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  • Author or Editor: R. E. McDonald 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

Storage of `Marsh' white seedless grapefruit (Citrus paradisi Macf.) for 2 weeks at 5C resulted in the development of chilling injury (CI). Electrolyte leakage from chilled fruit did not increase significantly until CI had become severe, and was therefore considered to be of limited value as an early indicator of CI. In contrast to electrolyte leakage, respiration and ethylene evolution were significantly higher in chilled than in nonchilled fruit, even before the onset of visual symptoms of CI. Respiration rates ranged from ≈8 to 11 and 5 to 7 ml CO2/kg per hour in chilled and nonchilled fruit, respectively. Ethylene evolution was not detected from nonchilled fruit, whereas chilled fruit produced from 45 to 250 nl ethylene/kg per hour. Results of this study indicate that electrolyte leakage does not increase until visible pitting of the flavedo has occurred, whereas stimulation of respiration and ethylene evolution occur early in the development of CI.

Free access

Grapefruit (Citrus paradisi) flavedo is a rich source of peroxidase (POD) (EC 1.11.1.7). Changes in POD have been related to senesence and environmental stress in a variety of plant tissues. However, due to the large number of POD isoenzymes as well as the broad substrate specificity, measurement of POD activity in crude extracts is of limited value for gaining an understanding of the role of POD in vivo. We have begun to purify and characterize POD isoenzymes from grapefruit flavedo. HPLC gel permeation chromatography reveals 2 peaks of POD activity with apparent MW of 66 kD and 30 kD. Native PAGE (8% bis-acrylamide, pH 8.8) followed by activity staining indicates that the PODs differ in Pi; the 30 kD POD migrates anodally, whereas the 66 kD POD does not migrate. Isoelectric focusing has been used to separate flavedo PODs into acid (Pi ca 4.0) and basic (Pi > 8.5) forms. Treatment of grapefruit with ethylene (2 ppm 72 hours) induces a basic POD not present in freshly-harvested fruit or in nonethylene-treated controls.

Free access

`Marsh' white grapefruit (Citrus paradisi Macf.) harvested from exterior canopy positions were less tolerant of 0.5 or 1.0 kGy irradiation than were interior fruit. Irradiation at 0.0, 0.5, or 1.0 kGy resulted in 0.0%, 24.3%, and 37.5% surface pitting of fruit, respectively. Pitting was reduced 30% by temperature conditioning with vapor heat at 38 or 42 °C for 2 hours. Exterior canopy fruit had ≈2-fold more pitting, had greater weight loss, and were firmer than interior canopy fruit. Fruit weight loss increased and firmness decreased as conditioning temperature and irradiation dose increased. Total soluble solids, titratable acidity, and flavor decreased with increasing irradiation dose. The peel of exterior canopy grapefruit was damaged more by irradiation than was that of interior fruit, but irradiation damage was reduced by temperature conditioning.

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Quality changes of supersweet corn (Zea mays L.) were monitored during storage at 1, 4, or 10C, unwrapped or wrapped in stretch or shrink film. Film-wrapping maintained freshness and reduced moisture loss better than lack of wrapping. Wrapping in shrink film resulted in lower O2 and higher CO2 concentrations within packages than wrapping with stretch film. Film-wrapping in shrink film maintained total soluble solids content better than stretch-wrapping or no wrapping.

Free access

Storage of `Marsh' white seedless grapefruit (Citrus paradisi Macf.) for 2 weeks at 5C resulted in the development of chilling injury (CI). Electrolyte leakage from chilled fruit did not increase significantly until CI had become severe, and was therefore considered to be a poor index of CI. In contrast to electrolyte leakage, respiration and ethylene evolution were consistently higher in chilled than in nonchilled fruit, even prior to the onset of visual symptoms of CI. Respiratory rates ranged from 8.0 to 10.7 and 4.6 to 6.7 ml/kg/hr in chilled and nonchilled fruit, respectively. Ethylene evolution was not detected from nonchilled fruit, whereas chilled fruit produced from 45.6 to 249.3 ml/kg/hr ethylene. Ethylene production was maximum following 2 weeks at 5C. Results of this study indicate that increases in electrolyte leakage do not occur until considerable tissue damage has occurred, whereas stimulation of respiration and ethylene evolution occur early in the development of CI.

Free access

Blueberry cultivars Sharpblue (mainly Vaccinium corymbosum L.) and Climax (V. ashei L.) were band-harvested on three occasions and manually packaged into 0.275 liter fiber-pulp cups or automatically packaged in vented polystyrene cups. Berries were evaluated after 1,2, or 3 weeks of storage at 1C and after 2 additional days of storage at 16C, a time frame that simulated a merchandising period. Weight loss of fruit packaged in polystyrene cups was <1% during 3 weeks of storage at 1C, whereas weight loss of berries packaged in fiber-pulp cups was ≈5.0% after similar storage. `Sharpblue' berries were softer at harvest and after each storage duration than `Climax' berries. Decay increased to ≈7% for `Climax' and 28% for `Sharpblue' after 3 weeks of storage at 1C. Package type did not affect decay incidence after 3 weeks of storage; but after 2 additional days at 16C, decay incidence was slightly higher for berries packaged in polystyrene compared with those packaged in fiber-pulp cups. `Sharpblue' should be packaged only in fiber-pulp cups and marketed quickly after harvest to avoid excessive decay.

Free access

Abstract

Fruit of ‘Bonita’ and ‘Beckyblue’ rabbiteye blueberry (Vaccinium ashei Reade) cultivars were harvested weekly, then stored in two different types of consumer baskets and subjected to five time/temperature storage regimes. Fruit increased in total soluble solids (TSS) and pH and decreased in acidity (Ac) with advancing harvest dates. Total soluble solids and pH of ‘Bonita’ fruit were significantly lower and Ac higher than for fruit of ‘Beckyblue’. After 3 weeks of storage at 1°C plus 3 days at 16°, ‘Beckyblue’ had higher (8 times) decay than fruit of ‘Bonita’. There were no cultivar differences in fruit firmness or weight loss due to storage, but fruit weight was reduced significantly when packaged in molded pulp fiberboard baskets. Fruit of ‘Bonita’ can be used for both domestic and export markets, requiring long storage duration, but ‘Beckyblue’ fruit should be limited to domestic markets.

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