A review on mechanism, quality preservation and energy efficiency in Refractance Window drying: a conductive hydro-drying technique

Thermal drying consumes up to 25% of the industrial energy consumption in developed countries. Refractance Window (RW) is a relatively new drying method that it is characterized by maintaining a relatively low temperature inside the food and short drying times. A RW dryer uses circulating hot water as a means to convey thermal energy to materials to be dehydrated. A RW dryer can produce high-quality products with retaining heat sensitive vitamins, co­­­­lor, phytochemicals content and antioxidant activity close to the freeze-dried products, while the cost of the RW equipment is less than 30 percent of the cost of a freeze-dryer and the energy consumption of RW is less than 50 percent of the energy consumption for a freeze-dryer. Early understandings heat transfer mechanism in RW drying suggested that the moist material on a thin plastic sheet over hot water, creates a “window” for infrared radiation(IR) and as the material dries, the “window” gradually cuts off the radiation. Recently a conjugate heat and mass transfer model showed that a major portion of thermal energy is transferred via conduction; some of the researchers proposed the term “conductive hydro-drying” for the name of this technology. Another important parameter in RW drying is air convection. Forced air convection causes lower product temperature and higher moisture loss in comparison with natural convection. Although many studies have been conducted on this technology, there are still many types of food materials for which RW drying and process optimization have not yet been investigated

An Update on Applications of Power Ultrasound in Drying Food: A Review

Ultrasound is sound waves with above the human hearing range frequency that is approximately 20 kHz. Application of power ultrasound in combination with other food processing methods including drying, is considered to be an emerging and promising technology. The use of novel non-thermal technologies, such as power ultrasound, is suitable to facilitate the drying of heat sensitive food materials. Ultrasound enhance heat and mas transfer which result in faster moisture removal during drying due to heating, vibration and synergistic effects. These effects could lead to product quality preservation in terms of color, texture, vitamin C and antioxidants content, by the use of milder drying conditions, and in some cases can promote better energy efficiency. In this article, after a brief review on the history of ultrasonic drying, different methods are categorized and combinations of ultrasound with novel drying methods and their effects on phytochemicals are discussed with the focus on the recently published articles. Studies showed that the quality of ultrasonically dried products was usually higher than conventionally dried products. However, the effect of ultrasonic drying on the texture and nutritional value of the products should be further investigated

Three-dimensional printing of foods: a critical review of the present state in healthcare applications, and potential risks and benefits

Three-dimensional printing is one of the most precise manufacturing technologies with a wide variety of applications. Three-dimensional food printing offers potential benefits for food production in terms of modifying texture, personalized nutrition, and adaptation to specific consumers’ needs, among others. It could enable innovative and complex foods to be presented attractively, create uniquely textured foods tailored to patients with dysphagia, and support sustainability by reducing waste, utilizing by-products, and incorporating eco-friendly ingredients. Notable applications to date include, but are not limited to, printing novel shapes and complex geometries from candy, chocolate, or pasta, and bio-printed meats. The main challenges of 3D printing include nutritional quality and manufacturing issues. Currently, little research has explored the impact of 3D food printing on nutrient density, bioaccessibility/bioavailability, and the impact of matrix integrity loss on diet quality. The technology also faces challenges such as consumer acceptability, food safety and regulatory concerns. Possible adverse health effects due to overconsumption or the ultra-processed nature of 3D printed foods are major potential pitfalls. This review describes the state-of-the-art of 3D food printing technology from a nutritional perspective, highlighting potential applications and current limitations of this technology, and discusses the potential nutritional risks and benefits of 3D food printing

3D food printing applications related to dysphagia: a narrative review

Dysphagia is a condition in which the swallowing mechanism is impaired. It is most often a result of a stroke. Dysphagia has serious consequences, including choking and aspiration pneumonia, which can both be fatal. The population that is most affected by it is the elderly. Texture-modified diets are part of the treatment plan for dysphagia. This bland, restrictive diet often contributes to malnutrition in patients with dysphagia. Both energy and protein intake are of concern, which is especially worrying, as it affects the elderly. Making texture-modified diets more appealing is one method to increase food intake. As a recent technology, 3D food printing has great potential to increase the appeal of textured foods. With extrusion-based printing, both protein and vegetable products have already been 3D printed that fit into the texture categories provided by the International Dysphagia Diet Standardization Initiative. Another exciting advancement is 4D food printing which could make foods even more appealing by incorporating color change and aroma release following a stimulus. The ultra-processed nature of 3D-printed foods is of nutritional concern since this affects the digestion of the food and negatively affects the gut microbiome. There are mitigating strategies to this issue, including the addition of hydrocolloids that increase stomach content viscosity and the addition of probiotics. Therefore, 3D food printing is an improved method for the production of texture-modified diets that should be further explored

Influence of Persian gum and almond gum on the physicochemical properties of wheat starch

