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  • Author or Editor: R. E. McDonald x
  • Journal of the American Society for Horticultural Science x
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Abstract

Comparisons were made of some physical and chemical characteristics of lemons (Citrus limon L.) imported into western Europe from 11 countries of origin. Statistically significant differences in quality characteristics were found. Fruit from Chile, Cyprus, Israel, and the United States was the most uniform in yellow coloring. Lemons from Argentina, Israel, South Africa, and Uruguay tended to be rounder than more elongated fruit from Spain and Turkey. Thickest peels were found in Chilean, Greek, Italian, and Spanish fruit, and thinnest peels in South African and Uruguayan fruit. Regardless of origin, the largest fruit had the thickest peel and contained a lower percentage of juice. Israeli lemons had the highest percentage of juice and Argentine, Chilean, and Spanish fruit, the lowest. Total soluble solids (TSS) concentration was highest in juice of fruit from Cyprus and Turkey and lowest in fruit from South Africa and Spain. Total acid (TA) concentration was highest in Turkish fruit and lowest in Italian, South African, and Spanish fruit. Smaller fruit from most countries had higher concentrations of ascorbic acid than larger fruit. Chilean lemons had the highest, and Turkish and U.S. lemons the lowest, ascorbic acid levels.

Open Access

Abstract

Sap extracted by nitrogen gas pressure from branches and lateral roots of healthy and citrus blight-affected ‘Hamlin’ and ‘Valencia’ orange, Citrus sinensis (L.) Osbeck, trees on rough lemon (C. Union Burm. f.) rootstock in 2 commercial groves was analyzed for N, K, Ca, Mg, S, Na, Fe, Mn, Zn, Cu, CI, Si, and organic acids. The branch and root wood (from which the sap was extracted), leaves, and feeder roots were also analyzed. Sap extracted from branches of blight-affected ‘Hamlin’ trees in the spring had higher Zn, Cu, CI, and Si concentrations than sap of healthy trees. Nitrogen was increased twofold and Fe slightly increased with blight in the root sap. Branch sap collected from ‘Valencia’ trees in the fall showed no differences. Branch sap contained more organic acids than root sap and there was no difference between blighted and healthy trees. Citric and malic were the principal acids.

Open Access

Abstract

The standard ethanol sugar extraction method and a chloroform-methanol-ethanol (CHCl3-MeOH-EtOH) extraction were compared. Determinations of sugar tri-methylsilyl derivatives by gas-liquid chromatography were examined.

The CHCl3-MeOH-EtOH extraction was superior to the ethanol extraction. Complete recoveries of glucose were afforded by both methods; however, the ethanol extraction yielded maltose whereas the CHCl3-MeOH-EtOH method did not.

Deionization of sweet potato sugar extracts and authentic sugars with MB-3 ion exchange resin was undesirable because only small percentages of sugars were recovered.

Discrepancies were found in the recently published determination of sugar trimethylsilyl (TMS) derivatives by gas-liquid chromatography. Although it was reported that the quantity of the TMS product formed was essentially independent of time, at least 6 hr were necessary to completely form the penta-o-trimethylsilyl derivatives of fructose. The penta-o-trimethylsilyl derivatives of glucose were formed within 5 min as indicated in the literature. Anomerization from α- to β-fructose occurred after the introduction of the TMS reactants.

Open Access

The objective of this study was to determine the effects of prestorage heat treatments on chilling tolerance of tomatoes. Mature-green `Agriset' tomato fruit (Lycopersicon esculentum Mill.), either C2H4-treated or not, were immersed in 42C water for 60 min, held in 38C air for 48 hours, or not treated, and then stored at either 2C (chilled) or 13C (nonchilled) for 14 days before ripening at 20C. Heat-treated fruit stored at 2C and transferred to 20C ripened normally while nonheated fruit decayed before reaching red ripe. Color (a*/b* ratio), lycopene content, and internal quality characteristics of fruit were similar at the red-ripe stage irrespective of method of heat treatment. In red-ripe heat-treated fruit, free sterol levels were significantly higher in chilled fruit than in nonchilled fruit. Heating fruit in 38C air resulted in significantly higher levels of some free sterols compared with heating fruit in 42C water. Of the 15 flavor volatiles analyzed, six showed significantly decreased concentrations as a result of C2H4-treatment and seven showed decreased concentrations when stored at 2C before ripening. Some volatiles were decreased by the heat treatments. Prestorage short- and long-term heat treatments could allow for storage of mature-green tomatoes at lower temperatures with little loss of their ability to ripen normally.

