Investigating the Role Played by Osmotic Pressure Difference in Osmotic Dehydration: Interactions between Apple Slices and Binary and Multi-Component Osmotic Systems

This study was performed to investigate a strategy to interpret the osmotic dehydration (OD) process through a focused exploration of osmotic pressure dynamics. The investigation first delved into the relationship between dehydration rate and the osmotic pressure difference between food and an osmotic solution. Apple slices was used as a model food material, and the OD process was conducted via sucrose, glucose, and maltose. The positive correlation between the osmotic pressure difference between food and osmotic solution and the dehydration rate suggested that this pressure difference served as the primary driving force for mass transfer within the OD process; for example, in 60% wt sucrose solution, the osmotic pressure of the solution decreased from 15.60 MPa to 12.98 MPa in the first 30 min, while the osmotic pressure of fresh apple slices increased from 1.49 MPa to 4.05 MPa; and this correlation between dehydration rate and osmotic pressure difference in product tissue and osmotic solution followed a linear relationship. Then, the study went further to investigate augmenting osmotic pressure of osmotic solution (sucrose and fructose) by adding auxiliary solutes (sodium chloride and calcium lactate). The results showcased that augmenting osmotic pressure within a sugar-based solution could be realized through the introduction of additive solutes, and what is more important is that this augmentation displayed a synergistic effect, which was more pronounced in solutions of lower sugar concentration. For example, the osmotic pressure of 45%wt fructose solution was 8.88 MPa, which could be increased to 10.05 MPa by adding 0.075% wt NaCl, while adding 0.075% wt NaCl to 59.14% wt fructose solution could increase osmotic pressure from 20.57 MPa to 21.22 MPa. In essence, this study proposed a strategic approach to studying the OD process by spotlighting osmotic pressure as a pivotal factor.