In this study, the influence of different levels (0.1, 0.2, and 0.3% w/w) of Persian gum or almond gum were incorporated into wheat starch, and their influences on water absorption, freeze–thaw stability, microstructure, pasting, and textural properties were investigated. The SEM micrographs revealed that the addition of hydrocolloids to starch leads to the formation of denser gels with smaller pores. The water absorption of starch pastes was improved in the presence of gums, and samples containing 0.3% almond gum had the highest water absorption. The rapid visco analyzer (RVA) data showed that the incorporation of gums significantly affected the pasting properties by increasing the pasting time, pasting temperature, peak viscosity, final viscosity, and setback and decreasing breakdown. In all the pasting parameters, the changes caused by almond gum were more obvious. Based on TPA measurements, hydrocolloids were able to improve the textural properties of starch gels, such as firmness and gumminess but decreased the cohesiveness, and springiness was not affected by the incorporation of gums. Moreover, the freeze–thaw stability of starch was enhanced by the inclusion of gums, and almond gum exhibited better performance

Spray drying of dairy and soy proteins

Spray drying is a feasible drying method for the industrial-scale drying of protein-laden liquids in the food and pharmaceutical industries. Spray-dried dairy and soy protein powders are some of the most frequently used ingredients in the formulation of food and pharmaceutical products. They have special physicochemical and technological properties, including solubility, emulsifying, foaming, texturizing, binding, and surfactant properties. It is of paramount importance that both producers and consumers of dairy and soy protein powders know these properties thoroughly. The quality of dairy and soy protein powders during drying, storage, and rehydration can be affected by spray drying process conditions. Formulation, including the addition of wall materials such as maltodextrin, can improve the reconstitution and handling properties of protein powders. Hydrolysis of protein before spray drying can also increase the solubility and foaming capacity. Therefore, the information discussed in this chapter could be useful in order to obtain a high-protein powder spray drying yield and optimized product and particle characteristics

Effects of ultrasound and infrared assisted conductive hydro-drying, freeze-drying and oven drying on physicochemical properties of okra slices

Okra (Abelmoschus esculentus) is a nutritious vegetable but it is highly perishable and drying is one of the best methods for its preservation. Ultrasound and infrared assisted conductive hydro-drying (UIACHD) is a new patented drying method that can dry food materials with high quality and high energy efficiency. In this study, okra slices were dried using UIACHD with different settings and also by freeze-drying and oven drying. The UIACHD drying curves, moisture content, color, vitamin C content, hydrocolloids rheology and microstructure of the dried okra sample as affected by drying method were investigated. Drying curves showed that the application of ultrasound and infrared could increase the drying rate. In terms of quality parameters, UIACHD performed significantly better than oven drying and the quality of the products was comparable to freeze-drying. Flow and oscillation rheology tests showed that UIACHD drying could result in okra hydrocolloids with higher apparent viscosity and the application of ultrasound and infrared has preserved the rheological properties of the okra hydrocolloids. The microstructure of the dried okra slices was also well preserved by UIACHD. This study showed that UIACHD is a suitable drying method for maintaining the physicochemical quality of dried okra

Storage vats, vessels, and tanks

book chapter - No Abstract available

Infrared processing equipment for the food industry

Infrared (IR) heating can be regarded as a relatively new heating method that can be used for fast and efficient heat transfer. In this chapter, different types of IR emitters and IR heating methods, processing equipment, and their applications in the food industry are discussed. These applications include but are not limited to blanching, thawing, drying, cooking, baking, and roasting. IR heating has high thermal energy delivery efficiency that leads to faster heating and shorter processing time, which in turn leads to lower energy costs that are of great importance to the food industry as well as those who have concerns about preserving the environment. IR equipment is easy to control and has a fast response time. IR heating in combination with various conventional and novel processing methods can also improve product quality and reduce the processing time. Several researchers have studied such applications and we have tried to summarize them in this chapter

Combined ultrasound and infrared assisted conductive hydro-drying of apple slices

Conductive hydro-drying also known as Refractance Window drying is a relatively new drying technology, which uses hot water to carry thermal energy to materials to be dehydrated. It has a high retention of heat sensitive quality parameters (vitamins, antioxidants, and color) with better energy efficiency than freeze-drying as well as many other conventional drying methods. A new ultrasound and infrared assisted conductive hydro-dryer (UIACHD) was developed to increase drying rate while reducing required hot water temperature and increasing the drying material thickness. The goal of this study was to evaluate the performance of the new dryer and to compare the performance of a pilot scale continuous UIACHD with a freeze-dryer and a cabinet dryer in drying apple slices. The physiochemical characteristics of the dried apple slices including flavonoid content, total phenolic compounds, antioxidant activity, vitamin C content and color were measured. In addition, the energy consumption and energy efficiency of the dying methods were evaluated. Results showed that combining ultrasound and infrared with conductive hydro-drying can result in higher drying rates and lower product moisture content. Quality of UIACHD dried apple slices was close to the freeze-dried products and it was significantly better than the cabinet dried products. Moreover, the energy efficiency of UIACHD was considerably better than the cabinet dryer and the freeze-dryer. The results of this study showed that combining ultrasound and infrared with conductive hydro-drying can lead to an energy-efficient process with good quality retention ability