Physico-chemical properties of extruded cassava-chia seed instant flour Everlyne A. Otondi, John Masani Nduko * , Mary Omwamba Department of Dairy and Food Science and Technology, Egerton University, P.O. BOX: 536, 20115, Egerton, Kenya ARTICLE INFO Keywords: Cassava flour Chia seeds Extrusion Instant flour Flour blending ABSTRACT This study evaluated the effects of extrusion process parameters and blends of chia seed and cassava flours on the nutritional and functional properties of flour blends aiming at improving the nutritive quality of cassava flour and enhancing the use of cassava in the production of extruded products. Extrusion was carried out using a single- screw extruder with constant parameters; screw compression ratio (3:1); die shape (round), die diameter (10 mm), pitch angel 45  screw, screw speed (100 rpm), and feed rate (35 rpm). The effect of feed moisture and amount of chia seed on the proximate composition, and physical and functional properties was determined using standard methods. The protein, fat and ash contents significantly (p < 0.05) increased from 2.39 to 12.23%, 0.79–11.77%, and 2.59–4.04%, respectively, with increasing chia seed incorporation. Increase in chia seed incorporation significantly (p < 0.05) increased Bulk Density (BD) of cassava from 0.45 to 0.63g/cm 3 for 60% chia seed substitution ratio and 15% moisture conditioning and the Water Absorption Index (WAI) of cassava from 1.53 to 5.94% for 20% chia seed incorporation and 20% moisture conditioning, while reducing significantly the Water Solubility Index (WSI) from 55.48 to 17.48 g/g for 60% chia seed incorporation and 20% moisture conditioning. On the other hand, solubility and swelling power of the extruded flour blends varied in no particular direction with chia seed incorporation and feed moisture conditioning. The cassava-chia seeds blends exhibited potential for the production of nutritive extruded instant porridge flour (extrudate was milled to flour) with good physical and functional properties. 1. Introduction Cassava (Manihot esculenta C) is a perennial crop that has been ear- marked as a staple food crop in Africa due to its high resilience and adaptability to a wide range of ecological conditions in sub-Saharan Af- rica [1]. According to FAOSTAT [2], production in Sub-Saharan Africa was 157, 271,697 metric tons and Kenya produced 571,848 metric tons. Cassava is a tuberous root crop belonging to the family Euphorbiaceae, genus Manihot and the fourth most important dietary source of energy in the tropics after rice, wheat and maize [1]. Fresh cassava roots have a shelf-life of less than 72 h after harvest and post-harvest losses of about 23% have been reported in Kenya [3]. Cassava roots are consumed either in form of crisps or dried chips for ugali in all growing areas in Kenya [3]. Nutritionally, it is composed of 80% carbohydrates, 4% dietary fibre and 1–3% protein [1]. The unfermented cassava flour is low in protein, especially in the sulphur-containing amino acids methionine and cysteine. In Kenya, consumption of foods high in starch has led to an increase in the prevalence of non-communicable diseases such as dia- betes, obesity, and heart disease [3]. Hence, compositing cassava with nutrient dense foods can improve on the limiting nutritional components. Chia (Salvia hispanica L.) seeds are among the nutrient dense foods, harvested from an herbaceous plant that has been cultivated for centuries by the Aztecs of ancient Mexico [4]. They incorporated these seeds into their daily diet because of its high nutritional benefits and medicinal value. Chia seed is an oil seed which contains high amount of lipids (40%) with 60% omega 3 fatty acids, 15–24% protein content, 26–41% carbohydrates, 18–30% dietary fibre, vitamins, minerals, and a wide range of polyphenolic antioxidants, which safeguards the seeds from chemical and microbial breakdown [4,5]. Chia seed has been approved as a novel food by the European Parliament leading to its use in a wide range of foods [6]. It has high-quality protein with good amino acid balance, especially methionine and cysteine. Chia seeds are also gluten free, anti-allergenic and non-toxic on human health [4]. Cassava value addition has limited processing options in Kenya, hindering its utilization [3]. Hence, one method that can be employed for cassava processing is extrusion. Extrusion is the operation of forming and shaping a molten or dough-like material by forcing it through a restric- tion, or die [7]. Extrusion cooking is different from other processing * Corresponding author. E-mail address: jnduko@egerton.ac.ke (J.M. Nduko). Contents lists available at ScienceDirect Journal of Agriculture and Food Research journal homepage: www.journals.elsevier.com/journal-of-agriculture-and-food-research/ https://doi.org/10.1016/j.jafr.2020.100058 Received 3 May 2020; Received in revised form 8 July 2020; Accepted 13 July 2020 2666-1543/© 2020 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Journal of Agriculture and Food Research 2 (2020) 100058