Color, Texture, Rehydration Ability and Phenolic Compounds of Plums Partially Osmodehydrated and Finish-Dried by Hot Air

Effects of pretreatments using plasma functionalized water, osmodehydration and their combination on hot air drying efficiency and quality of tomato (Solanum lycopersicum L.) slices

The effects of pretreatments using plasma functionalized water (PW), osmodehydration (OD), and combined plasma functionalized water and osmodehydration (PO) on the drying characteristics, physicochemical and bioactive components of tomato slices during hot air drying at an air temperature of 55 °C and velocity of 1.5 m/s were evaluated. Results revealed that PW pretreatment led to an increase in lycopene compared to fresh samples, and shortened drying time, improved ascorbic acids, TPC, TFC, acidity, rehydration, porosity and hue, but reduced TSS, compared to dried control samples, while OD resulted in lycopene degradation during pretreatment, and prolonged drying time, increased TSS, but lowered acidity, rehydration, porosity and hue, compared to dried control samples. On the other hand, PO was found to overcome the shortcomings of OD with enhancement in the lycopene during pretreatment, and showed accelerated moisture transfer, improved bioactive, acidity, porosity, rehydration, hue and texture, but decreased TSS, when compared to dried control samples. Overall, the results showed the promising potential of PW and PO pretreatments for enhancing drying efficiency and product quality for the food industry.

Osmo-air drying of banana slices: multivariate analysis, process optimization and product quality characterization

In the present work, osmotic dehydration (OD) was applied as a pretreatment to hot air drying of banana slices and the effect of OD parameters on mass transfer characteristics, color profile was analysed. Principal component analysis (PCA) of OD process revealed that solid gain, weight reduction, water loss and total soluble solids were positively correlated with each other but were found to be negatively correlated with moisture content (MC) of sample. Response surface methodology was used for optimizing the OD of banana slices and and the optimum conditions were 61.26°Brix sucrose concentration at 50 °C for 6 h, resulting in moisture reduction from 75 to 49.78%. PCA-biplot of osmo-air drying (OAD) process showed the association among response parameters, which further revealed a positive correlation of MC with bioactive components. Additionally, OAD samples were also studied for microstructure and Fourier Transform Infra-red analysis. Addition of calcium lactate to sucrose solution resulted in preserving the firmness and bioactive components during osmosis, in addition to fortifying the sample with calcium. The present study provides new possibilities for food industries in preserving the ripe banana and developing calcium fortified functional food products.

Effects of Osmotic Dehydration on the Hot Air Drying of Apricot Halves: Drying Kinetics, Mass Transfer, and Shrinkage

This study aimed to determine the effects of osmotic dehydration on the kinetics of hot air drying of apricot halves under conditions that were similar to the industrial ones. The osmotic process was performed in a sucrose solution at 40 and 60 °C and concentrations of 50% and 65%. As expected increased temperatures and concentrations of the solution resulted in increased water loss, solid gain and shrinkage. The kinetics of osmotic dehydration were well described by the Peleg model. The effective diffusivity of water 5.50–7.387 × 10−9 m2/s and solute 8.315 × 10−10–1.113 × 10−9 m2/s was calculated for osmotic dehydration. Hot air drying was carried out at 40, 50, and 60 °C with air flow velocities of 1.0 m/s and 1.5 m/s. The drying time shortened with higher temperature and air velocity. The calculated effective diffusion of water was from 3.002 × 10−10 m2/s to 1.970 × 10−9 m2/s. The activation energy was sensitive to selected air temperatures, so greater air velocity resulted in greater activation energy: 46.379–51.514 kJ/mol, and with the osmotic pretreatment, it decreased to 35.216–46.469 kJ/mol. Osmotic dehydration reduced the effective diffusivity of water during the hot air drying process. It also resulted in smaller shrinkage of apricot halves in the hot air drying process.

Increase of mass transfer rates during osmotic dehydration of apples by application of moderate electric field

Osmotic dehydration (OD) is a drying process that consists in placing the food in contact with concentrated solutions of soluble solids to reduce its water activity. The use of moderate electric field (MEF) may promote increase of the mass transfer rates due to the non-thermal effects of electroporation and permeabilization of the cells. In this context, the objective of this study was to investigate the mass transfer process kinetics during apples OD assisted by MEF, evaluating the non-thermal effects of this emerging technology. The experiments were conducted with sucrose solutions (40, 50 and 60%, m/m) at 40 °C. Samples were submitted to electrical field strength (0, 5.5 and 11.0 Vcm−1), according to an experimental design. Results indicated that the application of MEF favoured water loss and solid gain. The effective mass diffusivities of water and solids increased as voltage applied increases. Moreover, MEF negatively influenced color and reducing capacity of the samples.

