Ways and Means for the Infusion of Bioactive Constituents in Solid Foods

The development and consumption of functional food, or foods that promote health not merely basic nutrition, is on rise. In recent years, industrial and consumer interests have focused on developing foods supplemented with bioactive constituents that provide greater physiological benefits. The direct addition of these components to liquid or fabricated solid foods has led to a wide range of new products appearing on the market. Osmotic dehydration, an operation in which food stuff is soaked in solution of low water activity, has been reported as a suitable technology for formulating new products because of the twofold effect that it has on food where it partially removes water and impregnates the food pieces (solid food matrix) with solutes from the osmotic solution. The article focuses on the impregnation of bioactive constituents having added advantage to human health such as antioxidants, minerals, vitamins, and probiotics. The infusion of enzymes and aroma also has been discussed. Application of ultrasound, vacuum, high pressure, and/or atmospheric impregnation techniques appears to be the feasible technologies for impregnation of solid food matrix for the incorporation of bioactive ingredients.     

Developments in osmotic dehydration technique for the preservation of fruits and vegetables

In recent years much attention has been focused on maintaining the freshness of fruits and vegetables by immersion of cellular materials containing water in an osmotic solution. It results in the development of intermediate moisture products having lower water activity, which is imparted by solute gain and water loss. During the process, chemical, physical and biological activities, which deteriorate the foods, are lowered considerably; hence extends the shelf life of food products. In this process moisture is withdrawn from the product at ambient temperature by diffusion, so phase change has been avoided. Besides, it helps to improve the nutritional and sensory attributes of food products and is less energy intensive process as compared to other drying techniques. Osmotic dehydration is influenced by various factors such as osmotic agent, time and temperature, solute concentration, solution to sample ratio, agitation and geometry of the materials. Recently, osmotic dehydration has been combined with several other methods namely, pulsed high electric field, high hydrostatic pressure, ultrasound, centrifugal force, vacuum and gamma irradiation. These techniques have been employed during or after osmotic treatment to enhance osmotic dehydration performance by increasing the cell membrane permeability and mass transfer rate. These combined operations reduce the drying time, minimizing further energy costs. In this study, various segments of osmotic dehydration techniques and its application in food processing as well as recent advances in osmotic dehydration have been reviewed.Industrial relevanceThe osmotic dehydration technique is gaining popularity as a mean of obtaining minimally processed food. This review paper deals with the kinetics and mechanisms of osmotic dehydration technique for the preservation of fruits and vegetables. The various factors effecting osmotic mass transfer rate in food have been reviewed. In this paper, the combined effect of osmotic dehydration and several other innovative techniques (pulsed high electric field, high hydrostatic pressure, ultrasound, centrifugal force, vacuum and gamma irradiation) on the quality and shelf life of fruits and vegetables have been reviewed. These techniques have been employed during or after osmotic treatment to enhance osmotic dehydration performance by increasing the cell membrane permeability. These combined operations reduce the drying time, minimizing further energy costs as well as improving the quality of fruits and vegetables during storage.     

Image analysis of osmotically dehydrated fruits: melons dehydration in a ternary system

Osmotic dehydration represents a technological alternative to reduce post-harvest losses of fruits. In this work, the osmotic dehydration of a ternary system (water/sugar/salt) was investigated for melon (Curcumis melo L.) dehydration using image analysis. Three kinds of sugars were used to formulate the osmotic solutions: sucrose, glucose and manitol. The process of osmotic dehydration was studied and the effects of the ternary osmotic system on the fruit shrinkage were investigated using image analysis technique. The experimental study allowed estimating the process parameters of the osmotic dehydration. The results showed the advantage of using high sugar and salt concentrations for the osmotic solution, mild temperatures, and the use of the osmotic treatment to reduce the total processing time to dry the fruit. Image analysis enabled to show how far the solid penetrates inside the fruit and to estimate the shrinkage factor of the fruit during the osmotic dehydration.     

