Mathematical description of the viscoelastic properties of discarded blueberries pretreated with osmotic dehydration and mechanical modification

Abstract

This study evaluated the impact of osmotic dehydration (OD) and cutting pretreatments on the viscoelastic properties of discarded blueberries using three mathematical models: Maxwell, Peleg, and Guo-Campanella. The OD process was conducted in a 50 °Brix sucrose solution with a partial longitudinal cut. Viscoelastic properties were assessed through stress-relaxation curves obtained from compression tests. The findings indicated that both cutting and OD significantly reduced the initial compression force. All three models accurately described the experimental data (R2 > 0.95), with the Maxwell model providing the best fit, followed by Guo-Campanella, and then Peleg. The Maxwell model effectively described the viscoelastic behavior by associating elastic elements with the solid part and viscous elements with the fluid part. It showed that the blueberry skin, being more resistant, exhibited purely elastic behavior, while internal structures combined both elastic and viscous elements. The Peleg model indicated that OD and cutting reduced the fruit's firmness. The Guo-Campanella model demonstrated a decrease in elastic modulus primarily due to OD. When blueberries were cut, the endocarp structure was most affected due to its empty spaces. OD drastically decreased the elastic and viscous properties by causing water loss and reduced turgor in the cells, impacting their mechanical properties. These findings should be considered to determine the potential positive or negative effects on subsequent processes, such as drying or overall product quality.