DEVELOPMENT AND CHARACTERISATION OF A FIBRE-RICH FOOD FROM ORANGE (Citrus sinensis Linn.) POMACE, SOYAMEAL AND WHEAT BRAN

Abstract

Consumers demand for high dietary fibre food products is on the increase. Food by-products such as pomace, wheat bran, and soyameal can be another veritable source of dietary fibre. Work had been done on the combination of two of the by-products (wheat bran and soyameal) while information on good fibre profile blends of the three by-products is sparse. This study was designed to develop high fibre food from orange pomace, soyameal and wheat bran. Orange pomace (5-30%), soyameal (10-80%) and wheat bran (10-70%) were subjected to a three-component mixture design at the lower and upper ranges to meet required daily nutrient intake. Thirteen generated formulations were subjected to extrusion (5Kg per cycle) at fixed cooking temperature (110 oC) and screw speed (290 rpm). The extrudates were analysed for chemical (proximate, dietary fibre, antinutrients and antioxidant) and functional (bulk density and water absorption index) properties using standard methods. Sensory characteristics of the extruded products were determined by a panel familiar with sensory analysis (9-point hedonic scale) after which three formulations with the best organoleptic properties were selected. These were tested on forty male Wistar rats for toxicity for 28 days (hematological and histopathological). Shelf-life was evaluated monthly based on moisture content and fungal count under ambient conditions (indoors) for a period of five months. Data were analysed using ANOVA at α0.05. Chemical composition of products were moisture (8.50-11.03%), ash (4.00-6.00%), protein (10.84-25.40%), fat (3.50-8.00%) and carbohydrate (39.18-59.34%). The formulations containing pomace (30%), soyameal (10%) and wheat bran (60%) had highest total dietary fibre (66.86%) and fibre fractions (insoluble 30.21% and soluble 36.65%). Lowest value of phytate (0.57 mg/g) and oxalate (0.86%) were obtained from mixture of pomace (23%), soyameal (27%) and wheat bran (50%), while lowest value of tannin (1.3 mg/g) was pomace (30%), soyameal (60%) and wheat bran (10%). Total phenol, flavonoid, carotenoid were 0.47-0.76, 2.13-8.21 and 0.02-0.14 mg/g) respectively. Bulk density and water absorption index ranged from 0.42 to 0.61 g/cm3 and 2.91 to 3.86, respectively. Highest sensory score (5.16) for the overall acceptability was obtained in the mixture of pomace (10%) soymeal, (80%) and wheat bran (10%). Tested diets on Wistar rats resulted in lower weight gain which was at variance with control diet (31.55-56.21 g). White blood cells ((5283-6400) ×109/μL), creatine (0.63-0.70 mg/dl) and glucose (133.3-139.7 mg/dL) showed no significant difference between rats fed control and tested diets. Necrosis was not found in the kidney and liver of the rats fed with control and tested diets. The extrudates had 3-month shelf stability (moisture; 8.50-10.99%, total fungal count; 6.00-7.51 log cfu/g). Significant variations were observed among the thirteen samples. The optimal blend for the high fibre food was pomace (5%), soyameal (47.50%) and wheat bran (47.50%). High fibre food was successfully produced from composite of orange pomace, soyameal and wheat bran. The use of orange pomace for the development of high fibre food will contribute a significant portion of fibre to human diet and also improve its disposal.