Osmotic dehydration assisted impregnation of curcuminoids in coconut slices

Osmotic treatment was explored as a method to infuse curcuminoids in coconut slices. The rate of mass transfer of moisture, solid and curcuminoids with or without application of ultrasound were studied over a range of concentration of osmotic solutions (0-50%). The diffusion coefficient of curcuminoids was 1.64 × 10⁻¹⁰ m²/s, when water was used in place of osmotic solute which was further enhanced by the application of ultrasound to 1.87 × 10⁻¹⁰ m²/s. Increase in the concentration of osmotic solution beyond 25% resulted in reversal in the direction of moisture and solid mass transfer. Ultrasound treatment resulted in higher moisture and solid mass transfer due to the breaking of cell structure as revealed by microstructure examination. HPLC analysis revealed that all the curcuminoids (curcumin, demethoxycurcumin and bisdemethoxycurcumin) were infused into the coconut matrix. The present study concluded that osmotic dehydration is a feasible technology for impregnation of functional ingredients into foods without altering its matrix.     

KINETICS of OSMOTIC DEHYDRATION of COCONUT

Osmotic dehydration rates were determined for coconut over a range of osmotic solution concentration (40–70°B) and temperature (25–45C). A semi-empirical relation for kinetics of osmotic dehydration has been proposed, which indicates the moisture diffusion as a function of concentration of osmotic solution and its temperature. Good agreement was observed between the observed and predicted values (correlation coefficient 0.90). the effective diffusion coefficients of water in coconut during osmotic dehydration were estimated and also the activation energy of the osmotic dehydration process of coconut was found as 1.75 × 10⁴ J/kg-mole.     

High-pressure-assisted infusion of bioactive compounds in apple slices

High-pressure treatment was explored as a technique for infusion of bioactive compounds (anthocyanin) into solid foods matrix (apple). The rate of mass transfer of moisture, solid, and anthocyanin content with or without the application of high pressure was studied over a wide range of concentration of osmotic solution (0–50% sucrose). The increase in concentration of osmotic solution resulted in reduced infusion of anthocyanin. However, high-pressure treatment resulted in higher moisture and solid mass transfer due to cell permeabilization (as revealed by microstructure analysis). It was revealed that high-pressure treatment resulted in higher infusion of the bioactive compound as compared to infusion at atmospheric pressure. The present study concluded that the high-pressure treatment of solid foods could be a feasible technology for infusion of bioactive compounds without significantly altering its matrix. This work elucidates important aspects of the science of pressure-enhanced infusion.Industrial relevanceApplication of high pressure was shown to be a feasible technique to enhance the infusion of bioactive compound (e.g., anthocyanin) in solid food matrix (apple) without significantly altering its natural solid food matrix. The application of high pressure may open up newer avenues for food industries to develop fresh-like and value-added products with improved nutrition.     

Structural Impact of Osmotically Pretreated Freeze-Dried Strawberries 0n Their Mechanical Properties

The paper investigates the impact of osmotic dehydration on the mechanical properties (i.e., structural changes and shrinkage) of freeze-dried strawberries. In the research, Senga Sengana strawberries were osmotically dehydrated in sucrose, glucose solution, and starch syrup and subjected to freeze-drying. The osmotic dehydration process strengthened the fruit structure by increasing their cell wall thickness. Osmotic pre-treatment limited the shrinkage of the strawberries by about 50%, while the compression force required for 25% deformation of the dried material was almost 2–963 times greater in comparison to the fruit not subjected to osmotic dehydration, dependent on the type of osmotic solution used.     

辣椒渗透脱水处理及渗后热风干燥特性及品质分析

以脱水率、固形物获取率、脱水率与固形物获取率比值、有效水分扩散系数、活化能、VC保留率、辣度、复水比、复原率和感官评价为考察指标,通过渗透脱水实验、渗后热风干燥实验和复水实验,考察了辣椒的渗透脱水特性、渗后热风干燥特性、复水特性和品质。结果表明:随着渗透温度的升高或渗透液中食盐含量的增加,辣椒的脱水率和固形物获取率增大。对渗透后的辣椒样品进行热风干燥处理发现,热风温度是影响热风干燥的最主要因素,其次是风速。辣椒样品的有效水分扩散系数随着温度的升高而增大,在风速为1.8 m/s的条件下,直接热风干燥辣椒样品和渗后热风干燥辣椒样品的活化能分别为(53.25±1.08)k J/mol和(44.42±0.88)k J/mol。渗后热风干燥样品的有效水分扩散系数、VC保留率、辣度、复水比和复原率均高于直接热风干燥样品,渗后热风干燥样品的复水特性和品质更好。     

EFFECT OF OSMOTIC TREATMENT WITH CONCENTRATED SUGAR AND SALT SOLUTIONS ON KINETICS AND COLOR IN VACUUM CONTACT DRYING

ABSTRACT

An experimental study of osmotic dehydration (OD) of selected heat‐sensitive products was carried out in a laboratory‐scale vacuum contact dryer. Cubes of potato and apple were examined as model heat‐sensitive objects. Experiments were conducted at different conduction heat input levels with wall temperatures in the range 35–45C under vacuum and also in pure vacuum without any external heat input. Detailed investigations were carried out of OD on drying performance, product temperature and color of the dried product.

