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Drying of Fruits and Vegetables
Published in Arun S. Mujumdar, Handbook of Industrial Drying, 2020
K. S. Jayaraman, D. K. Das Gupta
Osmotic dehydration is a water removal process that consists of placing foods, such as pieces of fruits or vegetables, in a hypertonic solution. Since this solution has higher osmotic pressure and hence lower water activity, a driving force for water removal arises between solution and food, while the natural cell wall acts as a semipermeable membrane. As the membrane is only partially selective, there is always some diffusion of solute from the solution into the food and vice versa. Direct osmotic dehydration is therefore a simultaneous water and solute diffusion process (51). Up to a 50% reduction in the fresh weight of the food can be achieved by osmosis. Its application to fruits and, to a lesser extent, to vegetables has received considerable attention in recent years as a technique for production of intermediate moisture foods (IMF) and shelf-stable products (SSP) or as a predrying (preconcentration) treatment to reduce energy consumption and/or heat damage in other traditional drying processes.
Osmotic Dehydration and Combined Processes for Tissue Modification and Selective Ingredient Impregnation and Encapsulation
Published in Magdalini K. Krokida, Thermal and Nonthermal Encapsulation Methods, 2017
E. Dermesonlouoglou, P. Taoukis, M. Giannakourou, Magdalini K. Krokida
Osmotic dehydration is a method traditionally used for a variety of food matrices for the partial removal of moisture and the uptake of solute, resulting in alteration of the composition of the original product. Temperature, concentration of the solution, type of osmotic compound, variety, geometry, and other properties of the raw material are among the most important process parameters and the optimization of their values is crucial for achieving the best final products. Application of treatments such as pulsed electric field, high pressure, gamma irradiation, vacuum, microwave, centrifugal force, or ultrasound in conjunction with OD procedure can accelerate the mass transfer and drying rates by the modification of the cell membranes. Through these combined techniques, apart from the enhancement of the OD process, the nutritional, functional, and sensory properties of the final product can be significantly improved. Among the different combinations, the simultaneous application of ME and OD, although only recently proposed in recent literature, seems promising as an innovative process to incorporate microcapsules into the intercellular spaces of fruit tissues. The most important advantage of this combined process is its versatility that allows for designing tailor made, healthy products with desired flavors and functional substances. In this context, further studies concerning the influence of OD and emulsion parameters on product stability and quality are necessary to sustain the benefits of this novel methodology.
Food Preservation Methods
Published in İbrahim Dinçer, Heat Transfer in Food Cooling Applications, 1997
Recently there has been increasing interest in using osmotic dehydration for partial drying of fruits and vegetables before drying and freezing processes. Some advantages of partial drying are [31]: saving in energy due to the reduced refrigeration load during drying and freezing,saving in packaging and distribution costs due to reduction in weight of the products, andhigh quality.
Pulsed pressure enhances osmotic dehydration and subsequent hot air drying kinetics and quality attributes of red beetroot
Published in Drying Technology, 2023
Yu-Peng Pei, Bao-Hu Sun, Sriram K. Vidyarthi, Zhi-Qiang Zhu, Sheng-Kun Yan, Yang Zhang, Jiqiang Wang, Hong-Wei Xiao
Preserved fruit is a very popular snack in China because of its attractive color, special flavor, and soft texture. Osmotic dehydration is one of the most frequently applied methods for producing preserved fruits, in which fruits or vegetables can be put into hypertonic solution, e.g., salt and/or sugar solution.[3] A simultaneous diffusion involving the outflow of water from food to solution and from solution to food occurs naturally due to the high osmotic pressure and low water activity.[4] The complicated cellular structure of the foodstuff, like a selectively permeable membrane, brings about the phenomenon that the diffusion rate of water moving through the permeable membrane is higher than that of the solute,[5,6] subsequently leading to the weight loss and gradual shrinkage of food. However, since only the high osmotic pressure and low water activity are in charge of the simultaneous diffusion, the osmotic dehydration process is inefficient and time-consuming,[3] which may result in the microbial contamination, increase in production cost, diminution in commercial value, and affect market competitiveness. Hence, to improve the process kinetics and final product quality, a series of methods facilitating osmotic dehydration have been developed.
