Physicochemical and emulsifying properties of pre-treated octenyl succinic anhydride (OSA) sago starch in simple emulsion system

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.

Dual Modification of Sago Starch via Heat Moisture Treatment and Octenyl Succinylation to Improve Starch Hydrophobicity

“…The DS and RE values of HMT-OSA starches were higher compared to native starch (N-OSA), indicating that more hydroxyl groups substituted per glucose unit with OSA in HMT starches. The same results have also been reported from previous studies on cassava starch [ 9 ], sweet potato starch [ 18 ], and sago starch [ 13 ]. The reduction in relative crystallinity as well as the movement of the chain of amylopectin double helices induced by HMT increased the amorphous area, and/or changed the orientation of the crystals, resulting in more sites for reaction.…”

“…OSA modifications in several types of starch sources have been reported in several scientific literatures such as sago starch [ 12 , 13 ], Indica rice starch [ 14 ], pearl millet starch [ 15 ], cassava starch [ 9 ], waxy corn starch [ 16 ], potato starch [ 11 , 17 ], and sweet potato starch [ 6 , 18 ]. Several methods of OSA-starch synthesis have been reported, but starch modification with OSA in aqueous media remains the most widely used because it does not require unsafe organic solvents and permits appropriate response results under slight experimental conditions (temperature around 30–35 °C and pH around 8.5) [ 19 ].…”

“…These changes are influenced by the degree of substitution (DS) and reaction efficiency (RE). Generally, the reaction between OSA and starch is inhibited due to the low solubility of OSA in water and uneven poor penetration of large OSA oil droplets into starch granules in an aqueous suspension [ 11 , 13 ]. Therefore, it has limited access to the interior of semi-crystalline starch granules.…”

“…These changes are influenced by the effect of moisture level, length of heating time, and heating temperature during the HMT process. Several studies have reported that pre-treatment of HMT before OSA esterification could increase the entry of OSA into starch granules and increase the reaction between OSA and the hydroxyl groups of starch increasing DS [ 13 ].…”