본 연구는 OSA 전분을 열처리 한 후, 이를 이용하여 제조한 OSA 전분 에멀션의 이화학적 특성 및 계면 흡착 구조 등을 조사하였다. 에멀션 중 지방구의 크기는 OSA 전분 농도의 증가와 더불어 지속적으로 감소하여 0.2 wt% 농도에서 최소값(0.31±0.01 μm)을 나타내었고, 그 이상의 농도에서는 변화가 없었다. 에멀션의 크리밍 안정도는 OSA 전분 농도가 높을수록 증가하였으며, 0.75 wt% 이상의 첨가 농도에서 크리밍 발생에 대하여 매우 안정하였다. 에멀션 중 OSA 전분의 계면 흡착량은 0.2 wt% 첨가 농도 이상에서 농도의 증가와 더불어 증가하였으며(0.2 wt% : 1.03 mg/m2→1.25 wt% : 5.08 mg/m2), 이는 계면에서 OSA 전분이 다층 구조를 이루는 것에 기인된 것으로 추정하였다. OSA 전분 에멀션의 pH를 조절하였을 때 산성 지역에서 지방구의 응집에 의해 크기가 증가하였으며, 이는 상대적으로 낮은 제타 전위에 기인된 것으로 사료되었다. 터비스캔에 의한 분산 안정도 또한 pH에 영향을 받아 산성 지역에서 낮았으며, pH 7 이상에서는 높은 분산 안정도 특성을 보였다. 공초점현미경을 이용하여 열처리된 OSA 전분이 흡착된 지방구 표면을 관찰한 결과, OSA 전분은 입자 형태가 아닌 두꺼운 계면막을 형성하는 것으로 나타났다. 따라서 에멀션 형성 전에 OSA 전분을 열처리할 경우, 전분의 호화과 정에서 용출된 아밀로오스와 아밀로펙틴이 지방구 표면에 막의 형태로 흡착되므로, OSA 전분 에멀션에 있어서 중요한 유화 안정화 기작은 ‘입체장애 안정화(steric stabilization)’인 것으로 사료되었다.

Surface-active substances in defatted rapeseed cake were obtained using a supercritical fluid extraction method. Then, it was purified by removing sinapine in the extract through a series of steps using a mixed solvent: diethyl ether and ethyl acetate (1:1, v/v). Emulsifying properties of purified surface-active substances were investigated, including fat globule size, zeta potentials and creaming stability and its antioxidant activity in emulsion systems were also studied by peroxide value and 1H-NMR spectrum. It was found that fat globules in emulsions with purified surface-active substances were much smaller than ones with the unpurified. In addition, as pH of the emulsion lowered and with increasing NaCl concentration in the emulsion, they were observed to increase, which led to worse creaming stability. These properties were reflected in changes of zeta potentials of emulsions. The oxidative stability was better in emulsions with purified surface-active substances than ones with Tween 20 or commercial lecithin, possibly resulted from the existence of sinapic acid in the extract. It was concluded that purified surface-active substances from defatted rapeseed cake could be simultaneously used as emulsifier and antioxidant agent in emulsion system.

In this study, the process of sinapine removal from surface-active substances extracted from defatted rapeseed cake was established by using a mixed organic solvent system (diethylether:ethyl acetate = 1:1, v/v). The emulsifying properties of the purified surface-active substances were investigated. Thin layer chromatogram showed that sinapine was removed and purified surface-active substances were found to have better emulsifying properties compared to a non-purified one or commercial soy lecithin. As for interfacial tension data, purified surface-active substances showed values lower (10-1 wt%: 3.20±0.57 mN/m) than the non-purified ones (10-1 wt%: 14.16±0.27 mN/m). In addition, we found that fat globule size in emulsions with purified surface-active substances was much smaller than in emulsions with non-purified substances or commercial soy lecithin. These results could be attributable to the increased amount of phospholipids in purified substances following sinapine-removal.

This study was carried out to investigate the emulsifying properties of surface-active substances from defatted rapeseed cake by supercritical CO₂extraction. Based on the interfacial tension data, a supercritical fluid extract (SFE) with the lowest value of 14.16 mN/m was chosen for evaluation which was obtained from No. 2 extraction condition (150 bar, 65℃, 250 g). For emulsions with SFE, some physicochemical properties (i.e., fat globule size, creaming stability, zeta potential etc) were investigated according to changes in SFE concentration, pH, and NaCl addition in an emulsion. It was found that fat globule size was decreased with increasing SFE concentration in emulsion, with showing a critical value at 0.5 wt%, thereby resulting in less susceptibility to creaming behavior. The SFE emulsion also showed instability at acidic conditions (pH<7.0) as well as by NaCl addition. This was coincided with zeta potential data of emulsion. In addition, SSL (sodium stearoyl lactylate) found to be suitable as a co-surfactant, as it helped considerably in decreasing fat globule size in emulsions and its optimum concentration to be over 0.03 wt%, based on 0.1 wt% SFE in emulsion.