EFFECT OF THE ALKALINE TREATMENT ON THE PRODUCTIVITY AND PHYSICAL PROPERTIES OF AGAR-AGAR FROM GRACILARIA VERRUCOSA

Abstract

The effect of the alkaline treatment on the yield of the extraction and physical properties of agar from Gracilaria verrucosa collected in Santa Verónica (Atlántico, Colombia) was investigated. The concentrations of sodium hydroxide solutions during the alkaline treatment were 3, 5, 7 and 10 /w/v), while temperature was mainteined in the range of 80-85 °C. The agar yield, gel strength, melting and gelification temperatures were determined. Although the maximum yield was obtained with 10 % sodium hydroxide solution, the maximum gel strength was obtained at 3 %. The agar-agar was used as a base of nutritive agar for 23 bacterial cultures and the productivity was measured using the ecometric method. From the bacterial strains tested, Salmonella Enteriditis, Salmonella Typhimurium, Salmonella Cholerauis and Morganella morganii did not grow in the test of commercial media. The measures of relative growth index showed that nutritive agar from G. verrucosa have the same or better properties than the comercial ones.