Yazar "Shewfelt, RL" seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • [ X ]
    Öğe
    Effects of harvesting maturity and off-plant ripening on the activties of lipoxygenase, hydroperoxide lyase, and alcohol dehydrogenase enzymes in fresh tomato
    (Food Nutrition Press Inc, 2002) Yilmaz, E; Scott, JW; Shewfelt, RL
    The specific activities of lipoxygenase (LOX), hydroperoxide lyase (HPL), and alcohol dehydrogenase (ADH) were determined at green, pink, and red stages of ripeness in twelve tomato cultivars ripened during storage. Also, the same measurements were done in six other cultivars harvested at breaker (BR) and red (RR), and ripened to full-red stage of maturity. LOX and HPL showed highest activities at the pink stage of ripeness, whereas ADH was most active at the red stage. Variability of enzyme activity among individual fruit and of hue angle within ripeness stage was great. There were differences among the twelve lines for each enzyme activity, suggesting the potential for altering tomato flavor by selecting lines with different enzyme patterns. Harvest maturity was not a factor in the activities of LOX and HPL, but effective in ADH activity. In almost all cultivars, ADH activity was found to be higher in red harvested counterparts.
  • [ X ]
    Öğe
    Enzymatic modification of tomato homogenate and its effect on volatile flavor compounds
    (Inst Food Technologists, 2002) Yilmaz, E; Baldwin, EA; Shewfelt, RL
    Lipoxygenase (LOX), alcohol dehydrogenase (ADH), and a combination of both enzymes were added to homogenates of red-ripe and mature-green tomatoes, which were then incubated and denatured with CaCl2. Headspace gas chromatographic analysis was performed to characterize patterns of 15 key volatiles. Hexanal, cis-3-hexenal, and trans-2-hexenal increased in untreated red homogenates, while LOX treatment led to an initial accumulation of the volatiles followed by degradation. ADH treatment resulted in increased levels of methanol and acetaldehyde in homogenates isolated from both maturity levels. Combination treatments in both maturity stages tended to degrade rather than accumulate pathway volatiles.