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- Author or Editor: Penelope Perkins-Veazie x
The postharvest life of blackberries is shortened by decay, leakage, and softness. Shelf life is shortened after periods of rainfall, and often fruit that appear firm in the field soften rapidly in storage. Blackberry selections of interest for advanced selections from plants without fungicide application are routinely screened for shelf life at Lane by storing fruit at 5 °C for seven days. Blackberry varieties are increasingly being used for farmer's markets, national, and international markets. A rapid test to gauge shelf life of blackberry varieties new to growers would be useful in determining the best type of marketing. Ripe blackberries were harvested from Clarksville, Ark., and transported in 260 g plastic clamshells on ice (about 5 °C) to Lane, Okla. Berries were weighed upon arrival and placed at 5 or at 20 °C for 7 and 2 days, respectively. Overall ratings were considerably worse at 20 °C compared to 5 °C, often with decay on all fruit in clamshells held at 20 °C. Separate subsamples of berries, placed individually in egg cartons and held over water at 20 °C (a 99% relative humidity) yielded Rhizopus, Collectotricum, and Botrytis cinerea growth after 24 hours. Because 2 days at 20 °C proved to cause decay in blackberries too quickly, fruit will be held for 1 day at 20 °C in the next season.
Raspberry (Rubus idaeus L., `Heritage') fruit were harvested at six stages of color development to determine the relationship between quality attributes and physiological changes during ripening. Soluble solids concentration and fruit weight increased, whereas titratable acidity decreased during ripening. Fruit darkened and color saturation increased with maturity. Raspberry fruit exhibited a nonclimacteric pattern of respiration, and ethylene (C2H4) was detected only after red pigment developed. Respiration and C2H4 production of whole fruit were similar to those of drupes. Ethylene-forming enzyme activity commenced in drupes and receptacle tissue from fruit at the yellow and mottled stages, respectively. These data indicate that ripening in raspberry fruit is independent of C2H4 production and is nonclimacteric.
Priming has been used to circumvent thermodormancy in lettuce seeds, but results have sometimes varied according to cultivar and seed lot. Two- and 3-year-old seeds of ‘Montello’ and ‘Green Lakes’ lettuce (Lactuca sativa L.) were aged at 41°C and 100% RH for 2, 3, or 5 days, dried, then primed for 20 hours at 15° in aerated 1% K3PO4 and redried at 7° and 45% RH. Germination at 25° was not affected by 2 and 3 days of accelerated aging or by priming of 2- and 3-year-old seeds. After 5 days of accelerated aging, germination decreased for both primed and nonprimed seeds. No germination occurred at 35° unless the seeds were primed. Natural aging led to a reduction in germination of primed ‘Green Lakes’ seeds at 35°. All accelerated aging treatments led to reduced germination of the primed seeds at 35°, regardless of cultivar. After prolonged accelerated aging (3 or 5 days), priming did not overcome thermodormancy. Accelerated aging greatly reduced germination rate at 25°. Priming for longer durations of 35 and 40 hours, after 3 days of accelerated aging, increased germination rates slightly at 25° but did not improve germination patterns at 35°. Only lettuce seeds of the highest quality could be effectively primed to overcome thermodormancy.
Ultraviolet light treatment has been used successfully to reduce postharvest fungal decay in tomatoes, strawberries, peaches, and citrus, presumably through elevated spore death and/or increased phytoalexins. The purpose of this experiment was to determine the effectiveness of UVC light as a postharvest treatment for blueberries. `Blue Crop' and `Collins' fruit were harvested from a local grower in 2003 and 2004 and exposed to 0, 1000, 2000, and 4000 Joules of light (354 nm) supplied from 30-W germicidal bulbs. Fruit were held at 5 °C for 14 days. Application of 1000 to 2000 J UVC light reduced decay incidence by 10% compared to controls. The major decay organism was ripe rot (Collectotrichum gloeosporioides). Total phenolics, total anthocyanin, and ferric reducing absorbance power differed with variety, increased with storage, and were similar among light treatments. Firmness of non-decayed fruit was not affected by storage or treatment. Application of UVC light offers a means for reducing fungal decay in blueberries if applied at rates between 1000 and 4000 J.
Switching from conventional to organic production requires a philosophical shift and recognition of different production system inputs plus postharvest handling challenges. First, and most obvious, is the replacement of common and readily available manufactured chemical inputs with approved “natural” or “nature-made compounds” (i.e., organic) for organic production. Many of these organic inputs may require new knowledge for successful implementation or may be less effective than conventional counterparts. Good orchard practices (e.g., cleanliness, bookkeeping) must be followed in an organic system just as they are in a conventional system. In addition, if processing (cider, sauces, or frozen fruit-sectioning preparations) is going to be part of the harvested operation, approved organic products will have to be used, and strict guidelines followed and documented. Organic versus conventional production system inputs can affect changes in the phytochemical and nutrient content of foods, and even change ripening patterns, which can affect harvest operations, marketing qualities, and consumer acceptance.