Thermal degradation kinetics of monomeric anthocyanins, colour changes and storage effect in elderberry juices

Abstract

Elderberry (Sambucus nigra L.) is considered an interesting fruit as food ingredient, due to its high content of anthocyanins that give products an attractive red colour. The aim of present study was to evaluate the kinetics of elderberry monomeric anthocyanin (MAcy) and colour degradation due to thermal processing and storage. Anthocyanins content was measured with pH-differential method. CIELab parameters were obtained with a Minolta Spectrophotometer, total phenolics were determined by Folin-Ciocalteu method. MAcy degradation and evolution of colour parameter a∗ were fitted to a first-order model. The degradation rate of a∗ was about three times lower than MAcy degradation rate. Activation energy for degradation of a∗ and MAcy were 140.6 and 144.6 kJ mol-1 respectively. Degradation rates (k) obtained during storage were 0.025 d-1 for MAcy and 0.0064 d-1 for a∗. During storage, 50% reduction of initial values was at 120 days for MAcy and at 432 days for colour parameter a∗ at 25°C. However, a high retention of polyphenols and antioxidant was noted. Kinetic parameters calculated for elderberry juice can be used to design a thermal treatment to obtain a high retention of colour and bioactive compounds.