Effects of Different Drying Methods and Temperature on the Drying Behavior and Quality Attributes of Cherry Laurel Fruit

This study aimed to investigate the effect of different drying methods and drying temperature on the drying kinetics, total bioactive compounds, phenolic profile, microstructural properties, rehydration kinetics, and color change of cherry laurel fruit. For this aim, hot air drying (HAD), ultrasound-assisted vacuum drying (USV), and freeze-drying (FD) were conducted on drying of cherry laurel. HAD and USV were conducted at 50, 60, and 70 °C. Drying times of the samples were 1980, 1220, and 770 min for HAD at 50, 60 and 70 °C, and 950, 615, and 445 min at 50, 60, and 70 °C, respectively, for USV. The total bioactive compound was significantly affected by both drying methods and temperature (p < 0.05). FD exhibited the highest total phenolic (TPC), total flavonoid (TFC), total anthocyanin (TAC), and antioxidant capacity value USV showed a higher amount of bioactive compounds than those of HAD at the same drying temperature. The content of total bioactive compounds significantly increased as the temperature increased for both HAD and USV (p < 0.05). The chlorogenic acid was identified as a major phenolic, and its amount significantly depended on drying methods (p < 0.05). SEM images described the surface characteristic of dried samples. HAD dried products showed higher shrinkage compared to FD and USV. All drying methods significantly affected the total color difference (ΔE) values (p < 0.05). This study proposed that USV could be as an alternative method to HAD due to higher bioactive compounds retention and rehydration ratio, shorter drying time, less color change, and shrinkage formation.

Effects of osmotic dehydration (with and without sonication) and pectin-based coating pretreatments on functional properties and color of hot-air dried apricot cubes

The objective of this study was to investigate the effect of osmotic dehydration (with and without sonication) and the use of different types of edible coating on functional and color parameters of dried apricot. Osmotic pretreatment was carried out in sorbitol solution of 35 °Brix at 55 °C for 30 and 45 min. Two levels of ultrasound frequency (25 and 35 kHz) were tested. Samples were coated using pectin + citric acid (CA), pectin + ascorbic acid (AA) and pectin alone after osmotic treatment and were dried at 60 °C. The results revealed that ultrasound assisted osmotic dehydration (UOD) led to the loss of total phenolic compounds (TPC) and vitamin C compared to osmotic dehydration (OD). TPC and β-carotene contents decreased with the increase in sonication frequency from 25 to 35 kHz. However, UOD pretreated samples showed higher antioxidant capacity and β-carotene content than OD apricots. OD improved color of hot-air dried apricot compared to UOD pretreatment. The use of pectin + AA coating increased TPC and vitamin C retention and total antioxidant activity of OD or UOD pretreated samples compared to pectin or pectin + CA coatings. UOD and pectin + AA coated samples showed lower L* and b*, and higher a* values, whereas coating with CA improved color of dried apricot cubes. Coatings containing CA or AA promoted β-carotene retention in dried apricot pretreated by OD and UOD.

The Effect of Heating Temperature on Total Phenolic Content, Antioxidant Activity, and Phenolic Compounds of Plum and Mahaleb Fruits

The effect of heating at different temperatures (60, 80, 90, 110, and 130 °C) on the total phenolic content, antioxidant activity, and phenolic compounds present in plum and mahaleb fruits was investigated. The antioxidant activity values and total phenolic contents of fresh plum (93.82% measured by DPPH method, 787.79 mg gallic acid equivalent (GAE)/100 g dry weight determined by Folin method) and mahaleb fruits (81.80%, 634.47 mg GAE/100 g dry weight) were higher than plum and mahaleb fruits dried at different temperatures (p < 0.05). Generally, the heating process caused a reduction in both total phenolic content and antioxidant activity for plum and mahaleb. While (+)-catechin (92.62 mg/kg), 1,2-dihydroxybenzene (132.15 mg/kg), gallic acid (107.01 mg/kg), and 3,4-dihydroxybenzoic acid (74.59 mg/kg) are the key phenolic compounds in fresh plum, (+)-catechin, 3,4-dihydroxybenzoic acid, 1,2-dihydroxybenzene, and syringic and caffeic acids were the major phenolic compounds of mahaleb fruits. The polyphenol content of fruits and the class of phenolics present are significantly affected by heating temperature.