Phytochemical composition and thermal stability of two commercial acai species, Euterpe oleracea and Euterpe precatoria

Acai fruit are native to the Amazon region of South America and two predominant species are commercially exported as fruit pulps for use in food and beverage applications. Detailed characterisation of the polyphenolic compounds present in the de-seeded fruits of Euterpe oleracea and Euterpe precatoria species were conducted by HPLC-ESI-MSn analyses and their thermal stability and overall influence on antioxidant capacity were determined. Anthocyanins were the predominant polyphenolics; in both E. oleracea (2247 +/- 23 mg/kg) and E. precatoria (3,458 +/- 16 mg/kg) species, and accounted for nearly 90% of the trolox equivalent antioxidant capacity in both E. oleracea (87.4 +/- 4.4 mu mol TE/g) and E. precatoria (114 +/- 6.9 mu mol TE/g) fruits. Various flavones, including homoorientin, orientin. taxifolin deoxyhexose and isovitexin; various flavanol derivatives, including (+)-catechin, (-)-epicatechin, procyanidin dimers and trimers, and phenolic acids, including protocatechuic, p-hydroxybenzoic, vanillic, syringic and ferulic acids, were also present in both species. Thermal stability of these compounds was evaluated, following a thermal holding cycle (80 degrees C for up to 60 min) in the presence and absence of oxygen. Both species experienced only minor changes (<5%) in non-anthocyanin polyphenolic contents during all thermal processes whereas 34 +/- 2.3% of anthocyanins in E. oleracea and 10.3 +/- 1.1% of anthocyanins in E. precatoria were lost under these conditions, regardless of the presence of oxygen. Proportional decreases (10-25%) in antioxidant capacity accompanied the anthocyanin changes. Results suggest that both acai species are characterised by similar polyphenolic profiles, comparable antioxidant capacities, yet only moderate phytochemical stability during heating. (C) 2009 Elsevier Ltd. All rights reserved.