Experimental investigation and mathematical modeling of water absorption in air-dried chestnuts

摘要

Chestnuts are characterized by limited shelf-life because of their high water activity andrnsugar content. For this reason, air-drying is typically performed to achievernphysicochemical and microbiological stability of such fruits. However, undesiredrnstructural changes can occur during drying owing to the achievement of high processingrntemperature. These modifications can affect water permeability ruling out the possibilityrnof uniformly rehydrating the dried fruit.rnThis contribution provides an experimental and modeling study of the rehydrationrnprocess of air-dried chestnuts. With the objective of characterizing the effect of therndrying temperature on water permeability, chestnuts previously dried at 40, 60 and 80rn℃ are rehydrated by immersion in water at 90 ℃ and sorption curves are constructed.rnUnder the explored processing conditions, a purely Fickian diffusion model fails torndescribe the evolution of the absorbed amount of water due to the occurrence ofrnswelling and starch gelatinization. Therefore, a mathematical model is formulatedrnsimultaneously accounting for the effect of diffusion, swelling and starch gelatinizationrnon the transport of water. Parametric estimation of the model parameters is performed,rnbased on the results of rehydration tests, by nonlinear regression techniques. In thisrnway, satisfactory agreement between model predictions and derived experimental datarnis achieved and valuable information about the influence of the drying pre-processingrnconditions on water transport are obtained.