Strawberry (Fragaria ×ananassa Duch.) fruit have a unique, highly desirable flavor and are one of the most popular summer fruits. Sugars, acids, and aroma volatiles contribute to the characteristic strawberry flavor, which is dependent on the proper balance of these chemical constituents. While sugars and acids are responsible for the sweetness and tartness of the fruit, aroma volatiles provide the unique, fruity flavors that characterize a fresh strawberry. The aroma of fresh strawberries is dependent on many factors. The large genetic variability in the nature of strawberry aroma results in differences in flavor among cultivars. In addition, the aroma changes dramatically during fruit ripening after harvest; therefore, it is important to preserve and enhance the ripe fruit aroma during postharvest handling. The loss of this desirable aroma or the development of objectionable aromas reduces the quality and marketability of fresh strawberries. In this review we will discuss the chemical nature of strawberry aroma and how it is affected by various factors, including cultivar, maturity, and postharvest environment. CHEMICAL COMPOSITION OF AROMA Volatile chemicals are responsible for the aroma and contribute to the flavor of fresh strawberries. These compounds comprise only 0.01% to 0.001% of the fruit fresh weight but have a major effect on its quality (Buttery, 1981). Fresh strawberries produce numerous volatile compounds; as many as 360 have been isolated (Latrasse, 1991) including esters, aldehydes, ketones, alcohols, terpenes, furanones, and sulfur compounds (McFadden et al., 1965). Esters are quantitatively and qualitatively the most abundant class of these compounds; 131 different ones have been identified in strawberry aroma (Latrasse, 1991). Esters provide the fruity and floral notes and they comprise from 25% to 90% of the total volatiles in fresh ripe fruit (Douillard and Guichard, 1990; Ito et al., 1990; Pyysalo et al., 1979; Schreier, 1980). Other classes of compounds, which may comprise up to 50% of strawberry volatiles, include aldehydes (Schreier, 1980) and furanones (Larsen and Poll, 1992). Alcohols account for as much as 35% of the volatiles, but normally contribute little to strawberry aroma (Larsen and Watkins, 1995b). While terpenes normally comprise <10% of strawberry volatiles and sulfur compounds <2%,

The chemical composition of the lowbush blueberry (Vaccinium angustifolium Aiton) cultivars Blomidon, Cumberland, and Fundy were examined at three stages of fruit maturity, before and after refrigerated storage, in a 2-year study. There were differences (P< 0.001) related to maturity and cultivar in berry fresh weight, percentage dry matter, fruit firmness, percentage soluble solids, titratable acidity, and the concentration of sugar, acids, and anthocyanins. Among the nine organic and phenolic acids measured, seven acids varied among the maturity groups and eight varied among the cultivars. Between the 2 years of study there was a 60% difference in total fruit acid content as well as in the relative amounts of each acid. The 2-year mean profile of lowbush blueberry acids was distinctly different from that recently reported for highbush (Vaccinium corymbosum L.) and rabbiteye blueberries (Vaccinium ashei Reade). The level of certain acids as well as the concentration of anthocyanins increased during cold storage. Estimation of sugar concentration by percentage soluble solids overestimated sugar concentration by 3070. Acid measurement by titration underestimated acid content as measured by HPLC by 61%. Results of this study illustrate the variation in the chemical composition of lowbush blueberry fruit among cultivars, maturities, and seasons, and can be used to compare lowbush blueberries with other Vaccinium species.

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Fruit extract of the European blueberry, or bilberry (Vaccinium myrtillus), is a major component of a great number of pharmaceutical and food supplement products. Compared to most small fruits, bilberry has a high concentration of anthocyanin pigments. Anthocyanins are of biomedical interest due to their properties as antioxidants and protein cross linkers. The major clinical applications for anthocyanins are in ophthalmology, blood vessel and connective tissue disorders, and diabetes. Bilberries are harvested from wild stands throughout Scandinavia, Eastern Europe, and at higher altitudes in southeastern France. Because they are wild, a wide array of genotypes make up the commercial product. As part of an investigation of the nutraceutical components of North American wild lowbush blueberries (Vaccinium angustifolium), we are comparing the anthocyanins and other phenolic components from fruit of commercially available Vaccinium species. We are particularly interested in the variation in composition among Vaccinium clones and species.

The effect of ethylene on tuber sprout growth and quality in potato (Solanum tuberosum L. `Russet Burbank') was tested in laboratory and commercial studies for 6 and 3 years, respectively, in comparison with untreated (laboratory study) and CIPC-treated tubers (laboratory and commercial studies). In both studies, ethylene was applied continuously at 166 μmol·m-3 for at least 25 weeks, beginning in early December (laboratory study) or early December to early January (commercial study). In the laboratory study, ethylene delayed the appearance of sprouts for 5 to 15 weeks, compared with untreated tubers. In the ethylene-treated tubers in both studies, sprouts appeared on many eyes but most of them remained very small (<5 mm long). Longer sprouts (>5 mm) appeared after 15 weeks but did not exceed 12 and 59 mm in the laboratory and commercial studies, respectively. Sprouts on ethylene-treated tubers were more easily detached up to 6 weeks after ethylene treatment ended, compared with untreated tubers. In both studies, ethylene treatment was not associated with decay, disorder or internal sprouting problems. In both studies, the Agtron fry color [or U.S. Dept. of Agriculture (USDA) color grade] of ethylene-treated tubers was darker than CIPC-treated tubers at almost all sampling times. Continuous exposure to ethylene was an effective sprout control agent but it produced a darker fry color, compared with CIPC-treated potatoes.