Controlling the drying process in vacuum foam drying under low vacuum conditions by inducing foaming by needle stimulation of the solution

Crystallization characteristics of amorphous trehalose dried from alcohol

“…The needle puncturing (stimulation) reliably induced foaming immediately after the start of the secondary drying. The amount of the remaining organic solvent in the dried sample was estimated to be less than 0.01 g/g-dry matter, based on drying profiles reported in our previous study (Hidaka et al, 2019;Satoh et al, 2017).…”

“…The foaming of the solution was not induced during the initial drying. After the initial drying, the sample solution was removed from the centrifugal concentrator and then punctured with a stainless steel needle (Hidaka et al, 2019;Satoh et al, 2017), followed by further vacuum drying (Second drying) for 30 min. The needle puncturing (stimulation) reliably induced foaming immediately after the start of the secondary drying.…”

“…Based on these findings, we conclude that the matrix pores and cavities may serve as a discontinuous area that interferes with the nucleation of sugar crystals and subsequent growth; The continuity of the sugar matrix is increased when the matrix pores and cavities are diminished due to the compression, resulting in sugar crystallization being facilitated . On the other hand, in the case of vacuum foam drying, the sugar in alcohol exists in the dissolved (liquid) and rubbery state until it is converted into a glassy solid (Hidaka et al, 2019). The flowable state of a sugar solution during vacuum foam drying is thought to result in minimizing the discontinuities in the sugar matrix and thus facilitate the subsequent crystallization of the sugar.…”