Effect of ohmic heating and vacuum impregnation on the osmodehydration kinetics and microstructure of strawberries (cv. Camarosa)

The influence of ohmic heating (OH) and vacuum impregnation (VI) on the osmotic dehydration (OD) kinetics and microstructure of strawberries were studied. Samples were immersed in a 65 °Brix sucrose solution and treated with OH (100 V) and VI (5 kPa). Osmotic treatments were carried out at 30, 40 and 50 °C for 300 min. Water loss, solid gain, color and firmness of the strawberries were measured. In addition, the microstructure was analyzed using electron microscopy (SEM) and (TEM). The results showed that applying OH during osmotic dehydration had significant effects on the mass transference kinetics and the microstructure of the treated samples. The greatest water loss was observed for the OD-OH treatment. The largest amount of solute gain was obtained for the VI-OH treatment. A loss in firmness was observed in the OD-OH samples at 50 °C. Color differences were related to an increase in clarity and a decrease in color chrome, and the least significant differences were observed for the samples treated at 30 °C. SEM observations showed that cell rupturing were more significant in the OD-OH than in the VI-OH samples. The application of OH and VI had beneficial effects on the acceleration of mass transference.

► Ohmic heating/vacuum impregnation treatments accelerate the mass transfer kinetics. ► Ohmic heating induce cellular breakage due to the electro-thermal effect. ► Vacuum application has beneficial effect on the maintenance of samples firmness. ► Color differences are related to an increase in clarity and a decrease in color chrome.