The effects of freezing and thawing on Alaria esculenta

Abstract

Seaweeds must be stabilised shortly after harvesting to avoid rapid deterioration. To handle large amounts harvested during a short period, freezing and frozen storage until utilisation or further processing is one of the methods used industrially. The aim of this study was to assess the effects of different freezing and thawing procedures on Alaria esculenta by analysis of the chemical composition of the seaweed and the drip loss expelled during thawing. Thawing of industrially frozen A. esculenta resulted in a drip loss of 57% of wet weight. The drip loss had a dry matter content of 7% of wet weight, of which 71% was mineral content. Analysis showed that, of the dry matter excluding ash, alanine, aspartic acid, and mannitol were the main components lost to the drip loss. Experiments with a second batch of A. esculenta looking at quick and slow freezing and thawing showed that quick freezing resulted in a significantly lower drip loss than slow freezing; 20% compared to up to 42% of wet weight. Dry matter and mineral content of the drip loss of these samples were all around 6% of wet weight and 31% of dry weight. For some applications it might be of interest to reduce the concentration of potentially toxic elements such as iodine and heavy metals, but due to a high loss of other biomass this was not very effectively done by freezing and thawing. For preservation purposes, quick freezing is the best alternative to retain seaweed biomass.