Effects of chitosan coating on mass transfer during osmotic dehydration of papaya

Review of osmotic dehydration: Promising technologies for enhancing products' attributes, opportunities, and challenges for the food industries

Osmotic dehydration (OD) is an efficient preservation technology in that water is removed by immersing the food in a solution with a higher concentration of solutes. The application of OD in food processing offers more benefits than conventional drying technologies. Notably, OD can effectively remove a significant amount of water without a phase change, which reduces the energy demand associated with latent heat and high temperatures. A specific feature of OD is its ability to introduce solutes from the hypertonic solution into the food matrix, thereby influencing the attributes of the final product. This review comprehensively discusses the fundamental principles governing OD, emphasizing the role of chemical potential differences as the driving force behind the molecular diffusion occurring between the food and the osmotic solution. The kinetics of OD are described using mathematical models and the Biot number. The critical factors essential for optimizing OD efficiency are discussed, including product characteristics, osmotic solution properties, and process conditions. In addition, several promising technologies are introduced to enhance OD performance, such as coating, skin treatments, freeze-thawing, ultrasound, high hydrostatic pressure, centrifugation, and pulsed electric field. Reusing osmotic solutions to produce innovative products offers an opportunity to reduce food wastes. This review explores the prospects of valorizing food wastes from various food industries when formulating osmotic solutions for enhancing the quality and nutritional value of osmotically dehydrated foods while mitigating environmental impacts.

Edible coatings as osmotic dehydration pretreatment in nutrient-enhanced fruit or vegetable snacks development: A review

Edible coatings (ECs) are thin layers applied on food to protect it and improve quality. They are made from bio-based materials such as polysaccharides, proteins, lipids, or their composites. The incorporation of functional agents, such as bioactive compounds, vitamins, or antimicrobials into the EC, has been investigated to control the shelf life of many food products from horticulture ones to processed food. Osmotic dehydration (OD) as a mild technology may also positively impact the availability of innovative fruit snacks and consequently influence consumer health. Combination of the EC with the OD aims to remove water through the semipermeable membrane while limiting the transfer of solutes from the dehydrated tissue and in the opposite direction from the osmotic solution to the food. The development trend of the snack market is expanding, especially with health-promoting properties. Consumers pay increasing attention to quality of food and its beneficial effects on health. This review attempts to provide the advancement of recent studies on the application of the EC before the OD of different fresh or fresh-cut fruit and vegetables. A fundamental theory related to the methodology of creating the EC, their composition, and the influence on the physicochemical properties of products that are osmo-dehydrated to a medium water content or additionally dried to a low water content have been described. Efforts have been exerted to introduce hydrocolloids used in the production of the EC, including new sources of biopolymers such as agricultural waste and by-products. The perspectives of using ECs in the technology of producing pro-healthy snacks are emphasized.

Synergetic effects of ultrasound and sodium alginate coating on mass transfer and qualities of osmotic dehydrated pumpkin

This research studied the effects of combined ultrasound and 3% sodium alginate (SA) coating pretreatment (US + Coat) on mass transfer kinetics, quality aspects, and cell structure of osmotic dehydrated (OD) pumpkin. The results of the pretreatment were compared with the results of control (non-pretreated osmotic dehydration) and other three pretreatment methods, which were 1) ultrasound in distilled water for 10 min (USC), 2) ultrasound in 70% (w/w) sucrose solution (US) for 10, 20 and 30 min, and 3) coating with 1%, 2%, 3% (w/w) SA. The coating pretreatments with SA resulted in a higher water loss (WL) but lower water activity and solid gain (SG) than other treatments. US pretreatments resulted in the highest effective diffusion coefficients of water (D_w) and solid (D_s) but the cell structure of the product was deformed. The 3% SA coating treatment had the highest WL/SG (5.28) but with the longest OD time (12 h). Using the US + Coat pretreatment gave satisfactory high WL/SG (5.18), D_w (1.09 × 10^-10 m²s^-1) and D_s (5.15 × 10^-11 m²s^-1), reduced the OD time to 9 h, and preserved the cell structure of the product. This research suggests that US + Coat pretreatment can be an effective processing step in the production of OD pumpkin.

