Influence of hot-air temperature on drying kinetics, functional properties, colour, phycobiliproteins, antioxidant capacity, texture and agar yield of alga Gracilaria chilensis

Effect of air temperature on drying kinetics, functional properties, phycobiliproteins (PE and PC), colour, antioxidant capacity, total phenolic content, texture and agar yield during drying of algae Gracilaria chilensis were studied. Drying curves were satisfactorily simulated with the Weibull model at 40, 50, 60 and 70 °C. Both, Rehydration Ratio and Water Holding Capacity decreased with increasing temperature. Low drying temperatures showed higher PE and PC concentration than higher temperatures (e.g. 60 and 70 °C). In particular, dehydration at 50 °C presented the higher values of these two pigments. The three chromatic coordinates (L∗, a∗ and b∗) were influenced by the treatments showing the highest ∆E value at 50 °C. Antioxidant activity as well as texture were notably influenced by increasing drying temperatures. At 70 °C, a maximum agar yield of 40 g/100 g was obtained. Results indicated that agar yield and quality of dried algae showed opposite behaviours leading to a compromise decision on operating conditions involved in the overall process. According to these results, optimization of the process based on economical aspects of the final dried product is required.

► The Chilean region between Coquimbo and Chiloé is an important producer of the red algae Gracilaria. ► In this study, convective dehydration (40-70 °C) was applied as a preservation technology. ► Colour, rehydration indices, texture and antioxidant activity of dried algae decreased with process temperature. ► A maximum agar yield was obtained at 70 °C. ► Agar yield and quality of dried algae showed opposite behaviours. A compromise decision on operating conditions is required.