Improve Shelf Life of Finished Formulations the Inherent Stability of an Emollient Is Important in Ensuring the Shelf Stability of the Finished Product

Improve Shelf Life of Finished Formulations The inherent stability of an emollient is important in ensuring the shelf stability of the finished product. Natural and synthetic oils, fats and waxes degrade over time due to oxidation. The elapsed time in which a material will degrade is influenced by a number of factors, including the degree of saturation, presence of antioxidants or pro-oxidants, and prior stress (UV exposure, excessive heating, repackaging etc.).

® Oxidative instability is primarily the process of oxygen attacking points of unsaturation. As www.floratech.com oxidation progresses shorter chain acids, aldehydes, and ketones are formed. These oxidation products degrade the original texture, odor, consistency and sensory attributes of both the emollient, and finished product. Minimizing oxidation is key to preserving finished product attributes.

Oxidative stability index (OSI) indicates the oxidative stability of an emollient. The OSI is expressed in hours and is measured by an Oxidative Stability Instrument.* Figure 3 contains many common emollients and their respective OSI (hours).

Polyunsaturates and Instability Polyunsaturates–Inherently Unstable Floraesters 60 (OSI=190) The OSI of emollients is inversely correlated 100 Floraesters 30 (OSI=165) with the degree of unsaturation. Inexpensive Floraesters 15 vegetable oils often contain high amounts of 80 polyunsaturates, and other undesirable elements Castor Oil 60 which are oxidatively unstable, (see Figure 1). Florasun 90 40 Emollients containing high levels of polyunsaturates have a significantly 20 High-Oleic Safflower Oil Almond Oil Sesame Seed Oil lower OSI, and are inherently unstable. (hours) Stability Oxidative Conversely, emollients with low unsaturation are 0 Traditional Sunflower Oil Wheat Germ Oil inherently stable. 0 20 40 60 80 Figure 1 Polyunsaturates (%)

Shelf Life: More Antioxidants Are Not The Answer Formulators often attempt to remedy emollients’ instability by adding antioxidants. Interestingly, antioxidant efficacy is positively correlated with an emollient’s inherent stability. Figure 2 shows that the OSI of inherently unstable emollients such as More Antioxidants Are Not The Answer high-oleic safflower oil and apricot oil may only be slightly improved by the addition 100 of tocopherols. 80 Conversely, the OSI value of inherently stable Florasun 90 60 High-Oleic Safflower Oil emollients such as Florasun 90 are significantly improved by the addition of tocopherols. This 40 Apricot Oil Traditional Sunflower Oil relationship, though counterintuitive, holds true for 20 most natural emollients: Stable emollients improve

Oxidative Stability (hours) Stability Oxidative significantly with the addition of antioxidants while 0 unstable emollients do not.

0 1000 2000 3000 4000 5000 Formulators who wish to achieve an oxidatively Figure 2 Tocopherols Added (ppm) stable formulation are well advised to use inherently stable emollients.

* OSI method - AOCS Cd 12b-92 [email protected] Oxidative Stability Index*

Floraesters 70 >600 Floraesters 60 Floralipids Moringa Butter

® Floraesters 30 Floralipids Moringa Oil Refined www.floratech.com Floraesters 20 Caprylic/Capric Triglyceride Figure 3 contains many Meadowfoam Oil common emollients and Floraesters IPJ their respective Oxidative Generally stable for use in cosmetics Floraesters 15 Stability Index (OSI) Generally unstable for use in cosmetics measured in hours. Floramac 10 Cocoa Butter An OSI less than 20 hours is generally considered Coconut Oil unstable. Floramac Macadamia Oil Refined Castor Oil The original oxidative state of an emollient is Mineral Oil important for ensuring Florasun 90 stability of the finished Babassu Oil product. Jojoba Oil Highly stable emollients Shea Butter contribute to highly stable Avocado Oil finished products. Palm Kernel Oil Unstable Emollients Traditional Macadamia Oil (OSI Value Less Than 10 Hours) Almond Oil, Argan Oil, Borage Olive Butter Oil, Canola Oil, Cottonseed Oil, Mid-Oleic Sunflower Oil Evening Primrose Oil, Grape Apricot Kernel Oil Seed Oil, Mango Butter, Olive Oil, Rice Bran Oil, Rose Hip Seed Oil, High-Oleic Safflower Oil Sesame Seed Oil, Soybean Oil, Traditional Sunflower Oil (30% 0 20 40 60 80 100 120 140 160 180 200 220 700 Oleic), Walnut Oil, and Wheat Figure 3 Germ Oil. OSI (hours)

Measuring Oxidative Stability To measure the OSI of an emollient, a sample of material is heated to 110°C under constant airflow, (see A on Figure 4). The exposure to the oxygen and heat simulates an accelerated passage of time. As oxidative degradation of the material begins, volatile short chain fractions break away from the molecule, are entrained in the airflow, captured in distilled water, and are detected by a conductivity A B

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probe, (see B on Figure 4).

The inflection point (the time at which conductivity

values rise rapidly) determines the OSI in hours and Oxidative Stability Instrument

indicates the point at which the oil becomes rancid. this document Figure 4