The Effect of a New Coating on the Drying Performance of Fruit and Vegetables Products: Experimental Investigation and Artificial Neural Network Modeling

A study on mass transfer using new coating materials (namely alginic acid and polygalacturonic acid) during osmotic dehydration—and hence in a laboratory-scale convective dryer to evaluate drying performance—was carried out. Potato and apple samples were examined as model heat-sensitive products in this study. Results indicate that the coating material containing both alginic acid and polygalacturonic acid causes higher water loss of about 17% and 7.5% and lower solid gain of about 4% and 8%, respectively, compared to uncoated potato sample after a typical 90 min osmotic dehydration process. Investigation of drying performance using both coating materials showed a higher reduction in the moisture content of about 22% and 18%, respectively, compared with uncoated samples after the 3 h drying period. Comparisons between the two proposed coating materials were also carried out. Samples (potato) coated with alginic acid demonstrated better performance in terms of higher water loss (WL), lower solid gain (SG), and notable enhancement of drying performance of about 7.5%, 8%, and 8%, respectively, compared to polygalacturonic acid. Similar outcomes were observed using apple samples. Additionally, an accurate model of the drying process based on the experimental dataset was created using an artificial neural network (ANN). The obtained mean square errors (MSEs) for the predicted water loss and solid gain outputs of the potato model were 4.0948e⁻⁵ and 3.924e⁻⁶, respectively. However, these values for the same parameters were 3.164e⁻⁵ and 4.4915e⁻⁶ for the apple model. The coefficient of determination (r²) values for the two outputs of the potato model were found to be 0.99969 and 0.99895, respectively, while they were 0.99982 and 0.99913 for the apple model, which reinforces the modeling phase.

Effects of sodium alginate-based coating pretreatment on drying characteristics and quality of heat pump dried scallop adductors

BACKGROUND

Drying efficiency and quality maintenance are the major concerns of both manufactures and consumers. Heat pump drying (HPD) is suitable for heat sensitive foodstuffs due to its ability to independently control the drying operation parameters. However, lower drying rate and energy efficiency in the later period of HPD are the bottlenecks that restrain its application. A novel approach using hydrocolloids as pretreatment coatings prior to drying was designed to solve these problems. The effects of sodium alginate (SA) coating, drying temperatures and air velocities on the drying characteristics and quality attributes of scallop adductors were evaluated.

RESULTS

Drying took place in the falling rate period. Drying time decreased with increasing temperature, air velocity and SA coating. The Two Term model and the Wang and Singh model gained the best fit for thin-layer drying of scallop adductors and SA film, respectively. Effective moisture diffusivity increased with temperature, velocity and SA coating and were in the range 7.352-14.620 × 10^-11 , 9.890-17.100 × 10^-11 and 2.348-4.604 × 10^-10  m²  s^-1 for uncoated scallop adductors, SA coated scallop adductors and SA films, respectively. The activation energies for SA films, coated and uncoated scallop adductors were 17.07, 20.78 and 26.17 kJ mol^-1 , respectively. Dried scallop adductors with SA coating pretreatment exhibited a significant lower value of shrinkage rate and hardness, and higher value of toughness than uncoated ones at 30 °C and 2.0 m s^-1 (P < 0.05).

CONCLUSION

Hydrocolloid coating is a promising pretreatment in improving HPD efficiency and enhancing quality attributes of dried scallop adductors. © 2019 Society of Chemical Industry.

