Modified starch is starch that has undergone physical, chemical, or enzymatic treatment, resulting in changes to its structure and physicochemical properties. Reasonable modification of natural starch can not only maintain its original green properties but also overcome its shortcomings in application. In April 2021, the National Medical Products Administration of China issued the "Inventory of Used Cosmetic Ingredients," which lists 40 starch-related cosmetic ingredients. Commonly used modified starches in cosmetics include granular cold-water-soluble starch, octenyl succinic anhydride modified starch, hydroxypropyl starch phosphate, cationic starch, and microporous starch.
Modified starches primarily function in cosmetics through their emulsifying, thickening, and adsorptive/encapsulating properties. They are mainly used in emulsion-based cosmetics, powdered cosmetics, and powdered molded cosmetics.
1. Application in Emulsion-Based Cosmetics
Emulsion-based cosmetics are the earliest, most widely used, and highest-volume cosmetic products, such as common moisturizers, facial cleansers, and nourishing creams. Modified starch exhibits excellent emulsifying, thickening, stability, and film-forming properties, making it suitable as an emulsifier, rheology modifier, and film-forming agent in cosmetics. In emulsion-based cosmetics, emulsifiers are a crucial component that significantly impacts the product's appearance, physicochemical properties, and storage stability. Currently, commonly used emulsifiers include anionic and nonionic surfactants, some of which can be irritating to the skin. Modified starch, as a gentle surfactant material, holds vast potential for development. With its thickening and gelling properties, modified starch also serves as a rheology modifier. STRCTURE®XL, a smooth, rich, and creamy starch-based polymer, enhances viscosity and foaming, and has been successfully employed by starch companies as a sensory modifier in bath product formulations. Furthermore, chemical modification can alter the structure and properties of starch, enhancing its film-forming capabilities, which in turn imparts better moisturizing, water-resistance, fragrance retention, and conditioning effects to cosmetics.
2.Application in Powdered and Molded Powder Cosmetics
Powdered cosmetics are formulated by blending various dry powder ingredients with functional chemical components, such as face powder, talcum powder, and powdered hair dyes. Molded powder cosmetics, on the other hand, are made by compressing a mixture of powders, colorants, and binders into metal containers, resulting in products like eyeshadow compacts, blushes, and pressed powders. Modified starch primarily finds application in these types of cosmetics as a substitute for talc. Although talc has undergone safety risk assessments and is considered safe for use in cosmetics under normal, reasonable, and foreseeable conditions, without posing a hazard to human health, consumers remain skeptical about its safety. As a result, many consumers opt to avoid products with ingredients whose safety is debated, prompting cosmetic manufacturers to seek alternatives to talc in their formulations. Studies have shown that certain starch-based materials, due to their excellent absorbency and smooth texture, can effectively replace talc in these products.
3.Application in Novel Cosmetics
Porous starch, with its remarkable microporous characteristics, can adsorb various cosmetic ingredients, particularly those with specific functions such as acne-fighting and whitening agents, as well as emollients like mineral oil-based substances. As a carrier in cosmetics, porous starch can effectively reduce skin irritation caused by the products, while enhancing their spreadability, smoothness, and glide, thereby increasing the contact area and utilization efficiency of active ingredients with the skin. Furthermore, other starch derivatives like polyoxyethylene sorbitan fatty acid esters (Tween) and sorbitan fatty acid esters (Span), either used alone or in combination, exhibit excellent emulsifying effects on microemulsions with minimal irritation. They are suitable for use as drug carriers and are also well-suited for transparent gel-type skincare and haircare products.
In recent years, many researchers have attempted to leverage the advantageous structural features of certain modified starches in conjunction with pharmaceutical carrier systems, sustained-release concepts, encapsulation technologies, and microcapsule technologies, applying them to the cosmetics industry to enhance product efficacy, compatibility, and stability. Currently, research on specialty cosmetics has largely focused on skin whitening and spot removal, with transdermal delivery of whitening ingredients being a pivotal area of development and investigation. Studies have shown that whitening agents encapsulated in liposomes or modified starches can more easily penetrate the dermis to exert their effects. For instance, loading active ingredients for skin whitening and spot removal into porous polymer microspheres and employing auxiliary methods such as penetration enhancers can accelerate the penetration of active components into the skin, significantly enhancing their efficacy. Research has also involved emulsifying and crosslinking soluble starch to produce starch microspheres with sustained-release properties, which achieved an adsorption capacity of up to 0.85 g/g for rose fragrance. Furthermore, starch microsphere sustained-release formulations with excellent covering power, moisture absorption, and moisturizing properties have been developed.
Microencapsulation involves encapsulating pigments, UV absorbers, active enzymes, and skin emollients in cosmetics into microcapsule products. These microcapsules can penetrate through the skin's barrier layers, such as the stratum corneum, to reach deeper tissue layers, allowing for the sustained release of active substances and achieving deep and long-lasting skin care effects. For instance, OSA (Octenyl Succinic Anhydride modified starch) is a hydrophilic and lipophilic modified starch with excellent emulsifying and film-forming properties, as well as low viscosity and easy drying characteristics, making it an ideal material for microcapsule walls. As a microcapsule wall material, OSA serves a dual purpose: it protects the core material and acts as an emulsifier during spray drying. In cosmetics, OSA is primarily used to encapsulate water-insoluble and volatile substances such as aromatic components and oils used in daily chemicals. Studies have found that microcapsules prepared using low-viscosity OSA as the wall material exhibit superior properties compared to those made from dextrin, maltodextrin, gum arabic, and other wall material raw materials, in terms of factors such as drying rate, oil encapsulation efficiency, powder dispersion ability and free flowability in water, and shelf stability.
Modified starches, with their product diversity, biodegradability, and excellent compatibility, have garnered increasing attention from domestic cosmetics enterprises and can serve as a new growth point for the domestic modified starch industry. However, there are still some application challenges that need to be addressed. For instance, further research and evaluation are required to assess the efficacy and safety of modified starches, and efforts should be made to improve their efficacy assessment and establish relevant systems. Additionally, technical issues such as low product purity and high impurity content need to be resolved. Optimization and improvement of existing preparation methods are necessary, and further exploration of the conversion mechanism is required to achieve high-efficiency conversion of starch raw materials. This will facilitate the widespread application of high-quality, cost-effective modified starches in the cosmetics industry, ultimately generating positive social and economic benefits.
References
[1] Wang Wen, Huang Jihong, You Qianqian, Feng Junwei, Su Xuefeng, Yang Mingqian. Research Progress of Modified Starches for Cosmetic Applications [J]. China Surfactant Soap and Detergent Industries, 2014, 44(07): 402-405.
[2] Wang Qiuli, Gao Heyi, Wang Lidan, Wang Ruihang, Huang Lixin. Research Progress on the Application of Modified Starches in Cosmetics [J]. China Surfactant Soap and Detergent Industries, 2017, 47(11): 651-654+662.
About the Author
Xiaonisha, a food technology professional holding a Master's degree in Food Science, is currently employed at a prominent domestic pharmaceutical research and development company. Her primary focus lies in the development and research of nutritional foods, where she contributes her expertise and passion to create innovative products.
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