`Gala' apples [Malus silvestris (L.) var. domestica (Borkh.) Mansf.] were treated with ethanol vapor (5 mL·kg-1 fruit for 24 hours at 25 °C), heat (4 days at 38 °C and >98% RH), or 1-methylcyclopropene (1-MCP; 1 or 0.625 μL·L-1 for 18 hours at 20 °C) before processing into slices, then dipped in anti-browning solutions or coatings, drained, and packaged in perforated polyethylene bags. Residual effects of pretreatments on fresh-cut slice physiological and quality attributes were investigated during storage for up to 19 days at 5.5 °C. Ethylene production was reduced by ethanol, heat, and 1-MCP pretreatments, while ethanol and heat also reduced slice respiration. Heat and 1-MCP pretreatments inhibited slice texture changes, while ethanol had no effect on instrumental texture measurements but reduced sensory firmness. Ethanol pretreatment increased the contents of ethanol and ethyl esters in slices but reduced acidity, while heat reduced both acidity and aroma volatile levels. Both ethanol and heat pretreatments led to lower sensory scores for apple flavor and ethanol-pretreated slices also received higher scores for altered flavor, although all scores were in the acceptable range. Slice acidity was best maintained by 1-MCP pretreatment. Shelf life based on appearance was 15 to 16 days for ethanol-pretreated slices and 12 days for heat-pretreated slices compared to that of control, which was 8 to 9 days, while 1-MCP pretreatment promoted decay development on the cut surface, which reduced the shelf life to 7 to 8 days. Obvious separations were determined between ethanol- and heat-pretreated slices and untreated control by canonical discriminant analysis of headspace volatile levels determined by GC and electronic nose. Therefore, pretreatments with ethanol and heat are very effective for prolonging visual shelf life at the expense of aroma quality.
Mature green mango (Mangifera indica L.) fruit were heated (100% RH) at 50C for 120, 180 or 240 min or 46C for 160, 220 or 280 min. The rate of mesocarp color (CIE a*) development was reduced in treated fruit, particularly in inner tissue. Rate of softening of mesocarp tissue was reduced after heat treatment; inner more than outer. Fruit treated at 50C remained more firm than control fruit 9 days after treatment, whereas fruit treated at 46C were more firm than controls 3 days after treatment, but were similar by 9 days. Electrolyte leakage from inner mesocarp tissue disks increased with increasing time at 50C, but was unchanged in fruit treated at 46C. However, after 3 days, electrolyte leakage returned to control levels. Ethylene-forming enzyme (EFE) activity of inner meso-carp tissue was greatly reduced in fruit treated at 50C (all times), and at 46C (220 and 280 min). After 3 days, EFE activity of fruit from most treatments had recovered to levels higher than controls. These data indicate that fruit may be able to recover from heat stress. Mild heat stress may increase postharvest shelf life by reducing the rate of softening.
Abstract
Clonal plants of four olive (Olea europaea L.) cultivars that originated in cool, moderately hot, and hot climates were examined for their photosynthetic potentials. Within 3 to 4 weeks, plants had fully expanded leaves; by 3 months the apparent photosynthesis, A, increased to a maximum of 5.4 µmol CO2/m2 per sec, while the water use efficiency (WUE) was 2.6 mmol CO2/mol H2O. The mean chloropohyll content was 0.564 mmol/chlorophyll (a + b)/m2. Mean assimilation rate was negatively correlated to leaf area. The values of A were three to four times less than those reported for apple and almond, whereas WUE was 22% greater. A values were proportional to stomatal conductance. Mesophyll resistance was higher than several C3 plants and the optimum temperature for photosynthesis varied among cultivars, seemingly according to the climate where they originated. Stomata opened and closed within 10 min in response to changes in humidity. Gas exchange properties were not affected by peltate removal.
data; a bbott Laboratories (gibberellin), Miller Chemical Co. (Vapor Gard), and Uniroyal (daminozide) for chemical supplies: and to the Virginia State Horticultural Society and a bbott Laboratories for partial financial assistance. The cost of
expanded; RLWC, relative leaf water content; SLW, specific leaf weight; VPD, vapor pressure deficit; WUE, water use efficiency. This is Florida Agricultural Station Series no. R-01055. The cost of puhlishing this paper was defrayed in part by the payment of
, specific leaf weight; tchl, total chlorophyll; VPD, vapor pressure deficit; WUE, water use efficiency. Florida Agricultural Experiment Station Journal Series no. R-O1O54. The cost of publishing this paper was defrayed in part by the payment of page charges
Abbreviations: A, carbon dioxide assimilation; g s , stomata1 conductance; PFD, photon flux density; RuBPcase, ribulosebisphosphate carboxylase; VPD, vapor-pressure deficit; WUE, water use efficiency. 1 Visiting Research Associate, Plant Research
Abbreviations: ET, evapotranspiration; ψ, water potential; VPD, vapor pressure deficit. 1 UC Cooperative Extension, 733 County Center III Court, Modesto, CA 95355. This work supported in part by a grant from the California Prune Board. The cost of
.7 mg·L −1 were extremely effective at killing conidia of Botrytis cinerea [Fuckeliana (de Bary) Fuckel] or Pencillium expansum Link on apples without causing any phytotoxic effects. AA vapor has also been used to protect grapes and strawberries
Abbreviations: DSI, drought susceptibility index; ET, evapotranspiration; AT, canopy - air temperature; VPD, vapor pressure deficit. 1 Associate Professor, Dept. of Plant, Soil and Entomological Sciences. 2 Research Geneticist, U.S. Dept. of