| Summary: | 碩士 === 國立嘉義大學 === 食品科學系碩士班 === 91 === When starch is dispersed in water with emulsifier and heated, the starch and emulsifier would interact to form starch-emulsifier complex. This thesis studied the effects of starch-emulsifier complexion on physical changes and on the stability of
O/W emulsion system. Tree different HLB emulsifiers and various kinds of cornstarch were used in this study. The extent of complexion ( ACI % )of straight chain starch with emulsifier was determined by reacting with I2/KI reagent and measuring the absorbance at 600 nm. The ACI% depended on the amount of emulsifier, heating extent, water content, and dispersion of emulsifier. To observe the effects of complex on viscosity in emulsifier F110-polysaccharides complex system, the viscosity was continuously monitored as temperature was raised from 50℃ to 95℃ and lowered back to 50℃. The increase in heat break down and set back viscosity were only observed in cornstarch complex. When excess amount (10%) of emulsifier was added, the viscosity of cornstarch gel decreased. However, for three other gels (xanthan gum; guar gum; sodium alginate ), no obvious viscosity changes were observed. The thermal properties of complex were also studied by DSC. The DSC curve of starch-emulsifier complex showed two endothermic peaks at 45~54℃ and 98~107℃. The first peak involved the melting of starch crystals. While the second is a typical endothermic peak involved the melting of complex. The DSC curve of waxy cornstarch also showed a 90~110℃ peak but with small DH of 0.05J/g. This result indicates small part of branch-chained starch can form complex with emulsifier. For three other gels (xanthan gum; Guar gum; Sodium alginate), only one endothermic peak at 47~53℃ was observed. The DSC peak at 98~107℃ is a good indicator for the formation of starch-emulsifier complex.
The emulsion activity (EA) and emulsion stability (ES) were used to indicate the effects of starch-emulsifier complex on O/W emulsion. The EA and ES for the emulsifier were 23.30% and 23.21% respectively; for the mixture of cornstarch and emulsifier 22.11% and 22.49%; for the mixture after complexing 18.23 % and 18.34%; for starch-emulsifier complex itself 3.08% and 7.74%. The experimental results indicated the complexing decreased the emulsion effect. With emulsifier F160, the measured surface tensions of blank solution, complexing mixture, and complex only were 18.08 mN/m, 9.02 mN/m, and 14.21 mN/m respectively. Which were larger compared with that of the mixture of cornstarch and emulsifier before complexing (4.72 mN/m) or the emulsifier (3.67 mN/m). As for oil drop size distribution, 70% were smaller than 5mm for the emulsifier solution or for cornstarch- emulsifier mixture before complexing; 60% were smaller than 10mm for the mixture after complexing; 60% were smaller than 20mm for the complex. Three different HLB emulsifiers showed similar results.
Aabove results indicated that the starch-emulsion complex did not increase the emulsion stability.
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