BACKGROUND DRYING IS ONE OF THE OLDEST PRESERVATION TECHNIQUES USED IN THE FOOD INDUSTRY. THIS TECHNOLOGY HAS EVOLVED AND DIFFERENT DRYING SYSTEMS HAVE BEEN APPLIED, SUCH AS CONVECTION, CONDUCTION, OR RADIATION, AND COMBINATIONS THEREOF. SCOPE AND APPROACH THIS REVIEW STUDIES THE VMD PROCESS WHOSE PRINCIPLE IS BASED ON THE ELECTROMAGNETIC RADIATION EMITTED BY THE MAGNETRON ON A FOOD MATRIX IN A REDUCED PRESSURE ENVIRONMENT AND WHICH IS TRANSFORMED INTO HEAT. VMD IS A PROMISING, FAST, AND EFFICIENT PROCESS FOR REDUCING MOISTURE CONTENT. BOTH RESEARCH AND INDUSTRIAL USE HAVE GROWN BY 303% IN THE LAST 20 YR. THE OBJECTIVE OF THIS REVIEW IS TO PROVIDE AN OVERVIEW OF MAJOR DEVELOPMENTS IN VMD RESEARCH AND ITS APPLICATION IN VARIOUS FOODS AND OTHER MATERIALS. BASED ON THE CHARACTERISTICS AND PARAMETERS OF THE VMD EQUIPMENT IN THE DRYING PROCESS, IT WAS POSSIBLE TO CLASSIFY THE EFFECT VMD HAS ON DIFFERENT FOOD MATRICES. KEY FINDINGS AND CONCLUSIONS THE REVIEW DESCRIBES THE PHENOMENOLOGICAL BEHAVIOR OF THE DRYING PROCESS AND HOW TO OPTIMIZE IT USING EQUIPMENT MODIFICATIONS WITH COMPUTER SIMULATIONS. THE DIFFERENT VMD SYSTEMS HAVE BEEN CLASSIFIED AS STATIC, ROTARY, CONTINUOUS FLOW, AND PROPRIETARY EQUIPMENT. IN ADDITION TO SOME CHARACTERISTICS OF PROCESS EFFICIENCY AND ENERGY CONSUMPTION, VMD EXHIBITS ENERGY CONSUMPTION SAVINGS OF APPROXIMATELY 50% COMPARED WITH OTHER DRYING SYSTEMS. FINALLY, PRODUCT QUALITY IS DISCUSSED UNDER DIFFERENT CONDITIONS, SUCH AS EQUIPMENT DESIGN AND TEMPERATURE UNIFORMITY. THUS, IT IS CHALLENGING TO DESIGN AND BUILT NEW VMD SYSTEMS WITH HIGHER ENERGY EFFICIENCY IN FOOD DRYING.

THE OBJECTIVE OF THIS STUDY WAS TO APPLY ELECTROHYDRODYNAMIC (EHD) AS A PRETREATMENT, INCLUDING SEVERAL VOLTAGES AND AN APPLICATION TIME OF LESS THAN 1 H, COMBINED WITH FREEZE DRYING (FD) TO DETERMINE THEIR INFLUENCE ON DRYING KINETICS AND DRYING RATE, FINAL MOISTURE CONTENT, REHYDRATION RATE, AND WATER ABSORPTION CAPACITY, ALSO, REHYDRATION AND WATER ABSORPTION CAPACITY RATES DERIVED FROM THE WEIBULL MODEL. THE BEST COMBINATION WAS COMPARED WITH SUN DRYING (SD) AND FD. INITIAL DRYING RATE INCREASED BECAUSE EHD INFLUENCED THE MOISTURE CONTENT ON THE PRODUCT SURFACE AS EXPOSURE VOLTAGE INCREASED. REHYDRATION AND WATER ABSORPTION HAD A HETEROGENEOUS BEHAVIOR, REGARDLESS OF VOLTAGE. THE 30 KV-30 MIN PRETREATMENT HAD BETTER DRYING KINETICS AND RATE AND WAS THEREFORE COMPARED WITH FD AND SD, SHOWING BETTER RESULTS IN THE DRYING PARAMETERS. HOWEVER, FOR REHYDRATION BEFORE 2.5 H, FD BEHAVED BETTER. THE WEIBULL MODEL HAD A GOOD FIT TO THE EXPERIMENTAL DATA FOR THE THREE TREATMENTS. CRUST FORMATION WAS GREATER IN THE SD TREATMENT, FOLLOWED BY EHD COMBINED WITH FD, WHICH WAS REFLECTED IN REHYDRATION.

