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- Author or Editor: Charles F. Forney x
Polar lipids were extracted from immature through overripe `Honey Dew' muskmelons (Cucumis melo L.) that were exposed to high or low levels of solar radiation. Fatty acid composition of the polar lipids changed and the percentage of unsaturated fatty acids increased as fruit ripened. The percentage of monounsaturated fatty acids palmitoleic and oleic acid as a percent of total fatty acids increased from 8% in melons of minimum maturity to >50% in overripe melons. Also, the ratio of unsaturated to saturated fatty acids increased from 2.2 to 5.0. Total polar lipid fatty acid compostion from middle mesocarp tissue (flesh) did not change as much during ripening as the polar lipid composition from the epidermis (peel). Peel tissue from the top of melons relative to the ground had unsaturation ratios of C18 fatty acids and C16 fatty acids 33% and 62% greater, respectively, than peel from the bottom of the melon. Melons of minimum maturity exposed to solar radiation had significantly more unsaturated C18 fatty acids than shaded melons. Increase in the percentage of unsaturated polar lipid fatty acids in `Honey Dew' melons may relate to increases in chilling tolerance reported to occur with ripening and solar exposure.
Volatile compounds make a significant contribution to the quality and storage life of fresh strawberries, blueberries, and raspberries. Strawberry aroma is composed predominately of esters, although alcohols, ketones, and aldehydes are also present in smaller quantities. The major volatiles contributing to aroma include ethyl butanoate, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, ethyl hexanoate, methyl butanoate, linalool, and methyl hexanoate. In lowbush (wild) blueberries, aroma is predominated by esters and alcohols including ethyl and methyl methylbutanoates, methyl butanoate, 2-ethyl-1-hexanol, and 3-buteneol, while highbush blueberry aroma is dominated by aromatic compounds, esters, terpenes and long chain alcohols. The aroma of raspberries is composed of a mixture of ketones and terpenes, including damascenone, ionone, geraniol, and linalool. The composition and concentration of these aroma compounds are affected by fruit maturity and storage conditions. As fruit ripen, the concentration of aroma volatiles rapidly increases. This increase in volatile synthesis closely follows pigment formation both on and off the plant. In strawberry fruit, volatile concentration increases about 4-fold in the 24-h period required for fruit to ripen from 50% red to fully red on the plant. In storage, volatile composition is affected by storage temperature, duration, and atmosphere. Postharvest holding temperature and concentrations of O2 and CO2 can alter the quantity and composition of aroma volatiles. The effects of postharvest environments on volatile composition will be discussed.
Freshly harvested heads of `Cruiser' or `Paragon' broccoli (Brassica oleracea L. Italica group) were heat treated by holding in water for 1 to 40 min at 42, 45, 48, 50, or 52C. Control heads were held in air at 20C or in 25C water for 40 min. Controls turned yellow in about 3 days at 20C. Treatments at 42C delayed yellowing by 1 or 2 days, while treatments of 45, 48, 50, and 52C prevented yellowing up to 7 days at 20C. Hot water treatments had no effect on water loss of broccoli during storage. Incidence of decay was greater in treated broccoli stored wet compared to the dry control. However, when free water was removed by spinning following treatment, no difference in decay was observed. Treatment of broccoli at 52C for 3 or more min sometimes induced a distinct off-odor. When broccoli was held at 0C for 3 weeks following treatment no differences were observed between control and treated broccoli. However, when broccoli was warmed to 20C following storage at 0C, yellowing of treated broccoli was inhibited. Hot water treatments also delayed senescence at 20C when broccoli was treated following 3 weeks of storage at 0C.
