Search Results

You are looking at 11 - 20 of 33 items for

  • Author or Editor: Sylvia M. Blankenship x
Clear All Modify Search

Scatchard plots for ethylene binding in apples (Malus domestica Borkh.), which were harvested weekly for 5 weeks to include the ethylene climacteric rise, showed C50 values (concentration of ethylene needed to occupy 50% of the ethylene binding sites) of 0.10, 0.11, 0.34, 0.40, and 0.57 μl ethylene/liter-1, respectively, for each of the 5 weeks. Higher ethylene concentrations were required to saturate the binding sites during the climacteric rise than at other times. Diffusion of 14C-ethylene from the binding sites was curvilinear and did not show any indication of multiple binding sites. Ethylene was not metabolized by apple tissue.

Free access

Abstract

2,5-NBD, a compound which competes with ethylene for binding sites and inhibits ethylene action in plant tissues, was applied to ‘Delicious’ apples (Malus domestica Borkh.) as a gas in either a closed or flowing system. Apples held in the closed system for 30 days at 25C in either 2000 or 4000 µl 2,5-NBD/liter were as firm as fruit held equally long at 5C; apples held in air at 25C were 19 N softer. Softening appeared to be mediated by ethylene. Soluble solids content and starch loss were similar for fruit held in air or in 2,5-NBD at 25C. The fruit’s internal ethylene concentration showed that 500 or 2500 µl 2,5-NBD/liter suppressed, but did not completely inhibit, autocatalytic ethylene production. The preserving effect of 2,5-NBD diminished after 50 days at 25C. Chemical names used: Bicyclo [2-2-l]-hepta-2,5-diene (2,5-norbornadiene; 2,5-NBD).

Open Access

Abstract

Gaseous mixtures of O2 + CO2 in N2 or ethylene in air were held in glass or plastic syringes for up to 30 hr under different temperatures and conditions. Concentration changes in the gases were followed over time to determine the best method to hold gas samples until analyses. At 25°C, ethylene loss was less from glass than plastic syringes. Twenty minutes at 25° was the maximum holding time before a statistically significant change in concentration occurred for 10 μl·liter−1 ethylene samples in plastic syringes. Plastic syringes absorbed ethylene. Ethylene loss from plastic syringes at 25° was linear within the constraints of the experiment over 30 hr, with the loss of 10 μl·liter−1 ethylene being more rapid than loss from 1 μl·liter−1. Carbon dioxide and O2 levels changed less from glass than plastic syringes at 25°. Holding ethylene or CO2 + O2-filled syringes under saturated NaCl or MgSO4, respectively, did not influence the change in CO2 or ethylene level from the syringes. The change in O2 concentration was less in plastic syringes held in a MgSO4 solution than plastic syringes held in air.

Open Access

Abstract

‘d’Anjou’ pear fruit (Pyrus communis L.) stored at −1°C for 125 days in 3% O2, or 153 days in 1% O2 storage had internal ethylene levels equal to those of air-stored fruit. Fruit softened faster during subsequent ripening at 20° after 1% or 3% O2 storage than after air storage. Endogenous ACC levels were 20 times higher in fruit stored in 1% or 3% O2 compared to air-stored fruit. Exogenous application of 5 mm ACC stimulated at 2-fold increase in ethylene production from 1% O2-stored fruit and a 4-fold increase in air-stored fruit. When 5 mm ACC, in combination with 0.05 mm cycloheximide (CHI), an inhibitor of protein synthesis, were supplied exogenously to disks cut from pears stored in air or 1% O2, the air-stored fruit produced 100 times more ethylene than 1% O2-stored fruit. Increased internal ethylene levels and accelerated softening during ripening of 1% or 3% O2-stored fruit suggests the need for rapid marketing of this fruit as compared to air-stored fruit. Chemical names used: 1-aminocyclopropane-l-carboxylic acid (ACC), 3-[2(3,5-dimethyl-2-oxocyclohexyl)-2-hydroxyethyl glutarimide (cycloheximide).

Open Access

Abstract

Internal ethylene levels, fruit firmness, soluble solids content, and starch–iodine reaction in ‘Delicious’ and ‘Golden Delicious’ apples (Malus domestica Borkh.) were measured weekly for 6 to 8 weeks during fruit maturation for 3 years. Internal ethylene level did not consistently correlate with minimum maturity as judged by agricultural inspection or optimum maturity as judged by a taste panel in either cultivar. Internal ethylene levels ranged from 0 to 26 μl·liter−1 in ‘Delicious’ and 0 to 41 μl·liter−1 in ‘Golden Delicious’ on taste panel harvest dates. Decreases in fruit firmness and increases in starch conversion and soluble solids content were observed prior to any increase in internal ethylene in both ‘Delicious’ and ‘Golden Delicious’. Thus, internal ethylene concentration is not a reliable index of maturity for harvest determination for immediate sale on the fresh market. The combination of fruit firmness decrease, soluble solids increase, and conversion of starch seem to be more closely tied to perception of maturity by both the agricultural inspectors and taste panel.

