Search Results

You are looking at 31 - 40 of 41 items for

  • Author or Editor: William S. Conway x
Clear All Modify Search

The effects of 36 organosilicone and conventional carbon-based surfactants on postharvest infiltration of radiolabeled and unlabeled Ca solutions into `Golden Delicious' apples (Malus domestica Borkh) were examined to devise a more efficient pressure infiltration technique to increase fruit Ca concentration. Radiolabeled Ca infiltration and the proportional increase in fruit Ca estimated by fruit weight gain from Ca solutions of known concentration were significantly enhanced by a range of surfactants having different chemical structures. Tween 60 and 80; Triton X-45, X-100, X-114, X-305, and X-405; and Silwet L-77 and L-7604 enhanced Ca infiltration. The two organosilicone surfactants, Silwet L-77 and Silwet L-7604, known for their greater capacity to lower the surface tension of solutions than conventional carbon-based surfactants, were the most effective at augmenting Ca infiltration. Applications of surfactants to fruit were as or more effective when used as a pretreatment rather than mixing the surfactant with the Ca solutions. The pressure necessary to increase Ca to levels considered sufficient to maintain fruit firmness and resist decay during storage could be lowered in fruit treated with organosilicone surfactants. Sequential postharvest surfactant and Ca treatments may be a practical means of increasing the Ca concentration in apples.

Free access

`Golden Delicious' apples (Malus domestica Borkh.) were treated after harvest with heat (air at 38 °C for 4 days or 42 °C for 1 day) or 2% CaCl2 (w/v; applied as a dip or pressure-infiltrated) or a combination of the two and stored at 0 °C for ≤6 months. Decay caused by Botrytis cinerea Pers.:Fr. after inoculation to a depth of 2 mm with a conidial suspension virtually was eliminated in stored fruit heated at 38 °C, regardless of Ca treatment. Apples punctured to a depth of 0.5 mm (but not 2 mm) and inoculated with B. cinerea on removal from storage were almost completely protected from poststorage decay if they had previously been pressure-infiltrated with 2% CaCl2, regardless of the heat regime. Heating fruit at 42 °C and dipping in 2% CaCl2 were only partially effective in preventing decay from either pre- or poststorage inoculations. Fruit firmness was not related to resistance to decay.

Free access

Heating `Golden Delicious' apples (Malus domestica Borkh.) for 4 days at 38C or pressure-infiltrating them with a 4% CaCl2 solution reduced decay and maintained fruit firmness during 6 months of storage at 0C. Heating reduced decay caused by Penicillium expansum Link ex Thorn by ≈30%, while pressure infiltration with CaCl2 reduced decay by >60%. Pressure infiltration with CaCl2 after heating reduced decay by ≈40%. Pressure infiltration maintained firmness best (>84 N), as measured with a manually driven electronic fruit-firmness probe, followed by heat and CaCl2 (76 N), heat alone (71 N), and no treatment (control) (60 N). Force vs. deformation (FD) curves from a puncture test with a fruit-firmness probe mounted in a universal testing machine showed that fruit heated before storage were firmer than all nonheated fruit, except those pressure-infiltrated with 4% CaCl2. However, FD curves also showed that apples pressure-infiltrated with 4% CaCl2 differed quantitatively from apples in all other treatments, including those heated.

Free access

Prestorage infiltration of `Golden Delicious' apples (Malus domestica Borkh.) with calcium (Ca) retarded texture changes during storage at 0C and inhibited ethylene production of the fruit at 20C. Infiltration of the fruit with the polyamines (PA) putrescine (PUT) or spermidine (SPD) also altered texture changes, but did not inhibit ethylene production. When the fruit were treated with Ca first and then with PA, cell wall-hound Ca concentrations increased 4-fold, but PA levels in the cell wall increased only slightly. When the fruit were treated with PA first and then with Ca, PA levels in the cell wall increased 3-fold, but Ca concentration increased only 2-fold. These results indicate that Ca and PA may he competing for the same binding sites in the cell wall and that the improvement of fruit quality during storage by these cations could involve strengthening of the cell wall.

Free access

Heat treatment of `Golden Delicious' apples (Malus domestica Borkh) at 38C for 4 days, pressure infiltration with 2 or 4% solutions of CaCl2, or a combination of both with heat following CaCl2 treatment affected both decay and firmness during 6 months storage at 0C. The heat treatment alone reduced decay caused by B. cinerea by about 30%, while heat in combination with a 2% CaCl2 solution reduced decay by about 60%. CaCl2 solutions of 2 or 4% alone reduced decay by 40% and 60%, respectively. Heat treatments, either alone or in combination with CaCl2 treatments, best maintained firmness (80 N), followed by fruit infiltrated with 2 or 4% solutions of CaCl2 alone (70 N) and then the nontreated controls (66 N). Instron Magness-Taylor and Instron Compression Test curves show that heat treated fruit differed qualitatively and quantitatively from nonheated fruit. A combination of heat treatment after CaCl2 infiltration increased surface injury over those fruit heated or infiltrated with CaCl2 solutions alone.