Freshly harvested heads of `Cruiser' or `Paragon' broccoli (Brassica oleracea L. Italica group) were heated by immersing in water at 42, 45, 48, 50, or 52C. Immersion times were decreased as treatment temperatures were increased and ranged from 20 to 40 minutes at 42C to 1 to 3 minutes at 52C. Control heads, dipped in 25C water for 0, 10, or 40 minutes, began to turn yellow after ≈3 days storage at 20C and 80% to 90% relative humidity. Immersion in 42C water delayed yellowing by 1 or 2 days; immersion in 45, 48, 50, or 52C prevented yellowing for ≤7 days. Water loss of broccoli during storage at 20C increased by ≤1% per day by some hot-water treatments. Immersion in hot water decreased the incidence of decay during storage at 20C. Immersion in 50 or 52C water for 2 minutes was most effective in controlling decay development. Broccoli immersed in 52C water for 3 minutes had a distinct off-odor. Control and treated broccoli held at 0C for 8 days following hot-water dips were similar in quality. Yellowing of heat-treated broccoli was inhibited when broccoli was warmed to 20C following storage at 0C. Hot-water treatments also delayed senescence at 20C when broccoli was treated following 3 weeks of storage at 0C. Immersion of broccoli in 50C water for 2 minutes was the most effective treatment for reducing yellowing and decay while not inducing off-odors or accelerating weight loss.
Volatile compounds are responsible for the aroma and contribute to the flavor of fresh strawberries (Fragari×anannassa), red raspberries (Rubus idaeus), and blueberries (Vaccinium sp.). Strawberry aroma is composed predominately of esters, although alcohols, ketones, and aldehydes are also present in smaller quantities. The aroma of raspberries is composed of a mixture of ketones and terpenes. In highbush blueberry (Vaccinium corymbosum), aroma is dominated by aromatic hydrocarbons, esters, terpenes and long chain alcohols, while in lowbush blueberries (Vaccinium angustifolium), aroma is predominated by esters and alcohols. The composition and concentration of these aroma compounds are affected by cultivar, fruit maturity, and storage conditions. Volatile composition varies significantly both quantitatively and qualitatively among different cultivars of small fruit. As fruit ripen, the concentration of aroma volatiles rapidly increases closely following pigment formation. In storage, volatile concentrations continue to increase but composition depends on temperature and atmosphere composition. Many opportunities exist to improve the aroma volatile composition and the resulting flavor of small fruit reaching the consumer.
High-quality cranberry (Vaccinium macrocarpon) fruit are required to fulfil the growing markets for fresh fruit. Storage losses of fresh cranberries are primarily the result of decay and physiological breakdown. Maximizing quality and storage life of fresh cranberries starts in the field with good cultural practices. Proper fertility, pest management, pruning, and sanitation all contribute to the quality and longevity of the fruit. Mechanical damage in the form of bruising must be minimized during harvesting and postharvest handling, including storage, grading, and packaging. In addition, water-harvested fruit should be removed promptly from the bog water. Following harvest, fruit should be cooled quickly to an optimum storage temperature of between 2 and 5 °C (35.6 and 41.0 °F). The development of improved handling, refined storage conditions, and new postharvest treatments hold promise to extend the storage life of fresh cranberries.
Studies were conducted over three seasons to determine the relationship of temperature and humidity on the storage life of fresh cranberry (Vaccinium macrocarpon Aiton) fruit. Each year, cranberries harvested from four commercial bogs were stored at temperatures ranging from 0 to 10 °C in combination with relative humidities (RH) ranging from 75% to 98%. Fruit were stored under these conditions for up to 6 months and were evaluated monthly for marketability, decay, physiological breakdown, weight loss, and firmness immediately after removal and after an additional week at 20 °C. The percentage of marketable fruit declined substantially over time in all storage conditions with 41% to 57% becoming unmarketable after 2 months as a result of both decay and physiological breakdown. Relative humidity had a greater effect on fruit storage life than temperature and after 5 months, the amount of marketable fruit stored in high (98%) and medium (88%) RH was 71% and 31% less than that stored in low (75% to 82%) RH. Rates of fresh weight loss increased as RH in storage decreased and was 0.41%, 0.81%, and 0.86% per month in fruit stored in high, medium, and low RH, respectively. Fruit firmness was not significantly affected by RH. The effects of storage temperatures ranging from 0 to 7 °C on marketable fruit after 2 to 5 months of storage were not significant. Only fruit stored at 10 °C consistently had fewer marketable fruit when compared with fruit stored at lower temperatures. Storage temperature had no significant effect on decay incidence. However, physiological breakdown was greatest in fruit stored at 10 °C. Rates of fresh weight loss increased with storage temperature, ranging from 0.35% to 1.17% per month for fruit stored at 0 to 10 °C, respectively. Contrary to previous reports, no evidence of chilling injury was found in cranberry fruit stored at 0 °C. Results suggest that cranberry fruit should be stored at 0 to 7 °C and 75% to 82% RH to retain marketable fruit.
