M. Isabel Minguez-Mosquera

Color-pigment correlation in virgin olive oil

The chlorophyll and carotenoid content of virgin olive oils from five varieties harvested at varying degrees of ripeness were determined. Colors were evaluated from the chromatic ordinates L*, a*, b* of the absorption spectrum. Oil color changes for different varieties or stages of ripeness are directly related to pigment content and a* and b* values. The statistical study made on both series of parameters proves that there is a good correlation between them. The carotenoid content and b* have one of the best correlation coefficients (r) and is easily measured. This methodology evaluates chlorophyll and carotenoid content, an additional attribute for evaluation of virgin olive oil quality.

Pigments present in virgin olive oil

The qualitative and quantitative control of pigments in ripe olives and in extracted virgin olive oil has increased our knowledge of the influence on these compounds in the areas of ripening of the fruit, storage time in the factory and the oil extraction process. As the harvesting time of the fruits increases, pigment content decreases. During storage, the presence of lipoxygenase has been detected, as well as a considerable decrease in chlorophylls and a small decrease in carotenoids. During the extraction process, the chlorophyllic fraction is destroyed in the greater part, and although the carotenoid fraction is also affected, its concentration increases in the oil with respect to that in the fresh fruit. In the pigment degradation, in addition to the acid-catalyzed reaction, the presence of lipoxygenase suggests a role for this enzyme.

Chlorophyll and Carotenoid Composition in Virgin Olive Oils from Various Spanish Olive Varieties

A study of chlorophyll and carotenoid composition of nine single-variety virgin olive oils from the main Spanish producing regions has shown differences depending on variety and ripening degree of the fruits. Pheophytin awas the major pigment in all the oils studied (44–58% total pigments), followed by lutein (18–38%) and β-carotene (6–17%). The chlorophyll pigments group also included pheophytinband in some cases chlorophyllsaandb. The carotenoid fraction also included the xanthophylls neoxanthin, violaxanthin, luteoxanthin, antheraxanthin, mutatoxanthin and β-cryptoxanthin. The mean provitamin A activity of the oils was 260 μg kg−1 expressed as retinol equivalent.cis-α-Carotene (tentative), mono- and di-esterified xanthophylls and pheophorbideawere pigments exclusive to Arbequina variety, a fact that could be used as a chemo-taxonomic differentiator of the oils of this variety. The ratio between the chlorophyll fraction and the carotenoid fraction was maintained in most cases around 1, demonstrating that the green and yellow fractions were in balance, notwithstanding their greater or lesser total pigment content. The considerable range in the lutein/β-carotene ratio (between 1·3 and 5·1 depending on variety) makes this ratio a differentiator of single-variety oils. Despite the different sources of the oils, some general trends have been shown which suggest what chlorophyll and carotenoid pigments should be expected in an olive oil so as to include it within the denomination ‘virgin’.

Action of chlorophylls on the stability of virgin olive oil

Virgin olive oil was used as substrate to study the influence of chlorophylls on its oxidative stability in light and in darkness. Chlorophylls a and b were added to this substrate, after which oils were stored at 36 ± 2°C for three months under artificial light (1340 lux) or in darkness. The effect of light was greater than that of the additives. The prooxidant action of chlorophylls in the presence of other pigments of the oil was not observed in this assay. During early storage, the rate of peroxide formation was lower in the samples with added chlorophylls, but later it equalled that of the control. In darkness, stability was greater in the samples containing chlorophylls, indicating a slight antioxidant effect, which was more marked for chlorophyll a.

Dertermination of chlorophylls and carotenoids by high-performance liquid chromatography during olive lactic fermentation

Abstract Eighteen pigments, including chlorophylls, carotenoids and their degradation products, were separated by reversed-phase ion-pair high-performance liquid chromatography during the lactic fermentation and later preservation phase of green table olives. The method consists of an elution gradient using two solvents: water-ion-pair reagent-methanol (1:1:8, v/v/v) and methanol-acetone (1:1, v/v). Absorbance detection of all the pigments is carried out spectrophotometrically at 430 nm. Pigment concentrations are calculated from an extension of Beers law. This procedure is compared with the external standard method. The analysis of variance showed no significant differences between the results given by the two methods.

High-performance liquid chromatographic study of alkaline treatment of chlorophyll

Abstract The degradation products of chlorophyll a and b obtained by alkaline treatment in the presence of atmospheric oxygen were studied. Reversed-phase ion-pair high-performance liquid chromatography, normal- and reversed-phase thin-layer chromatography and diode-array detection were used for the separation, isolation and preliminary identification of the following degradation products: Mg-rhodin g 7 , Mg-chlorin e 6 , MeO-lactone-chlorophyllide, Mg-purpurin, Mg-phytyl-rhodin g 7 , Mg-phytyl-chlorin e 6 , MeO-lactone-chlorophyll, Mg-phytyl-purpurin and some of their diasteroisomers. MeO-chlorophyll and OH-chlorophyyl were tentatively identified. The alkaline treatment did not induce the specific de-esterification of phytol in any of the cases studied and oxidation of the isocyclic ring was simultaneously observed.

