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Introduction to Cosmetic Materials
C H A P T E R
10 Introduction to Cosmetic Materials M. Hayase Kao Corporation, Odawara, Japan
10.1 INTRODUCTION No product can be designed without utilizing information about the properties of its materials. In this chapter, I will introduce various materials used in cosmetics. However, understanding the entirety of the perspective of cosmetic materials is not an easy task and cannot be done by only accumulating knowledge on independent materials. Therefore, I aim to provide a comprehensive overview on cosmetic materials by focusing on three aspects: the purpose of materials, precautions on choosing and using materials, and future challenges.
10.2 PURPOSES OF COSMETIC MATERIALS I will start by organizing the purposes of materials that are formulated in cosmetics. It is common for a single ingredient to have multiple functions and thus cannot be strictly classified for one function, but for easier understanding, each material is intentionally categorized in this chapter. It is also important to remember that cosmetics are complex systems composed of various materials. We will refer to biological structures of materials, which are also complex systems, to understand the entirety of cosmetic materials.
10.2.1 Formulation Structuring Materials In contrast to pharmaceutics development where the active component and its concentration is the main focus, cosmetic development must concentrate on the functions and user experience of the formulation itself in addition to the properties of the functional materials. Therefore, designing the structure of the formulation is considered an extremely important process in cosmetic development, and is as vital as, if not more than, considering new functional materials. I will categorize cosmetic materials that play important roles in forming the structure of formulations into the following three types. A wide variety of formulations is created by combining these three types, and also from their state in the product. 10.2.1.1 Water/Hydrophilic Base Materials As of 2016, life is yet to be found on planets other than Earth. One of the reasons is because Earth is the only planet known to have abundant water (hydrogen oxide) in liquid form. Proteins and lipids, which will be described later in this chapter, are also key materials in creating life. However, most of these materials need water in order to show their functionality. Likewise, oleaginous bases and amphiphiles are formulated in cosmetics in various forms, but water is required for these materials to show their unique functions. Water is the most universal ingredient used in cosmetics. Since water is so common we tend to take it for granted, but water is actually a unique substance. It provides a system for chemical reactions, and it also has significant characteristics, such as its property as a solvent, its low refractive index, and volatility. Hydrophilic base materials such as ethanol and polyols have the potential to partially replace water as formulation structuring materials. This replacement can change the characteristics of formulations such as the moisture-retaining property or the property as a solvent. Cosmetic Science and Technology: Theoretical Principles and Applications http://dx.doi.org/10.1016/B978-0-12-802005-0.00010-0
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10.2.1.2 Oleaginous/Hydrophobic Base Materials Organelles have been found to have structuring units of membranes composed of lipids. This shows how lipids and oleaginous substances are vital biological tissue-structuring substances. In many cosmetics, socalled “oils” and many oleaginous base materials (hydrophobic base materials) are used as structuring substances. Hair waxes and lipsticks are formulated with evenly distributed solid waxes or fats. Fragrances in translucent skin moisturizer are solubilized in the water phase. Oil-in-water creams have lipid particles dispersed in the water phase. These are some examples of how oleaginous bases are used in cosmetic formulation in various shapes. Among the various oleaginous bases used in cosmetics are materials such as hydrocarbons, esters, and ethers. Silicones and fluoride compounds and other hydrophobic-lipophobic substances are also often considered as oleaginous bases (oil-based materials in broad terms). Since these substances have a wide variety of structures, oleaginous base materials show various properties such as in their polarity, melting point, or compatibility. This large variety leads to various unique application experiences or specific functions (i.e., ultraviolet light absorption, promotion of percutaneous absorption) of cosmetic products. 10.2.1.3 Amphiphilic Substances Engels once said, “Life is the mode of action of proteins.” Borrowing his rhetoric, most cosmetics can be explained as “the mode of action of amphiphiles.” In most cases, various amphiphiles are used in cosmetics as surfactants or dispersion promoters. Amphiphiles are used as surfactants to emulsify, solubilize, or disperse oleaginous bases or hydrophilic bases to the other. These formulation methods are applied to formulate various formulations. There are also some amphiphiles such as higher fatty acids that change their function as surfactants or as oleaginous bases depending on the pH. On a side note, there are amphiphiles that are originally formulated in products as structuring materials, but are kept in the formulas for their functions such as moisturizing or to adjust the application touch. For example, solubilizers are not required for unscented products, but there are unscented skin toners that have surfactants dissolved at a concentration where it can solubilize oils.
