Sensory evaluation is essential for objective examination of products. Assessment methods should be established for objectively understanding the impressions of users and also for deciding the words and phrases to be used for advertising the new products. Quantitative evaluation by using instruments is a field in which future progress is expected, but does not yet always reflect the actual impressions felt by users and cannot substitute sensory evaluation by people.
Knowing the feels given by each ingredient of cosmetics helps designing formulations. Especially the alkyl groups of oils and surfactants affect the feel of use of the product directly. The properties of the alkyl groups are the key factor in designing the feel of cosmetics, and we should understand the chemical and physical properties and know the feel given by each ingredient. The beauty industry is vast and is dependent on some of the best beauty cosmetology colleges in Maharashtra to train future professionals to drive innovation in the industry.
Expressions of Sensory Properties
Good cosmetics give the feel consistent with the purpose of use when applied on the skin, hair, etc. The feel experienced by users varies by person, and so the expressions they use vary. However, objective and correct evaluation of sensory properties is an indispensable process in development of cosmetics products. In this chapter, expressions of sensory properties are classified and analysed to deepen our understanding of cosmetics materials.
Classification of Expressions
The senses given by cosmetics may vary by user. Users may also use various expressions to describe the feel. General positive impressions of using cosmetics include “moisturising,” “smooth,” “silky,” and “soft.” “Dry” is a negative expression. “Persistent” is used for both positive and negative impressions, but basically as a positive impression in this book. There are various similar expressions besides these six. Adverbs such as “very,” “strongly,” “rather,” and “slightly” are widely used combined with the expressions
Favoured Senses
1. By Purpose of Use
Senses favoured by users vary depending on the category of cosmetics, body part on which it is used, and season. For example, facial and hand creams have similar compositions, but the sense favoured by users differs. Preferred hand creams are those that make the skin “smooth” but not “slippery.” On the other hand, users demand for “moisturising” facial creams in general. The impressions felt from using skincare cosmetics are affected by seasonal temperature and humidity changes, and so the demanded sensory characteristics change by season.
2. By User
Favoured senses may also vary by user. For example, there is a big difference in favoured sense particularly of rinse-off hair care products between home users and professional beauticians. Home users prefer shampoos and conditioners that are quick to rinse off the “smooth (lubricious)” feeling. On the other hand, professional beauticians evaluate products that long retain the “smooth (lubricious)” feeling.
3. Sensory Evaluation
It is indispensable, although it involves very difficult tasks, to establish sensory evaluation methods for objectively understanding the impressions of users, and also for deciding the words and phrases to be used for advertising the new products. Measuring instruments are also used today to collect objective numerical data on friction, bending strength, etc. Quantitative evaluation by using instruments is a field in which future progress is expected. However, the results calculated from collected numerical data are often different from the actual impressions felt by users. At the moment, human sensory evaluation is superior to measuring instruments in perceiving the entire and versatile sensory characteristics of cosmetics products.
Points to Note in Human Sensory Evaluation
Personal impressions are somewhat included in all evaluations conducted by people. Understanding the trends of personal impressions helps correct evaluation. Knowledge on the formulation may affect the evaluation. Evaluation and review by members of the institute who are not engaged in the development of the product are more objective than those by people engaged in the development, and are thus informative and useful. Building such a relationship is recommended because it also helps you to obtain advice afterwards.
The most important and final sensory evaluation is the one conducted by users, including professional beauticians and home users. Answers can be obtained from a large number of people and can be statistically processed. Use of simple formats to guide the respondents is recommended to prevent diversities in answers and expressions. Each product should be evaluated separately for each process of use: for example, at application, at rinsing, when the hair is wet, during towel-drying, during blow-drying, and after finishing.
Sensory Properties of Alkyl Groups
It is very important to know the feels given by each ingredient of cosmetics. Especially the alkyl groups of oils and surfactants affect the feel of use directly. The alkyl groups determine the melting point (the larger the molecular weight, the higher the melting point) and polarity (by the number of oxygen atoms and chemical structures, such as double bonds, side chains, and functional groups). The functional groups determine the compatibility and interaction with other ingredients and affect the viscosity, consistency, appearance, hardness, spread, and the feel of use. The sense and texture felt by users highly depends on the structures of alkyl groups. The properties of the alkyl groups are the key factor in designing the feel of cosmetics, and we should understand the chemical and physical properties and know the feel given by each ingredient.
Sensory Properties of Oils
Oils have an alkyl group as the basic structure and include carbohydrates, which do not have an oxygen atom, esters and waxes, which have ester bonds, and higher alcohols and fatty acids, which have oxygen atoms at an end of the molecule. The alkyl and functional groups determine the sensory properties of oils.
Length of Alkyl Group and Sensory Properties
Short alkyl groups give a “coarse” touch, those of intermediate length give “lubricious” feeling, and long alkyl groups are “soft” and “moisturising.” Double bonds in alkyl chains increase “moisturising” and “oily” feeling; and branched chains give “silky” and “light” touch. Complicated molecular structures increase the “moisturising” and “oily” feelings. Oils of larger molecular weights have higher melting points, are solids at higher temperatures, and thus give less “lubricious,” less “silky,” and less “smooth” touches.
Waxes, which have higher melting points than oils, are “adhesive” and give a coated feeling. Ester bonds, hydroxyl groups, and carboxyl groups do not directly affect the feel of use, but affect the viscosity and consistency of products. Higher viscosities give more “smooth” and “soft” feeling, and low viscosities result in “lightness.” Increase the content of liquid oils to produce “lubricious” skincare cosmetics, and increase the solid oil content for reducing the “lubricious” feeling.
Conclusion
These are some of the sensory properties of cosmetic products. Sensory properties make a huge difference in how consumers perceive and react to certain products in the cosmetic industry. It is important to take into account human behaviour and consume expectations when formulating new products in the beauty industry. Pursuing a B.Sc. in Beauty Cosmetology can help you further understand the sensory properties of cosmetic products.