Abstract
A study was carried out to determine the physicochemical and emulsifying properties of pre-treated octenyl succinic anhydride (OSA) sago starch in simple emulsion. Sago starch was pre-treated with STARGEN enzyme (EN OSA: single pre-treatment), heat moisture treatment followed by STARGEN enzyme (HMT EN OSA: dual pre-treatment) before being esterified with OSA. The ability of the pre-treated OSA sago starch to stabilize emulsion was then investigated. Dual pre-treated starch, HMT EN OSA, had significantly highest degree of substitution (DS), (DS = 0.0179) compared to single pre-treated starch, EN OSA, (DS = 0.0159) and native OSA, N-OSA (DS = 0.0057). As compared to emulsions prepared by N-OSA and HMT EN OSA, EN OSA had significantly highest emulsifying activity throughout all starch concentrations and it produced a thick viscous emulsion layer directly after emulsification. This might be due to enzymatic pretreatments may retained granule’s original shape and smooth appearance which allow having a better fit during the emulsification process. The highest emulsion stability was observed with the emulsion index values of EN OSA stabilized emulsions was the most stable for all starch concentrations throughout storage study. After the 8th week of storage study, the EN OSA remains the highest emulsion index from 0.37 to 0.56 for 200 mg/mL oil to 500 mg/mL oil starch concentration. Light micrograph of EN OSA showed that starch particles accumulated at the oil-water interface and cover the oil droplets with higher degree of coverage than the HMT EN OSA and control. No spaces were observed in the EN OSA stabilized emulsion which indicated that EN OSA modified sago starch can effectively stabilize oil in water emulsion.
Highlights
Oil droplets stabilized by dispersed particles in water were originated from Ramsden (1903) and Pickering (1907)
In order to increase the hydrophobicity of starch, chemical modification of sago starch can be conducted by treatment with octenyl succinic anhydride (OSA)
These observations indicated that pre-treatment by enzyme and heat moisture treatment improved the efficiency of the subsequent OSA modification as HMT induced changes probably occur in the amorphous regions of the starch granules
Summary
Oil droplets stabilized by dispersed particles in water were originated from Ramsden (1903) and Pickering (1907). The use of particles to stabilize emulsions, such as modified starch, has received substantial and increased research interest because of their distinctive characteristics and promising technological applications in a range of fields. Pickering emulsion is an emulsion that is stabilized by solid particles which adsorb onto the interphase between the oil and water interfaces (Matos et al, 2016). The hydrophobic groups in the OSstarch granules introduced by OSA have an affinity for the oil phase, which can adsorb at the oil-water interface and form a physical barrier that prevents the separation of oil and water phases, and affecting the functional properties of the modified starch (Jiranuntakul et al, 2014)
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