Based on a full factorial experimental design, the effects of the feed ratio, atomizer speed, and inlet air temperature on properties of spray-dried orange juice powders were investigated. The results indicate that increasing inlet air temperature increases the particle size, average time of wettablity, and insoluble solids and decreases the bulk density and moisture content of the powder.Increasing atomizer speed results in increasing the bulk density and average time of wettablity of powder and decreases the particle size, moisture content, and insoluble solids of powder. Increase in feed flow rate increases the bulk density, particle size, and moisture content of the powder and decreases the average time of wettablity and insoluble solids of powder. With multivariable regression analysis the relationships between physical properties of orange juice powder and operating parameters with high coefficient were obtained.

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Background Making powder from whey is one of the most challenging parts of whey processing. The present study investigates the performance of a spray dryer for the preparation of whey powder. Its main objective is to categorize unknown samples using analysis of discrimination function between the operating variables and powder properties in two or more naturally occurring groups. In this work, spray drying was performed in a pilot-scale cocurrent spray dryer. The amount of solid content, inlet, and outlet air temperature was chosen as independent variables. The titratable acidity, PH, EC, TDS, analytical elements, particle size diameter, ingredients, and morphology were the response variables that quantify the powder quality. Results The PH of whey powder with 15 % solid content was lower than the PH of whey powder with 30 % solid content. Furthermore, the PH of the whey dried at inlet (outlet) air temperature of 180°C (106°C) was lower than the whey dried at 145°C (87°C). Substances with higher acidity had higher electrical conductivity (EC) as well. The mean particle diameters of the powders produced by pilotplant spray dryer were in the range of 11.26-18.23 lm. SEM picture showed that in pilot-plant spray dryer, there were a few shallow holes on the particle surfaces as well as a few wizened particles. Conclusions It was observed that in the materials with higher acidity, the EC was high and the PH was low. More solid content caused higher viscosities in the feed, which increased the droplet size and consequently, the particle size. By increasing the temperature and heating duration, the amount of PH reduced and the diameter of the particles increased. Moreover, by increasing the percentage of the solid content, the PH increased, while the solid mass carried away by the outlet air decreased. Small particles sprayed by the two-fluid nozzles, led to less amount of TDS. From the morphological point of view, as the industrial samples were exposed to heat longer as compared to pilot-plant samples, they produced spherical and smoother particles.