Optimisation of Spirulina platensis convective drying: evaluation of phycocyanin loss and lipid oxidation

The aim of the study was the optimisation of Spirulina platensis drying on convective hot air through the response surface methodology. The responses were thiobarbituric acid (TBA) and phycocyanin loss percentage values in final product. Experiments were carried out in perforated tray drier with parallel air flow, and the wet samples thickness and drying air temperatures were in range of 3–7 mm and 50–70 °C, respectively. The statistical analysis showed significant effect (P < 0.05) for air temperature and samples thickness. In the best drying condition, 55 °C and 3.7 mm, presented the phycocyanin loss percentage and the TBA values of approximately 37% and 1.5 mgMDA kg−1, respectively. In this drying condition, the fatty acids composition of the microalgae Spirulina did not show significance difference (P > 0.05) in relation to fresh biomass. The lipid profile of dried product presented high percentage of polyunsaturated fatty acids (34.4%), especially the gamma-linolenic acid (20.6%).

Evaluation of mechanical properties and water vapor permeability in Chitosan biofilms using Sorbitol and Glycerol

Chitosan biofilms were prepared with and without plasticizer (glycerol and sorbitol). The physical and mechanical properties of chitosan biofilms with and without plasticizer were evaluated. Chitosan was obtained from shrimp wastes and characterized. The film forming solution (FFS) was obtained through chitosan dissolution and drying. The solution had its pH adjusted to 6.0 and oven dried (40 8C, 24 h) with forced air circulation. Chitosan biofilms without plasticizer showed a tensile strength about 36% higher than biofilms produced with plasticizer. On the other hand, biofilms with plasticizer presented superior values of elongation. The permeability of the water vapor and color presented significant difference (p<0.05) between all biofilms. Chitosan/plasticizer biofilms showed higher values of water vapor permeability in relation to chitosan biofilms without plasticizer.