The relationship between maturity and quality of boiled products of 'akamoku' Sargassum horneri collected off Oshima Island (Fukuoka [Japan] Prefecture)

'Akamoku' Sargassum horneri belongs to the algae family and is widely distributed in coastal areas of Japan. Although historically a boiled form of akamoku has been consumed only in part of the Tohoku region of Japan, interest in akamoku as a food has recently been increasing in other areas. In this study, we made akamoku processed foods from fresh akamoku algae harvested from December 2005 to April 2006 in the Chikuzen Sea of Fnkuoka prefecture. The fresh akamoku algae were processed as follows: the algae were classified according to harvested period, and each of the algae was boiled with diluted seawater and then ground into small pieces. The tenacity, fucoidan content and color of the processed products were measured to evaluate quality. For products from akamoku algae collected from December 2005 to January 2006 (the early growth period), the fucoidan content was low (0.03-0.49 g/100 g (wet basis)) as was the tenacity (33-36 J/square m). On the other hand, the fucoidan content and the tenacity increased in the products using akamoku algae gathered from February 2006 to April 2006, which corresponded to the late growth period of akamoku. The amounts of fucoidan and tenacity in the product using akamoku algae in the late growth period were 0.57-0.66 g/100 g (wet basis) and 94-115 J/square m, respectively. The maturity rate of akamoku alga in the early growth period was 0%. Then the rate gradually increased with the time of the akamoku harvest, and finally reached 100% for akambku algae harvested in March 2006. The maturity rate of the algae body is proportional to the fucoidan content and the tenacity in the processed product. In other words, the maturity rate of the akamoku algae in fields is a good indicator of product quality. The color of boiled young akamoku is green, which is preferred by consumers. However, the color becomes brown gradually with the growth of the akamoku algae. From these results, we conclude that the alga body just before maturity is the most suitable for akamoku processed food.