Preparation and properties of insoluble dietary fiber from marc of Hovenia dulcis Thunb.

Marc from Hovenia dulcis Thunb. fruit is a new cheap source of insoluble dietary fiber(IDF). To utilize this resource comprehensively, the preparation of IDF from H.dulcis marc by chemical methods and its bleaching with hydrogen peroxide(H2O2)were studied. The nutritional components and functional properties of the product were also analyzed. According to the result of single factor analysis and orthogonal test, the reasonable technology of extraction is that the marc is immersed in 1.5 mol/L NaOH at 20 ℃ for 40 min with 8∶1(mL∶g) ratio of liquid to material,then filtered and washed to neutrality. The residue was transferred into H2SO4 solution of pH value 2.0 with 6∶1(mL∶g) ratio of liquid to material and soaked at 60 ℃ for 60 min,then washed to neutrality. The optimum processing conditions of decoloration were as follows: 5 % H2O2, pH value 12, 45 ℃, 5 h, then dried at 65 ℃ for 5 h, milled and sieved(380 μm). Under these conditions the IDF whiteness increased from 51.63% to 60.21%. The IDF yield is 74.02 % and purity increased from 62.62 % to 84.97 %(on dry base). Compared with the marc, water-holding capacity, oil-holding capacity, water-retention capacity and swelling capacity of IDF product increased from 2.4 to 4.3 g/g, 2.3 to 3.9 mL/g, 2.6 to 4.7 g/g and 2.8 to 4.6 mL/g, respectively.