Satsuma mandarins (Citrus unshiu) have been produced intermittently along the Gulf Coast for over a century. However, very little is known about the market potential for this citrus fruit in today's consumer markets. This study evaluated consumer preferences for seven external attributes over a range of levels: price ($1.07, $2.18, or $4.39/kg), color (green-yellow, yellow-orange, or orange), size (5.08, 6.35, or 7.62 cm in diameter), seediness (0, 3, or 7 seeds), blemishes (0, 1.91, or 3 cm in diameter), production region label (Alabama or U.S.A.), and organic production (yes or no). Consumers from grocery stores in nine cities in Alabama and Georgia were asked to evaluate 20 photographs of various combinations of these attribute levels using a seven-point intention-to-buy scale. 605 useable surveys were collected and a conjoint analysis was conducted to determine the strength of preference for the attribute levels and the relative importance for attributes. Three consumer segments were identified by cluster analysis of strengths of preferences: the no-blemish segment (37% of sample), the price-sensitive segment (23% of sample), and the no-seeds segment (41% of sample). A multinomial logit analysis identified several demographic, socioeconomic, and usage variables as significant determinants of segment membership.
Preharvest gibberellic acid (GA) applications at 10 ppm in 0.1% L-77 (v/v) surfactant or 20 ppm in 0.05% L-77 (v/v) caused `Marsh' grapefruit (Citrus paradisi Macf.) to be significantly more resistant to puncture and significantly delayed yellow color development. There was no difference between the two GA rates and applications in July were not found to be as effective as August or September applications. There was an overall significant increase in peel oil content in flavedo tissue as a result of GA treatment, but no significant difference between GA treatments. Limonin contents in GA-treated grapefruit albedo tissue were generally higher at both GA levels than in control fruit. GA treatments had no effect on juice quality characteristics and there was no difference in taste preference between GA-treated and control fruit. Because citrus fruit are resistant to attack by tephritid fruit flies prior to the occurrence of peel senescence and GA delays peel senescence, GA treatment should provide a biorational addition to existing fruit fly control strategies.
Studies were conducted between November 1999 and April 2003 to evaluate the effectiveness of compounds applied preharvest for reducing postharvest decay on many types of fresh citrus (Citrus spp.) fruit. Commercially mature fruit were harvested two different times after the compounds were applied, degreened when necessary, washed, waxed (without fungicide), and then stored at 50 °F (10.0 °C) with 90% relative humidity. Compared to control (unsprayed) fruit, preharvest application of benomyl or thiophanate-methyl resulted in significantly (P < 0.05) less decay of citrus fruit after storage in nine out of ten experiments, often reducing decay by about half. In one experiment, pyraclostrobin and phosphorous acid also significantly decreased total decay by 29% and 36%, respectively, after storage compared to the control. Only benomyl and thiophanate-methyl significantly reduced stem-end rot (SER; primarily Diplodia natalensis or Phomopsis citri) after storage, with an average of 65% less decay compared to the control. Though benomyl significantly reduced anthracnose (Colletotrichum gloeosporioides) in two of four tests with substantial (>20%) infection and phosphorous acid significantly reduced it once, thiophanate-methyl did not significantly reduce the incidence of anthracnose postharvest. The data suggests that preharvest application of thiophanate-methyl may reduce postharvest SER and total decay similar to preharvest benomyl treatments.
Polygalacturonase-inhibiting proteins (PGIPs) are believed to be one component of plants inherent defense mechanisms against fungal pathogens. We have purified a PGIP from mature grapefruit (Citrus paradisi cv. Marsh) flavedo using ammonium sulfate precipitation, preparative isoelectric focusing and ion exchange chromatography. Two peaks of PGIP activity were separated by isoelectric focusing, one at pH 6–7 and one at pH 9–10. The basic protein was more abundant than the neutral protein and was selected for further purification. The basic protein binds to S Sepharose at pH 6.1 and has an apparent Mr of ≈43,000 based on SDS-PAGE analysis. The protein is glycosylated as revealed by binding to ConA sepharose and is serologically similar to PGIPs from bean hypocotyl and pear fruit. Two dimensional PAGE analysis revealed the presence of two bands of similar Mr but with slightly different pIs (≈9.0–9.5). The N-terminal amino acid sequence of grapefruit PGIP shows high homology with PGIPs from fruit of other species and with a cDNA clone of PGIP that was isolated from a Citrus sinensis cv. Hamlin expression library. Grapefruit PGIP inhibits polygalacturonases from Aspergillus niger, and the citrus pathogen Penicillium italicum. We are interested in the role of PGIP in resistance of citrus fruit to postharvest decay fungi.
Abstract
Individual seal-packaging has been developed in the last decade as a new technique for postharvest handling of fruit and vegetables. This technique, mainly used with citrus fruit, may extend shelf life, reduce shrinkage, weight loss, the occurrence of various blemishes, and refrigeration costs. Individual seal-packaging helps in securing the beneficial aspects of a water-saturated atmosphere (WSA) and in mitigating its disadvantages. If the sealed fruit is not pretreated against decay, however, it may develop decay faster and have a higher percentage of stem-end rot than nonsealed fruit. The choice of films has been extended, but polyethylene of various densities is the main one used. These films offer an attractive appearance and characteristics, adapted to the needs of both the fruit as well as the machines which have been developed to seal individual fruit automatically. So far, this technique has been tested commercially in Israel, Australia, Florida, California, Arizona, Texas, Italy and Spain, and experiments are under way in other locations.
