Effect of gamma irradiation at various temperatures and packaging conditions on chicken tissues. I. Fatty acid profiles of neutral and polar lipids separated from muscle irradiated at -20°C.

Abstract

A lipid composition study on irradiated chicken muscle is reported. All muscle samples, packed either under air or vacuum, were gamma irradiated (-20°C) at 0, 1, 3, 6 and 10 kGy using 137Cs (dose rate = 0.1 kGy/min). Lipids were isolated from the muscle using a dry column extraction method with concominant isolation of separated neutral and polar fractions. Lipid isolates were converted to their methyl esters and analyzed by capillary column gas chromatography with computer assisted data storage, followed by data consolidation and statistical computer analysis. Separated fatty acid profiles for neutral and polar lipids were obtained as normalized reports (each fatty acid as percentage of total fatty acids) and as “gravimetric” reports (mg of each fatty acid/100 g tissue). In each set, side by side profiles allowed comparative and statistically valid (p < 0.05) conclusions to be made for the effects of different irradiation levels at -20°C on air or vacuum packed samples. Fatty acids were grouped into classes such as saturated and unsaturated, the latter subgrouped as monoenoic, dienoic and polyenoic unsaturated for ease of comparison. Separate analysis of polar fractions allowed detailed examinations of the polyunsaturated fatty acids to be made and gave profiles representative of muscle cells separate from contiguous intramascular adipose cells. Normalized reports showed only negligible occurrence of significant changes in fatty acid profiles of neutral muscle lipid fractions regardless of irradiation doses (0 to 10 kGy) in either air and vacuum packaging. These differences were not apparent when the data were compiled as gravimetric reports. The polar lipid fractions containing the nutritionally significant ω3 and ω6 fatty acids showed only slight changes in normalized and gravimetric reports and were similarly unaffected with increasing levels of irradiation. Additionally, no new fatty acids or other artifacts due to gamma-irradiation were observed in detectable amounts by gas chromatography in any lipid fractions.