Optimization of Instant Controlled Pressure Drop (DIC)-Assisted Dehydrofreezing Using Mechanical Texture Measurements Versus Initial Water Content of Apple

Abstract

This work deals with instant controlled pressure drop (DIC)-assisted dehydrofreezing process as an innovative preservation method. Its objective was to assess the impact of combined unit operations (air drying–DIC treatment–freezing/thawing) on apple firmness. Golden delicious apple samples with initial water content (W) of 700 % dry basis (db) were subjected to air drying reaching different W values (200, 166, 115, 64, 30 % db). Then, these partially dried samples were DIC-treated at different conditions following a design of experiment (DoE). Treated samples were frozen at −30 °C and thawed at 4 °C overnight. Values of firmness defined as puncture rupture force were used to define the textural impacts of different operations of partial air drying–DIC treatment–freezing/thawing. The results showed that the lower is the apple water content (between 200 and 30 % db), the higher is the firmness. DIC treatment had insignificant effect on firmness. Conversely, great firmness decrease was perceived for freezing/thawing of fresh and high water content samples (>200 % db). However, this freezing effect disappeared, and the firmness kept constant once the water content was lower than 166 % db. This “freezing critical level” was obtained at higher level (200 % db) for DIC-treated samples. DoE and response surface methodology (RSM) confirmed that water content was the most influencing DIC operative parameter in terms of apple firmness.