| Summary: | 碩士 === 靜宜大學 === 食品營養學系 === 90 === Rheological and electrophoretic properties of different molecular weight (150 kDa, 400 kDa, or 600 kDa) and concentration (0.1%, 0.5%, 1.0%, 1.5% or 2.5%) of chitosan (dissolved in 1% lactic acid solution) mixed singly or in combination with myofibrillar proteins were investigated. Effects of chitosan on thermal gelation characteristics of proteins were studied. Initial viscosity of chitosan solution at higher concentration (≥1.5%) increased with increasing chitosan molecular weight, and then decreased during heating process under constant shearing speed and shearing direction. The magnitude of decrease in viscosity was more apparent with increasing chitosan concentration. Results from temperature sweep of dynamic rheological analysis indicated an unchanged vsicoelastic property of chitosan solution at different molecular weight and concentration.
The storage modulus (G’) of porcine salt-soluble proteins (SSP) during thermal gelation process increased with rising temperature and this increasing tendency continued until the end of heating process. Addition of chitosan increased the initial G’ of chitosan/SSP mixture, but also decreased the G’ of SSP indicating an interference of chitosan with SSP gelation process and the gel strength SSP. Regardless of molecular weight, the higher the chitosan concentration strengthened the interference and lowered the G’ of chitosan/SSP mixture system. Tangent delta (tan δ) of chitosan/SSP mixture decreased with increasing temperature, and was higher than SSP solution at the end of heating process.
Results of SDS-PAGE from chitosan/SSP showed that disappearance of decreasing intensity of protein bands in comparison with SSP only. This indicated a possible interaction between chitosan and SSP resulting in aggregation and precipitation of proteins. Intensity and number of large molecular weight (> 66 kDa) protein bands increased with increasing chitosan concentration. This phenomenon was more pronounced for heated chitosan/SSP mixture and was attributable to the breakdown of chitosan/SSP linkages and degradation of SSP. As a result, releasing of large proteins was noted.
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