Laboratory work #3 Determination of dry matter content of various raw materials Thereotical concept
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LABORATORY WORK #3
Determination of dry matter content of various raw materials
Thereotical concept: All food products, their raw materials, consist of water and dry matter. The dry matter of the product includes carbohydrates, fiber, proteins, organic acids, mineral substances. The amount of dry matter is considered a universal indicator of product quality, therefore, the amount of dry matter in all raw and finished canned products is determined by GOST and technical specifications (TU). The amount of dry matter in products can be determined by physico-chemical, chemical and physical methods. In most cases, the most common methods for determining the amount of dry matter are drying products to constant weight and expelling water from the product. Among the physical methods, the refractometric method and density determination methods are widely used.
Purpose: determine the percentage of dry matter in all food products, raw materials and finished products.
Weight method for determining the amount of dry matter
Required reagents and equipments:
Bux or porcelain cup;
Figure 2. Pants
Procedure: This method is based on drying the product under atmospheric pressure at a temperature of 1050C or under low pressure at a temperature of 70°C in a drying cabinet until it reaches a constant weight. 10-12g of clean, heated sand is placed in a clean and dry bag, and the bag is dried together with a glass rod until it reaches a constant weight. The samples were cooled in a desiccator and weighed to the nearest 0.001 g. Then 5g of dried product sample is placed in the bag. The glass is mixed with the sand using a stick and weighed to the nearest 0.001g. When determining the dry matter of dried fruits, the sample is weighed without sand. The bag is placed in an open-top drying cabinet and dried at 105°C for 4 hours (Figure 1). After that, the bags are closed, cooled in a desiccator for 30 minutes and weighed. The measured pieces are dried for another 1 hour, cooled and weighed. This process is continued until the difference between the weights of two successively dried bags is 0.002 g. The percentage of dry matter, (%) is determined using the following equation:
Here, M is the weight of the bag together with sand and a glass rod, g;
M1 is the weight of the bag together with sand, glass rod and product sample before drying, g;
M2 – weight after drying together with sand, glass rod and product sample, g.
The difference between the dry matter content of simultaneously dried products should not exceed 0.2%.
Name the tasks of storage of raw materials.
What are the specific quality indicators of raw materials?
Name the types of raw material storage methods.
In what optimal conditions should dry raw materials be stored?
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