PRACTICAL APPLICATIONS

Osmotic treatment of potato and apple samples using concentrated sugar solution shows better osmotic dehydration as well as drying rate in a vacuum contact drying system. This information may help to select the osmotic agent in any industrial application for faster drying rate in vacuum contact drying specially for food products. Moreover this work shows the analysis to find out the starting point of precipitation of osmotic agent inside the products in terms of drying time, temperature and moisture content. This information will be helpful for critical analysis in osmotic dehydration technique which in turns may help for optimum design.

     

Effect of Maltodextrin,Sodium Chloride,and Liquid Smoke on the Mass Transfer Kinetics and Storage Stability of Osmotically Dehydrated Beef Meat

Osmotic dehydration is a non-thermal process for water removal from foods. The aim of the present study was (i) to investigate the effect of binary (NaCl and water) and ternary (maltodextrin, NaCl, and water) osmotic solutions with or without 0.5% liquid smoke on moisture loss, solids gain, and salt content during osmotic dehydration of beef meat and (ii) to evaluate the microbiological and oxidative stability of the processed meat. Osmotic processing resulted in 8.01–13.15% water loss and 3.53–7.59% solids gain depending on the concentration of the osmotic medium. Liquid smoke did not affect mass transfer phenomena (P > 0.05), except for the treatment with 25% NaCl. The applied models for the estimation of the apparent coefficients demonstrated a good fit with experimental data. The simplified Fick’s equations produced the best results. Osmotic treatment with binary and ternary osmotic solutions reduced total aerobic viable microbial counts (P > 0.05) of meat during storage at 4 °C for 9 days. Liquid smoke did not affect microbial counts, but it was very effective in inhibiting lipid oxidation during storage. The results demonstrate that osmotic dehydration with the addition of liquid smoke could effectively increase the shelf life of beef meat by at least 2 days.     

Characterisation of reused osmotic solution as ingredient in new product formulation

Osmotic dehydration (OD) with sugar solutions has been used in fruit preservation but part of the process's economic viability depends on the possibility of reusing the osmotic solution (OS) in successive dehydration cycles. Despite the increase in water content, OD promotes OS enrichment in certain water-soluble natural components extracted from fruits, such as vitamins and minerals. For this reason, to recycle it for new food formulation seems to be an attractive alternative. In this paper, changes in soluble solids, a_w, pH, electrical conductivity, density, viscosity and colour in osmotic solution used for kiwifruit dehydration in function of the ratio osmotic solution/fruit (20:1, 10:1 and 5:1) and the number of cycles (up to 10) have been studied. Microbiological analysis of OS and fruit compositional changes were also studied. The results show that during OD likewise water interchange between fruit and OS, a flow of mineral salts and sugar from the fruit to the OS, is produced. Nevertheless OS changes associated to the OD of kiwifruit under the conditions of this study allow OS reuse for at least 10 cycles without any problems related to fruit dehydration level, colour fruit changes, or considerable microbiological contamination.     

物理场辅助渗透脱水技术及其在果蔬干燥中的应用

渗透脱水是一种促进果蔬干燥、保持果蔬感官和功能特性、延长果蔬货架期的非热加工技术。渗透脱水技术的主要缺点是传质效率低,物理场辅助渗透脱水技术可有效地提升渗透脱水效率。物理场辅助渗透脱水技术包括:超声波辅助技术、真空辅助技术、高静水压和高压脉冲电场辅助技术,是近年来果蔬干燥研究的热点。通过研究归纳国内外相关文献,分别从果蔬渗透脱水的机理及其传质效率影响因素、物理场辅助渗透脱水技术及动力学模型、物理场辅助渗透脱水在果蔬干燥的应用3个方面综述了物理场辅助渗透脱水技术近年来的研究进展,总结应用中存在的问题,提出未来发展方向。     

Optimization of microwave frying of osmotically dehydrated potato slices by using response surface methodology

