SIALIC-ACID CONTENTS IN CHICKEN EGGS AND TISSUES

Sialic acid contents were determined as potential commercial sources in egg fractions (yolk, white, chalaza, yolk membrane and shell membrane), oviduct, and rooster comb and wattle tissues by the periodate-thiobarbituric acid method with a partial modification. In egg fractions, the concentration of sialic acid was highest (P < 0.05) in yolk membrane (13.7 +/- 0.5 mu g mg(-1)), higher (P < 0.05) in chalaza (5.1 +/- 0.2 mu g mg(-1)) and yolk (5.2 +/- 0.4 mu g mg(-1)) than in white (2.2 +/- 0.3 mu g mg(-1)), and lowest (P < 0.05) in shell membrane (0.6 +/- 0.1 mu g mg(-1)). In oviduct, the concentration of sialic acid was lower (P < 0.05) in magnum (3.7 +/- 0.6 pg mg(-1)) than in the remaining regions, among which the concentration was similar (5.6 +/- 0.3 mu g mg(-1)). The sialic acid concentration was similar in comb and wattle tissues (2.6 +/- 0.4 mu g mg(-1)). Sialic acid containing glycopeptide fractions were isolated from yolk, white, and comb and wattle tissues by papain proteolysis and gel chromatography.