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Marcio Eduardo Canto Pereira, Steven A. Sargent, Charles A. Sims, Donald J. Huber, Celso Luiz Moretti and Jonathan H. Crane

, flavor, and overall liking using a nine-point hedonic scale where 1 = dislike extremely, 5 = neither like nor dislike, and 9 = like extremely. Scores and comments were recorded directly into a computer using the software Compusense five (version 4

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Angela R. Davis, Penelope Perkins-Veazie, Richard Hassell, Amnon Levi, Stephen R. King and Xingping Zhang

wilt as well as strong plant vigor, although he reported that this rootstock also caused inferior texture and flavor in grafted ‘Honey Dew’ ( Cucumis melo var. inodorus ) fruits. If Cucurbita spp. are used as a rootstock with the melon ‘Earl

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Yasar Karakurt, Donald J. Huber and Wayne B. Sherman

Some nonmelting flesh (NMF) peaches develop a characteristic off-flavor during postharvest ripening. A study was conducted using NMF genotypes from the Univ. of Florida breeding program to investigate the off-flavor development in melting flesh (MF) and NMF peach genotypes and to determine the compositional changes associated with the development of off-flavor during postharvest ripening at 8 °C. The study revealed that there were certain chemical components that were consistently associated with the occurrence of off-flavor. Generally, there was a significant increase in total soluble phenolics, polyphenoloxidase (PPO) activity and ethanol content with the increase in the percentage of off-flavored fruit with time in storage at 8 °C in NMF genotypes examined. However, total sugars and total soluble solids decreased significantly during the storage period. These changes in chemical composition of NMF genotypes were not observed in MF genotypes, which did not show off-flavor development. Moreover, highly significant linear correlations were detected between off-flavor development and soluble phenolics, PPO activity, ethanol content, total soluble solids, and sugars in Fla. 92-21C and USDA 87P285, which had the highest percentage of off-flavored fruit. Specifically, soluble phenolics, chlorogenic acid, PPO activity, and ethanol were positively correlated, but soluble sugars and soluble solids were negatively correlated with the off-flavor development. Thus, it is suggested that the accumulation of soluble phenolic compounds and ethanol, and the reduction of soluble solids and sugars contribute to the of off-flavor in NMF genotypes.

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W.M. Randle

To test the effects of high nitrogen (N) fertilization levels on onion quality and bulb flavor, `Granex 33' onions (Allium cepa L.) were greenhouse grown in hydroponic solution culture with increasing N concentrations. Nitrogen was adjusted in the solutions with NH4NO3 and increased incrementally from 0.22 g·L-1 to 0.97 g·L-1 over five treatments. Plants were harvested at maturity and subjected to quality, flavor, and mineral analysis. As solution N increased, bulb fresh weight and bulb firmness decreased linearly. Gross flavor intensity, as measured by enzymatically developed pyruvic acid (EPY) increased linearly for N concentrations between 0.22 and 0.78 g·L-1, but EPY was reduced slightly in bulbs grown at the highest N level (0.97 g·L-1). Soluble solids content was unaffected by solution N concentration. Solution N had an affect on flavor quality. Methyl cysteine sulfoxide, which gives rise to cabbage (Brassica L. sp.) and fresh onion flavors upon eating, generally increased in concentration as solution N increased. 1-Propenyl cysteine sulfoxide, which imparts heat, mouth burn, pungency, and raw onion flavors increased between the two lowest N concentrations, and then decreased as solution N increased. Propyl cysteine sulfoxide, which imparts fresh onion and sulfur flavors upon eating, generally increased with increasing solution N concentration. Several minerals were also affected by solution N concentration. Total bulb N and NO3 - increased linearly while B, Ca, and Mg decreased linearly. Total bulb S and K increased and then decreased quadratically in response to increasing solution N. Nitrogen fertility can have a pronounced affect on onion flavor and as a consequence, needs to be considered when growing onions for specific flavor quality and nutritional attributes.