Free access

Mature-green `Sunbeam' tomatoes (Lycopersicon esculentum Mill.) were treated in varying order with C2H4, 42 °C water for 1 hour, 38 °C air for 2days, held 2 days at 20 °C (partial ripening), or not treated and then stored at 2 °C (chilled) for 14 days before ripening at 20 °C. Heat-treated fruit stored at 2 °C and transferred to 20 °C ripened normally, while 63% of nonheated fruit decayed before reaching the red-ripe stage. Partially ripened fruit developed more chilling injury, were firmer, were lighter, and were less red in color than fruit not partially ripened. Lycopene content and internal quality characteristics of fruit were similar at the red-ripe stage irrespective of sequence of C2H4 exposure, heat treatment, or a partial ripening period. Of the 15 flavor volatiles analyzed, 10 were reduced by storage at 2 °C, Exposure to C2H4 before the air heat treatment reduced the levels of four volatiles, while C2H4 application either before or after the water heat treatment had no effect on flavor volatiles. Two volatiles were decreased and two were increased by partial vipening, Storage at 2 °C decreased the level of cholesterol and increased levels of campesterol and isofucosterol in the free sterol pool. Exposure to C2H4 before or following heat treatments, the method of heat treatment, and partial ripening had little effect on free sterols, steryl esters, steryl glycosides, or acylated steryl glycosides in the pericarp of red-ripe fruit. A shortor long-term heat treatment of mature-green tomatoes could permit storage at low temperatures with little loss in their ability to ripen normally, whereas partial ripening did not reduce chilling injury.

Free access

Irradiation is being evaluated as a quarantine treatment of grapefruit (Citrus paradisi Macf. `Marsh'), but it can cause damage to the fruit. Research was conducted to determine if preirradiation heat treatments would improve fruit tolerance to irradiation as they improve tolerance to low temperature injury and to determine if canopy position influenced fruit tolerance to irradiation. Initially, grapefruit were irradiated at 0 or 2.0 kGy at a dose rate of 0.14 kGy·min-1 and selected biochemical changes were monitored over time. There was a marked increase in phenylalanine ammonia-lyase (PAL) activity following irradiation. Maximum activity (≈18-fold increase) was attained 24 hours after irradiation. Subsequently, grapefruit were harvested from interior and exterior canopy positions and irradiated at 0 or 1.0 kGy at a dose rate of 0.15 kGy·min-1 before storage for 4 weeks at 10 °C. Following storage, pitting of flavedo was the most evident condition defect noted as a result of irradiation. Pitting was observed on 27% and 15% of irradiated exterior and interior canopy fruit, respectively, whereas there was no pitting on nonirradiated fruit. Heat treatment before irradiation decreased susceptibility of fruit to damage. Pitting was 26%, 19%, and 17% when fruit were held 2 hours at 20 (ambient), 38 or 42 °C, respectively. Irradiation-induced PAL activity was reduced by temperature conditioning at 38 or 42 °C. Exterior canopy fruit flavedo contained higher levels of total phenols, including flavanols and coumarins compared with interior canopy fruit. Deposition of lignin was not related to canopy position. Neither irradiation nor heat treatment had an effect on total phenols or lignin deposition. Generally, cholesterol, campesterol, stigmasterol, β-sitosterol, and isofucosterol were found to be higher in four steryl lipid fractions in exterior canopy fruit compared with interior canopy fruit. Irradiation increased campesterol in the free sterol and steryl glycoside fractions and decreased isofucosterol in the free sterol fraction. Heat treatments had no effect on individual sterol levels. It seems that irradiation causes a stress condition in the fruit, which leads to pitting of peel tissue. Heat treatment before irradiation reduced damaging effects of irradiation.

Free access

Abstract

Strains of Penicillium digitatum (Sacc.) and P. italicum (Wehmer) resistant to thiabendazole and benomyl were isolated from decaying citrus fruits obtained from the Rotterdam, Netherlands, terminal market and originating from 18 countries. Significantly more Penicillium sp isolates with resistance to thiabendazole and benomyl were collected from grapefruit and lemons than from oranges. Significantly more isolates of P. digitatum than P. italicum grew on agar plates with 4, 10, or 40 ppm thiabendazole. A greater percentage of P. digitatum than P. italicum isolates grew on 4 and 10 ppm benomyl-agar plates, but a greater percentage of P. italicum than P. digitatum isolates grew on 40 and 80 ppm benomyl-agar plates. Both species were more resistant to thiabendazole than to benomyl, and often showed cross-resistance to the fungicides. Resistant Penicillium sp isolates produced larger colonies on 4 and 10 ppm thiabendazole and 40 and 80 ppm benomyl.

Open Access