Yield and Physical Characteristics of Agar from Gracilaria chorda Holmes: Comparison with Those from Southeast Asian Species.

Abstract

The yield, gel strength, viscosity, gelling temperature, melting temperature, and pH of agar obtained after alkali treatment (5% NaOH, 60-80-degrees-C, 2 h) of Gracilaria chorda from Japan were compared with those from G. fisheri of Thailand, G. coronopifolia, G. verrucosa, and G. sp. of the Philippines, and cultured or wild G. edulis of Malaysia. Agar with the highest yield (26.1%) and gel strength (gel strength (GS): 1139 +/- 18 g/cm2; gelling temperature: 40-degrees-C; melting temperature: 95-degrees-C) was obtained from G. chorda after alkali treatment at 80-degrees-C. These results indicate that G. chorda could be used as a principal source of agar. G. fisheri (GS: 716 +/- 8 g/cm2), G. verrucosa (GS: 608: 14 g/cm2), and G. sp. (GS: 621 +/- 4 g/cm2) may be utilized as supplementary materials in industrial agar production, although their respective yields at 14.3, 14.7, and 10.8% were low. Alkali treatment was not effective for cultured G. edulis of Malaysia; however, it may be used without alkali treatment (GS: 487 +/- 10 g/cm2) in conventional agar production. Wild G. edulis had a high agar yield (20.6%) but the gel strength was low (331 +/- 20 g/cm2). G. coronopifolia had the lowest agar yield (10.3%) and gel strength (201 +/- 5 g/cm2). Other alkali treatment conditions should be tried for wild G. edulis and G. coronopifolia.