62 International Journal of Food Science and Nutrition www.foodsciencejournal.com ISSN: 2455-4898 Received: 28-11-2021, Accepted: 13-12-2021, Published: 29-12-2021 Volume 6, Issue 6, 2021, Page No. 62-69 Optimization of extrusion process parameters for the antinutritional compositions of aerial Yam (Dioscorea bulbifera)-soybean (Glycine max) flour blends using response surface methodology Enobong O Umoh 1* , Madu O Iwe 2 , Phillipa C Ojimelukwu 2 1 Department of Agricultural Engineering, Akwa Ibom State University, Akwa Ibom State, Nigeria 2 Department of Food Science and Technology, Michael Okpara University of Agriculture, Abia State, Nigeria Abstract A study on the optimization of extrusion process conditions for antinutritional factors of aerial yam-soybean flour blends was carried out, using a laboratory scale single-screw extruder with the flour blending ratio of 25% aerial yam: 75% soybean. Response surface methodology based on Box-Behken design at three factors, five levels of barrel temperature (95, 100, 105, 110, and115 ), screw speed (85, 100, 115, 130, and145rpm) and feed moisture (31, 33, 35, 37, and 39%) were used in 20 runs. Adequate and significant (p< 0.05) regression models with high regression coefficient, R 2 0.9 were obtained, showing that the models can be used to navigate the design space. Results obtained showed that the anti-nutritional factors of the extrudates ranged between 0.79 0.002 and 5.11 0.008/100g hydrogencyanide (HCN), 12.48 0.025and 32.86 mg/100g phytates; 0.93 0.026 and 5.46 0.009/100g tannins; 45.81 0.024 and 102.71 1.244/100g oxalates. Analysis of variance showed that barrel temperature, screw speed and feed moisture significantly (p< 0.05) affected the HCN, phytates, tannins and oxalates content of the extrudates. Optimization results based on desirability concept indicated that a barrel temperature of 112.83 , screw speed of 127.87rpm and feed moisture of 32.59% would produce extrudates of preferable anti-nutritional factors. Keywords: optimization, extrusion, antinutritional, aerial yam, soybean, response surface Introduction Optimization process is essential in the area of formulation/development of acceptable food products from neglected food crops, and in controlling the process conditions or parameters in order to produce extrudates with the desired quality. The Aerial yam (Dioscorea bulbifera), is a perennial, semi- wild food crop that grows on vines, climbing unto poles and trees, which belongs to the yam family, Dioscoreaceae. The bulb is eaten after cooking, on peeling off the hard back. Its common names are: Air Yam, Air Potato, Bitter Yam, Aerial Yam, Potato Yam, among others. Discorea bulbifera is a vigorous climber plant native of West Africa (Hamon et al., 1995) [4] , cultivated for their bulbils which are consumed once cooked like potatoes in water with oil or roasted with local sauce (a combination of palm oil and other local spices). About 50-60 species of yam (Dioscorea spp.) are found in Nigeria but only 5 or 6 species are important as food (Ogbuagu, 2008) [7] . Unfortunately, some of these food crops have been under-exploited for their food values, for example, Dioscorea bulbifera (Ogbuagu, 2008) [7] . Soybean (Glycine max), an important oil seed belonging to the family, Leguminosae, is usually grown as a food crop. Three species of soybean exist. They include: Glycine ussuriensis-wild, Glycine max-cultivated and Glycine gracillis-intermediate. Glycine max is commonly grown throughout the world as a material of commerce. Soybean production and utilization as food arose in ancient China not later than the 11 th Century B.C. It then became grown in other parts of the world just in the 20 th Century. The major producing countries are the United States, Brazil, China, and Argentina (Iwe, 2003) [5] . Soybean has a unique chemical composition on an average-dry-matter basis; it contains about 40% protein and 20% oil. With this composition, it ranks highest in terms of protein content among all the legumes (Iwe, 2003) [5] . Substituting wheat flour with soybean up to 25% will go a long way to increase noodles variety, make them affordable to many and boost their nutritional content (Omeire et al., 2014). However, blending of aerial yam and soybean, and or extrusion cooking of the blend, has not been adequately studied for its potential application in food products formulation. Aerial yam is yet to gain recognition and popularity globally, as a food crop. Processing it into stable flour/blend, and subsequent extrusion processing to produce pasta, will increase the visibility of the crop in food trade, thereby bringing to limelight its potential food uses/values to the food industry. Despite the increased use of extrusion process, it is still a complex process that has to be optimized for specific applications based on the nature of raw materials and desired final product. Even within a given extrusion process, small variations in processing conditions affect process variables as well as product quality (Desrumaux et al., 1999) [2] . This study is therefore, aimed at optimizing the extrusion process parameters for the antinutritional factors of aerial yam-soybean flour blends, using Response Surface Methodology. Materials and Methods Soybean seeds and Aerial yam bulbs used in this study were purchased from Uyo Urban market in Uyo Local