Effect of pH on the copigmentation of anthocyanins from Cabernet Sauvignon grape extracts with organic acids

Cony Gauche,Elisa Da Silva Malagoli,Marilde Terezinha Bordignon Luiz

doi:10.1590/s0103-90162010000100006

Cony Gauche, Elisa Da Silva Malagoli + Show 1 more

Open Access

https://doi.org/10.1590/s0103-90162010000100006

Copy DOI

Abstract

Anthocyanins show low-stability when exposed to different food processing conditions. Copigmentation is one of the main reactions contributing to the in vivo color responsible to the stability of anthocyanins. In the aim of holding the red color, copigmentation effect of organic acids (caffeic, ferulic, gallic and tannic acids) combined with anthocyanins in crude Cabernet Sauvignon (Vitis vinifera L.) grape skin extract at pH values (1.0, 2.0, 3.0, 3.3, 3.5, 3.7, 4.0, 4.5) was evaluated in this research. The maximum copigmentation effect, revealed by the hyperchromic and bathochromic shifts in anthocyanin maximum absorbance wavelength, was obtained at pH 3.3 with every acid used. Anthocyanin stability was followed by measuring the loss of color, thus it was possible to determine the protecting effects of these copigments. Tannic acid was the best copigment in our model system, giving half-life time of 2,585 h. We are suggesting the formation of pyranoanthocyanins by the reactions of anthocyanins with caffeic and ferulic acid, these substances could be avoiding the observation of the copigmentation effect. Addition of organic acids could improve the anthocyanin stability; though, more studies are needed to justify the lack of copigmenting effect observed with the caffeic and ferulic acids.

Highlights

Anthocyanins play a critical role in the color quality of many fresh and processed fruits
The volume was completed with the model system of potassium chloride buffer (0.025 M chloride acid, potassium chloride) or citrate buffer (0.1 M citric acid, sodium citrate) at different pH values (1.0, 2.0, potassium chloride buffer; 2.5, 3.0, 3.3, 3.5, 3.7, 4.0, 4.5, citrate buffer) to obtain maximum absorbance values of 1,200 by the visible maximal wavelength displayed in the UV-visible spectra (Hitachi U2010, CA, USA)
The copigment effect on stability of anthocyanins from the crude extract of Cabernet Sauvignon grapes (Vitis vinifera L.) was followed until 60% or more of the pigments were degraded

Summary

Introduction

Anthocyanins play a critical role in the color quality of many fresh and processed fruits. Anthocyanins have a useful potential as natural colorants due to their attractive colors (Markakis, 1982); their usage in the food industry is limited due to their instability when exposed to factors like environmental variations, including temperature, light intensity and oxygen (Delgado-Vargas et al, 2000). Anthocyanins differ from other natural flavonoids due to their large range of colors and their ability to form resonance structures through pH variation (Lapidot et al, 1999). Some extracted anthocyanins have been used as colorings for food and beverages; many anthocyanins are unstable in neutral solutions and lose their color, their use for food and pharmaceutical products, among others, has been limited (Dougall and Baker, 2008)

Objectives

Methods

Results

Conclusion