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Enzymatic modification of whey prote...

Eissa, Ahmed Sherif.

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Enzymatic modification of whey protein gels at lowpH.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Enzymatic modification of whey protein gels at lowpH./
作者:	Eissa, Ahmed Sherif.
面頁冊數:	277 p.
附註:	Source: Dissertation Abstracts International, Volume: 65-11, Section: B, page: 5872.
Contained By:	Dissertation Abstracts International65-11B.
標題:	Engineering, Chemical. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3154197
ISBN:	0496146947

Enzymatic modification of whey protein gels at lowpH.
Eissa, Ahmed Sherif.

Enzymatic modification of whey protein gels at lowpH. - 277 p.

Source: Dissertation Abstracts International, Volume: 65-11, Section: B, page: 5872.

Thesis (Ph.D.)--North Carolina State University, 2005.

Whey proteins are widely used in a variety of food products due to their functional and nutritional properties. This study focuses on modifying whey protein gel properties at acidic conditions by enzymatic treatment. Enzymes offer a powerful tool to modify biopolymers in general, and proteins in specific. Transglutaminase enzyme is used in this study to induce &egr;-(gamma-glutamyl)lysine bonds between whey protein molecules at alkaline or neutral conditions, followed by subsequent acidification using glucono-delta-lactone (GDL) to form gels at the desired acidic pH.

ISBN: 0496146947Subjects--Topical Terms:

1018531
Engineering, Chemical.

Enzymatic modification of whey protein gels at lowpH.
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245 1 0 $a Enzymatic modification of whey protein gels at lowpH.
300 $a 277 p.
500 $a Source: Dissertation Abstracts International, Volume: 65-11, Section: B, page: 5872.
500 $a Chair: Saad A. Khan.
502 $a Thesis (Ph.D.)--North Carolina State University, 2005.
520 $a Whey proteins are widely used in a variety of food products due to their functional and nutritional properties. This study focuses on modifying whey protein gel properties at acidic conditions by enzymatic treatment. Enzymes offer a powerful tool to modify biopolymers in general, and proteins in specific. Transglutaminase enzyme is used in this study to induce &egr;-(gamma-glutamyl)lysine bonds between whey protein molecules at alkaline or neutral conditions, followed by subsequent acidification using glucono-delta-lactone (GDL) to form gels at the desired acidic pH.
520 $a We examine the viability of beta-lactoglobulin and alpha-lactalbumin for crosslinking and conclude that alpha-lactalbumin is easily crosslinked in its native state, while beta-lactoglobulin needs partial or complete denaturation to undergo the enzymatic catalysis. Denaturation of beta-lactoglobulin is done either by raising the pH to 8, or by thermal treatment (80°C for 1 hr) or by chemical denaturation using dithiothreitol (DTT). Crosslinks induced by transglutaminase increase the molecular weight of the whey proteins considerably to exceed 107 Da.
520 $a In the first part of this study, we investigate the cold-set gel formation by initially conducting the enzymatic reaction at pH 8 and 50°C then following up with acidulation by GDL to pH 4. The resulting gel exhibits superior rheological properties with higher elastic modulus and substantially higher fracture/yield stress and strain compared to cold-set gels with no enzyme.
520 $a In the second part of this study, we examine an alternative route for crosslinking, in which we preheat the whey protein first at 80°C for 1 hr at pH 7, and then conduct the crosslinking at 50°C. This procedure induces both disulfide and &egr;-(gamma-glutamyl)lysine bonds.
520 $a In the third part of this study, we investigate the relative roles of physical and chemical interactions that affect the properties of protein polymers and cold-set gels at pH 4, prepared using the same protocol as in the second part of the thesis.
520 $a In the fourth part of the thesis, we investigate the conformational characteristics of beta-lactoglobulin---the main constituent of whey proteins---subject to enzymatic crosslinking, using Fourier Transform Infrared (FTIR) spectroscopy.
520 $a In the fifth part of the study, we derive a transglutaminase-catalyzed polymerization model of beta-lactoglobulin based on probabilistic approach of non-linear polymers. Derived equations show critical gelation conversion of 5.8%.
520 $a In the last part of the study, we present a brief discussion of the effect of transglutaminase on hydrophobic associations in chemically (using DTT) denatured whey proteins. (Abstract shortened by UMI.)
590 $a School code: 0155.
650 4 $a Engineering, Chemical. $3 1018531
650 4 $a Agriculture, Food Science and Technology. $3 1017813
690 $a 0542
690 $a 0359
710 2 0 $a North Carolina State University. $3 1018772
773 0 $t Dissertation Abstracts International $g 65-11B.
790 1 0 $a Khan, Saad A., $e advisor
790 $a 0155
791 $a Ph.D.
792 $a 2005
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3154197