INSECT FATS FOR COSMETICS 197 percentage of relatively short chain FA’s (C12 and C14). It is also characterized by an extremely low degree of unsaturation (~21%) compared with ~61% for cricket and locust fats. By contrast, mink and macadamia nut oils contain 75.2% and 83% unsaturated fatty acids, respectively. All insect fats have a low percentage of palmitoleic acid (C16:1) compared with mink and macadamia nut oil. The palmitoleic acid is generally considered to be responsible for the good skin penetration properties of these oils (14). Both locust and cricket fats contain signifi cant amounts of saturated and unsaturated C18 chains, comparable with the mink and macadamia nut oils. The relative abundance of stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), and linolenic acid (C18:3) is consistent with previous fi ndings on insect fats (14,24). Based on the fatty acid composition, it is clear that cricket and locust fats are more suit- able for use in cosmetics. Oils or fats rich in linoleic acid and linolenic acid are known to reduce the TEWL and regenerate the lipid barrier of the epidermis (24,25). The skin feel may not be ideal based on the low amount of palmitoleic acid present, but this is not necessarily an issue, depending on the type of application. The use of BSF fat should be avoided in leave-on products as it its high lauric acid (C12:0) content is likely to cause adverse effects on the skin’s lipid structure. It is likely that a large fraction of the observed FFAs is lauric acid, which—as a FFA—is known to disrupt the skin barrier and increase the TEWL (26). However, the fatty acid profi le of the BSF fat is very similar to that of palm kernel oil and coconut oil. As such, BSF fat derivatives such as surfactants could fi nd similar uses as palm kernel oil and coconut oil derivatives in rinse-off products, such as soaps and shower gels. Note that the fatty acid composition of an organism depends on various factors, such as feed and life stage (24,27). The BSF fat is obtained from pre-pupae whereas the locust and cricket fats are extracted from adult animals. This may provide an explanation for the observed discrepancy in fatty acid composition. Liu et al. (27) have shown that large dif- ferences in fatty acid profi le occur among the different life stages of the BSF. However, the Table IV Fatty Acid Profi le in three Insect Species as Determined by GC–MS Fatty acid methyl ester Fatty acid-chain BSF % Cricket % Locust % Mink % Macadamia nut % Methyl decanoate C10:0 1 / / / / Methyl laurate C12:0 58 1 1 1 1 Methyl myristate C14:0 8 1 2 4 1 Methyl myristoleate C14:1 / 1 1 1 / Methyl palmitate C16:0 10 26 24 16 8 Methyl palmitoleate C16:1 2 1 1 15 22 Methyl heptadecanoate C17:0 1 / 1 1 / Methyl stearate C18:0 1 11 12 3 3 Methyl oleate C18:1 10 24 30 41 59 Methyl linoleate C18:2 9 35 17 17 3 Methyl linolenate C18:3 1 2 14 1 / Methyl arachidate C20:0 1 1 1 1 2 Methyl eicosanoate C20:1 / / / / 2 Methyl 5,8,11,14,17 eicosapentanoate C20:5 / 1 1 / / Methyl behenate C22:0 / / / 1 / Methyl lignocerate C24:0 / / / 1 /

JOURNAL OF COSMETIC SCIENCE 198 amount of lauric acid is high from the larvae stadium up to the adult fl y, suggesting that the high C12-content is probably species specifi c. SPREADABILITY AND VISCOSITY OF THE INSECT FATS The appreciation of a cosmetic product not only depends on its functionality, for instance hydrating or anti-wrinkle properties, but also on the skin feel. Major factors in skin feel are the lubricity, spreadability, and perceived greasiness (14).The latter is related to the rate at which an oil or fat penetrates the skin. The fatty acid composition plays an impor- tant role in skin feel. As a general trend it is expected, for natural plant and animal de- rived oils, that the higher the degree of unsaturation, the lower the viscosity, and the higher the penetration rate will be. This will result in a less greasy skin feel. This is, however, just a trend line, as notable exceptions exist. Often these deviations from the trend line are related to the presence of an unsaponifi able fraction. Mink oil, for example, is such a deviant oil with a good skin penetration despite its relatively high viscosity. The viscosity and spreadability of the insect fats were determined and compared with those of mink and macadamia nut oil (Tables V and VI). The viscosity of several other oils were measured as a control. A comparison of the values obtained in this work with those reported by Dietz (22) using a falling ball viscometer results in a correlation plot with r2—value of 0.889. This suggests that the relative order of the viscosities of the oils is correct. Both mink and macadamia nut oil, which have comparable fatty acid profi les, are charac- terized by a high viscosity and a low spreadability according to the classifi cation by Dietz (22). The value of 8.08 mm for macadamia nut oil is consistent with that reported by Akhtar et al. (28) The low spreadability is also the reason for adding dimethicone (with a viscosity of 350 cSt) to the formulation, as this will increase the spreadability of the hand cream. It is clear that the three insect fats have a lower spreadability and viscosity. This lack of any correlation with what would be expected according to the trend line is prob- ably due to the presence of a considerable amount of unsaponifi ables, as also seen in the TLC results. This demonstrates the diffi culty of making generalizations in the presence of compounds other than triglycerides. Table V Viscosity of Insect Fats and Selected Reference Oils Fat Viscosity (cP) Viscosity (cP) (18) Isopropyl myristate 13.3 4.6 Cyclopentasiloxane 13.3 4.6 Locust oil 20 / Cricket oil 23.3 / Octyl stearate 23.3 12.2 C12-C15 alkyl benzoate 25 11.8 Decyl oleate 25 13.5 C8/C10 Triglyceride 36.7 / BSF oil 41.7 / Octyldodecanol 60 44.7 Macadamia nut oil 83.3 / Mink oil 98.3 / Dimethicone 396.7 90