Effects of different extraction methods on physicochemical properties of dietary fiber from defatted olive (Olea europaea) pomace flour

Abstract

The current research aims to compare the effect of green (enzymatic and ultrasoundic) and conventional (acidic and alkaline) extraction methods on the yield (total-dietary fiber (TDF), soluble-dietary fiber (SDF) and insoluble-dietary fiber (IDF)), chemical composition, and hydration properties of olive-pomace DF. The rheological properties of doughs containing different amounts (0, 5, 10, and 15%) of SDF were investigated. The yield of TDF was 74.79 (ultrasonic method)- 90.2% (enzymatic method) which 12.12 -21.68 % of them was SDF. The moisture content of SDF was higher than IDF. The ash and protein contents of IDF were higher than SDF. The extraction method had no significant effect on the moisture and ash content of SDF. The lowest protein content was observed in DF extracted by the enzymic method (P < 0.05). The highest and lowest swelling-power and solubility-index were obtained for the fiber extracted by the enzymic and ultrasonic methods, respectively due to the level water absorption of this fiber. The enrichment of wheat flour with SDF extracted by enzymatic method showed by increasing the fiber level to 10%, the dough-development, stability time and FQN increased, while the softening-degree decreased significantly. Replacing 15 % wheat-flour with SDF led to increasing resistance to extension and energy of doughs. The extensibility of the dough increased significantly with the addition of 5% fiber, while the addition of 10% fiber reduced this index to less than the control value. Overall, although the performance of the enzymatic method was significantly higher than other ones, this method was very time-consuming which limits its application in food-industry. Using a combination of green methods to accelerate enzymatic extraction can be a topic for future research. Furthermore, the replacement of ⁓10 % of wheat flour with SDF showed acceptable rheological properties which can meet the expectation for high-quality and nutritional value bread.

Keywords

• dietry fiber
• enzyme
• ultrasound
• olive pomace
• doughs rheological properties