Effect of pulsed electric field pre-treatment on the debittering process of cherry kernels

Abstract

Cherry kernels occur in significant amounts as waste material during the processing of fruits. However, their subsequent use is limited due to the presence of cyanogenic glycosides, which are potentially dangerous to human health. In this study, the application of pulsed electric fields (PEF) was investigated as pre-treatment to improve the debittering process and to facilitate the degradation of cyanide precursors, naturally present in cherry kernels. Diverse PEF treatments were carried out at constant electric field strength of E = 2.2 kV/cm and specific energy input was varied between 10 and 50 kJ/kg, varying the number of pulses. Two different debittering procedures were performed with a common incubation time 0–20 h at 40 °C: a) incubation of whole kernels in deionized water; b) incubation of whole kernels without water stored in air at 80% relative humidity. HPLC analysis was used to examine the kinetics of the amygdalin and HCN contents. In both debittering methods, the PEF-treated samples with the highest intensity (2.2 kV/cm, 50 kJ/kg) showed higher and faster detoxification efficiency for the investigated compounds as compared to the untreated sample. In particular, the PEF treated samples incubated with water showed a reduction in the amygdalin and HCN contents of up to 86% (up to 72% of the raw material content.). Moreover, the PEF pre-treatment led to comparable efficiency in amygdalin reduction in both debittering processes: 86% reduction for the incubation with water and 81% for the incubation without water. Consequently, the combined application of PEF and the debittering process including incubation without water has remarkable potential as an industrial application due to its inherent reduced water consumption, and therefore, diminished wastewater management issues. A further advantage of this process is the minimizing of sugar loss typically occurring during the debittering through soaking.