Ph.D. Dissertation:

Production and Optimization of Functional Instant Powder Based on Almond by Extrusion Technology & Evaluation Shelf life by Using Intelligent Systems

The partially defatted almond flour-corn flour blends were extruded in a rotating twin-screw extruder. Processing parameters of feed including screw speed (120-220 rpm), moisture content (12-16%) and defatted almond flour-corn flour ratio (10:90-30:70) were optimized for physical and textural properties of blend extrudate samples. The experimental design was based on a combine design. Results of the first phase indicated that; by increasing the screw speed, the feed moisture and reducing the level of defatted almond flour, starch gelatinization improves and macrostructural characteristics (porosity, hardness and expansion ratio), microstructural features (SEM), functional properties (water solubility index and thermal characteristics) indicated greater compliance, however a negative effect was observed on the antioxidant activities and total phenolic compounds. According to optimization results, in order to achieve a product with the characteristic of 5.08 expansion ratio, density of 0.21 (g/cm3), hardness of 5.43 (N), water absorption index of 6.42, solubility in water index of 26.96, total phenolic compounds of 250/027 (mg/100g), the antioxidant activity of 16.75%, brightness of 67/101 and the overall acceptability of 4.33, production conditions were determined as follows: moisture content 13%, screw speed 220 (rpm) and partially defatted almond flour-corn flour ratio 20-80. The second phase of the research was conducted with the aim of optimizing the formulation of instant drink powder. In this stage, optimized sample of the first phase, was first milled and then formulated under the terms of 65-70% almond – corn extrudate powder, sugar 25-30% and stevia 0-5%. This phase of research was carried out in the form of mixture design. Optimization was determined based on characteristics of reconstruction and the flowability of the instant powder. Increasing the level of extrudate powder improves the characteristics of flowability but had a negative effect on powder dispersion in water. Stevia had a positive effect on emulsion formation, however at higher levels had a negative effect on the taste of the drink. In order to achieve optimal formula for instant drink powders with a repose angle of 24.610, dispersability of 65.41, wettability of 12.45 (s), hausner ratio of 1.02 and carr index of 15.26 were determined including 29.5% sugar, 0.53% Stevia and 69.9% extrudate powder. In the third phase of the research, in order to predict the shelf life of instant drink powders, Moisture adsorption isotherm and peroxide value of the product were assessed over a period of 8 weeks under different humidity conditions. The results indicated that, GAB model with a high coefficient of determination (R2 = 0.99) was well fitted to the manufactured sample adsorption isotherm. Also, shelf life at 25 0C, was predicted 7.85 months and at 35 0C, 4.2 months

Keywords: Extrusion, functional instant powder, almond, antioxidant activity, shelf life and moisture adsorpti