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

Effects of basil seed and guar gums coatings on sensory attributes and quality of dehydrated orange slices using osmotic-ultrasound method

In this work, the effects of gum coating (basil seed and guar gums), ultrasonic power, sonication time, and sucrose concentration on the osmosis dehydration parameters (water loss, solid gain, and rehydration rate), sensory attributes, color changes, and surface shrinkage of dehydrated orange slices using osmotic-ultrasound method were studied. The moisture loss and sucrose gain increased when the ultrasonic duration and sucrose level increased. The edible coating reduced solids absorption, with the lowest sucrose absorption in the basil seed gum-coated slices. Also, the coating increased rehydration rate of dried orange slices, with the highest rehydration ratio in the basil seed gum-coated slices (225.91 %). Edible coating with basil seeds gum improved the sensorial attributes of dried orange slices. The total color difference (ΔE) and surface shrinkage of osmotic dehydrated, dried, and rehydrated orange slices decreased with edible coating pretreatment and increasing in the sonication intensity. As the ultrasound duration enhanced from 5 to 15 min, the average surface shrinkage values of dried and rehydrated orange slices increased from 22.74 % to 26.36 %, and 12.18 % to 15.50 %, respectively. The current work confirmed that the gum coating has the potential to enhance appearance quality and sensorial attributes of osmotic-ultrasound dehydrated orange slices.

Effect of Biopolymer Dip-Coating Pretreatments as a Non-Thermal Green Technology on Physicochemical Characteristics, Drying, and Rehydration Kinetics of Santa Maria Pears

This research was conducted to determine the influences of biopolymer dip-coating pretreatments as a non-thermal green technology on the drying behavior, retention of bioactive compounds, and quality properties of pears. The fresh pears were washed, peeled, and diced into cubes of 5 × 5 mm with a 2 mm thickness and were dipped into 0.3% (w/v) solutions of sodium alginate (SA), pectin (PC), xanthan gum (XG), Arabic gum (AG), and gelatin (GE) before hot air drying (70 °C, 2.0 m/s). The weight loss of samples during drying was recorded online, and the moisture ratio (MR) and drying rate were plotted against drying time. Biopolymers significantly decreased the drying time (maximum 33.33% by SA) compared with uncoated samples except for XG. Moisture diffusion coefficients were determined according to Fick's second law of diffusion by plotting LnMR against drying time, and a linear regression analysis was applied to the data for the determination of moisture diffusion coefficients which ranged from 2.332 to 3.256 × 10^-9 m²/s. The molecular transport of momentum, heat, and mass were determined from Newton's law of viscosity, Fourier's law, and Fick's law, respectively. The results indicated that the friction drag force, convective heat, and mass transfer coefficients were 6.104 × 10^-6 N, 76.55 W/m²·K, and 0.0636 m/s, respectively. Mathematical modeling showed the suitability of the Midilli and Kucuk and the Peleg models for the prediction of drying and rehydration processes, respectively. Thermal conductivity, specific heat, and density of coated samples ranged from 0.559-0.579 (W/m·K), 3735-3859 (J/kg·K), and 850.90-883.26 (Kg/m³), respectively. The porosity was reduced due to the penetration of biopolymers into the cellular matrix of samples. The highest total polyphenol content and antioxidant activity belonged to the AG samples. The biopolymers covering the surface of samples produced a protection layer against the loss of bioactive compounds. Biopolymers can be successfully used as a non-thermal green process for improving the drying and quality characteristics of pears at the industrial level.