10.2.2 Adding Functions and Effects Proteins, lipids, and water are not the only necessary substances that are required to maintain life. In cosmetics, ingredients other than oleaginous bases, water (and water-soluble bases), and amphiphiles are required in the formulation, and many of these ingredients are added in order to add functions and effects. We will categorize these materials into three types to understand their details. 10.2.2.1 Materials That Add or Improve Functional Value Cosmetics are usually sold with various values added to appeal to the consumers. The most important value of these multiple values depends on each product. In cosmetics, there are both functional value and emotional value, and most products require both of these values. Functional value often connects directly to the main feature of the product, and cosmetic development focuses on how to improve these functional values. The functions and effects that create the functional values can be categorized into physiological and physical functions and effects. Physiological effects and functions are not limited to skin care and hair growth products, but are also expected in certain makeup cosmetics. Since the 1980s, dermatology has shown a large advancement and much information on healthy skin has been accumulated. New evaluation methods, such as experiments using cultured cells, have also been developed. Many new dermatological methods have been proposed in the fields of whitening and antiaging based on the information and development of studies in dermatology. Utilizing these new methods, a variety of materials such as vitamins, amino acids, peptides, and botanical extracts have been formulated to cosmetics as physiological active ingredients that aim to improve the physiological effects and function. On the other hand, physical functions such as cleansing, moisturizing, and occlusion also add value for cosmetics. Moisturizing and emollient properties are especially vital physical functions, and are the basic functions for cosmetics. In many regions and countries other than the United States sunscreens are also categorized as cosmetic products. Therefore, ultraviolet (UV) screening and absorption are also important physical functions for cosmetics. These physical functions are evaluated through physical property evaluation of formulations as well as through human use testing. The evaluation systems of these physical functions and effects have also progressed rapidly in recent years, and now we can gather more detailed information.
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The physical functions and effects are often found in the formulation itself. However, there have been attempts to add specific ingredients to change or improve the physical properties. For example, there are oleaginous materials that show unique functions such as water holding, occlusion, UV absorption, or promotion of percutaneous absorption. These functional oleaginous materials are used to partially replace the structuring oleaginous material to add their function to the formulation. It is important to understand that maximizing the effects or functions is not always the best choice for cosmetics, and mild effects are preferred in most cases. For example, cleansers are designed to have the optimal cleansing property, and strong cleansers that remove too much oil are not considered to be the best practice. 10.2.2.2 Materials That Add or Improve Emotional Value Many cosmetic products like perfumes value preference over functionality. Even antiaging creams, which have materials that show specific physiological effects, are not considered as just a percutaneous absorbent but are considered products to enjoy the feeling and scent. The emotional value of these preferences cannot be neglected in cosmetics, and cosmetics are designed to provide more emotional value. Among our five senses, sight, smell, and touch are the main focus in the preference of cosmetics. Color and smell are very distinct and consumers can tell slight differences, and they strongly influence the preference of products. There is an abundant variety of materials that directly change the sight and smell to meet consumers preferences, such as various pigments, coloring, and aromatic substances. Touch is the most important sense, and many materials are combined to adjust the touch of products. In most cases the structure of the formulation defines most of the touch and feeling. However, the application feeling and use experience can be improved or changed. Details of materials such as powders, polyols, polymers, and/or tonics are considered and chosen to improve the touch in formulation prescription design. There are even cases where the feeling of unstable formulations is preferred. Needless to say, balance of the touch and maintaining/improving the stability is vital in cosmetic formulation improvement. 10.2.2.3 Materials for Quality Control Most cosmetics are designed to have a long shelf life of at least three years (sometimes the storage period is not explicitly stated). Furthermore, the products are not always stored in the best condition during this long storage period. As such, the standards for the stability of a cosmetic formulation’s condition, color, and/or smell are strict, and many materials are formulated to stabilize the products. Although these materials do not directly appeal to the consumers, they are materials vital for providing safe and sound products to the consumers. Many cosmetic formulations use emulsification methods, but emulsions are thermodynamically unstable and in most cases they must be stabilized. Emulsion stabilizers such as polymers (e.g., carbomers and xanthan gum) or higher fatty alcohols are added to cosmetics to stabilize the emulsion. Putrefaction can change the composition of products and can lead to health issues or lower the appeal of the products. Preservatives and other antimicrobe methods are vital to cosmetics in order to prevent such degrading. On a side note, many preservatives function by working on the cell membranes of microbes, but their mechanism can affect the stability of the emulsion so the condition of the formulation must be observed carefully when adding or increasing preservatives. There are other materials such as chelating reagents, discoloration-preventing reagents, antioxidative reagents, and pH buffering agents that are formulated to cosmetics for stabilization.
