Cereals & Grains Association
Log In

Improving aqueous stability of sorghum 3-deoxyanthocyanin pigments for food colorant application.
D. HERRMAN (1), J. Awika (1). (1) Texas A&M University, College Station, TX, U.S.A.

The natural food color market has seen significant growth in the last decade; between 2007-2010 it experienced a 29% growth. In 2011, most food and beverage launches contained natural colorants.  Anthocyanins are among the most widely used natural colors. However, their stability to food processing conditions is limited. 3-Deoxyanthocyanins (3-DXA) are found primarily in sorghum and are a unique set of pigments that tolerate food-processing conditions better than anthocyanins.  This is because 3-DXAs are unsubstituted at C3 which results in lower electronegativity making the 3-DXAs less susceptible to H2O attack and color loss.  However, the 3-DXA pigments readily precipitate in aqueous solutions due to lower hydrophilicity limiting potential food application. The objective of this study was to determine effect of ionic gums and multivalent cations on aqueous stability of sorghum 3-DXAs. Ionic gums (acacia gum, alginate) at 0.01%, and 0.1%, and metal ions (Mg2+, Fe2+) at 0.2mM  were complexed with 3-DXA in pH 3 and 5 buffers. Spectra were recorded with a UV-Vis spectrophotometer. Pigment composition was monitored using HPLC-DAD; visual images were also recorded. Both acacia gum and alginate at 0.1% concentration significantly increased aqueous stability of 3-DXAs; acacia gum was remarkably effective, with no significant precipitation or loss of color after 45 days at 24°C. The alginate samples had 90% precipitation after 30 days at pH 3; controls showed 90% precipitation within 1 hour. Acacia gum was likely more effective because of its amphiphilic nature resulting in emulsiphication complex with 3-DXAs. Neither multivalent metal ion provided significant stabilization. Iron resulted in undesirable pigment browning.  Acacia gum is highly effective at stabilizing 3-DXAs in aqueous environments, increasing their potential application as a natural food colorants. 

View Presentation