Effects of Sodium Alginate Edible Coating with Cinnamon Essential Oil Nanocapsules and Nisin on Quality and Shelf Life of Beef Slices during Refrigeration

ABSTRACT

The effects of a new edible sodium alginate (SA) coating incorporating cinnamon essential oil nanocapsules (CEO-NPs) and nisin were investigated with beef slices in refrigerated storage for 15 days. All beef samples were analyzed for physicochemical properties (pH, weight loss, and total volatile base nitrogen) and antimicrobial activity against total bacteria. Changes in color parameters and sensory attributes of all beef samples also were evaluated. Incorporation of the complex of CEO-NPs and nisin into the SA coating retarded the growth of microorganisms and reduced lipid oxidation, as determined by pH, total volatile base nitrogen, and total bacteria counts. This treatment also extended the shelf life of beef slices to 15 days. The SA coating with CEO-NPs and nisin significantly reduced weight loss and improved color, odor, texture, and purge quality of the beef samples. These results suggest that treatment with the SA coating enriched with CEO-NPs and nisin can significantly retard the deterioration of beef slices, and the complex of CEO-NPs and nisin can improve antioxidant, antibacterial, and sensory properties of the SA coating. This new edible coating could be useful for preserving beef slices.

HIGHLIGHTS

Enhancing drying efficiency and quality of seed-used pumpkin using ultrasound, freeze-thawing and blanching pretreatments

Effects of blanching (BL), ultrasound (US) and freeze-thawing (FT) pretreatments prior to far-infrared drying (FIRD) on drying characteristics, water distribution, and quality parameters of seed-used pumpkin (SUP) slices were investigated in this study. US, BL and FT pretreatments significantly accelerated drying rate due to the destruction of cell structure. Modified Page model was the fittest model for predicting the FIRD process. Low field nuclear magnetic resonance (LF-NMR) results revealed that T₂ distribution curves of all pretreated samples moved rapidly to the positive x-axis direction, indicating an increase in the rate of water migration. The color of US-FIRD was closer to fresh SUP. BL-FIRD exhibited the highest free polyphenols content (241.28 ± 1.11 mg GAE/100 g DW) and total carotenoids content (129.69 ± 2.49 μg/ g DW), increasing by 45% and 34% respectively compared to the untreated sample.

Effect of Osmotic Pretreatment Combined with Vacuum Impregnation or High Pressure on the Water Diffusion Coefficients of Convection Drying: Case Study on Apples

The paper presents water diffusion coefficients as providing a significant contribution to the creation of a comprehensive database and knowledge of weight variation during the drying process of raw plant materials that is used for modelling the technological process and designing innovative products. Dehydration is one of the most widely used methods for improving the stability and durability of fruit and vegetables because it reduces water activity and microbial activity, and minimises the physical and chemical changes during storage. The considerable impact of pressure on heat exchange and weight during the convection drying process of osmotically pretreated apples is demonstrated. The course of the drying curves and the drying rate is determined by the use of pressures of 0.02 and 500 MPa. Varied pressure applied during osmotic impregnation significantly influences the value of the diffusion coefficient: the average determined for the entire course of the drying curve and the average determined in the intervals of the reduced water content. The lowest values of the average water diffusion coefficient are obtained for apples preboiled under overpressure conditions and, at the same time, the determined diffusion coefficients in the water content are characterised on the drying curve by a clearly decreasing course until the reduced water content reaches approximately 0.2.

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.

Current Applications of Ultrasound in Fruit and Vegetables Osmotic Dehydration Processes

Ultrasound (US) is a promising technology, which can be used to improve the efficacy of the processes in food technology and the quality of final product. US technique is used, e.g., to support mass and heat transfer processes, such as osmotic dehydration, drying and freezing, as well as extraction, crystallization, emulsification, filtration, etc. Osmotic dehydration (OD) is a well-known process applied in food processing; however, improvements are required due to the long duration of the process. Therefore, many recent studies focus on the development of OD combined with sonication as a pretreatment method and support during the OD process. The article describes the mechanism of the OD process as well as those of US and changes in microstructure caused by sonication. Furthermore, it focuses on current applications of US in fruits and vegetables OD processes, comparison of ultrasound-assisted osmotic dehydration to sonication treatment and synergic effect of US and other innovative technics/treatments in OD (such as innovative osmotic solutions, blanching, pulsed electric field, reduced pressure and edible coatings). Additionally, the physical and functional properties of tissue subjected to ultrasound pretreatment before OD as well as ultrasound-assisted osmotic dehydration are described.