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Article history
Received: 28 November 2019
Received in revised form: 19 May 2020
Accepted: 4 June 2020
Keywords
Actinomycetes cellulase,
crystallinity,
dietary fibre,
functional properties,
morphological characteristics,
thermal and non-thermal treatments
Abstract
Cassava pulp is a by-product of tapioca flour manufacturing, which mainly composed of starch and fibre. The purpose of the present work was to produce dietary fibre from cassava pulp fibre using Actinomycetes cellulase as a functional food. Crude enzyme was obtained from Actinomycetes HJ4(2a) isolates by separation of its biomass through centrifugation. Dietary fibre production was carried out with two substrates, derived from thermal and non-thermal treatments. In the thermal treatment, cassava pulp fibre was heated in an autoclave at 121°C for 1 h before hydrolysis by Actinomycetes cellulase. Enzymes at 0.1 U/g were used, and incubations were carried out in 0, 24, and 48 h. Cellulase produced dietary fibre (DF) were done by decreasing insoluble dietary fibre (IDF) value and increasing soluble dietary fibre (SDF) value with reaction time, although there was no significant difference in DF components in the thermal and non-thermal treatments. The functional properties of DF, namely, water holding capacity (WHC), oil holding capacity (OHC), and emulsifying activity (EA) increased with the reaction time, with the thermal treatment being significantly higher (p < 0.05) than the non-thermal treatment. Optimum conditions of hydrolysis were shown by thermal treatment in hydrolysis of 48 h in which 9.35% of SDF, 12.08 g/g of WHC, 3.12 g/g of OHC, and 64.53% of EA were produced. In the thermal treatment, a higher amount of hydrolysate by-products, as well as changes in morphological and crystallinity characteristics occurred.
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Introduction
Dietary fibre (DF) is a non-starch polysaccharide (cellulose, hemicellulose, pectin, gum, dextrin, chitin, and ß-glucan), lignin, and oligosaccharide that can modulate transit time through the intestine, but cannot be digested and fermented (Slavin, 2013; Wichienchot and Wan Ishak, 2017). DF can prevent gastrointestinal diseases such as constipation and digestive cancer (Raupp et al., 2004). Based on its water solubility and fermentability, DF is classified into two categories, namely, (1) soluble dietary fibre (SDF), which is water-soluble and well-fermented (e.g., pectin, gum, and mucilage), and (2) insoluble dietary fibre (IDF), which is insoluble in water and less-fermented (e.g., cellulose, hemicellulose, and lignin)...