Browsing by Author "Ondul, Eda"

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Cold Active Lipases
(Elsevier Science Bv, 2016) Ondul, Eda
The Contribution of Herbs To the Accumulation of Histamine in "otlu" Cheese
(Wiley, 2006) Ekici, Kamil; Coskun, Hayri; Tarakci, Zekai; Ondul, Eda; Sekeroglu, Ramazan
The aim of this study was to determine the effect of herbs and the use of raw milk on histamine accumulation in "Otlu" (Herby) cheese during ripening. Cow's milk was used for the cheese production. The milk was divided into two main groups: one was used raw and the other was pasteurized at 65C for 30 min. Each group was further divided into two subparts, one of which was used as control (without herbs), while 2% (w/v) of the herbs were added into the other to produce Herby cheese. All cheeses were ripened at 7C for 90 days. The cheese samples were analyzed in terms of histamine content, titratable acidity, dry matter, salt and degree of ripening on days 5, 30, 60 and 90. Total mesophilic aerobic bacteria (MAB) were also counted during ripening. The use of raw milk and the addition of herb both increased histamine formation in Otlu cheeses (P < 0.05). Moreover, higher water-soluble nitrogen values, as degree of ripening, were obtained from both raw milk and herb-added cheeses. The number of MAB was higher in raw cheeses (P < 0.05) and also herb-added cheeses. The study suggests that the addition of herbs may facilitate histamine formation in Herby cheese.
Immobilization of Candida Antarctica a and Thermomyces Lanuginosus Lipases on Cotton Terry Cloth Fibrils Using Polyethyleneimine
(Elsevier, 2012) Ondul, Eda; Dizge, Nadir; Albayrak, Nedim
In this study, cotton terry cloth fibrils were coated with 0.2% polyethyleneimine (PEI). Lipases from Candida antarctica A (CALA) and Thermomyces lanuginosus (TL) were immobilized on this support through adsorption followed by cross-linking with 0.2% glutaraldehyde. PEI-enzyme aggregates formation and growth of aggregates on cotton cloth fibrils lead to multilayer immobilization of the lipases. PEI and lipase was mixed to form PEI-enzyme complex/aggregate. The highest amount of enzyme precipitate was obtained at the PEI to enzyme ratio of 1/20-1/40 for both lipases. The effect of pH was also investigated for aggregates formation. The results showed that when pH values were below 8, aggregation and precipitation were not occurred for C. antarctica A lipase. However, pH did not affect PEI-enzyme aggregate formation for T. lanuginosus lipase. Immobilized enzyme amount was approximately 180 mg/g support and 200 mg/g support for T. lanuginosus and C. antarctica A lipases, respectively. Effect of the reaction temperature on the relative activity of the free and immobilized lipases at various temperature (30-80 degrees C) was studied. It was found that immobilization had no effect on the optimum temperature and it was 60 degrees C for both free and immobilized enzymes. The effect of operational and storage stability on activity of free and immobilized lipases were also investigated. Immobilized lipases exhibited that they could be stored at room temperature with a little activity lost during 28 days. (C) 2012 Elsevier B.V. All rights reserved.