HEMP-SEED AND OLIVE OILS 241 nm and at 262, 268, and 274 nm (ilK) were used to measure the increase in conjugated dienes and trienes, respectively. Both for the two kinds of hemp-seed oil and the commercial olive oil, K232 and ilK values were above the limits set for "extra virgin" oils. The absorptivity (0.1 % oil in 1-butanol) at 232 nm and the ilK value increased with temperature, as is shown for the hemp-seed oil (1998), heated for 24 hours at 40°C. Tables V and VI report the results of the spectrophotometric analysis carried out to evaluate whether the polymeric vehicles Sepigel 305 ® and Carbopol 1382® enhance the formation of conjugated dienes and trienes in vegetable oils in which they are dispersed. The combined results (Tables V and VI) show that both hemp-seed oils and the com­ mercial olive oil had much higher oxidative stability when dispersed in the Sepigel 305 ® than in the Carbopol 1382® system. IRRADIATION TEST Table VII shows the results of the irradiation test. Olive oil was much more photostable Table V UV-Visible Characterization of Oils Dispersed in Sepigel 305® System (emulsion 1) Hemp-seed Hemp-seed Extra-virgin Hemp-seed oil (1998) oil (1999) Olive oil olive oil oil (1998) (after 24 h (after 24 h (after 24 h (after 24 h (before heating) at 40°C) at 40°C) at 40°C) at 40°C) K232 2.80 (±0.21) 4.45 (±0.18) 4.23 (±0.10) 3.51 (±0.14) 3.51 (±0.09) J).K 0.015 (±0.003) 0.020 (±0.001) 0.020 (±0.004) 0.020 (±0.003) 0.020 (±0.003) Values in parentheses are standard deviations, determined on four samples. Table VI UV-Visible Characterization of Oils Dispersed in Carbopol 1382® System (emulsion 2) Hemp-seed Hemp-seed Extra-virgin Hemp-seed oil (1998) oil (1999) Olive oil olive oil oil (1998) (after 24 h (after 24 h (after 24 h (after 24 h (before heating) at 40°C) at 40°C) at 40°C) at 40°C) K232 2.76 (±0.13) 2.90 (±0.16) 4.04 (±0.18) 4.04 (±0.23) 2.55 (±0.17) J).K 0.010 (±0.001) 0.015 (±0.002) 0.030 (±0.006) 0.030 (±0.006) 0.010 (±0.004) Values in parentheses are standard deviations, determined on four samples. Table VII K232 and J).K Values of the Vegetable Oils after 2 Hours of UVB Irradiation Hemp-seed oil ( 1998) 5.54 (±0.11) 0.015 (±0.001) Hemp-seed oil ( 1999) 8.92 (±0.30) 0.035 (±0.005) Values in parentheses are standard deviations, determined on four samples. Olive oil 3.07 (±022) 0.095 (±0.002)

242 JOURNAL OF COSMETIC SCIENCE under UVB irradiation than the hemp-seed oils. The 1998 hemp-seed oil had higher photostability under UVB irradiation than the 1999 oil. MALONDIALDEHYDE (MDA) AND MONOALDEHYDE (MONO) Oil samples subjected to thiobarbituric acid assay were opportunity-treated to extract the colors, pink for MDA or yellow for MONO. The absorptivites of the prepared samples were measured at 450 and 535 nm for the MONOs and the MDAs, respectively. The results of the colorimetric analyses are in Table VIII. The 1999 hemp-seed oil had a higher peroxidation level than the 1998 oil. Contrary to expectations, the commercial olive oil also had a significant peroxidation level. CHLOROPHYLL The chlorophyll concentration observed in the hemp-seed oil was 0.0036% of the fat mass, while the extra-virgin olive oil had a lower chlorophyll content, only 0.0024%. Figure 1 shows an example of a UV-visible spectrum of hemp-seed oil (1998), diluted 1 :2 in maize-germ oil. CHLOROPHYLL PHOTOSTABILITY Pigments like chlorophyll are also involved in auto-oxidation and photo-oxidation mechanisms. For this reason, spectrophotometric determinations at 416 nm and 671 nm, before and after irradiation, were carried out. Figure 2 shows the results of spec­ trophotometric determinations at 416 nm and 671 nm, after UV A irradiation. The chlorophyll in the extra-virgin olive oil had a higher photostability than that in the 1998 hemp-seed oil, which degraded faster under UV A irradiation than under visible irradiation (see Figure 3). This is probably due to the composition of olive oil, which contains many more anti-oxidant components (such as BHT and tocopherols) that could protect the pigment against photodegradation. VITAMIN E IN HEMP OIL Qualitative tocopherol composition was determined in both hemp-seed oils (1998 and 1999). For the 1998 hemp-seed oil, the concentration of tocopherol was 8.2 · 10- 6 g/100 ml, and for the 1999 oil it was 2.5 · 10- 5 g/100 ml. The quantitative results obtained are reasonable when one considers the progressive degradation of this vitamin Table VIII Absorptivites at 450 nm and at 535 nm of Oil Samples Hemp-seed oil (1998) 0.063 (±0.09) 0.041 (±0.05) Hemp-seed oil (1999) 0.075 (±0.07) 0.048 (±0.08) Values in parentheses are standard deviations, determined on four samples. Olive oil 0.130 (±0.13) 0.087 (±0.03)