Does storage time influence yield and agar properties in the tropical agarophyte Gracilaria cornea?

摘要

The agar yield and quality characteristics of Gracilaria cornea from Yucatan, Mexico, were studied during 18 months of storage. Biomass was stored at a temperature of 22.1 +- 0.9 deg C and humidity of 59.8 +- 3.6%. The agar content varied erratically, but the average value was practically constant over the storage period with an average of 20.1 +- 1.5%. Gel strength, gelling and melting temperatures were negatively affected by the total storage time. No significant changes were found during the first five months for these characteristics with mean values of I 134 +- 57 g cm~(-2) 40.8 +- 0.4 deg C and 91.2 +- 0.9 deg C respectively. Agar degradation was evident after the fifth month and accounted for a 17% loss in gel strength and approx 7% in gelling and melting temperatures. Nevertheless, gel strength values remained around 930 i 23 g cm~(-2) with no significant changes until the end of the storage period. The decrease in gel strength showed a significant relationship with decrease in 3,6-anhydrogalactose but not variation in sulphate content. This was probably due to agar hydrolysis caused by enzymatic processes of endogenous and/or microbial origin. These results suggest that the tropical G. cornea had a similar resistance to degradation during storage to that observed for G. chilensis, a cold water species. Agar quality and yield in G. crimea after one and a half year of storage are within the range of food grade agar.