Foam-mat drying is an alternative method which enables the removal of water from high-sugar content juices and purees that are difficult to dry. The aim of this study was to investigate the effect of different foam-mat drying methods on some physical properties and aroma of apple puree powder. Apple puree was foamed with the addition of foaming agents. Foamed puree was dried as a layer using different techniques: convection drying, microwave drying, and freeze-drying. Also foamed puree with and without maltodextrin (6% or 15% w/w) was dried. Selected properties such as hygroscopicity, wettability, solubility, colour, water content, water activity, bulk density and the changes in retention of aroma compounds of apple powder were determined. The drying method affected the physical properties of apple powders. Foaming prior to drying allowed us to obtain less hygroscopic powders with low moisture content and water activity. The freeze-dried samples were characterized by lower wettability and solubility than powders obtained by air (convection) drying and microwave drying. The increase of maltodextrin addition from 6 to 15% resulted in a decrease of hygroscopicity, bulk and tapped density, and flowability of apple juice powders were also improved. The addition of maltodextrin to apple puree reduced the wetting time of freeze-dried powders but only high concentration of the carrier significantly improved wettability of powders The convection drying of foamed apple puree enabled us to obtain instant powder with higher retention of apple aroma.
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机译：泡沫垫干燥是一种替代方法，可以从高糖含量果丛和难以干燥的泥浆中去除水。本研究的目的是探讨不同泡沫垫干燥方法对苹果粉末的一些物理性质和香气的影响。 Apple Puree用加入发泡剂发泡。使用不同的技术将泡沫纯成干燥作为层：对流干燥，微波干燥和冷冻干燥。还用麦芽糖糊精（6％或15％w / w）干燥泡沫纯细胞。测定了诸如吸湿性，润湿性，溶解度，颜色，含水量，水活性，散装密度和苹果粉香气化合物的含水量的变化等特性。干燥方法影响了苹果粉的物理性质。在干燥之前泡沫使我们能够获得具有低水分含量和水活性的更少的吸湿粉末。通过通过空气（对流）干燥和微波干燥获得的粉末，冻干样品的特征在于润湿性和溶解度。麦芽糖糊精的增加从6〜15％加入导致吸湿性的降低，体积和溅射密度，并且还改善了苹果汁粉末的流动性。向苹果酱添加麦芽糖糊精降低了冷冻干燥粉末的润湿时间，但只有高浓度的载体显着提高了粉末的润湿性，使泡沫苹果酱的对流干燥使我们能够获得苹果香气保留更高的速溶粉末。
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