59D-21 |
Characteristics of protein-based wall materials cross-linked with microbial transglutaminase |
H. K. SHIM, E. Y. Lee, and J. Park. Dept. of Biotechnology, Yonsei University, 134, shinchon-dong, seodaemoon-gu, Seoul, 120-749, South Korea
As an important nutrient in food,
proteins possess many excellent functional properties. These properties allow
them to be a good wall material for the encapsulation of food ingredients.
However, protein-based wall materials have a limitation for the nutrient
delivery system (NDS) due to fast degradation in the stomach. Microbial
transglutaminase (MTGase) is applicable to various protein-based wall materials
to enhance physicochemical properties suitable for the sustained release
through the intestine. Effects of MTGase treatment on physical
properties and pepsin digestibility of protein-based wall materials were
investigated. Isolated soy protein (ISP), Na-caseinate,
whey protein, egg yolk, and soluble wheat protein were selected as
protein-based wall materials. MTGase was dissolved in tris-acetic acid buffer. The
viscosity and the elasticity of the protein solutions were measured using the
Rheometer®. O/W emulsion (corn salad oil:protein solution=1:5) was
prepared by homogenization with the Ultra TurraxTM at 13,500 rpm and
emulsion stability was measured. MTGase induced cross-linking of proteins was
observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis
(SDS-PAGE). The digestibility of cross-linked proteins was assayed by addition
of pepsin (975 U/mg protein) to ISP and Na-caseinate solution. When ISP and Na-caseinate were treated
with MTGase for 30 min, the viscosity was increased more than 200%, whereas
viscosity of whey protein, egg yolk, and soluble wheat protein was increased
only 10-40%. ISP and Na-caseinate solution began to show elasticity after 50
min and turned into elastic gel after 8 h. MTGase modification resulted in
significant increase in the stability of O/W emulsion prepared with
Na-caseinate. MTGase-treated ISP and Na-caseinate showed much higher resistance
to pepsin compared to unmodified ISP and Na-caseinate. MTGase-treated proteins had improved
physical properties and pepsin resistance. These results suggested that
MTGase-treated proteins can be used as wall materials for the NDS.
Session 59D, Food Chemistry: Proteins and Physicochemical Properties
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