Free access

A pilot test was conducted over a 3-year period to determine the feasibility of using postharvest pressure infiltration of calcium into apples to maintain and/or improve the quality of fruit under commercial storage conditions. Fruits obtained from three different orchards were treated each year. `Golden Delicious' fruits were treated the first year, while `Delicious' fruits were treated the 2nd and 3rd years. In all treatments and years, there was a significant increase in calcium concentration of apples from all calcium chloride (CaCl2) treatments. In general, calcium concentration of treated fruit varied significantly among the three orchards. Firmness also varied among orchards, and was related to fruit calcium concentration. `Golden Delicious' apples were more susceptible to skin injury caused by CaCl2 treatment than were `Delicious' fruits. There was also an increase in infection as a result of some of the treatments, possibly due to injury caused to lenticels by the pressure applied or as a result of calcium injury.

Full access

Structural changes in the cuticle could be partially responsible for the differences in uptake of infiltrated Ca in apple fruit. We examined the relationship between the surface structure of epicuticular wax of `Golden Delicious' apple and Ca uptake by the fruit. Apples were nontreated or pressure infiltrated with distilled water, or with 0.14 or 0.27 mol·L-1 CaCl2 solutions 2 weeks before optimum harvest time, at optimum harvest, or after 2, 4, or 6 months of storage at 0 °C. Examination of the fruit surface with low-temperature scanning electron microscopy revealed that cracks in the epicuticular wax became wider and deeper as storage duration increased. After 6 months of storage, the cracks extended through the cuticle. Uptake of Ca by the infiltrated fruit was greater after 6 months of storage than after shorter storage intervals. These data indicate that as storage duration increased, epicuticular wax cracks became deeper and Ca uptake by the fruit increased.

Free access

Decay caused by Botrytis cinerea is significantly reduced by increasing the calcium concentration of apple fruit tissue. Electron microscope studies have revealed that cracks in the epicuticular wax may be an important pathway by which calcium penetrates into the fruit and increases the calcium concentration. In fruit inoculated with B. cinerea, the decay induced compositional changes in the cell walls of high-calcium fruit were smaller than those observed in the low calcium treatment. The effect of calcium in reducing decay is associated with maintaining cell wall structure by delaying chemical changes in cell wall composition. B. cinerea produced five polygalacturonase isozymes in vitro but only one in vivo. Among the cations studied-m was the most potent inhibitor of polygalacturonase activity in in vitro studies. Its mode of inhibition appears to involve the alteration of substrate availability for hydrolysis, rather than any direct effect on the active sites of the enzyme.

Free access

`Golden Delicious' apples (Malus domestica Borkh) were pressure-infiltrated at harvest with a 4% CaCl2 solution either without prior heat treatment or following 4 days at 38C. Examination of the apple surfaces from both treatments by low-temperature scanning electron microscopy revealed that heat treatment changed the pattern of epicuticular wax. The epicuticular wax of nonheated fruit exhibited numerous deep surface cracks that formed an interconnected network on the fruit surface. The epicuticular wax of heat-treated fruit did not exhibit a similar network of deep cracks. This apparent obstruction or elimination of deep cracks may limit the CaCl2 solutions from entering the fruit. The heated fruit contained significantly less Ca than the fruit that were pressure-infiltrated with CaCl2 solutions but not heated. These results indicate that cracks on the fruit surface may be an important pathway for the penetration of CaCl2 solutions.

Free access

Increasing the calcium content of apples with postharvest CaCl2, treatment has a beneficial effect on physiological and pathological storage problems. The optimal time after harvest during which the fruit can be successfully treated has not been investisated. This study examined the relationship between calcium uptake and the changes in surface cracking in the epicuticular wax of the fruit after various storage intervals. Apples were pressure infiltrated with 0, 2, or 4% CaCl, solutions at harvest or four or six months after storage at 0 C. Examination of the epicuticular wax with low temperature scanning electron microscopy revealed that as the storage duration increased, the numerous cracks on the fruit surface became deeper and wider, until, after six months storage, the cracking extended through the thickness of the cuticle. Calcium uptake in fruit pressure infiltrated with the CaCl2 solutions after six months storage was greater than fruit treated at previous storage intervals. As storage duration increased, epicuticular wax cracks became deeper and calcium uptake increased.

Free access