Effect of Sucrose On some Physical Properties Of Different Philippine Agars
Jumelita B. Romero*1, Marco Nemesio E. Montaño2, Florina A. Merca1, Rowena Grace O. Rumbaoa2, and Ronald D. Villanueva2
1Institute of Chemistry, University of the Philippines Los Baños, College, Laguna, Philippines
2Marine Science Institute, University of the Philippines Diliman, 1101 Quezon City, Philippines
3Mindanao State University Tawi-Tawi, Bongao, 1702 Tawi-Tawi, Philippines
The effect of sucrose on some gelling properties of agar extracts from six Philippine agarophytes: Gracilaria eucheumoides, G. firma, G. salicornia, Gelidiella acerosa, Gracilariopsis heteroclada and Laurencia flexilis were investigated with Bacto-agar, as reference. Sucrose-agar gels consisted of 50% sucrose in 1.5% (w/w) agar solution. Control gels contained 1.5% aqueous agar solution. Addition of sucrose resulted in significant increase (p<0.05) in the gel strength and the gelling and melting temperatures of gels prepared from G. eucheumoides, G. firma, G. salicornia, L. flexilis, G. heteroclada and Bacto-agar. On the other hand, syneresis index decreased. Similar effects were observed with Gelidiella acerosa agar except for its gel strength which decreased in the presence of sucrose. Chemical analysis indicated high 3,6-anhydrogalactose and low sulfate contents of agar samples. The FT-IR spectra indicated sulfation at C-4 on the galactose residues of G. eucheumoides, G. firma, G. salicornia and L. flexilis agars. These agars were classified “sucrose-reactive” based on their gel strengths which increased more than twice that of the control upon sucrose addition.
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