| Summary: | 碩士 === 東海大學 === 食品科學系 === 98 === Chitin was treated with NaOH solution (57%, w/v) under high temperature treatment (100℃) for 160 min to cleave acetyl group and became 80~90 % deacetylated chitosan. Pre-emulsions that were carried out by adding oil (10, 30, 50, 70, 90 and 120 mL oil/100 mL chitosan solution, 3 mL/interval) into chitosan solution (1.5 % concentrations, pH 6.0) and homogenizing with polytron homogenizer (9500 rpm), then, were passed through the high pressure homogenizer at different pressures (500, 1000, 1500 and 1800 bar) and recycled in some passes (1 to 7 passes). The emulsions were determined on the droplet size and stability for four weeks.
From the above result, emulsions that had nano-droplets and good stability were chosen for tests of thermal and freeze-thawing stabilities. Thermal stability was treated at 5℃, 25℃, 60℃, 100℃ and 121℃ for 30 min, then stored at room temperature for 4 weeks. Freeze-thawing treatment was carried out by freezing at -18℃ and thawing at 25℃ for 1 hr, individually; five freeze-thawing cycles were made. The treated emulsions were determined the droplet size, viscosity and stability.
As result, emulsions that were emulsified under suitable conditions showed nano size droplets and good stability. Lower oil/chitosan solution ratio, higher homogenizing pressure and more number of passes gave smaller droplet-sizes and more stable emulsions, group A: 1500 bar, 30 mL oil/100 mL chitosan solution, 3 passes; group B: 1500 bar, 50 mL oil/100 mL chitosan solution, 7 passes; group C: 1500 bar, 70 mL oil/100 mL chitosan solution, 7 passes; group D: 1500 bar, 90 mL oil/100 mL chitosan solution, 6 passes and group E: 1500 bar, 120 mL oil/100 mL chitosan solution, 7 passes. On the thermal test, increasing treatment temperature showed the emulsions slightly increasing in droplet-size and decreasing in viscosity, but still remaining in nano droplets and stable above 26 days. Especially, group A and B appeared no separation after any temperature treatment during four weeks.
On the freeze-thawing resistance, all emulsions were stable and gave no separation in 5 freeze-thawing cycles. Droplets of group A, B and C still remained in nano size.
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