Warm (20C) or cold (3C) broccoli florets (Brassica oleracea L., Italica Group) were sealed in bags of two types of nonperforated flexible polyvinylchloride film, TPM 87 or RMF 61, and kept at 5C for 7 days. Temperature of the warm florets cooled to 5C in ≈ 8 hours. Warm broccoli had 40% to 50% more CO2 and 25% to 30% less O2 than cold broccoli in packages of both film types 6 hours after sealing. After 48 hours, however, concentrations of CO2 in bags of cold and warm broccoli had reached a steady state of ≈ 14.5% in TPM 87 bags and 6% in RMF 61 bags. Concentrations of O2 were more variable. After 48 hours, O2 concentrations were ≈ 2% to 4% in TPM 87 bags and 5% to 10% in RMF 61 bags. Initially, warm florets were rated lower for color, turgidity, and general appearance than initially cold ones after 7 days at 5C. Objectionable off-odors were formed from florets held in TPM 87 packages that had O2concentrations of <1.5%.
Methanethiol (MT) is a volatile compound responsible for the unpleasant odor evolved when fresh broccoli (Brassica oleracea L., Italica group) is held under anaerobic conditions. Inductive atmospheres can develop in storage, transportation containers, or modified atmosphere packages, resulting in reduced quality. To determine if related vegetables are capable of producing MT, 12 different vegetables from the genus Brassica were cut into ready-to-eat forms. Fifty-gram samples were sealed in 500-mL glass jars and flushed with N2. After 24 h in the dark at 20 °C, headspace samples from the jars were analyzed for MT and other volatiles. Headspace concentration of MT was greatest in broccoli florets, followed by pak choi (Brassica rapa L., Chinensis group) leaf blades, savoy cabbage (Brassica oleracea L., Capitata group), broccoflower (Brassica oleracea L., Botrytis group), and green and red cabbage (Brassica oleracea L., Capitata group). Broccoli stems, kale (Brassica oleracea L., Acephala group), Brussels sprouts (Brassica oleracea L., Gemmifera group), pak choi petioles, rutabaga (Brassica napus L., Napobrassica group) root, cauliflower (Brassica oleracea L., Botrytis group) florets, Chinese cabbage (Brassica rapa L., Pekinensis group), and kohlrabi (Brassica oleracea L., Gongylodes group) tubers produced <3% of the MT produced by broccoli florets. Green tissues appeared to have a greater capacity to produce MT than nongreen tissues. Anaerobic production of CO2 and ethanol did not relate to the vegetable's ability to produce MT. The production of dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) were also induced by the anaerobic conditions. Green cabbage produced the greatest concentration of DMDS, followed by savoy cabbage and broccoli florets. Production of DMTS was similar to the pattern observed for MT, but DMDS production was not highly correlated with MT production.
A plastic tent was designed and constructed for the controlled atmosphere (CA) storage of fresh blueberries. The CA tent was suspended from pallet racking in a standard cold room and held two standard pallets stacked 6 feet high with flats of packaged blueberries. The tent was sealed with two air-tight zippers and a small water trough, resulting in an air-tight chamber that successfully maintained CA storage environments. The CA tent was easily set up and removed to allow flexibility in use of storage space. To provide efficient use of storage space, tents could be stacked two or three high on pallet racking. The tent was easily loaded and unloaded by a single person using a forklift. CA tents provide an economical alternative to traditional CA rooms for the storage of small quantities of fresh blueberries and allows greater flexibility in marketing than traditional CA storage rooms. CA tents are suitable for the storage of other fresh produce that benefits from CA environments.