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  • Author or Editor: G. Eldon Brown x
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Abstract

Mature ‘Valencia’ oranges when sprayed 2 months prior to harvest in the spring of 1969 with a 1 or 3% solution of Pinolene, a liquid polyterpene plastic film former, were greener at harvest, lost less wt, and had better appearance than control fruit after 9 weeks of storage. Fresh and fixed sections of peel from control and plastic-treated ‘Hamlin’ orange fruit from trees sprayed 2 months before harvest with a 1% solution of Pinolene were observed with a scanning-electron microscope after harvest. The surfaces of control fruit showed considerable variation with some areas having essentially no epicuticular wax platelets while other areas were completely covered. On sprayed fruit, plastic often partially masked the wax platelet edges. On control fruit, the openings to the outer stomatal chambers were usually unobstructed although the stomatal pores between the guard cells were often plugged. In most cases, the openings to the outer stomatal chambers of sprayed fruit were partially or completely obstructed with plastic.

Open Access

Abstract

Free phenolic constituents increase more than 2-fold in injured peel of oranges (Citrus sinensis Osbeck) cv. Valencia after 48 hr at 30°C and 96 to 98% relative humidity (rh). Concomitantly, conjugated phenolic compounds decrease to near depletion as a heavily lignified layer forms on injured cells. At 5°C all wound healing processes slow down. Infection of injured tissue by Penicillium digitatum Sacc. at 27°C inhibits lignin synthesis and the disappearance of conjugated phenolic compounds, but does not interfere with the usual increase in free phenolics. Mycelium of P. digitatum contributes little to the level of phenolic compounds of decayed fruit tissue. Extracts of free phenolic substances from healed tissue d) not exhibit fungistatic activity on P. digitatum spores, Lignin formation provides a mechanical barrier which retards or inhibits penetration of injured tissue by P. digitatum.

Open Access

Abstract

Growth of fungi from the surface of excised peel taken from Florida citrus fruit interfered with controlled studies on pigment changes of the flavedo. Control of these fungi was not achieved even though whole fruits were dipped in various concentrations of sodium hypochlorite before removing discs of peel for incubation in culture on a defined medium (5). Normally, the presence of fungal growth was evident on all discs of excised peel after 3 to 5 days incubation at 30°C. Development of a technique to control these fungi was necessary to allow longer incubation of discs to observe pigment changes.

Open Access

Abstract

Applications of lead arsenate to ‘Temple’ oranges lowered the titratable acid content but not the soluble solids or percentage juice. The percentage total decay, peel injury, and creasing were not appreciably influenced by the lead arsenate sprays. Fruit from trees sprayed with lead arsenate passed legal maturity standards 15 to 20 days earlier than fruit from non-sprayed trees.

Open Access

Peeling and storage characteristics of citrus fruit infused with water or enzyme solution were compared. Fruit were vacuum- or pressure-infused with water or water-containing pectinase. The enzyme treatment did not affect peeling times of white or red grapefruit, oranges, or tangelos. Pressure and vacuum infusion methods produced similar results. Grapefruit and oranges infused with water had significantly less juice leakage and were firmer than fruit infused with enzyme. Microbial levels and respiration rates and ethylene emanation during storage were the same for enzyme- and water-treated fruit.

Full access

Abstract

Freeze-damaged ‘Marsh’ grapefruit (Citrus paradisi Macf.) and ‘Pineapple’ orange [Citrus sinensis (L.) Osbeck] fruit were sealed in polyethylene shrink film and stored for 6 weeks at 15°C in an attempt to prevent segment dehydration. Although the film greatly restricted water loss from the fruit, segment dehydration was similar to that observed for waxed fruit. During dehydration of freeze-damaged segments of ‘Valencia’ orange fruit, the relative water content of the adjacent mesocarp tissue increased. However, no differences were found in the soluble carbohydrate levels in mesocarp tissue adjacent to damaged and undamaged segments. The results indicate that the mesocarp tissue is not only in the pathway of water loss from free-damaged citrus fruit, but also accumulates water from damaged tissues. Furthermore, segment tissue membranes and walls appear to be differentially permeable to sugars and water.

Open Access

A postharvest peel disorder, morphologically similar to chilling injury (CI), was detected on nonchilled `Marsh' white grapefruit (Citrus paradisi Macf.). Like CI, the disorder was characterized by pitting of the peel caused by the collapse of oil gland clusters. This disorder is distinguished from CI in that pitting developed within the first 10 days of postharvest storage on fruit held at high (21.0C), but not low (4.5C), temperatures and on waxed fruit, but not unwaxed fruit. Pathogens isolated from pitted fruit were similar to those of nonpitted fruit. No preharvest pitting or visual clues of fruit susceptibility were observed.

Free access

An enzymatic peeling process is currently used to produce peeled citrus fruit that are convenient for consumption. By this process, fruit are scored and infused with pectinase or pectinase and cellulase solution and are incubated at 20 to 45C for 0.5 to 2 h. While enzyme solution apparently weakens of the albedo and thus improves separation of the fruit from its peel, we expect that enzyme infused into the flesh reduces storage quality. In these studies, fruit were vacuum- or pressure-infused with or without pectinase in water. The time required to peel white `Marsh' and `Ruby Red' grapefruit infused with solution containing enzyme were only 10% to 20% less than for fruit infused with water alone. `Hamlin' orange and `Orlando' tangelo peeling times were not improved by enzyme treatment. This suggests that water is the primary operative component of the enzyme solution and that the enzyme is an active, but nonessential, supplement. For white grapefruit and oranges stored at 5, 10, 15, or 25C, nonenzyme-treated fruit had significantly less juice leakage than enzyme-treated fruit. For example, 0.2% and 5.0% of the peeled fruit weight was lost by non-enzymatically and enzymatically peeled fruit, respectively, for vacuum-infused oranges stored at 5C for 7 days. Moreover, the enzyme treatment significantly reduced firmness, as determined by a sensory panel. Microbial levels and rates of respiration and ethylene emanation during storage were not significantly affected by enzyme treatment. Similar results were found for vacuum- and pressure-infused fruit.

Free access

The fungicides thiabendazole (TBZ) or imazalil were applied at 1 g·liter-1 at 24 or 53C to `Marsh' and `Redblush' grapefruit (Citrus paradisi Macf.) to reduce fruit susceptibility to chilling injury (CI) and decay. Generally, there was more CI and decay on `Marsh' grapefruit than on `Redblush'. Severity of CI was lower in grapefruit that had been dipped at 53C than at 24C. Fruit dipped in fungicides had less CI than fruit dipped in water alone. Imazalil was more effective in reducing CI than TBZ. Fungicides reduced decay at both temperatures, and imazalil was better than TBZ. Chemical names used: 2-(4-thiazolyl)benzimidazole (thiabendazole, TBZ); 1-[2-(2,4-dichlorophenyl)-2-(2-propenyloxy)ethyl] -1H -imidazole (imazalil).

Free access