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Teri A. Hale, Richard L. Hassell, Tyron Phillips and Elizabeth Halpin

Taste panel perception and preference of pericarp tenderness in three phenotypes (su, se, and sh2) of sweet corn (Zea mays) harvested at three different maturities were compared to the readings received from a penetrometer. Pericarp tenderness perception by taste panel correlated with penetrometer measurements when phenotypes and maturities were compared. The penetrometer showed significantly lower readings for sweet corn harvested at early maturity than those harvested at late maturity. This was also noted in the panelists' perception of tenderness, with the early and mature harvest samples being preferred over those from the late harvest. The only difference between cultivars within phenotypes was noted in sh2 `Rustler' and `AXC904'. `Rustler' received the greatest overall pentrometer values and lowest panel ratings; conversely, `ACX904' had low penetrometer values and was perceived as tender and very acceptable to panelists. Correlations between penetrometer readings and panel perception of pericarp tenderness indicate that a puncture force, using a 0.118-inch (3.0 mm) probe, of greater that 0.95 g/inch2 (0.147 g·cm-2) indicated a tough pericarp and lower than 0.70 g/inch2 (0.109 g·cm-2) indicated a tender pericarp.

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Teri A. Hale, Richard L. Hassell, Tyron Phillips and Elizabeth Halpin

Increased value of fresh sweet corn (Zea mays) during the last decade has lead to increased interest into the characteristics that increase marketability. Sweetness was examined over three phenotypes (su, se, and sh2) to determine if there was an optimum phenotype or cultivar within a phenotype. Each phenotype was isolated to prevent cross-pollinization. Cultivars were grown on sandy loam soil located at the Clemson University Coastal Research and Education Center (Charleston, S.C.). Early, mature, and late harvest dates were also evaluated to determine the optimal harvest date(s) for maximum flavor. High performance liquid chromatography was used to determine sucrose, fructose, glucose, and total sugars. Panelists' evaluation of sweetness and its acceptability significantly correlated with the high performance liquid chromatography analysis for sucrose and total sugars (sweetness, R = 0.70 and 0.61; acceptability, R = 0.64 and 0.55). Sucrose correlated with the total sugars (R = 0.95). As maturity increased, the ability of the taste panel to identify differences in phenotypes also increased. Although sucrose and total sugar levels were different between se, sh2, and su, taste panelists indicated no difference between se and sh2. Sh2 cultivars were considered sweet and acceptable on all harvest dates, but su was only acceptable to panelists at early maturity.

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Teri A. Hale, Richard L. Hassell and Tyron Phillips

The refractometer has been proposed as a rapid, inexpensive technique for determining sugar levels in fresh sweet corn (Zea mays). High performance liquid chromatography (HPLC) analysis of sugars in three phenotypes (su, se, and sh2) of sweet corn harvested at three maturities indicated that sucrose content was highly correlated with the total sugars (R = 0.95). Sucrose and total sugar concentration were significantly different among all phenotypes. Soluble solids concentration (SSC) was high in su and se compared to the lower SSC of sh2. Early, mature, and late harvested samples differed in sucrose and total sugar content. Sugar concentration varied within phenotypes at each maturity level. Sh2 indicated no difference in sucrose and total sugars at early and mature harvests, but increased at late harvest. In contrast, sucrose and total sugar content decreased between early and mature harvests, then increased to highest levels at late harvest in se and su phenotypes. Overall, phenotype SSC increased significantly from early to late harvests, probably due to increased water-soluble polysaccharides in the su and se cultivars. Unlike other crops, a negative relationship was found in sweet corn between SSC and sucrose or total sugars, with an overall correlation of –0.51. This relationship was most affected by maturity, especially mature and late harvested sweet corn. Among phenotypes, sucrose, total sugar, and SSC were poorly correlated. Our results indicate that a refractometer should not be used to estimate total sugars or sucrose of sweet corn.

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Richard L. Hassell, Robert J. Dufault, Tyron Phillips and Teri A. Hale

Seeds of pale coneflower (Echinacea pallida), purple coneflower (Echinacea purpurea), feverfew (Tanacetum parthenium), and valerian (Valeriana officinalis), classified as “old” (1-year-old seed) or “fresh” (seed crop produced in the current year), were germinated at 62, 65, 69, 72, 75, 78, 82, 85, 89, and 92 °F, (16.7, 18.3, 20.6, 22.2, 23.9, 25.6, 27.8, 29.4, 31.6, and 33.3 °C). The optimum germination temperature, defined in this study as the temperature range within which the percent germination is greatest in the shortest period of time, was determined. Old and fresh pale coneflower seed germinated optimally after 5 days at 69 °F. Old purple coneflower seed required 5 d at 78 to 82 °F, but fresh seed germinated optimally after 3 days at 75 °F. Old feverfew germinated optimally after 5 days at 65 °F, but fresh seed germinated to its optimum after 5 days at 69 °F. Old and fresh valerian seed germinated to its optimum after 3 days at 75 °F.