HAZELNUT TESTA AS A BY-PRODUCT: NUTRITIONAL COMPOSITION, ANTIOXIDANT ACTIVITY, PHENOLIC COMPOUND PROFILE AND DIETARY FIBER CONTENT

Objective: The aim of this study is to determine hazelnut testa which is a good example of agro-food by-products as a potential source of natural antioxidants and functional food ingredients. Material and Method: Ultrasound assisted extraction (UAE) was used for less analysis time in both determination of dietary fiber and the phenolic compounds. The total dietary fiber contents were determined using both the Association of Analytical Chemistry (AOAC) methods and the enzymatic-chemical method. Result and Discussion: The results presented that hazelnut testa had a relatively high phenolic content both the extract obtained by CE (1413.32 mg gallic acid equivalent (GAE)/g dry matter) and UAE in 5 min (1420.86 mg GAE/g dry matter). The extract obtained by UAE possessed higher antioxidant activity than the extract obtained by CE in both antioxidant activity methods. Three phenolic compounds identified in the extract obtained by CE while four phenolic compounds found in the extract obtained by UAE. In the enzymatic-chemical method, the dietary fiber in the extract obtained by CE contained 68.93% while the extract obtained by UAE was 70.69%. Our results suggested that hazelnut testa can be used in the preparation of low calorie, high fiber, and antioxidant-rich foods, food supplements, and active pharmaceutical ingredients