Important building blocks

All fats and oils are naturally occurring esters, formed from condensation reactions between the alcohol glycerol and different long chain fatty acids. Oils contain more carbon-carbon double bonds than fats, and their lower melting point is related to the higher degree of unsaturation. The presence of carbon-carbon double bonds in the oil molecules distorts the long fatty acid chains and the molecules’ shape. As a result, the molecules cannot pack closely together¹. Oil compositions vary greatly and determine their unique characteristics.

Plant oils

The use of plant oils for hair and skin application dates to antiquity. Although our ancestors used them without understanding how these efficacious materials worked – they just knew that they did! It was not until around 1950 that scientists understood that oils worked to moisturise the skin by sealing in moisture. Hydrophobic lipids coat the skin, acting as a barrier to retain water that would usually be lost through evaporation. In addition to their occlusive, coating effect, plant oils are often rich in vitamins, antioxidants, and essential fatty acids².

Many natural (plant) oils are used in cosmetics and their usage tends to go in and out of fashion. However, certain stalwarts resurface frequently thanks to their impressive skincare benefits and pleasing marketing stories. 

Argan oil: This native of Morocco has been used for centuries for cosmetic and culinary purposes. Argan oil has high levels of omega 6, known for the important role it plays in the structure of cell membranes. It is highly moisturising and recommended for acne-prone skin due to its high levels of linoleic acid which helps regulate sebum production and control breakouts. Its tocopherol content makes it ideal for combating skin ageing and drying. It is well known for its hair fortifying benefits and is particularly good for curly hair.

Jojoba oil: Actually, a liquid wax made up of esters of saturated and mono-unsaturated, fatty acid and fatty alcohols. This oil is a good emollient and moisturiser for young skin types because it regulates sebum production and is non-comedogenic. Its anti-inflammatory properties make it a good option to treat inflamed skin conditions².

As sustainability becomes less of a trend in personal care product development and increasingly a standard requirement, it is likely that we will see more brands using upcycled materials, including oils, as the inclusion of these will help contribute to the product’s overall sustainability profile and attractiveness to consumers who wish to make more environmentally friendly choices.

Grapeseed oil is one such material, it is ideal for upcycling as a by-product from wine production. This lightweight oil is an excellent moisturiser that penetrates skin without leaving any greasiness. This oil is very rich in unsaturated fatty acids, its linoleic acid (omega 6) helps preserve skin integrity, whilst oleic acid softens skin making it more supple². 

Essential oils

Essential oils are concentrated plant extracts obtained through mechanical pressing or distillation. They retain the natural smell and flavour of their source. Each essential oil has a unique composition of chemicals, and this variation affects the smell, absorption, and effects on the body. The chemical composition of an essential oil may vary within the same plant species, or from plant to plant³.

They are a vital part of a perfumers’ palette and can feature in every layer of their carefully crafted creations, from the bright, tangy top notes to the full-bodied heart, right through to the long-lasting accords found at the base. In the world of perfumery, essential oils are not only coveted for their beautiful, natural aroma, they’re also widely recognised for their mood enhancing properties⁴.

With each essential oil having their own unique composition and benefits, these special oils often form the foundation of many evocative fragrance blends used in personal care, from uplifting shower gel fragrances, to calming body butters. 

Oils as building blocks

Esters are naturally derived materials that can be specifically created with a chosen start point and formed by the condensation reaction between an alcohol and a carboxylic acid – known as esterification. There is a vast potential of derivatives which may be utilised in cosmetic formulations. Complex esters can be created using molecules that have multiple acid or alcohol functional groups. In creating esters, new combinations not found in nature can be created, or commercial quantities scarce in nature can be produced.

Capylic/capric triglyceride is a very common ester with a medium-light skin feel. It may be made from palm kernel or coconut oil. It is used in a wide variety of cosmetic applications and may be blended with natural oils to lighten the feel of a product.

A speciality ester, such as Trimethylolpropane Triisostearate⁵, is a liquid tri-ester of Trimethylolpropane and Isostearic acid and has been developed to have excellent cushion and play time, improving the application of solid delivery systems such as lipsticks⁶.

Surfactants

Many surfactants are plant-derived, with the most common sources being palm and coconut. The most common surfactants are Sodium Lauryl Sulfate (SLS), Sodium Laureth Sulfate (SLES), and Sodium Coco Sulfate (SCS). They are effective at lifting dirt and can enhance the foaming properties of wash products⁷.

The manufacturing of SLS and SLES begins with lauric acid, the main fatty acid found in palm kernel oil and coconut oil. Lauric acid then undergoes a series of chemical reactions to obtain SLS. SLS is a very efficient surfactant but is harsher than SLES and for this reason, used less often. The ethoxylation of SLS results in SLES, which is milder but with similar cleaning properties⁷.

While plant-derived synthetic surfactants avoid the use of petroleum, they are associated with significant negative environmental impacts of their own⁷. In recent times the use of palm oil has been controversial as rainforests are cut down to make space for palm production. Whilst it is right that this topic has led to criticism and questioning, it is worth noting that palm is the most efficient oil retrieved per hectare, double that of the next best plant option, coconut. The pressure on the planet’s natural resources is great and a way in which to relieve this would be to create lab-made surfactants. Technologies are constantly evolving that could make these a viable choice in the future. 

References:

¹ 16 SCS Diploma in Cosmetic Science – Oils, Fats and Waxes module

² Olvea, www.olvea.com

³ Essential Oils, https://www.niehs.nih.gov/health/topics/agents/essential-oils/index.cfm

⁴ Fragrance Oils, https://www.fragrance-oils.com

⁵ Pelemol TMPIS

⁶ Phoenix Chemical, Inc., https://phoenix-chem.com/

⁷ Dispersa | “Green” Surfactants: Does plant-derived imply sustainability?, https://www.dispersa.ca/blog/green-surfactants-does-plant-derived-imply-sustainability/