The induction period (IP), determined using accelerated methods such as the Rancimat test, is a parameter that has been used to predict the shelf life of virgin olive oil. The oxygen radical absorbance capacity (ORAC) has recently been proposed as a quality index of virgin olive oil because it measures the efficiency of phenolic compounds in the protection against peroxyl radicals. This study aims to investigate relationships between the ORAC and IP values and proposes ORAC as a new parameter of virgin olive oil stability. The concentrations of phenolics, o-diphenols, tocopherol, β-carotene, lutein, and ORAC and IP values were determined in 33 virgin olive oils. Regression analyses showed that both ORAC and IP values correlate with total phenols and o-diphenols with highly significant indices, whereas the correlations of both ORAC and IP with tocopherols, β-carotene, and lutein were not significant. The ORAC values correlate with the IP values with low but significant indices (R = 0.42; P < 0.02). The results confirm the key role of phenolic compounds in accounting for the shelf life of virgin olive oil and suggest that the ORAC parameter may be used as a new index of quality and stability. Paper no. J10173 in JAOCS 79, 977-982 (October 2002). FIG. 2. Regression analysis between oxygen radical absorbance capacity (ORAC) values and total phenolics for 33 virgin olive oils. Values are the average of four determinations. TE, Trolox equivalents. The SD are less than 5%. FIG. 3. Regression analysis between ORAC values and o-diphenolic compounds for 33 virgin olive oils. Values are the average of four determinations. The SD are less than 5%. For abbreviations see Figure 2. FIG. 4. Regression analysis between the Rancimat induction periods and the total phenols (A) and o-diphenols (B). Values are the average of four determinations. The SD are less than 5%.

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The quality of extra-virgin olive oils (EVOO) from organic and conventional farming was investigated in this 3-year (2001-2003) study. The oils were extracted from Leccino and Frantoio olive (Olea europaea) cultivars, grown in the same geographical area under either organic or conventional methods. Extra-virgin olive oils (EVOO) were produced with the same technology and samples were analyzed for nutritional and quality parameters. Volatile compounds were measured with solid-phase microextraction combined with gas chromatography and mass spectrometry (SPME-GC-MS). Sensory evaluation was also completed by a trained panel. Significant differences were found in these parameters between organic and conventional oils in some years, but no consistent trends across the 3 years were found. The acidity of organic Leccino oils was higher than conventional oils in 2001 and 2002 but not in 2003; Frantoio oils were never different. Organic Leccino oils had higher peroxide index than conventional oils in 2001 and 2002 but it was the reverse in 2003. Organic Frantoio oils had lower peroxide index in 2001, but values were not statistically different in the other years. The concentrations of phenols, o-diphenols, tocopherols, the antioxidant capacity and the volatile compounds showed differences in some years and no difference, or opposite differences, in others. Sensory analysis showed only slight differences in few aromatic notes. Our results showed that organic versus conventional cultivation did not affect consistently the quality of the high quality EVOO considered in this study, at least in the measured parameters. Genotype and year-to-year changes in climate, instead, had more marked effects.

(PN) S U M M A R Y Expression of glucose-6-phosphate dehydrogenase (G6PD) activity is high in tongue epithelium, but its exact function is still unknown. It may be related either to the high proliferation rate of this tissue or to protection against oxidative stress. To elucidate its exact role, we localized quantitatively G6PD activity, protein and mRNA using image analysis in tongue epithelium of rat and rabbit, two species with different diets. Distribution patterns of G6PD activity were largely similar in rat and rabbit but the activities were twofold lower in rabbit. Activity was two to three times higher in upper cell layers of epithelium than in basal cell layers, whereas basal layers, where proliferation takes place, contained twice as much G6PD protein and 40% more mRNA than upper layers. Our findings show that G6PD is synthetized mainly in basal cell layers of tongue epithelium and that it is posttranslationally activated when cells move to upper layers. Therefore, we conclude that the major function of G6PD activity in tongue epithelium is the formation of NADPH for protection against oxidative stress and that diet affects enzyme expression in this tissue.