower leaves.

Squalene in grapefruit wax as a possible natural protectant against chilling injury.

The influence of temperature conditioning on stored grapefruit against chilling injury (CI) as related to the fruits neutral lipids in the peel was investigated. Squalene, a highly unsaturated C30 isoprene hydrocarbon, was found to be present in the epicuticular wax of grapefruit. The optimal temperature for biosynthesis of squalene in grapefruit was 15°C; this is also the temperature reported previously as the optimum temperature for conditioning grapefruit against chilling injury. Control and temperature-conditioned grapefruit were stored monthly over three seasons from 1986 to 1989. Fruits were rated for chilling injury and the levels of squalene were determined. An inverse relationship found between CI and squalene level suggested that squalene may protect grapefruit from CI.

Hydrocarbons from epicuticular waxes of Citrus peels

Abstract The hydrocarbon fraction of the epicuticular wax layer of peel from 5 cultivars of Citrus was monitored at various stages of fruit development. GLC