Abstract
With the expected ban on ethylene dibromide fumigation, cold exposure remains the only quarantine treatment for citrus fruit against the Mediterranean fruit fly. Following a cold treatment, ‘Marsh’ grapefruit (Citrus paradisi Macf.) developed chilling injury (Cl), mostly in the form of slight peel pitting on 3% to 10% of the fruit depending on the season and on other factors. There was no difference in the incidence of Cl between fruit treated at 0°C for 10 days or at 2.2° for 16 days as regulations require. The cold treatment also enhanced decay development during long-term storage of the fruit at 11°. Mold rots developed on Cl peel pitting, and their incidence increased from 1.7% to 3.5% during a storage period of 12 weeks. The presence of the fungicide Thiabendazole (TBZ) in the wax coating of the fruit reduced the incidence of Cl by more than 50%. Delayed cooling, i.e., keeping the freshly harvested packed fruit for 6 days at 17°C prior to initiation of cold treatment, reduced the incidence of Cl by the same extent. By combining a TBZ treatment with delayed cooling, the susceptibility of grapefruit to Cl can be reduced, and cold treatment can be practiced with a low risk of Cl and subsequent decay development.
Abstract
Seal packaging of orange [Citrus sinensis (L.) Osbeck cvs. Valencia and Shamouti], grapefruit (Citrus paradisi Macf. cv. Marsh) and lemons (Citrus limon Burnt, f. cv. Eureka) with high-density polyethylene (HOPE) film (0.01 mm in thickness) delayed softening and inhibited weight loss and deformation of the fruit more than cooling. Sealed fruit at 20°C and 85% relative humidity (RH) had better appearance and were firmer than non-sealed fruit at their lowest temperature possible without chilling injury and 85–90% RH. HOPE seal-packaging also inhibited chilling injury of grapefruit and lemons stored at 5° and 2°C, respectively. The C02 content of grapefruit was unaffected by seal-packaging, hut it was lower at cooler temperatures. Decay of citrus fruit depended more on the storage temperature than on the type of packaging. However, in storage up to 1 month, no significant difference was found in most experiments in decay percentage between orange, grapefruit, and lemon sealed with HOPE and stored in a packing house (13 to 25°C), and non-sealed fruits, at the lowest temperatures possible without chilling injury of 2, 10 and 14°C, respectively.
Juice quality of `Valencia' sweet orange [Citrus sinensis (L.) Osb.] trees on Carrizo citrange [C. sinensis × Poncirus trifoliata (L.) Raf.] or rough lemon (C. jambhiri Lush.) rootstocks was determined for fruit harvested by canopy quadrant and separated into size categories to ascertain the direct role of rootstock selection on juice soluble solids concentration (SSC) and soluble solids (SS) production per tree of citrus fruit. SS production per fruit and per tree for each size category was calculated. Juice quality was dependent on rootstock selection and fruit size, but independent of canopy quadrant. Fruit from trees on Carrizo citrange had >20% higher SSCs than fruit from trees on rough lemon, even for fruit of the same size. Large fruit accumulated more SS per fruit than smaller fruit, despite lower juice content and SSC. Within rootstocks, SS content per fruit decreased with decreasing fruit size, even though SSC increased. Rootstock effect on juice quality was a direct rather than an indirect one mediated through differences in fruit size. The conventional interpretation of juice quality data that differences in SSC among treatments, e.g., rootstocks or irrigation levels, or fruit size, are due to “dilution” of SS as a result of differences in fruit size and, hence, juice volume, is only partly supported by these data. Rather, accumulation of SS was greater for fruit from trees on Carrizo citrange than rough lemon by 25% to 30%.
Abstract
The ultrastructure of leaf and fruit surface waxes of citrus developed similarly. The wax layers of immature leaves and fruits were initially amorphous. Small protrusions and isolated regions of upright platelets then developed. All surfaces eventually cracked and uplifted to form large flat irregular plates. Epicuticular wax concentrations (μg/cm2) of new spring flush leaves were initially high, declined rapidly in March-April, and increased to June maxima after which levels declined slightly. Fruit epicuticular wax concentration generally declined in May-June and then increased into November. Secondary alcohols dominated citrus leaf waxes in March-April but quickly decreased or were diluted to trace levels. Overall, the major citrus leaf wax fractions were primary alcohols, with paraffins 2nd in importance. Aldehydes and fatty acids were dominant in citrus fruit waxes. For each cultivar, the relative proportions of individual wax fractions changed during the year. The intracuticular waxes were mainly fatty acids. The relationships between wax ultrastructure and chemistry in developing leaves and fruits are discussed.
Abstract
Bearing ‘Valencia’ orange trees growing in a commercial orchard adjacent to a known source of fluoride air pollution were sprayed periodically over a 3-year period with Ca(OH)2 and CaCl2 sprays. These materials in spray and dust forms have been used successfully in the Pacific Northwest to protect gladiolus and peaches from the harmful effects of fluoride-containing atmospheres. It has been postulated that calcium reacts with fluoride gases to produce insoluble and therefore nontoxic CaF2.
Results of these studies indicated that under conditions of high fluoride air pollution, application of lime sprays may improve citrus fruit production, but the mechanism of protection or improvement was not as simple as previously postulated. Immediately adjacent to the source where fluoride air pollution was at a maximum, applications of both Ca(OH)2 and CaCl2 were associated with increased internal fluoride accumulation by ‘Valencia’ orange foliage. With increased distance and therefore diminishing air pollution, an apparent reversal in effect was observed with the calcium sprays resulting in reduced internal accumulation of fluoride.
Although the effects of CaCl2 sprays on fluoride accumulation closely paralleled those obtained with Ca(OH)2, fruit production was not improved where CaCl2 sprays were applied, possibly as a result of induced chloride toxicity.