Abstract
The effects of extrusion conditions, teff-to-rice blend ratio (25-100%), feed moisture content (21-25%) and barrel temperature (130- 150°C) on the physico-chemical properties and the sensory attributes of extruded product from teff-rice blend was investigated. The physico-chemical properties (specific length, bulk density, expansion, water absorption index (WAI), water solubility index (WSI) and hardness), and sensory acceptability (flavor, color, texture and overall acceptability) were significantly (p<0.05) influenced by the extrusion conditions. Increasing barrel temperature resulted in higher expansion, lower density, reduced hardness and higher WAI, and WSI. Increase in the proportion of teff resulted in increased density, hardness, and WSI whereas increase in teff proportion brought about a decrease in expansion and WAI. Increasing feed moisture content resulted in higher density, lower expansion, higher WAI, lower WSI, higher hardness and lower crispness. The sensory scores reduced with increase in the proportion teff. The numerical optimization revealed that the optimal extrusion conditions for the best result were extrusion temperature of 150°C, feed moisture content of 21.2% and blending ratio of 40% teff with a desirability value of 0.901. The graphical optimization revealed that the best results were found between 140 to 150°C, 21 to 22% feed moisture and 25 to 46% of teff proportion.
Highlights
Teff (Eragrostis teff [Zucc.] Trotter) is a major food grain in Ethiopia but is a minor cereal crop worldwide
Increase in the proportion of teff resulted in a decrease in expansion ratio (ER)
The graphical optimization revealed that the best results were found for between 140 to 150oC, 21 to 22% feed moisture and 25 to 46% of teff proportion
Summary
Teff (Eragrostis teff [Zucc.] Trotter) is a major food grain in Ethiopia but is a minor cereal crop worldwide. Studies on the extrusion of teff to produce snacks indicated that teff extrudates are found to be denser and have limited expansion as compared to products made from rice, wheat and corn (Kebede et al, 2010; Sisay et al, 2018) This limitation could be improved by blending teff with cereals which have better expansion and digestibility properties (Gopirajah and Muthukumarappan, 2017; Sisay et al, 2018). Minweyelet et al / Food Research 5 (2) (2021) 173 - 183 cereal feeding greater size of the population worldwide and sources of income for f millions of people (Hagenimana et al, 2006; Dalbhagat et al, 2019) It is non-allergic, gluten-free source of carbohydrate, vitamins and minerals with a low fat (Dziezak, 1991). Because of its many functions as well as nutritional properties, rice could compensate for the limitations of teff in extrusion cooking of different food products
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