Influence of Propylene Glycol Buffers on the Stability of Red Cabbage Anthocyanins
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Date
2020-05
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The Ohio State University
Abstract
Although synthetic colorants have been widely used for decades, recent consumer trends have caused increased interest in developing natural colorants from anthocyanins. Despite their potential to produce a wide variety of colors, they are restricted in their use as colorants because of their instability in retaining color. Our objective was to determine how a common water activity reducing additive in the food industry, propylene glycol, affected the stability of anthocyanins in different buffer solutions. Non-acylated, mono-acylated, and di-acylated anthocyanins were extracted from red cabbage (Brassica oleracea var. capitata f. rubra) and pigment samples were combined with buffers consisting of varying percentages of propylene glycol. The anthocyanin concentration and performance of the samples were analyzed with SpectraByColor software and a Shimadzu spectrophotometer. Results indicated that anthocyanin intensity appeared to decrease in propylene glycol, suggesting that anthocyanin hydration occurred even with very low water levels. Contrary to the hypothesis that increasing propylene glycol content and lowering water activity would decrease the hydration of anthocyanins and increase the color intensity of the pigments, it was observed that increasing propylene glycol (<100%) resulted in an increasing loss of pigment intensity. This experiment can help to determine the type of additives necessary for optimal performance of anthocyanins in commercial products without synthetic colorants, and to encourage future explorations in developing natural food colors that are more pigmented and more stable than what are currently used.
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Keywords
natural colorants, HPLC isolation, anthocyanin chemistry, acylated anthocyanins