hydrocarbons [e.g., trichloroethylene (TCE), methylene chloride], and terpenes (e.g., α -pinene, d -limonene) ( Jones, 1999 ; Suh et al., 2000 ; Wolkoff and Nielsen, 2001 ; Won et al., 2005 ; Zabiegała, 2006 ). Benzene and toluene, octane, TCE, and α
Dong Sik Yang, Svoboda V. Pennisi, Ki-Cheol Son, and Stanley J. Kays
Jinhe Bai, Elizabeth Baldwin, Jack Hearn, Randy Driggers, and Ed Stover
standards for both harvests ( Elston et al., 2005 ). Other important terpene compounds included two terpene alcohols, linalool, and α-terpineol and two terpene aldehydes, citral and sinensal ( Tables 1 and 2 ). Both linalool and α-terpineol were detected
Jawwad A. Qureshi, Barry C. Kostyk, and Philip A. Stansly
-spray applications of multiple MoA insecticides tested over the most effective single MoA active ingredients sprayed alone for control of D. citri or P. citrella . Tank mixing with synthetic plant terpenes (Requiem 25 EC, Unknown MoA) did not improve the
Michael A. Jordan, Kenneth McRae, Sherry Fillmore, and Willy Renderos
Volatile compounds contribute to carrot (Daucus carota) flavor. However, effects of postharvest treatments on these compounds are not defined. To characterize treatment effects, fresh carrots (cv. Sunrise) were treated with 0 or 1.0 μL/L 1-methylcyclopropene (1-MCP) at 10 °C for 16 h, then exposed to 0, 0.3, or 1.0 μL/L ozone (O3) at 10 °C for 1, 2, or 4 days, and subsequently stored at 0 °C for up to 24 weeks. Twelve terpenes were identified in the headspace over whole carrots, including dimethylstyrene (22.5%), alpha-pinene (19.1%), caryophyllene (15.8%), beta-pinene (9.1%), p-cymene (8.3%), limonene (7.7%), gamma-terpinene (6.7%), myrcene (4.7%), gamma-terpinolene (4.5%) camphene (1.0%), alpha-phellandrene (0.52%), and sabinene (0.03%). Most terpenes responded similarly to treatments and storage. Immediately after treatment with 1.0 μL/L O3 for 1, 2, or 4 days, total terpene concentrations were 45%, 85%, and 87% greater than concentrations in non-treated controls. Caryophyllene, beta-pinene, and sabinene did not increase in response to the O3 treatment unlike the other terpenes. 1-MCP reduced terpene concentrations by an average of 18%. O3 treatments also stimulated stress volatile production. Ethanol headspace concentrations were 8-, 21-, and 43-times greater than the nontreated controls immediately following treatments with 0.3 nL/L O3 for 4 days or 1.0 μL/L O3 for 2 or 4 days, respectively. However, after 8 weeks, no differences among treatments were observed. Hexanal production also was stimulated by all O3 treatments, being 2- to 11-times greater than controls immediately following treatment. 1-MCP reduced O3-stimulated ethanol and hexanal production by 23% and 8%, respectively.
Jan-Louis Bezuidenhout and Hannes Robbertse
Discoloration of the lenticels of some mango cultivars is a serious problem, affecting the economic value of the fruit. Mango fruit lenticels develop from ruptured stomata on fruit from 20 mm in `TA' and `Keitt' and 30 to 40 mm in `Kent'. Lenticels enlarge as the fruit grow due to stretching of the fruit surface. Adult lenticels of `TA' and `Keitt' are larger in size than those of `Kent'. `Kent' lenticels are also better insulated than `TA' and `Keitt', having a thick cuticle in the lenticel cavity and, in some instances, a phellogen is also present where `TA' and `Keitt' lack both of the above mentioned. Resin present in the skin of the fruit play an important role in the discoloration of `TA' and `Keitt' lenticels. Resin of both `TA' and `Keitt' fruit contain a considerable amount of an aggressive compound termed terpenes. These terpenes are volatile and able to move out of the resin ducts via the sublenticellular cells to the outside of the fruit. The integrity of tonoplasts situated in sublenticellular cells are lost due to the presence of terpenes, causing vacuolar bound phenols to come into contact with polyphenol oxidase, present in the cell walls. The product of the resultant reaction is a quinone, accumulating as a brownish deposit in the cell walls, the black markings visible from the outside. This is the spontaneous discoloration process. Lenticel discoloration may also occur due to maltreatment, i.e., rough handling, to high temperatures, extended period on brushes on the packline, breaking of the cold chain, and spilling of resin onto the surface of the fruit.
B.H. Alkire and J.E. Simon
An experimental steam distillation unit has been designed, built, and tested for the extraction of essential oils from peppermint and spearmint. The unit, using a 130-gal (510-liter) distillation tank, is intermediate in size between laboratory-scale extractors and commercial-sized distilleries, yet provides oil in sufficient quantity for industrial evaluation. The entire apparatus-a diesel-fuel-fired boiler, extraction vessel, condenser, and oil collector-is trailer-mounted, making it transportable to commercial farms or research stations. Percentage yields of oil per dry weight from the unit were slightly less than from laboratory hydrodistillations, but oil quality and terpene composition were similar.
J. Kays and Wayne J. McLaurin
Flavor is a primary trait in the selection of foods. The role of flavor in acceptance of the sweetpotato, flavors status as a selection trait in existing breeding programs, and our current understanding of the flavor chemistry of the sweetpotato was reviewed. The sweetpotato, unlike most staple crops, has a very distinct and dominant flavor. In typical breeding programs, however, flavor is generally one of the last traits screened. A tremendous diversity and range of flavors has been reported within the sweetpotato germplasm (e.g., acidic, bland, baked potato, boiled potato. carrot, chalky, chemical, citrus, earthy, Ipomoeo/terpene, lemon, musty, pumpkin, salty, squash (titer type), starchy, sweet, sweetpotato (traditional), terpene, and turnip. These results indicate that the genetic diversity for flavor present in sweetpotato germplasm will allow making substantial changes in the flavor of new cultivars, thus potentially opening previously unexploited or under-exploited markets. Implementation involves solving two primary problems: 1) identification of desirable flavor ideotypes; and development of procedures that allow maximizing the selection of specific flavor types.
Gael Benoteau and Andrew G. Reynolds
The potential for interference by specific C6 compounds in the colorimetric quantitation of grape (Vitis vinifera L.) monoterpenes was investigated in model solutions and muscat and neutral-flavored grape cultivars. The unsaturated C6 aldehyde 2-hexen-1-al (2HX) showed color absorption at 608 nm in distilled water after reaction with an acidified vanillin solution. Absorbance also increased significantly when 2HX was added to a series of linalool solutions; ≈2.5 mg 2HX per liter of a 1-mg·liter–1 linalool solution increased the absorbance by >10%. Adding 2.5 mg 2HX per kilogram of `Gewürztraminer' berry homogenate significantly increased apparent free volatile terpene (FVT) concentrations to 121% of unadulterated control treatments but did not affect potentially volatile terpenes (PVT). Adding 2HX also increased apparent FVT concentration in `Perlette' and `Flame Seedless'. Both neutral-flavored table grape cultivars contained some FVT and PVT as a consequence of their muscat ancestries. FVT and PVT quantitation by colorimetric methods may be subject to significant error if the concentration of 2HX and other unsaturated C6 compounds in grape berries or must are >5 mg·liter–1. However, low concentrations of unsaturated C6 compounds (<80 μg·liter–1) in British Columbia wines suggest that there is a low probability of significant interference with this method.
Charles F. Forney
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.
Charles F. Forney
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.