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Drying
Published in Pau Loke Show, Chien Wei Ooi, Tau Chuan Ling, Bioprocess Engineering, 2019
Chung Hong Tan, Zahra Motavasel, Navin Raj Vijiaretnam, Pau Loke Show
In industrial food drying, mechanical drying is mostly used. Mechanical drying encapsulates various types of drying methods including hot air convection, freeze drying, microwaving, vacuum drying, fluidized bed drying, and vacuum-assisted microwave drying. In convective drying, hot air is blown through the material either by cross flow or parallel flow. Convective drying saves a great amount of time compared to traditional solar drying. However, for food that loses its aroma at high temperatures, such as fruits and vegetables, freeze drying is preferred. In freeze drying, the food is flash frozen and then put in a pressure reduction system that causes the water to sublimate directly. For microwave drying, food is dried by using volumetric heating. Microwaves causes vibrations in polar molecules (for example, water) by inducing alternating electrical fields. Since food usually contain 52%–99% water, it can be dried effectively using microwaves. However, when it comes to mass production of dry food, convective dryers are most often used because they are cheaper compared to other drying methods such as freeze drying, vacuum drying, and microwaving. Even so, the products that are dried by these mechanical methods are often poor in color, flavor, texture, and rehydration qualities (Kumar et al., 2015).
Effects of Process Conditions of Intermittent Drying on Quality of Food Materials
Published in M. Azharul Karim, Chung-Lim Law, Intermittent and Nonstationary Drying Technologies, 2017
Chung-Lim Law, Nghia Duc Pham, Sami Ghnimi, A.M. Nishani Lakmali Abesinghe, Mohammad U.H. Joardder, Tony Petley, Scott Muller, M. Azharul Karim
The application of intermittent food drying is gaining more interest because of its better drying performance, energy saving, and product quality improvement. The intermittent process can be made by varying drying conditions such as a heat source, airflow, pressure, humidity, and effective drying time depending on types of sample. Among many intermittent drying researches, most of the practice has been done in convective and microwave drying due to the fact that the conventional application of those drying methods often results in severe quality degradation and high power consumption. The application of the intermittent drying technique can be conducted on drying methods in tandem or simultaneously to utilize the advantages of each drying method. However, its high drying performance can only be achieved by acquiring an in-depth understanding of the effects of process parameters on the food quality attributes and the mechanism of quality degradation. A robust and accurate model that is flexible to be adapted for different products is necessary for better prediction of food quality.
Drying of Agricultural Crops
Published in Guangnan Chen, Advances in Agricultural Machinery and Technologies, 2018
D. M. C. C. Gunathilake, D. P. Senanayaka, G. Adiletta, Wiji Senadeera
Food drying is a complex process involving mass and heat transfer accompanied by physical and structural changes. The combined effect of higher surface area per unit volume and absence of skin shows higher drying rates in many materials. Materials with skin may experience case-hardening during drying. The expected qualities, such as texture and color at the end of drying, depend on physical changes occuring during the drying process. Drying takes place in the falling period for most of the grains and food materials. Many empirical and fundamental models are also available to describe the drying behavior more accurately. Both the increase in drying rate with drying temperature and diffusion of moisture through the material can be described by an Arrhenius relation.
Performance analysis and drying kinetics of beetroot slices dried in an innovative solar dryer without and with thermal storage unit
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Vishnuvardhan Reddy Mugi, Mulatu C. Gilago, V.P. Chandramohan
Food drying is a process of removal of moisture, and it is a popular technique for the preservation of food materials for a longer duration without degradation of their quality. From ancient days to now, open sun drying (OSD) has been practiced to dry food materials. However, there are several drawbacks to this method including the requirement for huge areas, longer drying duration, high labor costs, and disturbance from insects (Essalhi et al. 2018). As a result, an indirect solar dryer (ISD) seemed to be a viable alternative to OSD with several advantages over the OSD. Solar air collector (SAC) heats the air and allows it to flow through the trays of drying cabinets to eliminate moisture from the food materials in the ISD. ISDs are extensively used in different regions of the globe to avoid post-harvesting losses and provide high-quality food materials. The performance of ISD is again enriched when the airflow is encouraged by fans or blowers and such dryers are called active ISDs (AISDs) (Gilago and Chandramohan 2022).
Drying kinetics of dried injera (dirkosh) using a mixed-mode solar dryer
Published in Cogent Engineering, 2021
Senay Teshome Sileshi, Abdulkadir Aman Hassen, Kamil Dino Adem
Dehumidification of food using heat as driving force is called food drying process. Food drying helps to preserve and extend shelf-life of food. Additionally, it decreases the weight and volume of product and reduces the space and storage requirements. Since ancient time, open sun drying is a common practice to store and preserve food and different agricultural products especially in developing countries, as it is the cheapest method. Similarly in Ethiopia, injera is dried for household consumption and for commercial purpose by using open sun drying and it is called dirkosh. Furthermore, injera is dried to avoid mould spoilage and in times of food scarcity (Zewdu, 2012). Dirkosh can be prepared by simply spreading injera out on apparel mat. But this technique suffers from many drawbacks, for example it is labour intensive, demands large area and susceptible for attack by insects and fungus which leads to poor quality and contamination. In addition, some commercial enterprises prepare dirkosh using electric oven and this dirkosh preparation method requires additional financial capacity to procure electric oven dryer and to pay for electric bill. Consequently, poor quality of dirkosh and inefficient injera drying practise is common in Ethiopia.
Air dehumidification with advance adsorptive materials for food drying: A critical assessment for future prospective
Published in Drying Technology, 2021
Mohamad Djaeni, Dewi Qurrota A’yuni, Misbahudin Alhanif, Ching Lik Hii, Andri Cahyo Kumoro
As an important part of the food processing step, drying is performed by removing moisture from food by vaporization or sublimation, which consequently reduces the water content and inhibits chemical, enzymatic, or microbial degradation reactions. Food drying aims to enhance storage and lifetime, preserve nutritional quality, reduce the weight and bulk volume of the food products to ease transportation and storage, and provide wider convenience and variety for consumers.[1] A vast number of food products, including grains, fruits, vegetables, meat products, dairy products, and marine products, is routinely preserved by drying.[2] Drying generally involves moisture removal from a wet feedstock by promoting the state changes of water from solid or liquid into the vapor phase through sufficient application of heat. Various methods with corresponding advantages and drawbacks can be applied to dry food materials for specific purposes. The existence of numerous dryer designs reported in published literatures is the result of the variations in the physical and chemical attributes of the product, methods of heat introduction, operating temperature and pressure, and quality requirements on the dried food products, among others. Unfortunately, most drying processes are considered as energy-intensive processes that subsequently lead to a considerable alteration of the product quality characteristics as a result of prolonged exposure to high-temperature drying air. Drying food materials is an extremely complicated process that involves simultaneous transports of heat, mass, and momentum and is accompanied by transformation of physical, chemical, and state condition.[3,4]