RESUMEN

The grape pomace industry produces large quantities of protein-rich seeds, which can be a sustainable non-animal protein source; their techno-functional properties could be exploited to improve the colour stabilisation and modulating the astringency of red wines in warm climates. This study aims to optimise the methodology of obtaining protein hydrolysates from defatted grape seed meal residue. Five assays using different quantities of enzyme and raw materials were considered. Based on the protein purity, hydrolysates yield, colour and molecular weight distribution achieved, optimal conditions were the hydrolysis of the alkaline protein concentrate with the highest amount of enzyme. The products obtained showed the lowest colour parameters, with the lightness contributing the most to the colour differences, which were visually perceptible (ΔE*ab > 3). The hydrophobic amino acids remained within the peptide sequence, leaving polar and charged amino acids in terminal positions, which could affect the wine equilibrium related to colour stabilisation.

Asunto(s)

RESUMEN

The evolution during ripening of Beta vulgaris (var. Pablo) on colour and betalain composition, not previously conducted in conjunction in red beets, has been examined. According to the results, it could be asserted that the ripening stage significantly (p < 0.05) influenced on all the studied parameters. On the basis of the betalain content, the optimum ripening stage corresponded to a medium weigh-to-calibre ratio, in the light of the significantly (p < 0.05) higher content of betalains, especially betanin and vulgaxanthin I. Moreover, colour attributes also differed during ripening, having the medium-ripened beetroots a significantly (p < 0.05) more reddish hue (hab) and lower lightness (L*), probably due to the higher content of betaxanthins in this stage. The colour differences among red beets in the stage II and the rest of stages were visually appreciable (ΔE*ab > 3) and mainly qualitative. A new range of opportunities for diversification of colorant market, from a nutritional and colorimetric point of view, could be possible by employing red beets with different stages of ripening.

Asunto(s)

RESUMEN

The effects of different pHs (4, 5 and 6), temperatures (4, 20 and 80 °C) and storage (up to 12 days) on differential tristimulus colorimetry and betalain content related to the colour of yellow pitaya (Selenicereus megalanthus) have been investigated. The peel of the yellow pitaya was extracted with different solvents to see its colorant capacity. Highly-acidic extracts (pH 4) showed the lowest betalain content, chroma (C* ab = 60 against 70) and the yellow component of the colour (b*). Storage temperature manifested a great influence on CIELAB parameters when yellow pitaya peel was added to highly-acidic foodstuffs, with a tendency towards red hues (h ab , from 100° to 85°) and remarkable changes on lightness (L*, from 90 to 75) as temperature increased. However, low-acidic extracts (pH 5 and 6) were superior from a colour stability standpoint, not being influential the temperature of storage. All colour changes according to pH and temperature were visually appreciable by human eyes (∆E* ab  > 3). New opportunities for diversification of colorant market could be possible by employing yellow pitaya peel as natural resource.

RESUMEN

The effect of adding an enzymatic hydrolysate of grape seeds (EH-GS) during Syrah wine fermentation in a warm climate has been evaluated. We focused on the polyphenolic composition as well as the application of differential and tristimulus colorimetry to colour data. This is the first attempt at using this oenological alternative to avoid common colour losses of red wines elaborated in a warm climate. The addition of 250g (simple dose, SW) of EH-GS to 120kg of fermentation material promoted a significant (p<0.05) increase in the polyphenolic content of stored wines, especially in benzoic acid, hydroxycinnamic acid derivative, flavonol and anthocyanin levels. This increase could promote a higher copigmentation percentage and maximum colour stabilization (C(∗)ab) without significantly changing the wine tonality. Unexpectedly, the use of a double quantity (DW) of EH-GS resulted in significantly less chroma than for control wines (CW), demonstrating visually perceptible colour changes (ΔE(∗)ab>3 CIELAB units).

Asunto(s)

RESUMEN

Three different varieties of Opuntia ficus-indica (R, red; Y, yellow; RY, red-yellow) have been considered in this study. Attention was focused on differential tristimulus colorimetry and on the analysis of individual betalains (HPLC-DAD-ESI-ToF-MS) and phenolic content, scarcely previously reported in these kinds of samples. The importance of this research stems from the elucidation of the parts and varieties of cactus pear more optimal for use as natural colorants and sources of phenolics and betalains. Thus, the RY pulp was appropriate to obtain colorants with high color intensity (C*(ab) = 66.5), whereas the whole Y fruit and R pulp reached powerful and stable yellow and red colors, respectively (C*(ab)/h(ab), 57.1/84.7 and 61.1°/81.8°). This choice was also based on the visually appreciable differences (ΔE*(ab) > 5) among samples, mainly quantitative (%Δ(2)L, %Δ(2)C). In addition, seeds of all Opuntia varieties showed significantly (p < 0.05) similar phenolic content (around 23.3 mg/g) and color characteristics.

Asunto(s)

RESUMEN

The potential use of ulluco (Ullucus tuberosus) extracts to be added as natural colorant to other products has been studied. The stability of ulluco extracts at different pHs and temperatures over time has been thoroughly conducted. Our attention was focused on the tristimulus colorimetry, differential colorimetry and betalains related to color. On the basis of the results, although ulluco extract adjusted to pH4 showed a significantly lower color intensity (C*ab~40), the stability of red hue (hab) over time was higher. Betalain content showed the same trend, and lower values in highly-acidic extracts have been reported. It could be also affirmed that visually appreciable color changes (ΔE*ab>2) were induced when pH changed and different temperatures were applied. Despite of the vivid red color of the initial extracts, ulluco extracts added to low-acidic foodstuffs showed a tendency towards yellowish tonalities (values of hab from 45° to 80°), mitigated by using refrigeration storage conditions (hab values from 45° to 55°).