Preparation of Cu(II) complexes of oxidized chlorophylls and their determination by thin-layer and high-performance liquid chromatography

Abstract Different allomerization products of pheophytins a and b have been obtained by alkaline treatment in the presence of atmospheric oxygen and isolated by normal phase thin-layer chromatography (NP-TLC) and semi-preparative high-performance liquid chromatography (HPLC). 3 1 ,3 2 -Didehydro-151-hydroxy-15 1 -hydroxy-rhodochlorin-15-acetic acid δ-lactone-15 2 -methyl-17 3 -phytyl ester ( a and b ) and 3 1 ,3 2 -Didehydro-rhodochlorin-15-glyoxylic acid-17 3 -phytyl ester ( a and b ) have been identified as principal products. Identification was based on UV-Vis and mass spectra, retention times and R F values. The molecular mass of allomerized pheophytins was confirmed by positive-ion fast-atom bombardment mass spectrometry and positive/negative ion electrospray mass spectrometry. The corresponding Cu(II) complexes of these compounds were prepared by chelation reaction with CuCl 2 and separated by reversed-phase ion-pair high-performance liquid chromatography (RP-IP-HPLC) using a gradient of water and ion suppressor-methanol-acetone. The Chromatographic characteristics in NP-TLC and RP-IP-HPLC of the Cu(II) complexes are reported. The corresponding UV-Vis spectra obtained with an on-line diode-array detector have been included.

Involvement of copper and zinc ions in green staining of table olives of the variety gordal

The presence of metalochlorophyllic complexes of copper has been detected in table olives showing the alteration known as green staining. These compounds are absent in the healthy fruit. The possible implication of fungicidal treatment of olive trees in this alteration has been studied. No alteration was produced in table olives prepared with fruit from trees with and without fungicidal treatment and the differences found between copper levels in the fruit were not significant. The possibility that the copper involved in this alteration is of extraneous origin was, therefore, discarded. On the other hand, there were no significant differences in the levels of copper in random samples of fruits with and without green staining. Therefore, although the green-staining alteration is the result of the formation of complexes of copper with chlorophyll derivatives, it seems clear that the simple presence in the fruits of copper, by itself, does not lead to the appearance of green-staining.

Digestive stability, micellarization, and uptake by Caco-2 human intestinal cell of chlorophyll derivatives from different preparations of pea (Pisum sativum L.).

The digestive stability, efficiency of micellarization, and cellular accumulation of the chlorophyll pigments of different preparations of pea were investigated, using an in vitro digestion procedure coupled with human intestinal Caco-2 cells. Fresh pea (FP), cooked fresh pea (CFP), frozen pea (FZP), cooked frozen pea (CFZP), and canned pea (CP) were subjected to simulated digestion. Although after digestion the pigment profile was modified for all samples, except CP, allomerization reactions and greater destruction of chlorophylls were observed in only FP, which should be due to enzymes in FP that were denaturalized in the rest of the test foods. A pigment extract of CFZP was also subjected to in vitro digestion, showing a positive effect of the food matrix on the pigment digestive stability. The transfer of the chlorophyll pigments from the digesta to the micellar fraction was significantly more efficient in CFZP (57%, p < 0.0001), not significantly ( p > 0.05) different between CFP, FZP, and CP (28-35%), and lowest in FP (20%). Pheophorbide a stood out as the most-micellarized chlorophyll derivative in all of the samples, reaching levels of up to 98%. Incubation of Caco-2 cells with micellar fractions at the same concentration prepared from each test food showed that pigment absorption was considerably lower ( p < 0.006) in cells incubated with FP, whereas there were no differences among the rest of the preparations. Therefore, factors associated with the food matrix could inhibit or mediate the chlorophyll pigment absorption. These results demonstrated that the industrial preservation processes of peafreezing and canningas well as the cooking have a positive effect on the bioaccessibility and bioavailability of the chlorophyll pigments with respect to the FP sample, emphasizing CFZP with greater bioaccesibilty degree.

Decoloration of vegetable oils and oleoresins with recovery of unaltered pigments

The present study confirms that N,N-dimethylformamide for the extraction of chloroplast pigments from vegetable tissues shows no differences from the usual acetone or methanol. Therefore, it can be applied to fats, as it allows separation of lipids and pigments by means of phase distribution between light petroleum ether and N,N-dimethylformamide. The ether phase retains the decolored fatty matter, and the pigments dissolved in N,N-dimethylformamide can be recovered totally unaltered.This method has been applied to oleoresins and oils from different products and origins. Satisfactory results have been obtained in terms of the degree of decoloration and the percentage of oil recovered. At the same time, the unaltered pigment concentrate obtained from the hypophase could be used as a color enhancer in the chemico-pharmaceutical industry.