Extraction of dietary fiber from kinnow (Citrus reticulata) peels using sequential ultrasonic and enzymatic treatments and its application in development of cookies

The paradigm shifts from discarding horticulture byproducts to exploiting them for their bioactive potential has encouraged research on non-conventional extraction techniques such as extraction using microwave, ultrasound, high-pressure, etc. Kinnow peels, a primary residue of kinnow processing industry, are profuse with polysaccharides, such as dietary fiber which can be isolated and used as a functional ingredient in fortified/enriched foods. In the present study, ultrasound-assisted extraction (UAE) and ultrasound-assisted-enzymatic extraction (UAEE) have been optimized to maximize dietary fiber yield from kinnow peel waste. Total dietary fiber (TDF) of 52.042 ± 0.862% was observed using UAE at 38% amplitude, liquid to solid ratio (LSR) of 40 mL/g, at 44 °C, after sonication time of 13 min, which increased to 60.974 ± 0.827% upon sequential enzymatic treatment. The WHC, OHC, and GAC of extracted dietary fiber ranged between 8.17 and 9.24 ± 0.11 g/g, 2.96–4.68 ± 0.09 g/g, and 1.56–2.28 ± 0.04 mmol/g. The physicochemical characterization of dietary fiber using analytical instruments and its functional properties such as oil/water holding, and glucose adsorption capacities proved that kinnow peels dietary fiber can be used to develop fiber-enriched products. The extracted fiber has been used to develop cookies which showed good nutritional, sensory, and textural properties with an overall acceptability of 7.15–7.84. This research will be helpful in scale-up studies on the valorization of different citrus peels through an extraction approach.