10.3 PRECAUTIONS ON CHOOSING AND USING COSMETIC INGREDIENTS Many consumer goods such as foods, pharmaceutical products, and detergents use materials similar to cosmetic materials. However, the purposes, regulations, and quality targets of cosmetics differ in many ways compared to these other products. Such differences relate to the precautions of using these materials as ingredients for cosmetics. As mentioned previously, the shelf life of cosmetics is long, so in addition to stabilizing the cosmetics, the materials themselves must have high stability. Furthermore, based on the fact that the frequency or amount a cosmetic product is used cannot be strictly controlled, safety is a priority that must be considered as much as possible. Due to these conditions that are different from other products, there are many quality standards that apply only to cosmetic materials. Many countries control cosmetics under the same regulations of pharmaceutical products for production, sales, and usage. However, the prerequisite regulations of cosmetics are very different from pharmaceutical products and also change depending on the era or region. For example, the recent regulations against animal testing strongly influence cosmetics development. Evaluations of percutaneous absorption and safety of cosmetics and their
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ingredients are designed based on evaluation methods of pharmaceutical products. Most of the testing shared the same methods, namely in vivo methods on small animals and in vitro methods on excised skin. However, animal testing has been restricted for cosmetics in Europe, followed by self-regulations by manufacturers under the animal rights movement, making these evaluation methods no longer available for cosmetics development. Although the quality standards and restrictions mentioned in this chapter must be considered, they are not the only points to keep in mind. There are other factors that must be considered due to the nature of cosmetics as products chosen by preference. Unlike other consumer products, cosmetics are strongly affected by personal principles based on opinion, taste, and beliefs. It is not rare that some materials are avoided in cosmetic prescription since they are against their principles, even if there is no scientific basis to back up these claims. For example, perfumes, ethanol, and methyl parahydroxybenzoate are generic materials that have long been used in cosmetics, but there are many customers who do not think well of these ingredients. In order to meet the personal principles of such consumers, there are products in the cosmetics market where manufacturers willingly choose not use these materials in their formulation. Such principles against materials based on cultural differences exist not only in the consumers’ minds but also in the formulators in the development stage. Formulators often pass on their preferences when they teach their methodology. For example, alkyl benzoate is a product that is widely used in Europe but is rarely used in Japan. The choice of polyols also differs between the preferences of formulators in Europe and Japan. In this way, materials are sometimes chosen depending on the preference of the formulator. Another important aspect to consider is that the development standards also vary depending on the region. Today cosmetics are not developed, produced, and sold in specific regions, so it is important to know the material regulations of each country. However, the local legal regulations are not the only factor that is important under such situations. The development style of cosmetics varies from region to region, and the requirements for materials also have regional differences. There are also cases where the stability standards of cosmetic formulation differ depending on the region. In Europe, prototypes are scented even for evaluation, but in Japan, the testing prototypes are usually unscented. Since the experimental styles differ, the acceptable chronological smell change of materials also differs. Furthermore, quality targets differ depending on the region, and as a result the acceptable stability can also differ. In Japan transparent soluble formulations are usually sold as skin toners, whereas in Europe emulsions are sold as skin toners. Due to this difference, the accepted sedimentation of materials differs for skin toners. These differences in acceptance influence to the option of materials in different regions.
10.4 FUTURE CHALLENGES IN COSMETICS MATERIAL DEVELOPMENT The largest possible challenge in cosmetic materials is the sustainability of obtaining materials. In future cosmetic material development and use, two contradicting challenges must be cleared: the increased material demand and the limited supply of resources. As cosmetic engineers, our wish is to deliver the value of cosmetics to more people around the world. This wish leads to expanding business, and as a result more resources will be needed in the future. There are many parts of the world where cosmetics are not used in daily life. When globalism expands and cosmetic use spreads to these people, consequently the demand for materials in the future will be much larger than current use. However, every resource on Earth is believed to be limited. The resources that can be used in cosmetics are even more limited. A reason for the limited choice of resources is that some materials are used exclusively for cosmetics. In the past, cheap materials with easy acquisition were mainly used, just like any other industrial product. However, to meet the high requirements of safety and stability as mentioned in this chapter, cosmetics materials must meet specific regulations, and now some materials are used exclusively for cosmetics. Furthermore, there are many materials where cosmetic manufacturers voluntarily stopped using them although their use is common in other industries, such as petroleum-derived materials and animal-derived materials. This voluntary limitation also narrows the resources available for cosmetics. Additionally, there can be movements to restrict the distribution of specific resources to cosmetics in the future, like campaigns to restrict the use of edible biomass in cosmetics. Biomass has gained attention as an industrial material that can replace petroleum resources as biologically derived resources. Since cosmetics can potentially be orally consumed, edible raw materials are preferable whenever possible, and biomass is an anticipated raw material for cosmetics. However, some believe that edible biomass should be prioritized for food products considering the global population growth. As mentioned before, the restrictions regarding resource access in the cosmetics industry are strict compared to other industries. On the other hand, cosmetics are undoubtedly a necessity for a moderate lifestyle in today’s society,
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just as electronics, automobiles, movies, and books are. As this lifestyle spreads with globalism, the necessity of cosmetics is also likely to spread. Of course, cosmetics are not vital for maintaining life like food, but this definitely does not mean that they should disappear from the world. As cosmetic engineers we have the duty to continue supplying cosmetics, and to do so we also have the duty to propose methods for obtaining resources. Here I will show two possible options on maintaining access to such resources.
