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J. K. Kibet ¹, N. Rono ¹, F. I. Okanga ¹, C. C. Kurgat ¹

Affiliations
1 Department of Chemistry, Egerton University, P.O Box 536 –20115, Egerton, KE

Abstract

The environmental fate of thermally released organic toxins including radical formation from high temperature cooking has received mounting global concern due to the potential health impacts associated with them. Therefore, this contribution investigates the thermal degradation kinetics of pyrolysis products of red meat under conditions representative of high temperature cooking. Evolution of selected molecular toxins was monitored using an in-line Gas Chromatography hyphenated to a mass spectrometer (GC-MS) in the temperature range 500 - 525°C. The primary focus is to propose a kinetic model for the thermal destruction of bio-hazardous byproducts; 2-(ethylthio)phenol, indole and 2,3-dimethylhydroquinone within a temperature region 723 and 798 K using pseudo-first order rate law. A reaction time of 2.0 s was employed in line with the average residence time in combustion systems. Nonetheless, for the formation kinetics of 2-(ethylthio)phenol), various cooking times were chosen. Kinetic results showed that the destruction rate constants for indole, 2,3-dimethylhydroquinone, and 2-(ethylthio)phenol at 798 K were 1.19, 1.42, and 1.35 s^-1 respectively. GC-MS results revealed the amount of 2-(ethylthio)phenol evolved decreased with increase in the cooking time. The scission of the phenyl-sulphur linkage in 2-(ethylthio)phenol was determined using the density functional theory (DFT) and found to proceed with an energy barrier of 319.31 kJmol^-1. The band-gap energy for 2-(ethylthio)phenol was calculated using Chemissian and found to be 5.298 eV. The kinetic behavior of combustion by-products from red meat is important in understanding the formation of environmentally toxic free radicals from high temperature cooking considered harmful to human health and natural ecosystems.

Keywords

2-(Ethylthio)Phenol, Cooking Time, Rate of Destruction, Toxicity.

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C. C. Kurgat ¹, J. K. Kibet ¹, P. K. Cheplogoi ¹, S. C. Limo ², P. M. Kimani ¹

Affiliations
1 Department of Chemistry, Egerton University P.O Box 536 - 20115, Egerton, KE
2 Department of Physics, University of Eldoret, P.O. Box 1125-30100, Eldoret, KE

Abstract

The popularity of tobacco use worldwide has kicked off one of the greatest clinical debates on human toxicology and public health in general. Accordingly, this study investigates some of the alkaloids in tobacco believed not only to be addictive and carcinogenic but also as precursors for other related medical problems. The characteristic behaviour, identification and product evolution of β-nicotyrine and 3,5-dimethyl-1-phenylpyrazole in tobacco is reported extensively in this study for the first time. Two commercial cigarette brands coded SM1 and ES1 were explored for evolution of major alkaloids over a modest temperature range of 200 - 700 ̊C for a total pyrolysis time of 3 minutes using a tubular quartz reactor, typically in increments of 100 ˚C using nitrogen as the pyrolysis gas at a residence time of 2.0 seconds under 1 atmosphere pressure. The heating rate of the heater was ~ 20 ˚C s^-1. The pyrolysate was passed over 10 mL analytical grade methanol and analyzed using a Gas-Chromatography hyphenated to a mass spectrometer (GC-MS) with a mass selective detector (MSD). GC-MS results showed that nicotine was the major alkaloid in both cigarettes reaching a maximum at ~ 400 ˚C (8.0 x 10⁸ GC-Area counts) for ES1 cigarette and 500 ˚C (~2.7 x 10⁸ GCArea counts for SM1 cigarette. Clearly, the ratio of nicotine for ES1 to SM1 is approximately 3 indicating that ES1 cigarette is rich in nicotine. Based on this data alone, ES1 cigarette was found to be more addictive.

Keywords

Alkaloid, Pyrolysate, Toxicology, β-Nicotyrine.

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