Extraction of antifreeze proteins from cold acclimated leaves of Drimys angustifolia and their application to star fruit (Averrhoa carambola) freezing

Antifreeze proteins (AFPs) have the ability to modify ice crystal growth and thus there is great interest in identifying new sources of these compounds. All extracts of cold acclimated leaves of Drimys angustifolia, obtained using different buffers, inhibited recrystallization and they presented similar SDS-PAGE profiles, with bands close to 20 and 37 kDa. The extract obtained using Tris-HCl/DDT buffer (pH 8) was used in the pre-treatment of frozen star fruit (Averrhoa carambola) by immersion or vacuum infiltration. The treatments did not affect the titratable acidity, pH, soluble solids, ascorbic acid content and colour. However, only star fruits that were vacuum infiltrated with AFPs retained their drip loss constant after 15 days. Moreover, with this treatment the star fruit firmness was maintained on thawing after 60 days of storage. The vacuum infiltration of Drimys angustifolia AFPs into the star fruit allowed an initial cryoprotection, indicating that the application of AFPs can increase the quality of frozen star fruit.