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

BACKGROUND: 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. OBJECTIVE:The aim of present study was to evaluate the kinetics of elderberry monomeric anthocyanin (MAcy) and colour degradation due to thermal processing and storage.METHODS: 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. RESULTS: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 25ºC.However, a high retention of polyphenols and antioxidant was noted.CONCLUSIONS: Kinetic parameters calculated for elderberry juice can be used to design a thermal treatment to obtain a high retention of colour and bioactive compounds.