Affiliations 

  • 1 †School of Chemical Sciences, Universiti Sains Malaysia, Penang, Malaysia
  • 2 §Division of Inorganic and Physical Chemistry, Institut Teknologi Bandung, Bandung, Indonesia
  • 3 ⊥National Institute of Education, Nanyang Technological University, Singapore
  • 4 #Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia
  • 5 ΔFaculty of Chemistry and Pharmacy, University of Sofia, Sofia, Bulgaria
J Agric Food Chem, 2015 May 13;63(18):4655-63.
PMID: 25897618 DOI: 10.1021/acs.jafc.5b00380

Abstract

The efficiency of zeolite X nanocrystals (FAU-type framework structure) containing different extra-framework cations (Li(+), Na(+), K(+), and Ca(2+)) in slowing the thermal oxidation of palm oil is reported. The oxidation study of palm oil is conducted in the presence of zeolite nanocrystals (0.5 wt %) at 150 °C. Several characterization techniques such as visual analysis, colorimetry, rheometry, total acid number (TAN), FT-IR spectroscopy, (1)H NMR spectroscopy, and Karl Fischer analyses are applied to follow the oxidative evolution of the oil. It was found that zeolite nanocrystals decelerate the oxidation of palm oil through stabilization of hydroperoxides, which are the primary oxidation product, and concurrently via adsorption of the secondary oxidation products (alcohols, aldehydes, ketones, carboxylic acids, and esters). In addition to the experimental results, periodic density functional theory (DFT) calculations are performed to elucidate further the oxidation process of the palm oil in the presence of zeolite nanocrystals. The DFT calculations show that the metal complexes formed with peroxides are more stable than the complexes with alkenes with the same ions. The peroxides captured in the zeolite X nanocrystals consequently decelerate further oxidation toward formation of acids. Unlike the monovalent alkali metal cations in the zeolite X nanocrystals (K(+), Na(+), and Li(+)), Ca(2+) reduced the acidity of the oil by neutralizing the acidic carboxylate compounds to COO(-)(Ca(2+))1/2 species.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.