Open Access

Abstract

High performance liquid chromatography of mature ‘Beurre d'Anjou’ and ‘Beurre Bosc’ pear (Pyrus communis L.) fruit flesh showed that the major phenolics at harvest were chlorogenic acid, catechin, and arbutin. Neither cultivar contained epicatechin nor p-coumaroyl quinate. During 160 days at –1°C the chlorogenic acid content of d'Anjou increased significantly. In ‘Bosc’, chlorogenic acid levels decreased during storage. Catechin content increased linearly while arbutin levels remained nearly constant in both cultivars. Coincident with the completion of the cold requirement for initiation of ripening and endogenous ethylene production, i.e., 20 days for ‘Bosc’ and 50 days for ‘d'Anjou’, there was an appearance of low levels of a p-coumaric acid derivative and trace amounts of epicatechin/p-coumaroyl quinate. At 120 days epicatechin/p-coumaroyl quinate increased in ‘d'Anjou’ but not in ‘Bosc’. There is a coincidence, and perhaps relationship, between ethylene production and the quantity as well as the composition of phenolics present during storage. Bruising pear fruit after 120 days of storage caused a 30% increase in chlorogenic acid and a 50% increase in catechin, but no increase in p-coumaric acid derivatives.

Open Access

Abstract

Forty-six days at –1°C were required to stimulate ethylene synthesis in harvested ‘d'Anjou’ pears (Pyrus communis L.). The effect of exogenous ethylene on changes in quality parameters and organoleptic properties, and the effect of cold temperature on the development of ethylene production, were studied during the 46 days at –1°. Pears were held in 10 or 50 ppm exogenous ethylene at 20° after 30 or less days at –1°. Respiration increased from 8 to about 19 mg CO2·kg-1·hr-1 in fruit held in ethylene over a 12-day period, whereas fruit held in air showed only a slight increase. Firmness of fruit held in ethylene decreased from 66 to 12 N over 12 days at 20°. No significant change in firmness occurred in fruit held in air at 20°. The volume of extractable juice was unchanged in fruit held in air, but declined in fruit held in ethylene. The soluble solids content was not affected by ethylene treatment. Taste panel evaluation determined that fruit held 30 days at –1° then held 10 days in ethylene at 20° were ripe, sweet, and juicy, but fruit held in air were comparable to fruit never held at 20°. Pear flesh disks cut from fruit held 21 days at –1° did not convert exogenous 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene, but did so when cut from fruit held 41 or 50 days at –1°. Only with the onset of ethylene production was endogenous ACC detectable in pear flesh. During the 46 days at –1° required for initiation of ethylene production, the capacity to convert ACC to ethylene developed first, followed by production of ACC and ethylene.

Open Access

`Fuji' apples (Malus domestica Borkh.) were harvested at three maturities for three consecutive seasons. Fruit firmness, soluble solids concentration, starch—iodine index (SI), and internal ethylene concentration were measured at harvest. Fruit were stored in 0 °C air storage for 8 months. Fruit firmness and other maturity indices were measured monthly during storage. Using a stepwise regression procedure, harvest maturity indices were used to predict firmness after air storage. When all maturity indices measured were represented in the model, R 2 = 0.29, 0.34, and 0.26 at 4, 6, and 8 months, respectively. Use of only SI and fruit firmness in the model gave R 2 values of 0.25, 0.29, and 0.24 for 4, 6, and 8 months, respectively. Although R 2 values were low, they were highly significant. The model using fruit firmness and SI resulted in the best fit. Thus, an equation was developed using months of air storage, firmness, and SI at harvest. Actual firmness values correlated fairly well with predicted firmness values, usually within ≈5 N. On Washington apples, predicted values were 4.3 and 3.7 N too low compared to actual firmness values after 3 or 5 months' storage. In 1993, when predicted and actual firmness values were compared for Pennsylvania apples, predicted values ranged from 2.6 to 8.3 N too high after 3 months' storage, depending on harvest date. In 1994, Pennsylvania fruit stored 4 months had predicted values 0.5 N too high to 6.3 N too low, depending on harvest date. It may be possible to develop and refine models for an apple variety that would be applicable to several regions.

Free access

Mature green tomatoes (Lycopersicon esculentum Mill. cv. 674) were gassed with 160 to 275 μl/liter ethylene, depending upon the experiment, from either a Catalytic Generator or gas cylinder. Tomatoes were evaluated during subsequent ripening for fruit color development and taste. The combined results of two triangle difference taste tests indicated that the panel could tell a slight difference in taste of tomatoes based on gassing method. However, panelists did not reveal a strong preference for tomatoes from either method or consistently mention a certain characteristic that made the two groups of tomatoes different. Gas chromatographic analyses of the effluent from the Catalytic Generator indicated that several compounds other than ethylene were present.

Free access

A field study was initiated in 1981 in western North Carolina to determine the influence of eight groundcover management systems on quality of `Redchief Red Delicious' apple (Malus domestica) grafted onto rootstock of M VIIA. Management systems included: bare soil, Secale cereale mulch, minimal cultivation, Festuca arundinacea, Dactylis glomerata, Poa pratensis, Muhlenbergia schreberi and Rubus sp. Thus far, fruit quality data indicate that fruits produced in plots of cool-season grasses are smaller and less mature than those produced in vegetation-free plots or plots of warm-season grasses. A negative correlation was noted between high fruit quality and water deficit stress as measured by water potential and stomatal conductance.

Free access