Effects of kernel roasting on the physicochemical, compositional, thermal, and spectrometric profiles of palm kernel oil

Abstract

There is limited comparative data on how roasting affects the quality, composition, and usability of palm kernel oil, despite its wide application as an edible and industrial oil. This study investigated the influence of roasting on the characteristics of palm kernel oil obtained from unroasted (Sample A) and roasted (Sample B) kernels to determine how thermal processing impacts yield and quality parameters. The physicochemical properties, proximate composition, and elemental composition of the oils were determined, and characterization was carried out using Differential Scanning Calorimetry (DSC), Fourier-Transform Infrared Spectroscopy (FTIR), and Gas Chromatography-Mass Spectrometry (GC-MS). Sample B (oil derived from roasted kernels) exhibited a significantly (p < 0.05) higher yield and a desirable nutty, caramel-like flavor compared to Sample A (oil derived from unroasted kernel). Conversely, Sample A recorded significantly higher (p < 0.05) acid, iodine, and saponification values, as well as higher ash (0.13%), lipid (96.36%), and protein (2.62%) contents, compared with Sample B, which contained 0.08% ash, 94.35% lipid, and 1.76% protein. FTIR spectra of both samples showed similar absorption patterns, suggesting that roasting did not markedly alter the fundamental functional groups. However, the DSC thermogram of Sample B displayed a broader endothermic peak, indicating changes in fatty acid profile or crystal structure, which was further supported by compositional differences observed in GC-MS analysis. Overall, roasting enhanced the yield and sensory quality of palm kernel, demonstrating its potential as a cost-effective method for improving the oil’s value and application in food and cosmetic industries.