10.4.1 Exploring New Raw Materials The first option to consider is to explore new raw materials. There are many materials that have not yet been thoroughly examined. We must look toward materials that have not been focused on, including unused industrial coproducts or other materials that can be obtained from other industries in large quantities. One direction that has large potential for future development is marine resources. Currently algae-derived substances are used as thickeners in cosmetics. Fish-derived cholesterols, esters (orange roughy oils), and collagen hydrolysates are now replacing other cosmetic materials. Not limited to these examples, there are currently many materials that are already utilized in cosmetics, but many more are unexamined materials that can also potentially be applied to cosmetics. Unicellular algae-derived materials have especially gained attention. These unicellular algae contain commonly used materials such as polysaccharides and pigments and are also being investigated for application to produce oils. When considering appropriate distribution of resources, another direction that should be explored is to actively utilize resources that are difficult to use in other industries. Materials for any industrial product should have a low cost and have easy acquisition, but not all materials meet such requirements. Cosmetics are somewhat unique where there are some products that are more expensive than food products even though they have less content, and there are even products that limit their availability for exclusiveness. These characteristics of cosmetics can be harnessed by actively using materials that do not meet the cost/supply requirements in other industries in order to keep resources. An example of utilizing such materials is using high-cost materials. Due to the characteristics of cosmetics mentioned before, cosmetics with “meaningfully expensive” materials are accepted with certain products. No matter what the product is, the costs of materials cannot and should not be ignored in development. However, even if the cost is expensive in development, there is a high possibility that they can be developed if they are for cosmetics materials. Of course, the cost for materials should be low even for cosmetics, and efforts should be taken to lower the cost. It may also be possible to utilize materials with low production yield if they are for cosmetics. Jojoba is a plant that takes time to grow, and edelweiss can only be grown in special highlands. Jojoba seed oil and edelweiss extract are materials that have lower production yield compared to other industrial botanical materials and do not appear to be suitable for industrial materials. However, this is not a much of a problem in cosmetics that have limited production volume. These materials can be marketed as materials that do not require much water for cultivation, or for their rarity, and are optimal for cosmetics since they can add value. Utilizing such rare materials is another possibility for securing resources in cosmetics.
10.4.2 Redesigning Production Methods New materials should not be made only from resources but also from production methods. Enzyme transformation and fermentation are material production methods that have gained attention for future resource access. There is an abundant variety of microbe resources on Earth, and since ancient times humans have used them to produce or change substances. As consumers become more conscious about sustainability or environmental load, there is high expectation in fermentation-produced materials since they do not have petroleum-derived substances in their structures and also from their biodegradability. As shown in Fig. 10.1, many materials that are produced with fermentation are now used in cosmetics. There are materials such as hyaluronic acids, which were traditionally obtained from animal derivatives but are now being replaced with fermented materials in cosmetics. Squalane and propanediol were previously unable to be produced with fermentation methods, but in recent years these materials have been produced with fermentation. Surfactants are vital to many cosmetic formulations, and materials such as mannosylerythritol lipid B, sodium surfactin, sophorolipid derivatives, and cerebrosides produced by Sphingomonas are already used in cosmetics today, and new materials such as lactic-fermented rice are proposed as well. Physiological activators such as some vitamins and coenzymes are also produced with fermentation. If enough effort is put into research, it is now becoming possible to produce most of the components of cosmetics with only fermented
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Cerebrosides Lactic Fermented Rice
FIGURE 10.1
Fermented Products Used in Cosmetics.
materials. Recently attention has also been focused on algae, along with fungi, and the polysaccharide derived from euglena is already used in cosmetics. It is not hard to imagine that a wider variety of fermented materials will be more commonly used in cosmetics, and promoting this method will lead to a more stable supply of cosmetic materials.
10.5 CLOSING REMARKS It is vital to understand the materials that are currently used for cosmetics and to utilize this knowledge in order to develop and expand new materials for the evolution of cosmetic technology. Gathering information on cosmetic materials from multiple aspects is effective to understand the nature of the materials. In addition to the aspects we have studied in this chapter, there are other materials (animal-derived materials, botanical materials, synthesized materials) and other products (skin care products, makeup products) that can help understand and organize cosmetic materials. I hope this chapter has provided the first step to understand cosmetic materials from multiple perspectives.
