Development Of Hydrophobic OSA Starch And Its Application In Liquid Foundation

As a natural renewable,low-cost,green and environmentally friendly resource,starch has the advantage of being easily modified,and has great potential for development in the application of cosmetic powder raw materials.Liquid foundation products are the foundation of makeup,and the consumer base is huge.Because of the long-lasting makeup time and high frequency of use,liquid foundation products with natural ingredients are more popular with consumers.Filler is the core component of liquid foundation,which serves as improving skin feel,filling,thickening,softing focus,etc.It often uses powdery raw materials such as talc,silica,and bentonite.Such fillers are thick and greasy.Moreover,some fillers will cause skin discomfort or allergies and have certain safety risks.Therefore,developing green and safe fillings has a practical value.Starch is a natural microsphere,which can be used as a powdery raw material for cosmetics,but natural starch has strong hydrophilicity,which is easy to agglomerate and settles,and has poor stability.The OSA modification gives hydrophobicity to the natural starch,enhancing its stability in the liquid foundation system,and provides the product a better skin feel,which has certain application value.This thesis is based on the development of a starch filler suitable used in liquid foundation.WMS,RS and PS with different particle sizes were used as raw materials to prepare OSA starch with different additive amounts.This thesis built a stability evaluation system of starch fillers in liquid foundation systems,and explored OSA starch suitable for use in liquid foundations.The main research contents are as follows:Firstly,this article selected starches from different sources and change the amount of OSA added to prepare OSA starches with different degrees of substitution,which were used as fillers in the liquid foundation samples.The stability of OSA starch was measured by the measurement of apparent viscosity,storage experiment,accelerated experiment,and rheology experiment.The multi-index comprehensive evaluation method was adopted to establish a comprehensive stability evaluation system,and the samples were compared with the blank sample and scored.After calculation,the stability score of the blank sample is-0.40,and the stability scores of the natural starch are all lower than 0.The stability scores of the OSA starches in the liquid foundation are in the range of 0.10～0.52.With the increase of the amount of OSA added,the stability scores showed a trend of first increasing and then decreasing.Secondly,this article measured the properties and structures of different OSA starches,and conducted correlation analysis with their stability in liquid foundation.The results showed that the degree of substitution(DS)of OSA starch increases as the amount of OSA increases when other reaction conditions are consistent,and the reaction efficiency decreases.The reaction efficiency of starches from different sources and OSA reagent were different.The reaction efficiency of WMS was 52.45%～61.62%,the reaction efficiency of RS was43.93%～56.11%,and the reaction efficiency of PS was 34.76%～50.16%.The particle morphology and particle size of starches modified by OSA did not change significantly.The dispersibility results showed that the particle size played a major role in the sedimentation of OSA starch.The larger the particle size,the faster the sedimentation rate.Different raw material OSA starches have different crystal structures.PS-OSA starch belongs to type B crystal structure,and its crystallinity is greatly affected by modification,from 14.38° to 7.93°;WMSOSA starch and RS-OSA starch are both type A crystals,the structure and crystallinity changes are not obvious.The contact angles(CA)of the three natural starches are all less than 53°,the hydrophobicity of OSA starch increased with the increase of DS.When the degree of substitution of OSA starch with type A crystal structure reached 0.020,the hydrophobicity of starch began to be greater than that of hydrophilicity;OSA starch with type B crystal structure showed strong hydrophobicity when the degree of substitution was 0.012.At the same time,the correlation analysis results showed that the degree of substitution and particle size of OSA starch was significantly correlated with their stability score in the liquid foundation,and the correlation coefficients were 0.451 and-0.312,respectively.Observation of the dyed liquid foundation samples under a laser confocal microscope verifies the conjecture that the OSA starch filler is distributed at the water-oil interface in the liquid foundation system.The smaller the particle size of OSA starch,the closer the contact angle is to 90°,and the better its stability in the liquid foundation system.Finally,through the stability evaluation system,three different OSA starches(WMS-7,RS-5,PS-3)of different raw materials that meet the market requirements were screened out.These starches can be used as liquid foundation fillers to prepare corresponding liquid foundation samples.The comprehensive application performance of the samples,including physical and chemical indicators,moisture retention,skin efficacy test and skin feel evaluation,were measured and compared.The results showed that RS-5 had the best application performance.The liquid foundation made by RS-5 improved skin gloss by 0.79 and moisturizing degree by 15.21%;its friction value was the smallest,which was 72.64% lower than the friction value before use,and had a smooth skin feel.Therefore,the optimal synthesis conditions of OSA starch for liquid foundation are: RS is used as raw material,OSA addition amount is 5%,and the reaction is carried out at 35°C and p H 8.0～8.5 for 4 h.