Estudo do processo combinado de desidratação osmótica e secagem convectiva para o Jambolão (Syzygium Cumini)

Abstract

Jambolan (Syzygium cumini) fruits are ellipsoid-shaped berries that belong to the Myrtaceae family and present a fleshy pulp, which involves a single seed. The fruit peel has a thin film that displays an intense purple color in the final stage of maturation, due to the presence of anthocyanins. Recent studies have evaluated the action of the main biological activities involving the different parts of the jambolan tree, which have indicated the presence of anti-inflammatory and antidiabetic potentials. Although jambolan has important phytochemicals in its composition, the fruit is little known by the Brazilian population and, for this reason, its consumption is not very expressive during the short harvest period (30 to 40 days). Thus, in order to take advantage of the technological potential of jambolan and prolong the shelf life of the fruit, which is very perishable, the objective of this research was to study the combined process of osmotic dehydration (OD) and convective drying of jambolan, in order to extend its expiry date and add value to the fruit. For this, an initial study was carried out to evaluate the proximate composition of the fruit’s pulp and seed and to study the stability of these fractions during storage, through moisture desorption isotherms (25-55oC), where the energy demands (thermodynamic properties) were estimated, which are required for the dehydration of the fruit. Then, the physical-chemical and biometric characterization of the fruits were carried out and the effect of the main variables, involved in the OD of jambolan, was evaluated through a fractional factorial design 2 6-2 . Finally, the effect of OD on the drying kinetics of fruits at 50, 60 and 70oC was evaluated; depending on the content of monomeric anthocyanins and phenolic compounds. The results indicated that the moisture levels that guarantee the greatest degradative stability to the jambolan pulp and seed during storage are 8 g H2O/100 g (dry basis - db) and 5.1 g H2O/100 g db, respectively. It was also observed that the energies involved dehydration process were higher for pulp than seed. The biometric analysis showed that the jambolan pulp and peel contribute with more than 70% of the fruit weight and the composition analysis indicated promising amounts of anthocyanins (147 ± 1.85 mg.100-1g) and phenolic compounds (391 ± 18.89 mg GAE.100-1g). The selection of variables for the jambolan OD process showed that temperature, sucrose concentration, calcium lactate concentration and pressure had significant effects on the water loss response, which is of great importance in OD. On the other hand, losses of monomeric anthocyanins (46.6%) and phenolic compounds (26.9%) were observed after 72 hours of OD. Finally, the research showed that the fruits submitted to OD required shorter drying times than the fruits not submitted to this pre-treatment. These results indicate that the combination of OD and convective drying is a relevant technological alternative for the conservation of jambolan fruit.