Effects of ultrasound-assisted blanching on the processing and quality parameters of freeze-dried guava slices

In this work, ultrasound-assisted blanching (UAB) has been applied to study its effect on different physical and chemical characteristics and the total process time (TPT) of freeze-dried guava slices (DGS). Additionally, the process energy consumption was estimated, and the overall process was modeled. UAB was applied at 5- and 10-min exposure times and at 65 degrees C to evaluate the polyphenol oxidase (PPO) and peroxidase (POD) activities. Then, guava slices were freeze-dried and the TPT with and without UAB were compared. Also, the total polyphenol content (TPC), antioxidant activity (AA), and total color change (TCC) of the DGS were measured. TPT decreased significantly for both UAB exposure times. Moreover, at 65 degrees C and 10 min UAB 36.0 2.0% and 99.5 +/- 1.0% reduction in PPO and POD, respectively, were observed. UAB samples resulted in lower TPC and AA. A significant reduction of the TCC was achieved with UAB. UAB decreased energy consumption during the process. Practical applicationsFreeze-drying preserves the quality of a product to a greater extent than other drying techniques, such as convective drying. However, the use of freeze-drying is limited by the high investment and operating costs. In this work, it is demonstrated that ultrasound-assisted blanching (UAB) can markedly reduce the total lyophilization time during the processing of guava slices relative to that attained without this treatment (control). Additionally, due to the enzymatic inhibition achieved by UAB, the color of the dried material in storage was preserved to a greater extent than it was without this treatment. Although the use of ultrasound (US) entails additional equipment and personnel costs, the significant reduction in operational costs can allow the investment to be recovered.