Microwave frying of osmotically dehydrated potatoes was optimized by using response surface methodology. Osmotic dehydration was applied prior to microwave frying in order to reduce oil uptake and to evaluate the effect of osmotic dehydration on quality of microwave fried potatoes. Moisture content, oil content, hardness and color of the fried potatoes were used as quality parameters. Microwave power level (400, 550, 700 W), frying time (1.5, 2.0, 2.5 min) and osmotic dehydration time (15, 30, 45 min) were the independent variables in the study. Osmotic dehydration treatment was conducted using 20% (w/w) sodium chloride solution at 30 °C. Moisture content of the fried potatoes decreased whereas oil content, hardness and ΔE value of potatoes increased with increasing frying time and microwave power level. The increase in osmotic dehydration time reduced moisture content and oil content and increased hardness of fried potatoes. The optimum condition was found as frying at 400 W microwave power level for 1.5 min after 39 min of osmotic dehydration time.     

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.     

Acceleration of mass transfer rates in osmotic dehydration of elephant foot yam (Amorphophallus paeoniifolius) applying pulsed-microwave-vacuum

The elephant foot yam slices were processed with combined pulsed-microwave-vacuum osmotic drying. Osmotic dehydration at ambient (28 °C and 45% RH) was carried out using different levels of sucrose concentration (30, 40, 50 and 60% w/w), salt concentration (5, 7.5, 10 and 12.5% w/w) and dehydration time (10, 20, 30, 50, 70, 90 and 120 min). During the osmotic dehydration, pulsed microwave vacuum (15 kPa pressure, 1 W/g power density and 1.853 pulsating ratio) was maintained for 2 min over the sample and solution to enhance the mass transfer. For this purpose, the osmotic dehydration experiments were conducted in the microwave-vacuum cavity. Azuara model predicted the moisture loss and solid gain by elephant foot yam slices during osmosis. It was observed that both the moisture loss and the solid gain increased with increasing concentration of the osmotic solution. The optimum conditions found in the process were 40% w/w sucrose concentration, 6% w/w salt concentration and 70 min osmotic dehydration time, resulting in to 42.80% moisture loss (initial weight) and 14.65% solid gain (initial weight). Further, samples were dried using microwave vacuum dryer up to moisture content of 5–6% d.b. by varying microwave power density (2, 4, 6 and 8 W/g) and pulsating ratio (1.312, 1.625, 1.983 and 2.250). Page model was fitted to the data to study the microwave vacuum drying kinetics. The microwave vacuum drying at 1.625 pulsating ratio with microwave power density 4 W/g yielded a product with the highest overall acceptability score. Guggenheim, Anderson and deBoer (GAB) model was used in the study of the sorption behavior of dehydrated elephant foot yam and shelf life prediction.Industrial relevanceThe production of elephant foot yam in India and South East Asia is comparatively higher than other vegetables. Although, it is nutritious product and good source of energy, food industries are not interested to process elephant foot yam using a time consuming traditional osmotic dehydration process followed by hot air drying. Therefore, present research work was undertaken from industry suggestion to develop accelerated osmotic dehydration process for elephant foot yam using novel pulsed-microwave-vacuum combination followed by finish drying by microwave-vacuum. This research has been carried out to decrease industrial processing time, energy consumption and improving quality of the product. Industry will start adopting this new hybrid process of drying elephant foot yam on large scale.     

Significance of osmotic temperature treatment and storage time on physical and chemical properties of a strawberry-gel product

BACKGROUND: The development of fruit‐based foods that maintain the nutritional and sensory properties of fresh fruit may help to stimulate fruit consumption by consumers. The possibility of formulating a fruit‐gel product with osmodehydrated fruit and the reused osmotic solution (OS) obtained from the dehydration step has been demonstrated. However, the conditions of the osmotic process can significantly affect the properties of the obtained product. In this work an osmotic process at 22 °C for 6 h and at 30 °C for 3 h was employed to formulate a strawberry‐gel product. RESULTS: Significant losses of ascorbic and citric acids and anthocyanins were observed and some relevant volatile compounds of the strawberry aroma profile were developed during the osmotic process. Changes in all analysed parameters occurred mainly during the first 2 days of storage. The flux of anthocyanins from the fruit to the gel gave an attractive appearance to the formulated product. These changes were more marked for samples obtained at 30 °C. CONCLUSION: Osmotic treatment at 30 °C was more suitable for formulation of the product, because the presence of nutritional/functional compounds in the OS, and consequently in the gel matrix, was higher and the aroma and colour were more stable and homogeneous during storage. Copyright © 2011 Society of Chemical Industry     