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10 Introduction to Cosmetic Materials M. Hayase Kao Corporation, Odawara, Japan
10.1 INTRODUCTION No product can be designed without utilizing information about the properties of its materials. In this chapter, I will introduce various materials used in cosmetics. However, understanding the entirety of the perspective of cosmetic materials is not an easy task and cannot be done by only accumulating knowledge on independent materials. Therefore, I aim to provide a comprehensive overview on cosmetic materials by focusing on three aspects: the purpose of materials, precautions on choosing and using materials, and future challenges.
10.2 PURPOSES OF COSMETIC MATERIALS I will start by organizing the purposes of materials that are formulated in cosmetics. It is common for a single ingredient to have multiple functions and thus cannot be strictly classified for one function, but for easier understanding, each material is intentionally categorized in this chapter. It is also important to remember that cosmetics are complex systems composed of various materials. We will refer to biological structures of materials, which are also complex systems, to understand the entirety of cosmetic materials.
10.2.1 Formulation Structuring Materials In contrast to pharmaceutics development where the active component and its concentration is the main focus, cosmetic development must concentrate on the functions and user experience of the formulation itself in addition to the properties of the functional materials. Therefore, designing the structure of the formulation is considered an extremely important process in cosmetic development, and is as vital as, if not more than, considering new functional materials. I will categorize cosmetic materials that play important roles in forming the structure of formulations into the following three types. A wide variety of formulations is created by combining these three types, and also from their state in the product. 10.2.1.1 Water/Hydrophilic Base Materials As of 2016, life is yet to be found on planets other than Earth. One of the reasons is because Earth is the only planet known to have abundant water (hydrogen oxide) in liquid form. Proteins and lipids, which will be described later in this chapter, are also key materials in creating life. However, most of these materials need water in order to show their functionality. Likewise, oleaginous bases and amphiphiles are formulated in cosmetics in various forms, but water is required for these materials to show their unique functions. Water is the most universal ingredient used in cosmetics. Since water is so common we tend to take it for granted, but water is actually a unique substance. It provides a system for chemical reactions, and it also has significant characteristics, such as its property as a solvent, its low refractive index, and volatility. Hydrophilic base materials such as ethanol and polyols have the potential to partially replace water as formulation structuring materials. This replacement can change the characteristics of formulations such as the moisture-retaining property or the property as a solvent. Cosmetic Science and Technology: Theoretical Principles and Applications http://dx.doi.org/10.1016/B978-0-12-802005-0.00010-0
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10.2.1.2 Oleaginous/Hydrophobic Base Materials Organelles have been found to have structuring units of membranes composed of lipids. This shows how lipids and oleaginous substances are vital biological tissue-structuring substances. In many cosmetics, socalled “oils” and many oleaginous base materials (hydrophobic base materials) are used as structuring substances. Hair waxes and lipsticks are formulated with evenly distributed solid waxes or fats. Fragrances in translucent skin moisturizer are solubilized in the water phase. Oil-in-water creams have lipid particles dispersed in the water phase. These are some examples of how oleaginous bases are used in cosmetic formulation in various shapes. Among the various oleaginous bases used in cosmetics are materials such as hydrocarbons, esters, and ethers. Silicones and fluoride compounds and other hydrophobic-lipophobic substances are also often considered as oleaginous bases (oil-based materials in broad terms). Since these substances have a wide variety of structures, oleaginous base materials show various properties such as in their polarity, melting point, or compatibility. This large variety leads to various unique application experiences or specific functions (i.e., ultraviolet light absorption, promotion of percutaneous absorption) of cosmetic products. 10.2.1.3 Amphiphilic Substances Engels once said, “Life is the mode of action of proteins.” Borrowing his rhetoric, most cosmetics can be explained as “the mode of action of amphiphiles.” In most cases, various amphiphiles are used in cosmetics as surfactants or dispersion promoters. Amphiphiles are used as surfactants to emulsify, solubilize, or disperse oleaginous bases or hydrophilic bases to the other. These formulation methods are applied to formulate various formulations. There are also some amphiphiles such as higher fatty acids that change their function as surfactants or as oleaginous bases depending on the pH. On a side note, there are amphiphiles that are originally formulated in products as structuring materials, but are kept in the formulas for their functions such as moisturizing or to adjust the application touch. For example, solubilizers are not required for unscented products, but there are unscented skin toners that have surfactants dissolved at a concentration where it can solubilize oils.
