The objective of this work was to make emulsion with starch for natural cosmetics. For the cosmetic product with the high portions of natural grade ingredients, we could not use chemical stabilizers. Thereby, we investigated the effects of the amphiphilic starch and its stabilization for liposome emulsion. In this study, we conducted a starch crystallinity study to find the effect of gelatinization and retrogradation of amphiphilic starch with various types of gums using XRD, DSC and Cryo-FE-SEM techniques. To the best of our knowledge, there has been no report on the stabilization of liposome emulsion for cosmetics with native starch.

본 연구는 전분을 함유한 천연 화장품 에멀젼 제조를 위해 수행되었다. 천연 원료의 성분비가 높은 화장품을 제조하기 위해서 일반적으로 활용되고 있는 제형 안정화에 용이한 화학적 안정화제는 사용할 수 없었다. 따라서 우리는 양친매성 전분이 리포좀 에멀젼에 미치는 영향 및 안정화에 관해 조사했다. 양친매성 전분의 호화와 노화에 영향을 주는 요인을 찾기 위해, 여러 종류의 검들과 혼용 시 전분 결정화 연구를 XRD, DSC와 Cryo-FE-SEM 분석을 통하여 수행했다. 화학적으로 가공되지 않은 전분을 가지고도 화장품에서 리포좀 에멀젼 안정화 제형을 만들 수 있었다.

Keywords: starch crystallinity, gelatinization, gum, liposome, emulsion stability

Starch is completely biodegradable, nontoxic and renewable natural raw material, which is a semicrystalline polymer that can be found in most plants. Most starches are heterogeneous materials of polysaccharides: amylose is a mixture of linear Dglucose units linked α(1-4), and amylopectin is a mixture of branched D-glulcose units linked α(1-4) and 5% α(1-6) branch linkages. The glucose residues have various average numbers from 250 to 5000 for amylose, and from 10000 to 100000 for amylopectin.¹ The relative proportions of amylose to amylopectin depend on the plant source.² We used tapioca starch, which has the ratio of 18:82 of amylose to amylopectin.
Tapioca starch (TS) from cassava roots, is used as thickener in food industries for its high viscosity, clear paste, and low cost, compared to other starches.³ In cosmetic industries, especially natural cosmetics, TS has been used for oil absorption and lubricant function with powder. However, we invented it as the emulsion stabilizer by gelatinization. Precisely, the shape of starch granule and the degree of crystallinity varies with its source. The relative proportions of amylose to amylopectin are the major determinants for physicochemical properties of starch.⁴ This amylose is known to form a helix with different lipophilic ligands. These structural characteristics are important because lipid-amylose complex influences its interaction with the other components in food⁵ and cosmetic systems.
After gelatinization, we were able to make more stable emulsion. Nevertheless, we needed to control the degradation of starch because native starch generally became crystallized by degradation after gelatinization.^6,7 Because crystallization makes the emulsion unstable, we researched the method that makes more stable emulsion with TS. In the food industry, we found that the miscibillity of starch with other gums, especially xanthan gum, that could affect the pasting and gelatinization of TS.^8-11 For natural cosmetics we used guar gum and arabic gum, and tested the effects from the gelatinization properties of TS. Guar gum, among natural gums, was used as effective viscosity increasing agent. Guar gum made from ground endosperm of Cyamopsis tetragonolobus is an edible thickening agent that contains galactomannan which forms hydrocolloid. It is mainly used as a gelling agent, natural thickener, soil stabilizer, bonding agent, hydrocolloid, natural fiber, fracturing agent and flocculants. It is nearly odorless powder and white to yellowish white with bland taste. In cold or hot water, it could form highly viscous thixotropic sol.¹² Arabic gum was used as a stabilizer against syneresis because of its anionic properties from glucuronic acid like xanthan gum. Arabic gum made from removing the bark of trees such as Acacia Senegal is a highly branched heteropolysaccharide. Its backbone consists of β-galactopyranose units to which L-ramnopiranosas residues of L-arabinofuranoses, and glucuronic acid are connected. Therefore, it has various molecular weight between 250000 and 1000000 g/mol. It is a compact molecule in natural state, and it has its high solubility (50%) and the low viscosity in hydrocolloid system.^13-17
In order to control retrogradation of starch, food additives such as guar gum and arabic gum could change the water activity in starch-water systems. Starch retrogradation is controlled by many factors including additives, water content, storage temperature and storage time in the system. Natural gum additives can greatly control the extent and rate of starch retrogradation by interfering with the reassociation of starch chains or by competition for water with starch.¹⁸ Studies of moisture bonds form during bread storage could be insighted the mechanism of staling slowing effect. On the other hand, it could be explained as a result of a lower content of unbound moisture and lower content of water at the beginning of the storage period.¹⁹ In the presence of arabic gum, swelling power of starch controlled, and other additive such as sucrose could inhibit water absorption by limiting the water availability of starch.²⁰ With these kinds of gums, we investigated the degradation control of starch, and it is expected that this study is the only one with the effects of amphiphilic starch and its stabilization for liposome emulsion for natural cosmetics.