Optimization of osmotic dehydration of melons followed by air-drying

Osmotic dehydration represents a technological alternative to reduce post‐harvest losses of fruits. In this work, the influence of the osmotic solution concentration and osmotic solution to fruit weight ratio was examined on the osmotic dehydration of melons under vacuum. The process of osmotic dehydration followed by air‐drying was studied and modelled so that it could be optimised. The developed model has been validated with experimental data and simulations have shown that how the operating conditions affect the process. An optimisation was done using the model in order to search for the best operating condition that would reduce the total processing time.     

Microwave vacuum drying of osmotically dehydrated mandarin cv. (Sai‐Namphaung)

Mandarin [mandarin cv. (Sai‐Namphaung)] was subjected to osmotic dehydration prior to microwave vacuum drying. Osmotic solutions were varied using different ratios of sucrose to glycerol (9:1, 7:3 and 5:5 w/w). Because of the decreased moisture content and solid gain during osmotic dehydration, dielectric properties of mandarin were changed significantly (P ≤ 0.05). The osmotically dehydrated mandarin was then dried further using microwave vacuum drying at 4.8 and 6.4 W g^?1. Among thin layer models, page model was the best to describe the drying of osmotically dehydrated mandarin. An increase in the microwave power could increase drying rate without significant effect on hardness of dried samples. Nonetheless, the hardness was significantly (P ≤ 0.05) reduced by an increase in the glycerol ratio in the osmotic solution. The increase in microwave power and glycerol ratio significantly (P ≤ 0.05) decreased β‐carotene content and thereby affected colour of the dried mandarin.     

Shelf life modelling of osmotically treated chilled gilthead seabream fillets

The shelf life extension of osmotically treated chilled gilthead seabream (Sparus aurata) fillets was studied. Water-loss, solid-gain, salt content and water activity were measured. Osmotic pretreatment with 40, 50 and 60% maltodextrin (DE 47) plus 5% NaCl solutions caused substantial water loss (12.3–77.0%) and solid enrichment (2.5–34.1%) with higher solution concentrations showing the highest values of mass flow. Quality indices (colour, microbial growth, TVB-N, sensory scoring) were estimated during refrigerated storage and kinetically modelled. Temperature dependence of quality loss rates was modelled by the Arrhenius equation. Shelf-life at 5°C was 4d for untreated fillets and 9, 11 and 13d for fillets treated with 40, 50 and 60% maltodextrin, respectively.Industrial relevanceThe objective of the present study was to evaluate the effect of osmotic pretreatment on the quality characteristics of gilthead seabream and to investigate the potential of using osmosis as a minimal treatment to extend the shelf life of fish products. Osmotic solution concentration had a significant effect on the osmotic dehydration of gilthead seabream fillets. Pretreated samples were found to have improved quality stability during subsequent refrigerated storage, in terms of microbial growth and organoleptic degradation, resulting in a significant shelf-life extension at all storage temperatures.     

Effects of pretreatment ultrasound bath and ultrasonic probe,in osmotic dehydration,in the kinetics of oven drying and the physicochemical properties of beet snacks

Osmotic dehydration and ultrasound are pretreatments used in order to reduce costs and processing time in the drying of food. We investigated the effect of the ultrasonic bath and an ultrasonic probe in osmotic solution, as a pretreatment of the drying process in an oven, for beet snacks. Different conditions of pretreatments (TP: ultrasonic probe treatment; TB: ultrasonic bath treatment) were performed and analyzed for water loss (WL) and solid gain (SG). After the snacks were ready, we evaluated the drying kinetics, aw, Brix, color, texture, and anthocyanin content. No difference was observed between treatments for SG and WL. The pretreatments TP5, TP10 and TB20 decreased by 22.2% the drying time in the oven. Regarding the snacks, there was no difference in texture. The colors of TP5, TP10, and TB10 were similar to the control, as well as the a_w value of the TP5 and TP10. The TP5 had the highest anthocyanin content. The use of ultrasound probe in osmotic solution for 5 min, as a predrying treatment, is a viable technology as it reduces pretreatment and drying time without impairing the quality of the final product.

Practical applications

The use of ultrasound as a pretreatment in the drying of fruits reduces the drying time. Drying is an important process in obtaining new products, in addition to increasing shelf‐life.