Before the dried fruit products are dried, whether dried or artificially dried, some processing must be carried out to facilitate the drying of raw materials and the improvement of product quality. Raw material processing includes raw material selection and raw material handling.
(1) Selection of raw materials. When the fruit is dried, the influence of the raw material itself on the dried product should be considered. The general requirements for raw materials are: high dry matter content, thick meat, dense tissue, less crude fiber, good flavor and color, and not easy to brown.
(2) Processing of raw materials. Pretreatment of raw materials includes cleaning, peeling, blanching, and smoldering. Sulfur treatment often uses two methods: one is burning sulphur in a smoked room for fumigation; the other is immersing the raw materials in a sulphite solution of 0.2% to 0.5% (based on effective sulphur dioxide). Smoked sulfur is better than soaking sulfur. Smoked sulphur is used more in dried fruit because it has a good color protection effect on dried fruit products.
(3) Methods for dehydrating fruit products. The main use is natural drying and artificial drying. Natural drying is the use of natural conditions such as solar radiation, hot air to dry fruit, including drying and drying. This method is still used throughout the world. Natural drying is simple and easy, requiring only a drying field and simple drying equipment, extensive management, low production costs, and the masses have a wealth of experience. However, the natural drying speed is slow, the quality of the product varies greatly, and it is not easy to achieve an ideal water content requirement. Moreover, due to the limitation of the weather, the products are often rotted and lost due to the rainy weather, and the products are also deteriorating by the deterioration of the quality of the products, causing environmental pollution and affecting human health. Manual drying is a drying method that manually controls dewatering conditions. Therefore, without the limitation of weather conditions, the speed of drying can be greatly accelerated, the drying time can be shortened, and the decay rate can be reduced. As a result of the timely and prompt manual drying, high-quality products can be obtained, thereby increasing the grade and value of the product. However, artificial drying requires dry equipment, plus necessary auxiliary housing and energy consumption, etc., which are costly and technically complex. There are many manual drying methods used today, including baking, tunnel drying, drum drying, foam drying, spray drying, solvent drying, film deposition, pressurization drying, and freeze drying. Each method is not necessarily suitable for the drying of various raw materials. It is necessary to adopt appropriate drying methods depending on the raw materials and the requirements of the products.
A Viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid. For liquids with viscosities which vary with flow conditions, an instrument called a rheometer is used. Thus, a rheometer can be considered as a special type of viscometer. Viscometers only measure under one flow condition.
In general, either the fluid remains stationary and an object moves through it, or the object is stationary and the fluid moves past it. The drag caused by relative motion of the fluid and a surface is a measure of the viscosity. The flow conditions must have a sufficiently small value of Reynolds number for there to be laminar flow.
At 20 Â°C, the dynamic viscosity (kinematic viscosity Ã— density) of water is 1.0038 mPaÂ·s and its kinematic viscosity (product of flow time Ã— factor) is 1.0022 mm2/s. These values are used for calibrating certain types of viscometers.
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