Increasing Pyranoanthocyanin Formation with Use of Caffeic Acid and Heat for Production of Naturally Derived Food Colorants

Research Poster
Nicole Straathof
M. Monica Giusti
Department of Food Science and Technology

There is consumer and regulatory push to replace artificial colorants with naturally derived ones for health and environmental reasons. Anthocyanins (ACN), plant pigments, are antioxidants in the body but are unstable in foods. In aged red wines, ACN with free hydroxyl group at C5 condensate with fermentation products to form pyranoanthocyanins (PACN). PACN are more stable but form inefficiently. This study attempted to produce PACNS efficiently using high cofactor concentration and heat.

Elderberry anthocyanins were semi-purified from a commercial source. Caffeic acid (CA), the cofactor, dissolved in 15% ethanol, was diluted with buffer to achieve ACN:CA molar ratios of 1:50, 1:100, 1:150, and 1:200 and incubated at 65°C for 5 days. PACN formation was monitored over time. The effect of temperature was tested using ACN samples incubated with or without CA at 25°C, 50°C, and 75°C for 7 days. Changes in composition were monitored using uHPLC with PDA-MS/MS detectors. 

Higher CA levels seemed to protect pigment integrity, with ACN:CA 1:150 ratio showing highest tinctorial strength after 48 hr. PACN formation rate was fastest between 24 and 48 hr for all ACN:CA ratios and after 120 hr all ACN had degraded or converted to PACN. PACN formed faster at higher temperatures, reaching ~90% PACN in 24 hours and ~100% PACN in 48 hr at 75°C. However, sample held at 75°C for 72 hr degraded significantly.

These results suggest PACN could be produced efficiently from elderberry ACN and CA if heated to produce more stable pigments with potential as food dyes.