Short Communication: Osmotic Dehydration of Physalis-Influence of Ultrasound Pretreatment.

Physalis peruviana Linnaeus belongs to the family Solanaceae, and its potential cultivation is currently being explored due to its high productivity, sensory aspects and presence of several bioactive compounds. The shelf life of fresh physalis after harvesting is short, and its water content is high; therefore, osmotic dehydration, an alternative technology, could reduce the postharvest loss of this fruit. However, one factor that has hindered the application of this technology is the waxy skin of the fruit; in this context, the aim of the present work was to evaluate the effect of the pretreatment using an ultrasound probe (frequency, 20 kHz; amplitude, 80 %; for 30 min) on mass transfer during osmotic dehydration (ODU) and compare the results of the osmotic dehydration process without ultrasound (OD). The results showed that after 10 h, the loss of moisture was 47.6 ± 3.8 % and 46.1 ± 0.9 % for OD and ODU, respectively. The results for total sugar (normalized) showed a gain of 2.01 ± 0.22 and 2.05 ± 0.26 (g glucose g of fruit) for OD and ODU, respectively. The carotenoid values were not observed to be influenced significantly by pretreatment; the ratios between the initial and final values of carotenoids were 0.74 ± 0.04 and 0.78 ± 0.06 for OD and ODU, respectively. The effective mass diffusivity of water calculated was 3.24 ± 0.49 × 10 m s for OD and 3.34 ± 0.11 × 10 m s for ODU, and the values founded were statistically equal (Tukey; p > 0.05). Additionally, the water activity and total color difference were measured for both the OD and ODU processes after 10 h, and statistically equal results were observed. Thus, for the conditions analyzed in this work, osmotic dehydration without and with an ultrasound probe as pretreatment showed no influence on the parameters studied. However, the food industry is constantly investigating new preservation technologies to improve and/or to replace of traditional food preservation techniques, and the treatment using ultrasonic waves has been used in conservation of fruits because it modifies the structure of the fruit increasing the water loss in the processing. [ABSTRACT FROM AUTHOR]