Proximate Composition of Debittered Orange Fiber

The total dietary fiber was determined in accordance with AOAC 991.43 method, using the enzymatic assay kit Total Dietary Fiber (Megazyme International Ireland Ltd, Wiclkow), following the manufacturer's instructions.

Fat content was determined according to Official Method (27). Briefly, two grams of each sample were grinded and hydrolyzed using chloridric acid. Fats were extracted with a mixture of equal volumes of ethyl ether and petroleum ether and subsequently weighed after removal of the solvent. The extraction was repeated three times, at the end of which the solvent was removed by evaporation to constant weight of the sample.

Protein content (Nx5.7) was assessed according to the Official Method (27), by a semiautomatic Kjeldal apparatus (Velp UDK139). Briefly, two grams of grinded sample were mixed with 20 ml of sulphoric acid (98%), mineralized at 420°C for 60 min, two Kjeldahl tablets of 5 g were used as catalyzer agent. The digested sample was diluted with 100 ml of distilled water, transferred in the distillation unit added with 50 ml of sodium hydroxide (0.5 M) and distilled with boric acid (4%). Finally, the distilled sample was titrated with hydrochloric acid (0.25 M).

The content of sugar moiety of carbohydrates was determined in accordance with the Lane and Eynon method, with some modification, as reported by Khan (28). The starch was calculated as difference.

Ash content was determined using the dry ashing technique with a muffle, in accordance to A.O.A.C (2000) method. Ten grams of grinded sample were weighed and introduced in the muffle apparatus at 550°C. The ash content was expressed on dry basis and calculated using the following equation: