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Michael Lay-Yee and Kellie J. Rose

`Fantasia' nectarine fruit [Prunus persica (L.) Batsch var. nectarina (Ait.) Maxim.], held at 0C for ≤ 1 week following harvest, were forced-air heated either immediately after removal from cold storage or after an overnight pretreatment at 20C. Fruit were heated to 41,43, or 46 ± lC for 24,36, or 48 hours. Following treatment, fruit were stored for 3 weeks at 0C, held at 20C for 1 or 5 days, and then assessed for quality. No significant damage, relative to nonheated controls, was observed in pretreated fruit subjected to 41C for 24 hours. Nonpretreated fruit given the same treatment showed only a slight increase in damage relative to controls. Higher temperatures and longer treatment times, however, were associated with an increased incidence of fruit damage (scald, internal browning, or decay). Heat treatment was associated with reduction in ethylene production and titratable acidity of the fruit following storage.

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S.B. Sterrett, M.R. Henningre, and G.S. Lee

Abbreviations: DAP, days after planting; IBS, internal brown spot; IHN, internal heat necrosis. 1 Associate Professor. 2 Professor. 3 Extension Horticulturist—Vegetables. Research supported in part by a grant from Anheuser Busch Co. We gratefully

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George H. Clough

In a 3-year study on a fine sandy loam soil, potato (Solanum tuberosum) cvs. `Atlantic' (1989), `Frontier' (1990, 1991) and `Russet Burbank' (1989-1991) response to rate and time of Ca fertilization was evaluated. Calcium was applied preplant at 0, 90, 180, and 270 kg·ha-1 as CaSO4 and side-dress at lay-by at 0, 67 and 134 kg·ha-1 as Ca(NO3)2, with treatments combined in a complete factorial. Preplant Ca fertilization increased soil Ca each year. Calcium fertilization had little effect on yield or grade distribution. Tuber P, K and S concentrations increased with increasing preplant and sidedress fertilization rates in 1989. Concentrations of S and Ca in Russet Burbank and Frontier increased linearly with preplant CaSO4 application rate in 1990 and 1991. Little or no internal brown spot (IBS) occurred in Atlantic or Russet Burbank, but in Frontier IBS was reduced both years by pre-plant and/or side-dress Ca application. The incidence of IBS did not change after storage for 4 months for any cultivar. In 1990, Russet Burbank fry color improved as pre-plant Ca fertilization rate increased.

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Yousheng Duan, Zhiqiang Ju, Liye Ju, and Aixin Guo

Effects of 10% plant oils (corn, soybean, peanut, canola, sunflower, safflower, rape seed, linseed, and cottonseed), 100 mg·L-1 chlorine, or 100 mg·L-1 chlorine plus 10% oil combinations on pathogen (B. cinerea, P. expansum, or G. cingulata) infection and fruit decay in `Delicious' apples and `Ya Li' pears were studied. None of the oils showed inhibition on spore germination of the three pathogens by in vitro test. In inoculated fruit, oil treatments did not affect incidence but reduced severity of decay after 6 months storage at 0 °C plus 7 days at 20 °C, but no difference was found among the oils at the same concentration. In non-inoculated fruit, oils reduced fruit decay to low levels (4%) even in the most severe season. Oils also maintained fruit quality attributes, reduced water loses, and controlled scald in apples and internal browning in pears. Chlorine reduced incidence but did not reduce severity in decayed fruit. Fruit first drenched with chlorine then dipped in oil emulsions without pathogen inoculation remained decay free, while control fruit developed 10% to 15% or 13% to 23% decay after 6 months at 0 °C plus 7 days at 20 °C in both apples and pears, respectively.

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Xuetong Fan, David Buchanan, Luiz Argenta, and James Mattheis

Pre-climacteric `Gala' apple fruit treated with air (control) or 2 μmol·L–1 1-methylcyclopropene (MCP) were exposed to gamma irradiation at 0, 0.5, 1, or 1.5 kGy at 23 °C. Fruit were held at 20 °C for 3 weeks after treatment during which respiration rate, production of ethylene and other volatile compounds, fruit firmness, soluble solid content, titratable acidity, and irradiation injury were determined. MCP treatment reduced respiration and ethylene production and slowed loss of fruit firmness and titratable acidity. Irradiation induced increased respiration of MCP-treated fruit in a dosage-dependent fashion. Irradiation caused a decrease in ethylene production by control (non-MCP) fruit, and the magnitude of the decrease was dependent on irradiation dosage. Irradiation at 0.5, 1, and 1.5 kGy stimulated ethylene production of MCP-treated fruit for only 1 day after treatment. Irradiation induced internal browning and the injury severity increased with dosage. The severity and incidence of irradiation damage were higher in MCP-treated fruit than control fruit. The results indicate that ethylene is involved in mediating apple fruit responses to irradiation.

