Adel Dezyani; Aman Mohammad Ziaiifar; Seyed Mahdi Jafari; Mohammad Ghorbani; Alireza Sadeghi Mahoonak
Abstract
Introduction: High sensitivity of fruit and vegetables juices to heat has been resulted to the development of spray drying method for drying this category of products. Spray drying is a well-established and widely used method for transforming a wide range of liquid food products into powder form. The ...
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Introduction: High sensitivity of fruit and vegetables juices to heat has been resulted to the development of spray drying method for drying this category of products. Spray drying is a well-established and widely used method for transforming a wide range of liquid food products into powder form. The process involves spraying finely atomized solutions into a chamber where hot dry air rapidly evaporates the solution leaving the spray-dried particles. Spray-dried powders can be stored at room temperature for prolonged periods without compromising the powder's stability. Powders are cheaper to transport and easier to handle in manufacturing plants. Spray-dried powders are economical to produce compared to other processes, such as freeze-drying. Spray drying has many applications, particularly in the food, pharmaceutical and agrochemical industries. The conversion of high value food materials, such as fruit and vegetable extracts, into particulate form is not easy due to the presence of a high proportion of low molecular weight sugars in their composition which lead to the problem of stickiness. The particles stick to one another, to the dryer and to cyclone walls and remain there, forming thick wall deposits, while very little product comes out at the dryer's exit. This might lead to low product yield and operating problems. In general, the stickiness causes considerable economic loss and limits the application of spray drying on foods as well as on pharmaceutical materials. In order to reduce stickiness, different solutes have been used as carriers and coating agents for the spray drying. Some examples of these are Arabic gum, maltodextrins, starches, gelatin, methyl cellulose, gum tragacanth, alginates, pectin, silicon dioxide, tricalcium phosphate, glycerol monostearate and mixtures of some of them. Of these additives, maltodextrin offers a good compromise between cost and effectiveness. It has been found that it contributes to the retention of some food properties, such as nutrients, color and flavor, during spray drying and storage. On the other hand, the feed flow rate, the inlet and outlet air temperatures, atomizer speed, feed concentration, feed temperature and inlet air flow rate are important factors that have to be controlled in a spray drying process. Tomato paste is a typical example of a product that is very difficult to be spray dried due to the low glass transition temperature of the low molecular weight sugars present.
Materials and methods: This study was carried out to evaluate the effect of inlet air temperature of dryer (120, 150 and 180 °C) and concentration of drying aid or carrier agent of maltodexterin along with whey protein concenterate ratio of 4 to 1 (25, 37.5 and 50% w/w) on the quantitative and qualitative properties of tomato paste powder including moisture content, bulk density, solubility, powder morphology, amount of lycopene, and production efficiency. Response surface methodology was used to choose optimum conditions of the powder production process.
Results and Discussion:the results revealed that the production efficiency (not significant) and solubility (significant) were increased with increased higher inlet air temperatures of dryer; however, at these conditions moisture content (significant), bulk density (not significant) and amount of lycopene (significant) in the powder were decreased also higher concentrations of carrier agent increased the production efficiency, solubility and amount of lycopene in the powder; however, moisture content and bulk density of powder were decreased.
Conclusion: Optimal conditions in order to achieve maximum production efficiency, solubility, the amount of lycopene and the lowest moisture content of powder, bulk density were achieved at inlet temperature of 150°C and carrier agent concentration of (w/w) 50%.
