Evaluation of water loss and solute uptake during osmotic treatment of white radishes (Raphanus sativus L.) in salt-sucrose solution

White radish, scientifically known as Raphanus sativus L., is a yearly vegetable. Currently, it was being grown and widely used in the world, including Vietnam. These plants have been used as food or food processing. The osmotic treatment of vegetables involves the removal of water from plants in which the solids from the osmotic solution are transported to the plant material by osmosis. By this procedure, sucrose and saline solution are usually performed. White radishes were dehydrated in different hypertonic solutions by combined sucrose and NaCl at three different concentrations, including 9 runs. Mass transfer behaviour was applied according to three common models such as Fick’s second law, Weibull and Peleg’s equations based on the change of moisture and solid content of white radish during osmotic dehydration. The obtained results showed that the mass transfer was fast at initial stage and became slowly at the later stage. The effective moisture (Dm) and solid diffusivities (Ds) were ranged from 1.0186 to 1.2826x10-8 and from 1.0692 to 2.3322x10-8 (m2/s) respectively. The Peleg’s equation was found to be the best fitting for water loss and solid uptake thanks to the high determination coefficient (>97.64%) and the low average relative error (<3.174%). Raised up solution concentration resulted in higher water loss and mass gain.

Modeling antioxidative activity of osmo-dehydrated in molasses and successively lyophilized peach

Investigation and modeling of osmotic dehydration parameters on antioxidative activity of peach samples in combined dehydration methods of osmotic dehydration and lyophilization are done to produce the final product of preserved and enhanced antioxidative activity. Antioxidative activity of dehydrated peach samples was investigated by measuring DPPH radical scavenging capacity, and response surface methodology for developing mathematical models was applied. The results showed that combined osmodehydration and lyophilization processes have led to the increased antioxidative activity of dehydrated peaches samples. All three investigated osmodehydration process parameters affected the increase of DPPH values, where process time was found to be the most influential parameter. Maximal obtained DPPH value of 18.25% was achieved in osmotic dehydration process of 5 hours, in 80% concentration molasses, at a temperature of 50 °C and successive 5-hour lyophilization process. Developed mathematical model of DPPH response of dehydrated peach samples was statistically significant, while predicted and observed responses had good correlation, allowing good prediction of the peach samples’ antioxidative activity.

Effect of osmotic dehydration combined with citric acid on bioactive compounds in freeze-dried MD2 pineapple

The use of freeze drying process to prolong the shelf life of food products is considered mainstream in food industries due to its capability to retain the nutritional value. Citric acid and osmotic solution were used as a pre-treatment in this study to produce high-quality dried products. Four treatment groups were observed, including untreated (control), 1% citric acid (CA), 1% CA with 20% sugar solution (CAOD 20%), and 1% CA with 60% sugar solution (CAOD 60%). Physical properties such as moisture content; pH; total soluble solid; colour value; and bioactive compounds, such as vitamin C, total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activities were evaluated in freeze-dried pineapples. The result showed that CAOD 60% demonstrated a positive effect, with the least moisture content and the lowest value of colour changes (ΔE) at 5.69 ± 0.04% and 33.76 ± 2.17, respectively, as compared with that of other samples. In terms of phytochemical, the control and CA groups recorded higher retention of vitamin C, TPC, and TFC compared with other osmotic dehydration samples; however, there was no significant effect (p<0.05) on TPC and TFC. Interestingly, CAOD 60% possessed strong antioxidant activity, with the lowest IC50 value of 85.85 ± 5.93. From these findings, it was found that CAOD 60% resulted in positive effect on both the physical qualities and preservation of antioxidant activity, making it a recommended condition for pre-treatment in fruit preservation, which is essential in ensuring both the food security aspect and maintenance of its nutritional value.

Hybrid drying of ultrasound assisted osmotic dehydration (UOAD) and hot air drying of Eucalyptus deglupta

Eucalyptus deglupta is one of the promising medicinal plants from Mytracea family consisting of bioactive compounds that are to be used in medications. The bioactive compounds present in Eucalyptus deglupta were extracted at the best yield using a hybrid drying method consisting of ultrasound assisted osmotic dehydration (UOAD) and hot air drying in this study. The drying conditions of UAOD were optimised with response surface methodology (RSM) to attain the highest antioxidant activity via of DPPH radical scavenging assay. Four parameters were optimised with response surface methodology, namely concentration of sucrose (v/w), temperature (°C), duration of drying and intensity of ultrasound (%) ranged from 30% to 50%, 20°C to 60°C, 40 min to 100 min and 60% to 100%, respectively. A series of 27 combinations of the UAOD drying conditions were performed and followed by hot air drying performed at 60°C until a constant weight was achieved. A moderate scavenging activity of DPPH assay (56.12%) was achieved at a concentration of sucrose, temperature, duration of drying and intensity of ultrasound of 50%, 40°C, 100 min and 264 W, respectively.