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P. Perkins-Veazie, N. Roe, J. Lasswell, and J. McFarland

Growers in north and central Texas produce peaches of exceptional size and quality yet have no information on the best maturity stage/storage regime for maximum shelf life. `Majestic' peaches were harvested at five maturity stages, corresponding to hard green through full red, soft ripeness. Intermittent warming and/or delayed warming reduces chilling injury in peaches and these treatments were used on hard green through firm red stages. Fruit were held 4 weeks at 5 °C, 85% RH continuously (control); 1 day at 20 °C followed by 4 weeks at 5 °C (DS); 4 weeks at 5 °C with 1 day warming at 20 °C every 2 weeks (IW). Chilling injury symptoms (internal browning) were noted on control and IW peaches after 2 weeks storage. We concluded that hard green peaches are too immature and red peaches at velvet and full soft stages are too soft (<20N flesh resistance) to ship. Chilling injury appeared in peaches after 2 weeks storage at 5 °C but could be avoided by delaying storage for 24 hours after harvest.

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George H. Clough

In a 3-year study on a fine sandy loam soil, `Atlantic' (1989), `Frontier' (1990-91), and `Russet Burbank' (1989-91) potato (Solanum tuberosum L.) response to rate and time of Ca fertilization was evaluated. Calcium was applied preplant at 0, 90, 180, and 270 kg·ha-1 as CaSO4 and side-dressed at 0, 34, and 68 kg·ha-1 as Ca(NO3)2, with treatments combined in a complete factorial. Preplant Ca fertilization increased soil Ca concentration each year. Calcium fertilization did not affect tuber yield or grade distribution. Tuber concentrations of P, K, and Ca in `Russet Burbank', Ca in `Frontier', and S in all cultivars increased with increasing preplant Ca rate. `Russet Burbank' tuber P, K, Ca, and Cu concentrations and `Frontier' tuber S concentration increased as side-dressed Ca rate increased. Tuber concentrations of most nutrients decreased between midseason and harvest. The incidence of internal brown spot (IBS) was very low in `Atlantic' and `Russet Burbank' tubers and was reduced in `Atlantic' by preplant Ca application. In 1990, IBS severity and incidence in `Frontier' were reduced by preplant and side-dressed Ca fertilization. In 1991, after 4 months of storage at 7C, severity and percentage of tubers with IBS were reduced by preplant and side-dressed Ca fertilization. During storage, IBS decreased in `Russet Burbank'. Brown center in `Russet Burbank' decreased as side-dressed Ca rate increased. In 1990, `Russet Burbank' french-fry color improved as preplant Ca rate increased.

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Christopher Gunter, Senay Ozgen, Bjorn Karlsson, and Jiwan Palta

An increase in calcium concentration of potato tuber tissue has been shown to reduce soft rot severity and the incidence of internal physiological defects. Higher tuber calcium also seems to increase sprout vigor and maintain apical dominance by reducing subapical necrosis and sprout tip death. Preemergent applications of calcium at a rate of 0 and 26.5 kg·ha–1 from ammonium nitrate (PreAmNit), ammonium nitrate plus calcium nitrate (PreCaN), or calcium chloride plus calcium nitrate plus urea (PreCUC). A group of post-emergent split calcium nitrate plus calcium chloride plus urea (PostCUC) applications beginning with hilling and proceeding at 3, 6, and 8 weeks after hilling were also made at a rate of 56 kg·ha–1 calcium at each application time. From visual ratings of stand quality taken 64 days after hilling, we found plants receiving a preemergent application of nutrients or PostCUC had higher stand ratings than paired control plots. Internal tuber quality ratings revealed less internal brown spot in the PostCUC application in 168–364-g tubers. Yield of 112–168-g tubers was greatest from plants treated with PreCaN or PreCUC followed by PostCUC. PreAmNit plots had higher culls than the PreCUC plots. The non-split ammonium nitrate control (all nitrogen by hilling) produced a higher number of B-sized tubers than the PostCUC treatment. Also the PreAmNit+PostCUC had more B-sized tubers than PreCaN+PostCUC. In general the PostCUC treatment produced fewer small tubers and more large tubers than other treatments. These results suggest application of a small amount of calcium prior to emergence but after the sprouts have begun to develop improves seed performance. Furthermore these data show that supplemental calcium application during the season may improve tuber grade.

