Monitoring the debittering of traditional stoned green table olives during the aqueous washing process using an electronic tongue

Abstract

Stoned green olives are traditional table olives produced in the Northeast of Portugal. They are highly appreciated due to their sensory characteristics and levels of complex phenols with strong antioxidant activity, having a significant agro-economic relevance. During debittering, stoned olives are immersed in water, which is changed each 2 d during 20 d, leading to the reduction of initial bitterness turning them edible olives. So, monitoring the basic taste, total phenols contents and the bitterness index during washing is very important being a time-consuming and expensive task. Thus, the possibility of using an electronic tongue, coupled with chemometrics, for monitoring debittering of stoned green olives (cvs. Cobrançosa and Negrinha de Freixo), was evaluated for the first time. The electronic tongue allowed discriminating the different debittering time-periods (sensitivity ≥ 62%, internal-validation), monitoring the decrease of bitter and pungent intensities and the increase of the sweet intensity (0.793 ≤ R-Pearson ≤ 0.971; RMSE ≤ 1.388), assessing the decrease of the total phenols (R-Pearson≥0.934; RMSE ≤ 19.1 g GAE/kg) and of the bitterness index (R-Pearson ≥ 0.892; RMSE ≤ 0.864 g Oleuropein/kg). Therefore, the device could be a practical tool to monitor debittering of stoned green olives during washing.