Evaluation of mass transfer kinetics and quality of microwave‐osmotic dehydrated mango cubes under continuous flow medium spray (MWODS) conditions in sucrose syrup as moderated by dextrose and maltodextrin supplements
Published in Drying Technology, 2020
Bhakti Shinde, Hosahalli S. Ramaswamy
Osmotic dehydration (OD) has been generally recognized as a dehydration pretreatment which can result in better quality retention, better energy conservation, and a better acid to sugar ratio in dried fruits with superior sensory properties, and such products have been used as useful ingredients in many processed food formulations or complex foods. It has been demonstrated in previous work that osmotic pretreatment reduces enzyme activity and product water activity along with minor changes in product characteristics.[3] It also reduces enzymatic browning[3] and often retains or improves color[3–5] and texture[6–8] of the food product. Osmotic dehydration is a water removal technique, in which horticultural products such as fruits and vegetables are immersed in a hypertonic solution for a physical separation of moisture from the fruit to the concentrated solution due to osmotic forces. In general, in osmotic dehydration there is a significant amount of moisture loss, but also the process is associated with a simultaneous impregnation of solids from the osmotic solution.[9–11] Because this moisture loss is facilitated without causing the moisture to be vaporized as in traditional dehydration processes, significantly lower energy is required for accomplishing the moisture removal. Further, since the moisture content of osmotically dehydrated products is still generally high, they are usually coupled with other finished drying processes such as air drying, vacuum drying, or freeze drying to reduce the moisture content to the final target level. Generally, the combination of osmotic drying and a second-stage air-drying has been demonstrating to yield a better quality product and energy savings.[9,11] However, one of the serious problems with osmotic dehydration is that the process is inherently very slow often requiring several hours for reducing the initial moisture content by about 50%.
AHP-based procedure for optimization of microwave-assisted blackberry sugar osmotic process
Published in Drying Technology, 2018
ChunFang Song, Guiyi Luo, Tian Sang, Zhenfeng Li, Wanxiu Xu, G. S. V. Raghavan, Haiying Chen
There is a growing trend in consumer demand for blackberries, given their good taste and health-beneficial properties. Blackberries are notable for being a rich source of compounds, such as polyphenols, benzoic acid, hydroxycinnamic acid, and flavonoids, which are considered among the top rank of consumed antioxidant foods.[1] The blackberry fruit is also characterized by a high moisture content (nearly 90%, wet basis), which makes it a very perishable fruit and susceptible to fungal attack, about 60% of its nutrients are lost if processed improperly.[2] The perishable characteristics of blackberries impose very specific requirement on postharvest and transport practices. The development of more resistant and high-yielding cultivars has resulted in production levels that outweigh the in-season demand. Since the blackberries are high moisture fruits, are very fragile and are grown extensively in temperate and cool climates, sun drying is not usually possible. The fruits are usually preserved in frozen form, or they are freeze-dried. Osmotic dehydration is used to reduce energy required for freeze-drying which is the preferred method for small fruits. Osmotic dehydration is gaining popularity as a complementary processing step in the integrated food processing industry due to its quality and energy related advantages.[3] Madamba et al. determined the effects of osmotic treatment time, temperature, sugar concentration and thickness on the osmotic dehydration of ripe carabao mangoes and established optimum osmotic dehydration conditions.[4] It has shown that osmotic pretreatment improves quality of resulting dried products such as reduced discoloration of fruits from enzymatic browning, reduced the heat damage to texture and unwanted color change and increased sugar to acid ratio which improves the taste related attributes.[5] However, traditional osmotic dehydration generally experience a long period, which results in the great loss of nutritional quality and low efficiency.[6] Thus, the possibility of using microwave technology to produce superior quality dried blackberries are considered and developed for better value added product.