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Timothy W. Coolong and William M. Randle

To determine the extent to which sulfur (S) and nitrogen (N) fertility interact to influence the flavor biosynthetic pathway in onion (Allium cepa L.), `Granex 33' onions were grown in hydroponic solution culture with varying levels of S and N availability. Plants were grown at 5, 45, or 125 mg·L-1 sulfate (SO4 2-), and 10, 50, 90, or 130 mg·L-1 N, in a factorial combination. Total bulb S, total and individual flavor precursors and their peptide intermediates in intact onion tissue were measured. To measure the effect of S and N on alliinase activity, flavor precursors were also measured in onion macerates. Sulfur and N availability in the hydroponics solution interacted to influence all flavor compounds except S-methyl-L-cysteine sulfoxide. Levels of S-methyl-L-cysteine sulfoxide were influenced by N and S levels in the solutions; however, no interaction was present. At the lowest SO 4 2- or N levels, most precursors and peptides measured were present in very low concentrations. When SO 4 2- or N availability was adequate, differences among flavor compounds were small. Results indicated that S fertility had a greater influence on trans-S-1-propenyl-L-cysteine sulfoxide (1-PRENCSO) accumulation, while N availability had a greater influence on S-methyl-L-cysteine sulfoxide levels. Flavor precursors remaining in the onion macerates revealed that the percentage of intact precursors hydrolyzed by alliinase were not significantly influenced by either SO 4 2- or N levels in the solutions, except for 1-PRENCSO, which was affected by N levels. Nitrogen and S fertility interacted to influence the flavor biosynthetic pathway and may need to be considered together when manipulating onion flavor compounds.

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David Obenland, Paul Neipp, Sue Collin, Jim Sievert, Kent Fjeld, Margo Toyota, Julie Doctor and Mary Lu Arpaia

It is commonly believed within the citrus industry that handling, waxing, and storage of navel oranges may have undesirable effects on flavor. However, the effect of each potential influencing factor under commercial conditions is not completely understood. The purpose of this study was to systematically investigate these potential influences on navel orange flavor. Navel oranges were harvested on two separate dates, using three grower lots per harvest date, and the fruit run on a commercial packing line. Fruit were sampled at four different stages of the packing process: in the field bin; after the washer; after the waxer; and after packing into standard cartons. Fruit quality, flavor, and juice ethanol concentration were evaluated immediately after sampling and following 3 and 6 weeks of storage at 5 °C. The overall hedonic score, a measure of flavor, significantly declined from 6.5 to 5.7, as a result of 6 weeks storage. Fruit selected from field bins, from after the washer, and after the waxer were all judged by the taste panel to be equivalent in flavor. The packed fruit were judged to be slightly inferior in flavor. Titratable acidity declined while soluble solids increased as a result of storage; the stage of the packing process influenced neither. Waxing and storage both were associated with higher ethanol levels in the fruit.

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Pai-Tsang Chang and William M. Randle

Onion is classified as a salt-sensitive crop, though it is found in production on saline soils around the world. While onion flavor intensity has been studied in response to various growing conditions, little is known about its response to salt stress. To understand if NaCl affects growth, flavor development, and mineral content in onion, `Granex 33' plants were grown to maturity with six different concentrations of NaCl ranging from 0 (control) to 125 mm in nutrient solutions. NaCl affected onion fresh weight and altered onion flavor intensity and quality. Plants did not survive the 125 mm NaCl treatments and are not included in the results. As bulb Na+ and Cl- content increased in response to increasing NaCl concentrations, leaf and bulb fresh weight of mature plants decreased. Total bulb S content also decreased with increasing NaCl solution concentrations, while bulb SO4 2- content increasing linearly, indicating that less S was entering the S metabolic stream. Though bulb soluble solids content was not influenced by NaCl concentrations, pungency increased, but only at the highest NaCl concentration. Total flavor precursors and methyl cysteine sulfoxide content increased in response to NaCl, but only at the 100 mm treatment. 1-Propenyl cysteine sulfoxide was generally unresponsive to the salt treatment. Propyl cysteine sulfoxide content decreased then increased in responses to increasing NaCl levels, but was found as a minor flavor precursor. Peptide intermediates measured in the pathway leading to 1-propenyl cysteine sulfoxide and propyl cysteine sulfoxide decreased linearly with increasing NaCl exposure. While NaCl affected onion flavor in this study, severe reductions in growth would prevent onion production under similar saline conditions. For practical purposes, the effects of NaCl on flavor are, therefore, minimal.

