Influence of process conditions on the mass transfer of osmotically dehydrated jambolan fruits

Abstract

Jambolan (Syzygium cumini) is a tropical fruit rich in anthocyanin pigments, but its fragile skin and pulp present low protection against physical damages and microorganisms. In this sense, a preservative technology, as osmotic dehydration (OD), was studied to investigate the impact of some variables over this process. At first, fruits of jambolan were submitted to physical and physicalchemical analysis. Furthermore, whole fruits underwent OD following a fractional factorial design. The influence of the process variables: temperature (20-50ºC), sucrose concentration (30-60%), pressure (10-90 kPa), vacuum pulse time (5-15 min), calcium lactate concentration (0-4%) and number of vacuum pulse (1-3) was assessed on water loss (WL), solid gain (SG) and weight reduction (WR). In general, biometric analysis showed positive and significant correlation among the physical characteristics of jambolan. Physical-chemical assay demonstrated that the fresh fruit presents a potential source of bioactive compounds. The screening design showed that temperature, sucrose concentration, calcium lactate concentration and pressure affected the WL in jambolan. On the other hand, vacuum pulse time and number of vacuum pulse showed no influence on the WL, SG and WR; therefore, these variables must be fixed at the most economically viable level for any further trials.

Moisture desorption behavior and thermodynamic properties of pulp and seed of jambolan (Syzygium cumini)

“…Table 1 presents the proximate composition for both JP and JS (in wet basis – wb), as well as the results for a w at 25 °C. These findings corroborate to the results observed by Araújo and Pena (2021) , whose proximate composition, for JP, was: 84.80 ± 0.26 g/100 g moisture, 0.43 ± 0.01 g/100 g ashes, 0.56 ± 0.03 g/100 g total lipids, 0.48 ± 0.05 g/100 g total proteins, 13.90 ± 0.03 g/100 g carbohydrates; and the a w was 0.98 ± < 0.01 (25 °C). For JS, in turn, no studies have been found regarding its proximate composition.…”

“…Right after harvesting, ripe fruits were transported in polystyrene isothermal boxes to the Laboratory of fruits at UFPA. Posterior to discard of the injured jambolans, the fruits were rinsed in running water, and sanitized by immersion in hypochlorite solution at 20 mg/L of active chlorine for 15 min, followed by rinsing and drying with an absorbent paper, as described by Araújo and Pena (2021) . Then, jambolan pulp (JP) was separated from the jambolan seed (JS), with a stainless steel laboratory spatula, in order to proceed with the next analyzes.…”

Combined Pulsed Vacuum Osmotic Dehydration and Convective Air-Drying Process of Jambolan Fruits

“…For SG, the same authors observed the following values: 4.6% (AP), 7.6% (VP), and 9.3% (USVP). These ML and SG findings were reached after 5 h of the OD process, at 30 • C. On the other hand, the ML and SG values found by Araújo and Pena [26] varied from −1.06 to 21.35% and from −5.11 to 7.09%, respectively, in PVOD jambolan fruits, after 1.5 h of process, in treatments with different combinations of temperatures (20-50 • C), sucrose concentrations (30-60%), pressures (10-90 kPa), and calcium lactate concentrations (0-4%). However, SG slightly increased in the material after 8 h. Thus, the pressure and concentration gradients gradually decreased as time progressed, until the equilibrium condition was achieved.…”

“…The following set was chosen for the osmotic pretreatment: 60% sucrose, 4% calcium lactate, and 10 kPa absolute pressure (90% vacuum pulse). These conditions presented the greatest moisture losses in jambolan, according to the previous study from Araújo and Pena [26]. Additionally, to avoid significant depletion of bioactive compounds during PVOD (at elevated temperatures) [27], the set was fixed at 25 • C. The osmotic solutions were prepared by dissolving sucrose and calcium lactate in distilled water, at ambient temperature (≈25 • C).…”

“…There have been PVOD kinetics studies related to jambolan, using ultrasonic vacuum pretreatment [25], as well as other research emphasizing the selection of variables with significant effects over the fruit's OD [26]. However, as far as our knowledge is concerned, no studies have contemplated the use of OD pretreatment combined with air-drying conditions for this fruit.…”