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Characterization and Classification of Gamma-Irradiated Adipose Tissues Using Raman Spectroscopy and Chemometrics

Ramazan Kizil, Chemical Engineering, Istanbul Technical University, School of Chemical & Metallurgical Engineering, B-410 Chemical Engineering Department, Istanbul, 34469, Turkey and Joseph Irudayaraj, Agricultural & Biological Engineering, Purdue University, West Lafayette, IN 47907-2093.

Elucidation of irradiation damages to the structure of lipids is important to both cellular radiobiology and food irradiation fields. Lipid peroxidation is a major damaging process in membranes and liposomal dispersions and is responsible for the impairment of enzyme activities, chemically-induced toxicity and damages to DNA. Treatment of fats with ionizing radiation is believed to accelerate lipid oxidation via the action of various unstable free radicals.

Raman spectroscopy, a nondestructive analytical technique, was employed to characterize irradiation-induced changes in the chemical composition of adipose tissues at the molecular level. Adipose tissue is a connective tissue that functions as the major storage site for fat in the form of triglycerides.

We have investigated 1 kGy to 10 kGy gamma irradiation damages on the molecular structure of lamb, beef and porcine adipose tissues using Fourier transform Raman spectroscopy. Gamma irradiation-induced changes on the saturation level of fatty acids and the extent of lipid peroxidation were monitored by screening the C=C and C=O stretch related Raman scattering modes. The most irradiation sensitive vibrational modes was found to be the C-H stretch modes detected at 1302 cm-1 and 2800-3000 cm-1 region of Raman spectrum, probably due to the abstraction of hydrogen atoms from the aliphatic tail groups by the attack of free radicals. The irradiation perturbed Raman data was treated with a chemometric model, canonical variate analysis, to differentiate adipose tissues based on the extent of irradiation.

This presentation covers the radiochemistry of lipids and characterization of radiochemical changes upon irradiation at the molecular level. The potential of Raman spectroscopy along with a proper multivariate qualitative analysis method to discriminate adipose tissues with respect to the applied dose will be demonstrated. Since the proposed methodology investigates the radiation damages at the molecular level and can differentiate different dose irradiated tissues it has a potential for the rapid assessment of the safety and labeling of irradiated lipid containing food.