10.2.2 Adding Functions and Effects Proteins, lipids, and water are not the only necessary substances that are required to maintain life. In cosmetics, ingredients other than oleaginous bases, water (and water-soluble bases), and amphiphiles are required in the formulation, and many of these ingredients are added in order to add functions and effects. We will categorize these materials into three types to understand their details. 10.2.2.1 Materials That Add or Improve Functional Value Cosmetics are usually sold with various values added to appeal to the consumers. The most important value of these multiple values depends on each product. In cosmetics, there are both functional value and emotional value, and most products require both of these values. Functional value often connects directly to the main feature of the product, and cosmetic development focuses on how to improve these functional values. The functions and effects that create the functional values can be categorized into physiological and physical functions and effects. Physiological effects and functions are not limited to skin care and hair growth products, but are also expected in certain makeup cosmetics. Since the 1980s, dermatology has shown a large advancement and much information on healthy skin has been accumulated. New evaluation methods, such as experiments using cultured cells, have also been developed. Many new dermatological methods have been proposed in the fields of whitening and antiaging based on the information and development of studies in dermatology. Utilizing these new methods, a variety of materials such as vitamins, amino acids, peptides, and botanical extracts have been formulated to cosmetics as physiological active ingredients that aim to improve the physiological effects and function. On the other hand, physical functions such as cleansing, moisturizing, and occlusion also add value for cosmetics. Moisturizing and emollient properties are especially vital physical functions, and are the basic functions for cosmetics. In many regions and countries other than the United States sunscreens are also categorized as cosmetic products. Therefore, ultraviolet (UV) screening and absorption are also important physical functions for cosmetics. These physical functions are evaluated through physical property evaluation of formulations as well as through human use testing. The evaluation systems of these physical functions and effects have also progressed rapidly in recent years, and now we can gather more detailed information.
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The physical functions and effects are often found in the formulation itself. However, there have been attempts to add specific ingredients to change or improve the physical properties. For example, there are oleaginous materials that show unique functions such as water holding, occlusion, UV absorption, or promotion of percutaneous absorption. These functional oleaginous materials are used to partially replace the structuring oleaginous material to add their function to the formulation. It is important to understand that maximizing the effects or functions is not always the best choice for cosmetics, and mild effects are preferred in most cases. For example, cleansers are designed to have the optimal cleansing property, and strong cleansers that remove too much oil are not considered to be the best practice. 10.2.2.2 Materials That Add or Improve Emotional Value Many cosmetic products like perfumes value preference over functionality. Even antiaging creams, which have materials that show specific physiological effects, are not considered as just a percutaneous absorbent but are considered products to enjoy the feeling and scent. The emotional value of these preferences cannot be neglected in cosmetics, and cosmetics are designed to provide more emotional value. Among our five senses, sight, smell, and touch are the main focus in the preference of cosmetics. Color and smell are very distinct and consumers can tell slight differences, and they strongly influence the preference of products. There is an abundant variety of materials that directly change the sight and smell to meet consumers preferences, such as various pigments, coloring, and aromatic substances. Touch is the most important sense, and many materials are combined to adjust the touch of products. In most cases the structure of the formulation defines most of the touch and feeling. However, the application feeling and use experience can be improved or changed. Details of materials such as powders, polyols, polymers, and/or tonics are considered and chosen to improve the touch in formulation prescription design. There are even cases where the feeling of unstable formulations is preferred. Needless to say, balance of the touch and maintaining/improving the stability is vital in cosmetic formulation improvement. 10.2.2.3 Materials for Quality Control Most cosmetics are designed to have a long shelf life of at least three years (sometimes the storage period is not explicitly stated). Furthermore, the products are not always stored in the best condition during this long storage period. As such, the standards for the stability of a cosmetic formulation’s condition, color, and/or smell are strict, and many materials are formulated to stabilize the products. Although these materials do not directly appeal to the consumers, they are materials vital for providing safe and sound products to the consumers. Many cosmetic formulations use emulsification methods, but emulsions are thermodynamically unstable and in most cases they must be stabilized. Emulsion stabilizers such as polymers (e.g., carbomers and xanthan gum) or higher fatty alcohols are added to cosmetics to stabilize the emulsion. Putrefaction can change the composition of products and can lead to health issues or lower the appeal of the products. Preservatives and other antimicrobe methods are vital to cosmetics in order to prevent such degrading. On a side note, many preservatives function by working on the cell membranes of microbes, but their mechanism can affect the stability of the emulsion so the condition of the formulation must be observed carefully when adding or increasing preservatives. There are other materials such as chelating reagents, discoloration-preventing reagents, antioxidative reagents, and pH buffering agents that are formulated to cosmetics for stabilization.
