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FAHRETTIN GÖGTÜ MEDENI MASKAN AHMET KAYA 《Journal of Food Processing and Preservation》1998,22(5):345-357
Moisture sorption isotherms of Turkish delight were determined using the gravimetric static method of saturated salt solutions at 10, 20 and 30C. Isotherms were found to be of type III, typical of high sugar foods. The effect of temperature on moisture content was not significant (P>0.05). The sorption isotherms exhibited hysteresis at low water activities (aw < 0.5). At higher water activities the moisture content increased sharply as the temperature was increased, resulting in crossing of the isotherm curves at 0.65 water activity. Six models namely the BET, the GAB, the Halsey, the Henderson, the Chung & Pfost and the Iglesias & Chirife were evaluated to determine the best fit for the experimental data. The GAB and the Iglesias & Chirife models fitted well the data of Turkish delight in the temperature and water activity range investigated. However, the GAB model was not appropriate for the estimation of monolayer value. The Clausius-Clapeyron equation was used to examine the isosteric heats of sorption. 相似文献
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In this study, the soaking process, which is the first step of soy‐bulgur production to develop a new type food product, was investigated. the soaking operation was conducted at 30, 50 and 70C for 120 min and samples were taken from the soybean and soaking water at 10 min intervals. Moisture content and color (L, a, b and YI values) of soybean were measured, as well as soluble solids content and color (L, a, b and YI values) of soaking water during the soaking process. the results were analyzed by using ANOVA and Duncan test. Soaking time and temperature were significantly effective (P < 0.05) on all variables, except the time effect on the YI‐value. During the soaking, moisture content, lightness (L) and yellowness (b) increased and, redness (a) and yellowness index (YI) of soybean decreased. Soluble solids content, yellowness and yellowness index increased in contrast to a decrease in the lightness and greenness of the soaking water. As a result, soluble solids content in the soaking water increased, which illustrated the leaching of soluble solids from soybean to water. Color of soybean turned to lights, in contrast to darkening and opaqueness of water during soaking. Results showed that the moisture content, soluble solid content, L, a, b and YI values can be successfully modeled using polynomial equations, which can be used to estimate their changes during the soaking operation. 相似文献
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AHMET COLAK YASEMIN CAMEDAN ÖZLEM FAIZ ERTUGRUL SESLI YAKUP KOLCUOLU 《Journal of Food Biochemistry》2009,33(4):482-499
Lycoperdon perlatum Pers. (Lycoperdaceae, Agaricales, Agaricomycetidae, Agaricomycetes, Basidiomycota, Fungi) was evaluated for its esterolytic potential. Native electrophoresis of the crude extracts showed four bands having Rf values of 0.34, 0.39, 0.52 and 0.59. The esterase showed the highest activity toward a short-chain substrate, p -nitrophenyl acetate. Optimum reaction conditions for L. perlatum crude extract were attained at pH 8.0 and 40C. Esterolytic activity of enzyme extract was stimulated in the presence of Mn2 + , Fe2 + , Ca2 + and Zn2 + in the reaction mixture. The enzyme activity was stimulated by incubation at pH 6.0 but retained 77% of its original activity at its optimum pH after 24 h. Thermal inactivation was displayed after incubation for 20 min at various temperatures above 30C. At 1 mM final concentration, 2-mercaptoethanol, dithiothreitol, ethylenediamine tetraacetic acid and p -methylphenyl sulfonylfluoride inhibited the esterolytic reaction. These results support that the crude L. perlatum extract possesses an esterolytic activity having properties similar to other esterases.
Esterases catalyzing the cleavage and formation of ester bonds are known α/β-hydrolases (EC 3.1.1.X). Esterases are used for the synthesis of flavor esters for the food industry, modification of triglycerides for fat and oil industry and resolution of racemic mixtures used for the synthesis of fine chemicals for the pharmaceutical industry. Therefore, the search for new enzyme sources is important for the development of new enzymes and applications. 相似文献
PRACTICAL APPLICATIONS
Esterases catalyzing the cleavage and formation of ester bonds are known α/β-hydrolases (EC 3.1.1.X). Esterases are used for the synthesis of flavor esters for the food industry, modification of triglycerides for fat and oil industry and resolution of racemic mixtures used for the synthesis of fine chemicals for the pharmaceutical industry. Therefore, the search for new enzyme sources is important for the development of new enzymes and applications. 相似文献
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MEHMET HAKKI OMURTAG ATLLA
ZÜTOK AHMET YALIN AK
Z YUNUS
ZELK
RS 《International journal for numerical methods in engineering》1997,40(2):295-317
The main objective of the present work is to give the systematic way for derivation of Kirchhoff plate-elastic foundation interaction by mixed-type formulation using the Gâteaux differential instead of well-known variational principles of Hellinger–Reissner and Hu–Washizu. Foundation is a Pasternak foundation, and as a special case if shear layer is neglected, it converges to Winkler foundation in the formulation. Uniform variation of the thickness of the plate is also included into the mixed finite element formulation of the plate element PLTVE4 which is an isoparametric C0 class conforming element discretization. In the dynamic analysis, the problem reduces to solution of the standard eigenvalue problem and the mixed element is based upon a consistent mass matrix formulation. The element has four nodes and at each node transverse displacement two bending and one torsional moment is the basic unknowns. Proper geometric and dynamic boundary conditions corresponding to the plate and the foundation is given by the functional. Performance of the element for bending and free vibration analysis is verified with a good accuracy on the numerical examples and analytical solutions present in the literature. © 1997 by John Wiley & Sons, Ltd. 相似文献
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