Modeling of osmotic treatment of ostrich meat coated by tragacanth and salep

This study involved coating of ostrich meat pieces (30 × 30 × 20 mm) with tragacanth gum (0.25%, 0.5%, and 1%) and salep gum (1%, 2%, and 3%) before osmotic treatment with salt solution (5, 15, and 27%) with the immersing duration of 1, 2, 4, 12, and 24 h to accelerate the transfer of moisture and minimize solid gain. This study also involved the investigation of the efficiency of the Peleg's model, Azuara's model, and diffusion equation in modeling water gain/loss and solid gain in meat pieces. Water gain/loss and solid gain were significantly affected by osmotic and coating concentrations during osmotic treatment. The Peleg's model had the best efficiency in the prediction of water loss at 5% and 27% concentrations and solid gain at 27% concentration. Diffusion model showed a favorable performance in the prediction of water loss and solid gain at 27% and 15% concentrations, respectively. It can be concluded that coating pre-treatment could control solid gain and facilitate water loss/gain.

The Influence of the Osmotic Dehydration Process on Physicochemical Properties of Osmotic Solution

The osmotic dehydration (OD) process consists of the removal of water from a material during which the solids from the osmotic solution are transported to the material by osmosis. This process is commonly performed in sucrose and salt solutions. Taking into account that a relatively high consumption of those substances might have a negative effect on human health, attempts have been made to search for alternatives that can be used for osmotic dehydration. One of these is an application of chokeberry juice with proven beneficial properties to human health. This study aimed to evaluate the physicochemical properties of the OD solution (chokeberry juice concentrate) before and after the osmotic dehydration of carrot and zucchini. The total polyphenolics content, antioxidant capacity (ABTS, FRAP), dynamic viscosity, density, and water activity were examined in relation to the juice concentration used for the osmotic solution before and after the OD process. During the osmotic dehydration process, the concentration of the chokeberry juice decreased. Compounds with lower molecular weight and lower antioxidant capacity present in concentrated chokeberry juice had a stronger influence on the exchange of compounds during the OD process in carrot and zucchini. The water activity of the osmotic solution increased after the osmotic dehydration process. It was concluded that the osmotic solution after the OD process might be successfully re-used as a product with high quality for i.e. juice production.

Application of protein-phenolic based coating on tomatoes (Lycopersicum esculentum)

The aim of this study was to investigate the use of protein-phenolic based coating made from fermented rice bran on cherry tomatoes (Lycopersicum esculentum). Tests were performed with glycerol 3% (v/v), glycerol with protein-phenolic rice bran extract (5%), glycerol with protein-phenolic extract after 96 hours of fermentation (5%), and a control (without coating). The coated cherry tomatoes were kept at room temperature for 28 days. Mass loss, pH and acidity, total soluble solids, and carotenoids were determined every 96 hours. The coating made from the biomass extract reduced the carotenoid and acidity levels in the fruits studied by 17 and 21.1%, respectively, compared to the control. The coating proved an efficient barrier to water vapor with mass loss of 57% less than the control suggesting that it can be used as an alternative for vegetable tissue conservation.

Osmotic dehydration of fruits and vegetables: a review

The main cause of perishability of fruits and vegetables are their high water content. To increase the shelf life of these fruits and vegetables many methods or combination of methods had been tried. Osmotic dehydration is one of the best and suitable method to increase the shelf life of fruits and vegetables. This process is preferred over others due to their vitamin and minerals, color, flavor and taste retention property. In this review different methods, treatments, optimization and effects of osmotic dehydration have been reviewed. Studied showed that combination of different osmotic agents were more effective than sucrose alone due to combination of properties of solutes. During the experiments it was found that optimum osmosis was found at approximately 40 °C, 40 °B of osmotic agent and in near about 132 min. Pretreatments also leads to increase the osmotic process in fruits and vegetables. Mass transfer kinetics study is an important parameter to study osmosis. Solids diffusivity were found in wide range (5.09-32.77 kl/mol) studied by Fick's laws of diffusion. These values vary depending upon types of fruits and vegetables and osmotic agents.