OSMOTIC DEHYDRATION PROCESS COUPLED WITH OHMIC HEATING USING GRANNY SMITH APPLES AND ITS EFFECTS ON PRODUCT QUALITY

摘要

Osmotic dehydration is governed by the osmotic pressure difference (as a chemical potential) between thefood material (hypotonic medium) and the concentrated osmotic solution (hypertonic medium). The osmoticdehydration final product has a high quality but its water activity does not ensure stability during storage,requiring additional processing. In addition, the main limiting factor of the osmotic dehydration process isthe extended operating time. Ohmic heating is defined as a process where electric currents are passed throughfoods to heat them. The dissipation of electrical energy in the product-mass generates heat. Several studieshave shown that osmotic dehydration process can be accelerated through ohmic heating of food material.The objective of this study was to evaluate the quality of Granny Smith Apples when subjected toosmotic dehydration coupled with ohmic heating. Variables included in this study were temperature (40–60°C), voltage (100–140 V) and solution concentration (52–80% w/w) with a processing time of 90 min. Themoisture content, soluble solids, water activity and physical parameters such as color and texture, weredetermined. Measurements were made in triplicate at 0, 30, 60 and 90 minutes and correlated throughResponse Surface Methodology using a factorial Box-Behnken Design.According to the objectives of the study, a qualitative analysis was performed to check the effect ofincreasing the process temperature from 40 to 60 °C. Similarly, the effect of increasing the voltage from 100to 140 V was analyzed, and the increase of the solution concentration from 52 to 80 °Brix was also tested.The results of color difference and % loss of hardness were adjusted to a second-order regression equationwith correlation coefficients between 0.660 and 0.975, respectively. The optimal process conditions forminimizing color difference were 40 °C, 68 °Brix and 100 V and % loss of hardness were 42°C, 58 °Brixand 100 V.