The FTIR-ATR Spectroscopy As a Biosensing Strategy for Thermal Effects in Permissibility Verification of Lard-Adulterated Palm Oil

Ensuring authenticity of edible oils is vital for consumer trust, regulatory compliance and permissibility assurance, particularly for Muslim consumers. This study introduces a spectral biosensing strategy using Fourier transform infrared spectroscopy coupled with attenuated total reflectance (FTIR-ATR) and chemometric modelling to detect lard adulteration in palm oil (PO) under thermal stress. PO samples spiked with 1%-50% v/v lard were heated from 25 degrees C to 200 degrees C for 30 min, simulating industrial and culinary conditions. FTIR-ATR spectra showed distinct shifts in carbonyl and fingerprint regions due to lard incorporation and heat-induced lipid degradation. Discriminant analysis (DA) achieved 100% classification accuracy across the full spectrum (4000-650 cm-1), demonstrating strong discriminatory power. Partial least squares-discriminant analysis (PLS-DA) identified the fingerprint region (1000-650 cm-1) as most diagnostic, yielding robust performance with R 2 Y = 0.895, R 2 X = 1.000, Q 2 = 0.893 and 100% correct classification in both training and validation datasets. Principal component analysis (PCA) revealed clear clustering of pure and adulterated samples, even under severe thermal conditions. Moreover, using the optimised FTIR-ATR/PLS model, the lard adulteration in thermally treated PO could be reliably detected at levels as low as 1% v/v with LOD and LOQ ranges of 0.01%-1.14% and 0.02%-3.34% v/v, respectively. These findings position FTIR-ATR with multivariate chemometrics as a rapid, nondestructive and thermally resilient platform for lard detection in PO. The approach extends to broader food quality and safety monitoring in real-world processing scenarios.