engleski

The effect of light and temperature on stability of anthocyanins

Anthocyanins are flavonoids responsible for red, purple and blue colours of many fruits and vegetables. They are usually extracted from grapes, berries, red cabbage, apples, radishes etc. Many natural food colorants are anthocyanidin derived but they are relatively unstable and susceptible to degradation during processing and storage. The aim of this study was to investigate the stability of the anthocyanins from grape skin during the 10-week storage period. Extracts were prepared by classical procedure by maceration of grape skin in methanol containing small concentration of HCl (0.01%) and they were stored under the different conditions (daylight exposure at room temperature, at +4°C and at room temperature in dark). Total monomeric anthocyanins were determinated by the pH-differential method which is based in the structural transformation of the anthocyanin chromophore as a function of pH. Indices for anthocyanin degradation, polymeric colour, browning and colour density were determinated by bisulphite bleaching method. According to the obtained results, on the last day of the experiment there were no monomeric forms of anthocyanins in extracts exposed to the daylight and all other parameters of their degradation were significantly higher comparing to the extracts kept at +4°C or at room temperature but light protected.

anthocyanins; stability; temperature; light; spectrophotometric methods

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