Impact of thermal, high-pressure and ultra-shear pasteurisation technologies on beetroot juice metabolites using untargeted nuclear magnetic resonance spectroscopy

The impact of three food pasteurisation technologies, namely thermal, high-pressure and ultra-shear processing, on the metabolites of beetroot juice was evaluated using a processomics approach with nuclear mass resonance (NMR) as an analytical technique. Two batches of beetroots acquired from different local grocery stores were used for this study. Beetroot juice obtained from these batches was subjected to high-pressure processing (HPP) at 600 MPa and 25 °C for 5 min, ultra-shear technology processing (UST) at 400 MPa and 30 °C and thermal processing (TP) at 96 °C for 12 min. Principal component analysis (PCA) for the two batches indicated that both extrinsic factors such as processing parameters (temperature, pressure, shear and holding time) and intrinsic factors such as the origin of the beetroot influenced the PCA plot. When the influence of intrinsic parameters was minimised by studying a single batch processed by TP, HPP and UST, distinct clusters for different processing methods were formed, indicating that processing influenced the metabolites. While processing is not the main factor determining the final composition, as indicated by PCA with different batches, supervised techniques like orthogonal partial least-squares discriminant analysis (OPLS-DA) and random forest (RF) demonstrated that processing does impact the beetroot juice metabolome. Seven metabolites (leucine, alanine, valine, glutamine, gamma-aminobutyric acid, fructose and glucose) were identified as potential process-induced biomarkers.