Seasonal variation of nutritional and antioxidant properties of different Kappaphycus alvarezii strains (Rhodophyta) farmed in Brazil

Antioxidant potential, carbohydrate content, ash, minerals, proteins, and amino acids of Kappaphycus alvarezii farmed along the São Paulo coast, Brazil, were evaluated to support the best use of four strains and new applications with added value. Ash content ranged from 25.60 to 11.65%. Mineral contents varied from 10,130.90 ± 1,613.78 mg (100 g)−1 DW (summer 2018) to 12,561.20 ± 2,190.72 mg (100 g)−1 DW (summer 2017), and the highest mineral contents occurred in the green strain. Carbohydrate levels varied from 122.92 ± 15.11 mg g−1 DW (summer 2017) to 231.79 ± 16.86 mg g−1 DW (winter 2017), and the highest carbohydrate value was observed in the G11 strain. The highest protein amount was observed in the brown strain with 8.79 mg (100 g)−1 DW. The highest antioxidant potential of K. alvarezii was in spring 2017 for the brown strain. Total phenolic content ranged from 41.77 ± 15.41 to 366.58 ± 109.17 mg GAE g−1 DW, DPPH activity ranged from 13.29 ± 1.20 to 61.07 ± 3.43%, FRAP ranged from 58.73 ± 3.96 to 105.54 ± 6.60%, and ABTS varied from 95.29 ± 4.31 to 112.52 ± 1.41%. Therefore, nutritional and antioxidant properties of K. alvarezii varied according to strains and seasons, with the best result in the spring of 2017. In summer and autumn of 2017, the green strain had better nutritional and antioxidant profiles, whereas in the winter of 2017 and spring of 2017 it was the G11 strain and in the summer of 2018 it was the red strain.