VACUUM FREEZE-DRYING PROVIDES HIGH-QUALITY FOOD PRODUCTS. HOWEVER, IT REQUIRES LONG OPERATING TIMES AND HIGH ENERGY CONSUMPTION. HIGH VOLTAGE ELECTRICAL DISCHARGE (HVED) IS AN EMERGING TECHNOLOGY THAT COULD ENHANCE FREEZE-DRYING RATES AND FINAL PRODUCT QUALITY. THIS STUDY AIMED TO EVALUATE THE EFFECT OF HVED AT HIGH FREQUENCY (200 KHZ) ON FREEZE-DRYING KINETICS OF BLUEBERRIES (EFFECTIVE MOISTURE DIFFUSIVITY, DRYING TIMES) AND THE PHYSICOCHEMICAL PROPERTIES OF THE RESULTING FREEZE-DRIED FRUITS. BLUEBERRIES WERE PRETREATED AT DIFFERENT ELECTRIC FIELD STRENGTHS (10, 20, AND 30 KV/CM) AND OPERATIONAL TIMES (10, 20, AND 30 S) AND FREEZE-DRIED UNTIL CONSTANT WEIGHT. THE HVED TREATMENT AT 30 KV/CM AND 30 S EXHIBITED THE BEST MOISTURE DIFFUSIVITY VALUES AND REDUCED DRYING TIME BY AT LEAST 30% COMPARED WITH UNTREATED SAMPLES. SAMPLES TREATED WITH HVED AND FREEZE-DRIED PRESERVED THEIR SHAPE AND PREVENTED SHRINKAGE. APPLYING HVED AS A PRETREATMENT ELECTROTECHNOLOGY CAN HELP IMPROVE THE EF- FICIENCY OF FREEZE-DRYING AND THE QUALITY OF DRIED FOOD PRODUCTS.

SULFORAPHANE (SFN) IS AN ISOTHIOCYANATE OCCURRING IN BROCCOLI, WITH EXCEPTIONAL HEALTH-BENEFICIAL PROPERTIES, SUCH AS ANTICANCER, ANTI-INFLAMMATORY, AND ANTI-HYPERTENSIVE EFFECTS. PROCESSES TO MAXIMIZE SFN CONTENT IN BROCCOLI DEVELOPED UNTIL NOW ARE EXPENSIVE AND SFN BIOAVAILABILITY IN THE VEGETABLE IS NOT OPTIMAL. TO INCREASE SFN EXTRACTION YIELD FROM BROCCOLI FLORETS, IT WAS PROPOSED TO COMPLEMENT TRADITIONAL SOLVENT EXTRACTION WITH PULSED ELECTRIC FIELD (PEF) AS TISSUE DISRUPTION METHOD ENABLING THE REDUCTION OF MASS TRANSFER RESISTANCE IN VEGETABLE MATRICES. TISSUE DISRUPTION METHODS ENHANCE THE PERFORMANCE OF THIS PROCESS BECAUSE IT REDUCES MASS TRANSFER RESISTANCE. PEF IS AN INNOVATIVE TECHNOLOGY RECENTLY INTRODUCED IN THE FOOD INDUSTRY. WE STUDIED THE EFFECT OF ELECTRIC FIELD STRENGTH (10 AND 15?KV/CM) AND TIME OF EXPOSURE TO THE PEF TREATMENT (30, 90, AND 150?S) ON THE RECOVERY OF SFN FROM BROCCOLI FLORETS, USING A STATISTICAL FACTORIAL DESIGN. ELECTRIC FIELD STRENGTH AND EXPOSURE TIME SIGNIFICANTLY AFFECTED SFN RECOVERY IN A POSITIVE WAY. PEFS INCREASE SFN RECOVERY BY MORE THAN 50% COMPARED TO TRADITIONAL EXTRACTION. THIS RESULT WAS ACHIEVED AT 150?S EXPOSURE TO PEF AND 10 KV/CM.