Thai Purple Sweet Potato Flours: Characteristic and Application on Puffed Starch-Based Snacks

Characteristics and properties of 4 Thai purple sweet potato flours, Maejo 343, Phichit 65-3, Phichit 290-9 and Torperk were determined in terms of native and pre-gelatinized flours. Color, physicochemical properties and antioxidant activity of native and pre-gelatinized flours depend on their varieties. All native flours showed low redness (a*) and blueness (-b*) values but high pasting properties. Pre-gelatinized flours had a unique purple color and high antioxidant activity. Flours produced by Phichit 65-3 showed a deep intense purple color, high anthocyanins and good antioxidant activity. Both native and pre-gelatinized Phichit 65-3 flours were used as the main raw materials of air-puffed pre-gelatinized flours with different ratios at 10%, 30% and 50%. Increasing the content of pre-gelatinized flours improved color, expansion and antioxidant activity of snacks. Low hardness (9.55-11.65 kg) was presented in all snacks prepared from sweet potato flours. Purple sweet potato snacks prepared from 50% pre-gelatinized flour had good appearance, light texture, high anthocyanins and high antioxidant activity. Results showed that Thai purple sweet potato flours can be used to produce healthy snacks with improved appearance and texture. They also have potential as sources of natural colorants and antioxidants in food products.