A sub-zero crystallization process for the recovery of lactose

Ruben Halfwerk*, Doekle Yntema, Jaap van Spronsen, Albert van der Padt

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

In industry, lactose is generally produced by concentrating whey permeate by evaporation followed by a slow cooling process where lactose is crystallized. Here, an alternative method is presented whereby the concentration and crystallization steps are combined at sub-zero temperatures, so-called eutectic freeze crystallization. It was discovered that simultaneous crystallization of lactose and water (ice) is possible. The obtained lactose crystals had an average size of 10 μm and a thin triangular or tomahawk morphology. The process was analyzed in detail in two steps: freeze concentration and lactose crystallization at sub-zero temperatures. Freeze concentration experiments showed that concentrating to supersaturation was possible without excessive lactose crystallization. In the second step, lactose was crystallized at temperatures below zero from a 30 wt% lactose solution, without observation of significant primary or secondary nucleation. The amount of seed material had a large influence on the final yield, crystal size and morphology. The optimum seed amount was found to be at 0.08% of the total lactose; the resulting crystals had an average size of 26 μm and a tomahawk morphology. Although highly supersaturated conditions are present in the sub-zero crystallization of lactose, crystal growth is found to be the predominant process rather than nucleation.

Original languageEnglish
Article number110677
JournalJournal of Food Engineering
Volume308
DOIs
Publication statusPublished - Nov 2021

Keywords

  • Eutectic freeze crystallization (EFC)
  • Freeze concentration
  • Lactose
  • Sub-zero crystallization

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