Department of Food Technology, Engineering and Nutrition, Lund University, Lund, Sweden.
Department of Chemical and Environmental Engineering, University of Oviedo, Julian Claveria 8, Oviedo, Spain.
PLoS One. 2019 Feb 6;14(2):e0210690. doi: 10.1371/journal.pone.0210690. eCollection 2019.
This work investigates the stability of emulsions prepared by using octenyl succinic anhydride (OSA)-modified waxy maize starch in the form of granules, dissolved starch, and non-solvent precipitated starch as Pickering emulsion stabilisers. The aim of this study was to investigate the effects of different forms of starches on the stability of emulsion using light microscopy, light scattering, and static multiple light scattering. All starch samples were hydrophobically modified with 3% (w/w) n-octenyl succinyl anhydride (OSA). Starch polymer solutions were prepared by dissolving OSA- modified starch in water in an autoclave at 140°C. Non-solvent precipitates were obtained through ethanol precipitation of dissolved waxy maize. The stability of the oil/water emulsions were different for the three forms of starches used. The granule-based emulsions were unstable, with only a small proportion of the granules adsorbed onto oil droplets, as viewed under a light microscope. The emulsions were observed to cream after 2 hours. The dissolved starch and non-solvent precipitate-based emulsions were stable towards creaming for months, and they had almost 100% emulsifying index (EI = 1) by visual observation and EI ~ 0.9 by multiple light scattering measurements. The results from light microscopy and multiple light scattering measurements indicated the occurrence of coalescence for all three types of emulsions. The coalescence was fastest within days for the granule stabilised system while it was slower both for the dissolved starch and non-solvent precipitate-based emulsions. The latter demonstrated the least degree of coalescence over time. Thus, it was concluded that differences in starch particle size and molecular structure influenced the emulsion droplet size and stability. A decreased particle size correlates to a decrease in droplet size, thus increasing stabilisation against creaming. However, stability towards coalescence was low for the large granules but was best for the non-solvent precipitate starch indicating that there is a window of optimal particle size for stability. Thus, best emulsifying properties were obtained with the non-solvent precipitates (~ 120 nm particle size) where the emulsions remained stable after one year of storage. In conclusion, this study illustrated the potentiality of non-solvent precipitated starch as emulsion stabilizers.
这项工作研究了以颗粒形式、溶解淀粉和非溶剂沉淀淀粉存在的辛烯基琥珀酸酐（OSA）改性蜡质玉米淀粉作为 Pickering 乳液稳定剂制备的乳液的稳定性。本研究的目的是通过使用光显微镜、光散射和静态多重光散射来研究不同形式的淀粉对乳液稳定性的影响。所有淀粉样品均用 3%（w/w）n-辛烯基琥珀酰酐（OSA）进行疏水性修饰。淀粉聚合物溶液通过将 OSA 改性淀粉在 140°C 的高压釜中溶解在水中来制备。非溶剂沉淀是通过溶解蜡质玉米的乙醇沉淀获得的。三种形式的淀粉所制备的油/水乳液稳定性不同。基于颗粒的乳液是不稳定的，只有一小部分颗粒被吸附到油滴上，在光显微镜下观察到。乳液在 2 小时后观察到乳膏。基于溶解淀粉和非溶剂沉淀的乳液在几个月内稳定，通过肉眼观察乳化指数（EI=1）接近 1，通过多重光散射测量乳化指数 EI0.9。光显微镜和多重光散射测量结果表明，所有三种类型的乳液都发生了聚结。对于颗粒稳定体系，聚结在几天内最快，而对于溶解淀粉和非溶剂沉淀乳液，聚结较慢。后者随着时间的推移显示出最小程度的聚结。因此，可以得出结论，淀粉颗粒大小和分子结构的差异影响乳液液滴大小和稳定性。颗粒尺寸减小与液滴尺寸减小相关，从而提高了抗乳膏的稳定性。然而，对于大颗粒，稳定性对聚结的稳定性较低，而对于非溶剂沉淀淀粉，则稳定性最佳，这表明存在稳定性的最佳颗粒尺寸窗口。因此，非溶剂沉淀淀粉（120nm 粒径）具有最佳的乳化性能，乳液在储存一年后仍保持稳定。总之，本研究说明了非溶剂沉淀淀粉作为乳化稳定剂的潜力。
