Yazar "Yilmaz, E" seçeneğine göre listele

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    An oil dilution technique used in small-scale frying to reduce oil expenditure
    (Blackwell Publishing Ltd, 2004) Yilmaz, E
    An oil dilution technique was developed and it saved oil expenditure in doughnut frying by about 30% without any compromise in doughnut quality compared with standard small-scale control frying. Doughnut quality as evaluated by a sensory panel and absorbed fat content measurements, also supported the main findings. In addition, either the oil density, acid value or alkaline contaminant materials can be effectively used to monitor oil quality changes during frying.
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    Bio-imprinting of microbial lipase at air-water interface
    (Kluwer Academic Publ, 2002) Yilmaz, E
    Bio-imprinting has been introduced as a technique of interfacial activation of lipase for anhydrous reaction applications. In this study, air-water (bubble) interfaces were compared to amphiphile and substrate interfaces in microbial lipase bio-imprinting. Results indicated that the bubble interface is equally effective on lipase interesterification activity and produces a 4-4.5-fold increase compared with the enzymes as supplied. Interesterification activity can be explained in terms of effects upon the accessibility of the lipase active site. This technique provides an easier, cheaper and product-friendly way of lipase bio-imprinting.
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    Biotechnological production of prostaglandin
    (Pergamon-Elsevier Science Ltd, 2001) Yilmaz, E
    Prostaglandins (PGs) are the oxidation products of PG endoperoxide (PGH) synthase and other tissue enzvt-nes. They occur in a tissue-specific manner and act as local hormones. Biotechnological production of PGs has been of interest, but not yet fully established. Biological tissues have been used as PG sources, but this disturbs ecological balance, and the cost of production is very high for commercial purposes. On the other hand, various microorganisms have been shown to synthesize them de novo, or biotransform precursors to active molecules, but these processes have not been further evaluated. Using mammalian enzymes in free or immobilized form is a promising new approach to synthesize PG from fatty acid substrates. Rapid enzyme inactivation during the catalysis is the main problem to be solved. Optimization of factors in the reactions and the design of special reactors that will allow removal of products continuously from the reaction medium without affecting enzyme activity need immediate attention from researchers and the pharmaceutical industry. (C) 2001 Elsevier Science Inc. All rights reserved.
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    Combining the bioimprinting technique with lipase immobilization for interesterification
    (Kluwer Academic Publ, 2002) Yilmaz, E
    Lipases were bioimprinted, immobilized and bioimprinted-immobilized (coupled technique), and interesterification activities were compared. Bioimprinted-immobilized enzyme preparations gave 4-6.2-fold activity enhancements compared to solid enzyme preparations supplied by manufacturers. This increase was higher than that of bioimprinting alone and immobilization alone. Solvent-free media were equally effective and water addition caused erasure of bioimprinting. Also, new preparations showed higher thermostability and reusability.
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    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.
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    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.
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    Improving the application of microbial lipase by bio-imprinting at substrate-interfaces
    (Kluwer Academic Publ, 2002) Yilmaz, E
    Lipases have bio-imprinted with common substrate-interfaces and interesterification activities compared with amphiphile bio-imprinted counterparts. Bio-imprinting has yielded a 3.5- to 4.5-fold activity enhancement. Solvent-free medium was equally effective as hexane medium. Water addition erased the bio-imprinting effect. Bio-imprinting caused rate acceleration in the interesterification reaction and increased thermostability of the enzyme.
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    Orlistat-induced molecular bio-imprinting of microbial lipase
    (Kluwer Academic Publ, 2003) Yilmaz, E
    Some microbial lipases bio-imprinted with the reversible lipase inhibitor, Orlistat. Comparison of interesterification activities indicated that Orlistat bio-imprinting is equally effective as amphiphile imprinting and yields a 3.5-4.0-fold activity enhancement. Solvent-free incubation medium was as effective as hexane medium. Water addition into the incubation medium erased the bio-imprinting effect; hence, lid opening should be the mechanism of activation. This study provides additional proof to the hypothesis that lipase bio-imprinting is an active-site related phenomenon.