10.3 PRECAUTIONS ON CHOOSING AND USING COSMETIC INGREDIENTS Many consumer goods such as foods, pharmaceutical products, and detergents use materials similar to cosmetic materials. However, the purposes, regulations, and quality targets of cosmetics differ in many ways compared to these other products. Such differences relate to the precautions of using these materials as ingredients for cosmetics. As mentioned previously, the shelf life of cosmetics is long, so in addition to stabilizing the cosmetics, the materials themselves must have high stability. Furthermore, based on the fact that the frequency or amount a cosmetic product is used cannot be strictly controlled, safety is a priority that must be considered as much as possible. Due to these conditions that are different from other products, there are many quality standards that apply only to cosmetic materials. Many countries control cosmetics under the same regulations of pharmaceutical products for production, sales, and usage. However, the prerequisite regulations of cosmetics are very different from pharmaceutical products and also change depending on the era or region. For example, the recent regulations against animal testing strongly influence cosmetics development. Evaluations of percutaneous absorption and safety of cosmetics and their
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ingredients are designed based on evaluation methods of pharmaceutical products. Most of the testing shared the same methods, namely in vivo methods on small animals and in vitro methods on excised skin. However, animal testing has been restricted for cosmetics in Europe, followed by self-regulations by manufacturers under the animal rights movement, making these evaluation methods no longer available for cosmetics development. Although the quality standards and restrictions mentioned in this chapter must be considered, they are not the only points to keep in mind. There are other factors that must be considered due to the nature of cosmetics as products chosen by preference. Unlike other consumer products, cosmetics are strongly affected by personal principles based on opinion, taste, and beliefs. It is not rare that some materials are avoided in cosmetic prescription since they are against their principles, even if there is no scientific basis to back up these claims. For example, perfumes, ethanol, and methyl parahydroxybenzoate are generic materials that have long been used in cosmetics, but there are many customers who do not think well of these ingredients. In order to meet the personal principles of such consumers, there are products in the cosmetics market where manufacturers willingly choose not use these materials in their formulation. Such principles against materials based on cultural differences exist not only in the consumers’ minds but also in the formulators in the development stage. Formulators often pass on their preferences when they teach their methodology. For example, alkyl benzoate is a product that is widely used in Europe but is rarely used in Japan. The choice of polyols also differs between the preferences of formulators in Europe and Japan. In this way, materials are sometimes chosen depending on the preference of the formulator. Another important aspect to consider is that the development standards also vary depending on the region. Today cosmetics are not developed, produced, and sold in specific regions, so it is important to know the material regulations of each country. However, the local legal regulations are not the only factor that is important under such situations. The development style of cosmetics varies from region to region, and the requirements for materials also have regional differences. There are also cases where the stability standards of cosmetic formulation differ depending on the region. In Europe, prototypes are scented even for evaluation, but in Japan, the testing prototypes are usually unscented. Since the experimental styles differ, the acceptable chronological smell change of materials also differs. Furthermore, quality targets differ depending on the region, and as a result the acceptable stability can also differ. In Japan transparent soluble formulations are usually sold as skin toners, whereas in Europe emulsions are sold as skin toners. Due to this difference, the accepted sedimentation of materials differs for skin toners. These differences in acceptance influence to the option of materials in different regions.
10.4 FUTURE CHALLENGES IN COSMETICS MATERIAL DEVELOPMENT The largest possible challenge in cosmetic materials is the sustainability of obtaining materials. In future cosmetic material development and use, two contradicting challenges must be cleared: the increased material demand and the limited supply of resources. As cosmetic engineers, our wish is to deliver the value of cosmetics to more people around the world. This wish leads to expanding business, and as a result more resources will be needed in the future. There are many parts of the world where cosmetics are not used in daily life. When globalism expands and cosmetic use spreads to these people, consequently the demand for materials in the future will be much larger than current use. However, every resource on Earth is believed to be limited. The resources that can be used in cosmetics are even more limited. A reason for the limited choice of resources is that some materials are used exclusively for cosmetics. In the past, cheap materials with easy acquisition were mainly used, just like any other industrial product. However, to meet the high requirements of safety and stability as mentioned in this chapter, cosmetics materials must meet specific regulations, and now some materials are used exclusively for cosmetics. Furthermore, there are many materials where cosmetic manufacturers voluntarily stopped using them although their use is common in other industries, such as petroleum-derived materials and animal-derived materials. This voluntary limitation also narrows the resources available for cosmetics. Additionally, there can be movements to restrict the distribution of specific resources to cosmetics in the future, like campaigns to restrict the use of edible biomass in cosmetics. Biomass has gained attention as an industrial material that can replace petroleum resources as biologically derived resources. Since cosmetics can potentially be orally consumed, edible raw materials are preferable whenever possible, and biomass is an anticipated raw material for cosmetics. However, some believe that edible biomass should be prioritized for food products considering the global population growth. As mentioned before, the restrictions regarding resource access in the cosmetics industry are strict compared to other industries. On the other hand, cosmetics are undoubtedly a necessity for a moderate lifestyle in today’s society,
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just as electronics, automobiles, movies, and books are. As this lifestyle spreads with globalism, the necessity of cosmetics is also likely to spread. Of course, cosmetics are not vital for maintaining life like food, but this definitely does not mean that they should disappear from the world. As cosmetic engineers we have the duty to continue supplying cosmetics, and to do so we also have the duty to propose methods for obtaining resources. Here I will show two possible options on maintaining access to such resources.
