Pretreatments, dehydration methods and packaging materials: effects on the nutritional quality of tomato powder: a review

Pretreatments and drying are commonly used before drying tomatoes to inactivate enzymes, improve the drying process, and improve the quality of dried tomato powders. In this review, the effects of different pretreatments (osmotic solutions), dehydration methods, and packaging materials on the quality attributes of tomato powder were summarized. These include pretreatments and osmotic agent solutions (potassium metabisulfite, calcium chloride, sodium metabisulphite, ascorbic acid, citric acid, sodium chloride, and sodium benzoate), thermal blanching (steam blanching and hot water) and non-thermal-processes-like-freezing, sulfuring, etc. and drying methods (oven, sun, and indirect solar dryer). The tomato powders were dried to preserve, store, and transport them. Drying implies not only physical changes, which the consumer can easily detect through visual inspection but also chemical modifications. These are responsible for alterations in color, flavor, and nutritional value, which compromise the overall quality of the final tomato powder. Maximum lycopene, vitamin A, and C contents were found in freeze-dried and direct sundried than samples dried using other methods at low drying temperatures. Freeze driers showed in keeping the nutritional quality of tomato powder with a combination of different pretreatments. Different pretreatments including osmotic agent solutions have their own merits and demerits for the final tomato powder. To overcome the drawbacks of nutritional quality, non-thermal pretreatment categories may be a better alternative to thermal blanching, and more fundamental research is required for better design and scale-up.