73C-16

Anthocyanins have been utilized as natural substitutes for synthetic colorants in food materials. Although, they are known to be sensitive to high temperatures, light, changes in pH, SO₂, browning reactions, and other factors present during processing and storage of foods. Stabilization of anthocyanins by co-pigmentation with other phenolics has been studied, but not for pomegranate anthocyanins. We propose that co-pigments formed under certain conditions between pomegranate anthocyanins and other naturally occurring flavonoids, promote color enhancement and exhibit improved stability over time.

The objectives of this study were to evaluate the extent of co-pigmentation on pomegranate juice utilizing three established anthocyanin co-pigmenting phenolics, and to determine the temperature-stability effect of those phenolics on the juice.

Three phenolics, Rutin, Hesperidin and Ferulic Acid were solubilized and added at several molar-ratios (co-pig/pig) to single-strength pomegranate juice. To promote maximum co-pigmentation, the juice pH was buffered to 3.5. Samples were analyzed with a Beckman DL 7500 spectrophotometer. Changes in color were evaluated using the CIELCH scale for a D₆₅ standard illuminant and a 10˚ standard observer, and perceptible color difference ΔE* was also monitored. Monomeric, co-pigmented and polymeric anthocyanin contents were determined, together with flavone and total phenolic contents. Juice stability was evaluated over a 21-day period at two temperatures (25 and 40 C).

All three phenolics increased the content of co-pigmented form at the cost of both monomeric and polymeric forms. Of those phenolics, Rutin showed largest complexation effect, with a maximum solubility at a 6:1 molar ratio. Rutin co-pigment content increased by 111% with a corresponding increase in Chroma of 12.5%, and a maximum ΔE* of 29.3. Furthermore, Rutin co-pigmentation significantly increased the temperature-stability of anthocyanins at 25 C.

This study presents new qualitative and quantitative information of the stabilizing effect of co-pigmenting phenolics on pomegranate juice anthocyanins.