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Senay Ozgen, Christopher Gunter, Bjorn Karlsson, and Jiwan Palta

Potato tuber tissue is calcium-deficient. Consequently, increasing Ca concentration is desirable to improve tuber quality. The purpose of the present study was to determine the influence of supplemental Ca and N fertilization on internal quality of potato. Three products (calcium nitrate, calcium chloride, and gypsum) were used to increase tuber calcium concentration. We tested combinations of both soluble sources of calcium and gypsum. Each treatment had five replications and received same total amount of N, supplied either from ammonium nitrate, liquid N (UAN: 50% urea + 50% ammonium nitrate) and calcium nitrate or combination of these sources (at rate of 225 kg·ha–1). The total Ca was applied at the rate of 168 kg·ha–1. Application of N at emergence and hilling (nonsplit) was compared to split application of N and Ca at hilling, 2, 4, and 6 weeks after hilling. At harvest, ≈100 tubers from each replication were cut in half along longitudinal axis and visually inspected for internal defect in both years. Application of Ca, especially in split schedule and from soluble sources, significantly increased tuber tissue Ca concentration. In 1998, the incidences of hollow heart (HH) and internal brown spots (IBS) were very low. The treatment containing calcium nitrate and calcium chloride combination produced the lowest total defects, whereas application of gypsum was not effective at reducing defects. In 1999, application of all Ca sources including gypsum, reduced HH and IBS. Data from these studies suggest that tuber calcium level is increased by field applications of moderate amount of Ca and tuber quality is impacted by N and Ca application. Furthermore, seasonal climatic variations appear to have dramatic influence on the incidence of internal defects in potato tubers.

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Matthew D. Kleinhenz, Jiwan P. Palta, Christopher C. Gunter, and Keith A. Kelling

Three Ca sources and two application schedules were compared for their effectiveness for increasing tissue Ca concentrations in 170 to 284 g field-grown tubers of `Atlantic' potato (Solanum tuberosum L.). Additional observations were made of internal physiological defects. Paired measures of tissue (periderm and nonperiderm) Ca concentration and internal quality (±hollow heart, ±internal brown spot) were made on individual tubers produced in plots fertilized with N at 224 kg·ha-1 and Ca at either 0 or 168 kg·ha-1, supplied from either gypsum, calcium nitrate or NHIB (9N-0P-0K-11Ca, a commercial formulation of urea and CaCl2). Application of N and Ca at emergence and hilling (nonsplit) was compared to application at emergence, hilling, and 4 and 8 weeks after hilling (split). Tuber yield and grade were unaffected by treatments. Split Ca application (from either calcium nitrate or NHIB) increased mean tuber nonperiderm tissue Ca concentrations and the percentage of tubers with an elevated Ca concentration in both years compared with non-Ca-supplemented controls. Split Ca application also resulted in greater increases in Ca in nonperiderm tissue than nonsplit Ca application in 1994. Although the correlation coefficient between Ca level in periderm and nonperiderm tissue of >400 individual tubers was highly significant in both study years, linear regression analyses suggested the Ca level in the two tissues were poorly related. Split application was associated with a 37% reduction in the incidence of internal tuber defects, relative to nonsplit application in 1994. Calcium application did not affect tuber internal quality based on means analysis, but chi-square analysis suggested that Ca concentration and internal quality of individual tubers may be related. The incidence of internal defects was 16.4% in tubers with nonperiderm tissue Ca >100 μg·g-1 dry weight compared to 10.6% in tubers with nonperiderm tissue Ca >100 μg·g-1 dry weight. These data suggest that 1) it is feasible to increase tuber Ca levels by field applications of moderate amounts of Ca, 2) tuber quality is impacted by N and Ca application schedule, and 3) Ca concentrations in tuber periderm and nonperiderm tissues may be controlled independently.