José Santiago Álvarez Muñoz

Dependence between colour and individual anthocyanin content in ripening grapes

Abstract Three red grape cultivars of different coloration (Flame seedless, Exotic and Monastrell), grown in Murcia (southeast Spain) were analysed during ripening for external colour and individual pigment content. The application of the CIRG colour index, calculated from the coordinates hue angle (h), lightness (L*) and chroma (C*) of the CIELAB colour space, and defined as [(180-h)/(L*+C*)], permitted an objective evaluation of the colour at the different ripening stages. External colour and anthocyanic profile were closely linked. Cyanidin-3-glucoside was the most abundant pigment in Flame seedless (low pigmented cultivar), while malvidin-3-glucoside was the main anthocyanin in the cultivars Monastrell and Exotic (both of them with a high pigment content). Data derived from the study of the ratios between anthocyanins with different degree of hydroxilation and/or methoxylation leads to know information on differences between grapevines linked to the synthesis of these pigments. ©

Effect of electron beam irradiation on color and microbial bioburden of red paprika.

The effect of irradiation with electron beams on the microbiological quality and color properties of red paprika was examined. The irradiation doses ranged from 0 to 12.5 kGy. The counts performed were total mesophilic aerobic microorganisms, Enterobacteriaceae, coliforms, sulfite-reducing clostridia, molds, and yeasts. It was concluded that molds, yeasts, and sulfite-reducing clostridia were the most resistant species, although a 10-kGy dose of irradiation leads to optimum sanitation. Extractable color and apparent color were analyzed to appraise the incidence of the irradiation treatments in the color properties of red paprika. Extractable color was determined according to the American Spice Trade Association method, and apparent color was analyzed by reflectance using the CIELab color space. Data showed no significant differences between the color properties of irradiated and nonirradiated samples. Irradiation was a suitable procedure to minimize the bioburden of red paprika with small modifications of its color properties.

Dependence between apparent color and extractable color in paprika

The color properties of 96 paprika samples were evaluated by tristimulus reflectance measurements. The extractable color (ASTA units) of all these samples was also determined. The linear correlation between individual CIELAB parameters and extractable color was very poor. Several color indices used with other foods were shown to be of insufficient accuracy for predicting the extractable color in paprika. A new color index for paprika (PACI) is proposed based on the CIELAB coordinates L* (lightness), a* (red-blue), and h (hue angle), and it is calculated as “1000a*/(L*+h)”. This new index showed a high correlation with the logarithm of extractable color (r = 0.9662) and was able to distinguish between sample groups of different ASTA units.

Bis(pentafluorophenyl) derivatives of nickel(II) with anionic bidentate schiff base ligands

Abstract The hydroxo-complex [{(Ni(C6F5)2(μ-OH)}2]2− reacts with salicylaldehyde in a 1:2 molar ratio to give the mononuclear anionic derivative [Ni(C6F5)2(o-OC6H4CHO)]−. The coordinated salicylaldehydate does not react with amines but proton abstraction from the preformed salicylaldimines by the hydroxo-complex leads to the formation of the corresponding complexes [Ni(C6F5)2 (o-RN  CHC6H4O)]− [R  CH3,C2H5 CH(CH3)2 CH2C6H5 C6H5 p-ClC6 H4, p-BrC6H4, o-CH3C6H4, p-CH3C6H4, o-CH3OC6H4, p-CH3OC6H4, or [α-naphthyl]. All the complexes have been isolated as the [NnBu4]+ salts and have been characterized by partial elemental analyses, conductance measurements, thermal analysis, and spectroscopic (IR, V-UV, and 1H and 19F NMR) methods.