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T.M.M. Malundo, E.A. Baldwin, R.L. Shewfelt, H. Sisson and G.O. Ware

Fruit flavor is a function of sensory perception of taste, aromatic and chemical feeling factor components in the mouth. The specific role of sugars and acids in potentiating flavor perception of volatile compounds and chemical feeling factors is not well known for many fruits. This study was conducted to determine the effects of selected levels of sugars and acids on perception of 3 taste (sweet, sour, bitter), 6 aromatic (banana, grassy, orange peel, peach, pine/turpentine, sweet potato), and 2 chemical feeling factor (astringent, biting) flavor notes in diluted, fresh mango homogenate using a trained descriptive panel. Perception of all flavor descriptors except sour were enhanced by increasing the sugar concentration. An increase in acid concentration enhanced perception of sweet, sour and biting notes while lowering perception of the astringent, peach and pine/turpentine notes. Brix-to-acid ratio (BAR) was found to be an effective chemical indicator for perception of sourness but was not effective for perception of sweetness. These results provide insight into optimum balances of sugars and acids as they influence mango flavor perception specifically in preparation of juice blends, selection of cultivars for specific fresh markets, or determination of optimum ripeness in the marketplace.

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William M. Randle and Rachel Snyder

Mild onion consumption is increasing in the U.S. The ability to produce mild onions depends on selecting proper cultivars and growing them in an appropriate environment. A major decision in producing onions with mild flavor is determining when to stop applying sulfate to the crop. While adequate sulfur is necessary for good early onion growth, high levels of sulfur increase bulb pungency. A study was conducted where sulfate was eliminated from the fertility program at biweekly intervals during onion growth and development. Mature bulbs were then analyzed for flavor precursors and their biosynthetic intermediates, and pungency. Pungency linearly increased from 3.7 to 5.1 μmols pyruvic acid from the earliest cut-off date to the latest cut-off date, respectively. While total milligrams of flavor precursors did not significantly change in response to sulfate elimination, the methyl cysteine sulfoxide: 1-propenyl cysteine sulfoxide ratio did. Methyl cysteine sulfoxide concentration decreased in a quadratic manner while 1-propenyl cysteine sulfoxide linearly increased as sulfate fertility was extended in the growing season. Changes in individual precursors will significantly affect flavor perception as well as flavor intensity.

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Jyh-Bin Sun, Ray F. Severson, William S. Schlotzhauer and Stanley J. Kays

Thermal degradation of fractions from sweetpotato roots (`Jewel') was conducted with gas chromatographymass spectrometry to identify precursors of critical flavor volatiles. Upon heating (200 C), sweetpotato root material that was insoluble in methanol and methylene chloride produced similar volatile profiles to those from sweetpotatoes baked conventionally. Volatiles derived via thermal degradation of the nonpolar methylene chloride fraction and the polar methanol fraction did not display chromatographic profiles similar to those from conventionally baked sweetpotatoes. Initial reactions in the formation of critical volatiles appear to occur in the methanol and methylene chloride insoluble components. Maltol (3-hydroxy-2-methyl-4-pyrone) was found to be one of the critical components making up the characteristic aroma of baked sweetpotatoes. Integration of an analytical technique for the measurement of flavor into sweetpotato breeding programs could potentially facilitate the selection of improved and/or unique flavor types.