10.4.1 Exploring New Raw Materials The first option to consider is to explore new raw materials. There are many materials that have not yet been thoroughly examined. We must look toward materials that have not been focused on, including unused industrial coproducts or other materials that can be obtained from other industries in large quantities. One direction that has large potential for future development is marine resources. Currently algae-derived substances are used as thickeners in cosmetics. Fish-derived cholesterols, esters (orange roughy oils), and collagen hydrolysates are now replacing other cosmetic materials. Not limited to these examples, there are currently many materials that are already utilized in cosmetics, but many more are unexamined materials that can also potentially be applied to cosmetics. Unicellular algae-derived materials have especially gained attention. These unicellular algae contain commonly used materials such as polysaccharides and pigments and are also being investigated for application to produce oils. When considering appropriate distribution of resources, another direction that should be explored is to actively utilize resources that are difficult to use in other industries. Materials for any industrial product should have a low cost and have easy acquisition, but not all materials meet such requirements. Cosmetics are somewhat unique where there are some products that are more expensive than food products even though they have less content, and there are even products that limit their availability for exclusiveness. These characteristics of cosmetics can be harnessed by actively using materials that do not meet the cost/supply requirements in other industries in order to keep resources. An example of utilizing such materials is using high-cost materials. Due to the characteristics of cosmetics mentioned before, cosmetics with “meaningfully expensive” materials are accepted with certain products. No matter what the product is, the costs of materials cannot and should not be ignored in development. However, even if the cost is expensive in development, there is a high possibility that they can be developed if they are for cosmetics materials. Of course, the cost for materials should be low even for cosmetics, and efforts should be taken to lower the cost. It may also be possible to utilize materials with low production yield if they are for cosmetics. Jojoba is a plant that takes time to grow, and edelweiss can only be grown in special highlands. Jojoba seed oil and edelweiss extract are materials that have lower production yield compared to other industrial botanical materials and do not appear to be suitable for industrial materials. However, this is not a much of a problem in cosmetics that have limited production volume. These materials can be marketed as materials that do not require much water for cultivation, or for their rarity, and are optimal for cosmetics since they can add value. Utilizing such rare materials is another possibility for securing resources in cosmetics.
10.4.2 Redesigning Production Methods New materials should not be made only from resources but also from production methods. Enzyme transformation and fermentation are material production methods that have gained attention for future resource access. There is an abundant variety of microbe resources on Earth, and since ancient times humans have used them to produce or change substances. As consumers become more conscious about sustainability or environmental load, there is high expectation in fermentation-produced materials since they do not have petroleum-derived substances in their structures and also from their biodegradability. As shown in Fig. 10.1, many materials that are produced with fermentation are now used in cosmetics. There are materials such as hyaluronic acids, which were traditionally obtained from animal derivatives but are now being replaced with fermented materials in cosmetics. Squalane and propanediol were previously unable to be produced with fermentation methods, but in recent years these materials have been produced with fermentation. Surfactants are vital to many cosmetic formulations, and materials such as mannosylerythritol lipid B, sodium surfactin, sophorolipid derivatives, and cerebrosides produced by Sphingomonas are already used in cosmetics today, and new materials such as lactic-fermented rice are proposed as well. Physiological activators such as some vitamins and coenzymes are also produced with fermentation. If enough effort is put into research, it is now becoming possible to produce most of the components of cosmetics with only fermented
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Cerebrosides Lactic Fermented Rice
FIGURE 10.1
Fermented Products Used in Cosmetics.
materials. Recently attention has also been focused on algae, along with fungi, and the polysaccharide derived from euglena is already used in cosmetics. It is not hard to imagine that a wider variety of fermented materials will be more commonly used in cosmetics, and promoting this method will lead to a more stable supply of cosmetic materials.
10.5 CLOSING REMARKS It is vital to understand the materials that are currently used for cosmetics and to utilize this knowledge in order to develop and expand new materials for the evolution of cosmetic technology. Gathering information on cosmetic materials from multiple aspects is effective to understand the nature of the materials. In addition to the aspects we have studied in this chapter, there are other materials (animal-derived materials, botanical materials, synthesized materials) and other products (skin care products, makeup products) that can help understand and organize cosmetic materials. I hope this chapter has provided the first step to understand cosmetic materials from multiple perspectives.
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