Geographical discrimination of Asian red pepper powders using 1H NMR spectroscopy and deep learning-based convolution neural networks.

This study investigated an innovative approach to discriminate the geographical origins of Asian red pepper powders by analyzing one-dimensional 1H NMR spectra through a deep learning-based convolution neural network (CNN). 1H NMR spectra were collected from 300 samples originating from China, Korea, and Vietnam and used as input data. Principal component analysis - linear discriminant analysis and support vector machine models were employed for comparison. Bayesian optimization was used for hyperparameter optimization, and cross-validation was performed to prevent overfitting. As a result, all three models discriminated the origins of the test samples with over 95 % accuracy. Specifically, the CNN models achieved a 100 % accuracy rate. Gradient-weighted class activation mapping analysis verified that the CNN models recognized the origins of the samples based on variations in metabolite distributions. This research demonstrated the potential of deep learning-based classification of 1H NMR spectra as an accurate and reliable approach for determining the geographical origins of various foods.

Changes of molecular mobility of ascorbyl palmitate and α-tocopherol by phospholipid and their effects on antioxidant properties in bulk oil.

Molecular mobility of ascorbyl palmitate and α-tocopherol in the presence of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were determined by NMR relaxation technique. Synergistic effects of DOPC on the antioxidative capacities of ascorbyl palmitate were evaluated in DPPH radical scavenging assay and bulk oil matrix. NMR relaxation technique can provide information on the mobility of protons. Molecular mobility of two protons in hydroxyl group of ascorbyl palmitate decreased by 85 and 78% in the presence of DOPC compared to those without DOPC. However, proton mobility of α-tocopherol increased by 41% when DOPC was present. DOPC significantly enhanced the DPPH reactivity in medium chain triacylglycerol, while this effect was not observed in α-tocopherol. Mixture of ascorbyl palmitate with DOPC showed synergistic antioxidant properties in corn oil at 60 °C. DOPC may make protons of ascorbyl palmitate in more rigid state, which can enhance hydrogen donating ability and antioxidant properties of ascorbyl palmitate in bulk oils.