Characterisation and sensory evaluation of formulated low glycemic index biscuits from Baccaurea angulata pomace

Abstract

The addition of fruits fiber in bakery products such as biscuit has been shown to improve blood glucose response. Bacaurea angulata is one of the underutilized fruit, which may have some potential benefits to health. The effect of two different ways of drying, which are hot air drying and freeze drying on chemical properties of B.angulata was examined. The chemical analysis includes proximate analysis, antioxidant properties and dietary fiber composition. Four different amount of hot air dried B.angulata pomace (0 %, 10 %, 20 % and 30 %) were incorporated in the biscuit formulations substituting wheat flour. Shortening content was reduced to 40 %, 30 % and 20 % of the weight flour. The effects of supplementation of hot air dried B.angulata pomace on physical qualities as well as sensory properties of sixteen biscuits were determined. Four formulations with the highest overall acceptance score were selected for further analysis on chemical properties and blood glucose response. There were full fat control biscuit (FFC), full fat with 10 % pomace biscuit (FF10), full fat with 20 % pomace biscuit (FF20) and 40 % fat with 10 % pomace biscuit (RF10). Blood glucose response was assessed on twenty healthy non-diabetic subjects, where they were required to consume reference food (glucose drink) and four test biscuits after an overnight fasting in different sessions with at least one day gap. Each test meals contained 50g available carbohydrate. Blood samples were collected from finger-pricks in fasted subjects before each test (0 min) and at 15, 30, 45, 60, 90 and 120 minutes after consumption of reference or test biscuits. The GI was calculated as ratio of incremental areas under curve (IAUC) of test biscuits with IAUC of reference food. Hot air dried pomace contained significantly higher moisture and lignin in comparison to the freeze-dried pomace. In contrast, freeze-dried pomace showed significantly higher total ash, cellulose and resistant starch. There were no significant differences in total, insoluble, soluble dietary fiber and total fructan content with different types of drying. Freeze-dried pomace also sustained better antioxidant activity showed by significantly lower IC50 value of DPPH and ABTS, 39.78±0.69 mg/ml and 4.98±0.39 mg/ml respectively in comparison to the hot air dried pomace. The physical and sensory properties of pomace fortified biscuits were significantly affected by fat and pomace level, where FF10 biscuits showed the best preferences among consumers. However, further chemical studies suggested greater nutritional values in FF20 biscuit, where it contained the highest total dietary fiber (6.65±2.90 g/100g) and resistant starch (0.4±0.14 g/100g) although not significantly different from FFC biscuit. FF20 biscuit also contained significantly higher antioxidant properties, DPPH (0.76±0.29 mg TE/g) and ABTS (3.69±0.15 mg TE/g) in comparison to other type of biscuits. All four tested biscuit types, including the FFC biscuit, showed low GI ranging from 44 to 54. Therefore, fortification of biscuits with B.angulata pomace was suitable to produce low GI food.