Seasonal variation of agar from Gracilaria vermiculophylla, effect of alkali treatment time, and stability of its Colagar

Abstract

Gracilaria vermiculophylla, from Baja California Sur, Mexico, was studied in order to determine the seasonal variation of yield and quality of native and alkaline agar during 2007-2008. The highest alkaline agar yield was obtained in summer (17%) and the highest gel strength in spring (1,132 gcm −2 ). The highest melting temperature was 98°C (winter). The highest gelling temperature was 68°C (summer). The values obtained are within the range of the most important Gracilaria species harvested worldwide. During the agar extraction step, the best results were obtained after 30 min of alkali treatment with sodium hydroxide (7%), after which the quality decreased significantly. We produced Colagar from G. vermiculophylla which consists of the seaweeds treated with sodium hydroxide and dried. The yield and quality of the agar obtained from the Colagar shows stability in both yield and quality during 1 year of storage, suggesting that alkali treatment is a good method of avoiding agar hydrolysis during storage.

Seasonal variation in agar composition and properties from Gracilaria gracilis (Gracilariales, Rhodophyta) of the Patagonian coast of Argentina

“…Positive relation between biomass production and agar yield has been informed for G. gracilis (Rebello et al ., ; Marinho‐Soriano & Bourret ), Gracilaria sp. (Chirapart & Ohno ), G. verrucosa (Yenigül ) and G. vermiculophylla (Vergara‐Rodarte et al ., ). On the other hand, an inverse relation between seawater temperatures and agar yields has been reported by Bird and Ryther () and Mollet et al .…”

Optimization of yield and quality of agar polysaccharide isolated from the marine red macroalga Pyropia yezoensis

“…Measurements of the two parameters were performed at 20°C under conditions where each sample was compressed to 80% of its original height with a crosshead speed of 1 mm/s. The melting temperature and gelling temperature for the agar products was determined as described in [11][12] with slight modifications. A 1.5% w/v agar with 70 mm height was prepared in a test tube (10 mm diameter, 90 mm height) and then an iron ball (5 mm diameter, 1 g) was placed on the surface of the gel and the tube was clamped in a water bath that was programmed to increase in temperature by 1°C /min.…”

“…The capacity of agar to gel, with concomitant high water absorption, contributed to the epoch-making advance of using agar to solidify media in plates for bacterial culture [2][3]. Although not all red seaweeds contain agar, Gracilariaceae including Gracilaria, Curdiea, and Hydropuntia [4][5][6][7][8][9][10][11][12][13][14][15][16][17], as well as Gelidium and Pterocladia of the Gelideales [6,[18][19][20][21][22][23][24] are major agar sources [25]. Agar from these seaweeds represents complex polysaccharide structures consisting of agarose and agaropectin [1].…”

Integral Utilization of Red Seaweed for Bioactive Production

“…The agar properties are dependent on the species and environmental characteristics of the collection or cultivation area, such as season, life cycle and geographical features [36,37] and the storage, extraction processes and postharvest storage [24,32,38,39,40,41]. The quality of agar is determined by the type, pattern and degree of substitution as well as molecular weight, chemical composition (pyruvate, methyoxyl and sulfate) and physical properties (gel strength, gel syneresis, viscosity, gelling and melting temperatures) that determine its market value [30,32,42].…”