SIALIC-ACID CONTENTS IN CHICKEN EGGS AND TISSUES

Sialic acid contents were determined as potential commercial sources i n egg fractions (yolk, white, chalaza, yolk membrane and shell membran e), oviduct, and rooster comb and wattle tissues by the periodate-thio barbituric acid method with a partial modification. In egg fractions, the concentration of sialic acid was highest (P < 0.05) in yolk membra ne (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 lo wer (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.