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- Author or Editor: Eric Curry x
- HortTechnology x
With the development of improved postharvest technology, the shelf life of fruit and vegetables has increased dramatically in many parts of the world. Presently, dietary recommendations for these commodities are based on the bioavailability of essential nutrients at the time of optimum harvest. Few people, however, are fortunate enough to have available freshly harvested produce all year and, therefore, must consume fruit and vegetables that have been stored under the best conditions available. The question, then, is whether nutritional quality changes with storage method and length. Little is known concerning the effects of storage on nutrient content or bioavailability. Furthermore, if levels of these antioxidants do indeed change, perhaps dietary recommendations should reflect this as well. The data in this study indicate that there are significant changes in the levels of natural antioxidants in two apple cultivars at harvest and after an extended period in cold storage.
Experiments were conducted over several years to distinguish symptoms of sodium hypochlorite- or calcium hypochlorite-induced peel injury from other superficial maladies on ‘Gala’ and ‘Golden Delicious’ apples (Malus domestica), and to evaluate factors implicated in injury incidence and severity. ‘Royal Gala’ apples treated by dipping in freshly prepared aqueous sodium hypochlorite for 10 min showed moderate peel injury at the lowest treatment concentration of 150 mg·L−1 when treated immediately after harvest, whereas no injury was observed on fruit treated at even the highest concentration of 2400 mg·L−1 when fruit were kept at −1 °C for 3 months before treatment. At lower rates, rinsing fruit after treatment reduced injury on fruit dipped for 2 min, whereas after a 10-minute treatment, rinsing had no effect. Warm fruit (field heat) generally had a higher incidence of peel injury compared with fruit placed at −1 °C for 24 h before treatment. When ‘Golden Delicious’ apples were treated by dipping for 2 min in freshly prepared aqueous solutions of sodium hypochlorite or calcium hypochlorite at an equimolar hypochlorite ion concentration of 0.008 M (600 mg·L−1 sodium hypochlorite), treatment temperature had a greater influence on incidence of peel injury with sodium hypochlorite than with calcium hypochlorite. Analysis of nonpolar solvent-extractable epicuticular waxes indicated differences due to treatment among several extracted compounds. Microscopic examination of injured peel tissue indicated altered appearance of wax platelets.
Vegetable oil emulsion (VOE) was applied to `Gala' and `Fuji' apple (Malus ×domestica) trees after harvest to hasten defoliation and reduce apple scab (Venturia inaequalis). Applied at 2%, 4%, or 6%, VOE applied to whole trees in the fall induced leaf drop, with the highest concentration causing the most defoliation. At the same concentration, VOE applied in early, mid, or late October had similar effects on leaf drop. VOE treatment reduced respiration and stimulated ethylene production in shoot tissue within 24 hours of application. None of the treatments affected tree hardiness during the winter, or shoot growth the following spring. Return bloom density was unaffected; however, VOE tended to delay anthesis by 2 to 5 days. Under controlled conditions, `Gala' and `Fuji' trees inoculated with scab spores developed 48% and 65% scab, respectively. VOE-induced defoliation reduced scab by 50% to 65%. VOE-induced defoliation plus manual leaf removal from the orchard floor, or VOE-induced defoliation in late fall (15 Oct.-15 Nov.) plus application of 5% lime sulfur in early spring, controlled scab to <5% on both leaves and fruit. Neither lime sulfur nor urea applied in late fall at 2% induced defoliation or controlled scab. VOE at 4% plus 2% lime sulfur and/or 2% urea applied in late fall, however, defoliated `Gala' trees effectively and controlled scab on fruit to <7% the following spring. In the `Fuji' planting, the combination of 4% VOE plus 2% lime sulfur and 2% urea reduced scab on fruit from 21% in controls to 0%.
Lenticel breakdown disorder (LB), most prevalent on ‘Gala’ (Malus × domestica) apples, especially in arid regions, has also been observed on other common cultivars. Depending on the preharvest environment, fruit maturity, and length of storage, LB usually appears as one or more round, darkened pits, centered on a lenticel, ranging in diameter from 1 to 8 mm. Symptoms are not visible at harvest nor are they usually apparent on unprocessed fruit after storage. However, following typical fruit processing and packing, symptoms are fully expressed after 12 to 48 h. Because the 3 to 4 weeks preceding ‘Gala’ harvest are usually the hottest and least humid, we theorized that desiccation stress was a main causative factor. Thus, several unique lipophilic formulations were developed that might reduce desiccation potential during this period of hot arid weather and rapid fruit enlargement. Emulsions of lipophilic formulations were applied to whole trees at various dosages and timings. In 2005, using a single handgun application 1 day before harvest, the best treatment reduced LB by about 20% in fruit stored 90 days at −1 °C. The following season, the best treatment from a single handgun application 7 days before harvest reduced LB by 35% after 90 days at −1 °C, whereas 3 weekly applications beginning 3 weeks before harvest reduced LB in similarly stored fruit by as much as 70%. In 2007, the best single treatment applied 1 week before harvest using a commercial airblast sprayer reduced LB by almost 50% after 90 days at −1 °C.