The dry matter (or otherwise known as dry weight) is a measurement of the mass of something when completely dried.
The dry matter of plant and animal material would be its solids, i.e. all its constituents excluding water. The dry matter of food would include carbohydrates, fats, proteins, vitamins, minerals, and antioxidants (e.g., thiocyanate, anthocyanin, and quercetin). Carbohydrates, fats, and proteins, which provide the energy in foods (measured in kilocalories or kilojoules), make up ninety percent of the dry weight of a diet. Water content in foods varies widely. A large number of foods are more than half water by weight, including boiled oatmeal (84.5%), cooked macaroni (78.4%), boiled eggs (73.2%), boiled rice (72.5%), white meat chicken (70.3%) and sirloin steak (61.9%). Fruits and vegetables are 70 to 95% water. Most meats are on average about 70% water. Breads are approximately 36% water. Some foods have a water content of less than 5%, e.g., peanut butter, crackers, and chocolate cake. Water content of dairy products is quite variable. Butter is 15% water. Cow's milk ranges between 88-86% water. Swiss cheese is 37% percent water. The water content of milk and dairy products varies with the percentage of butterfat so that whole milk has the lowest percentage of water and skimmed milk has the highest.
In the sugar industry the dry matter content is an important parameter to control the crystallization process and is often measured on-line by means of microwave density meters.
Fat in Dry Matter (FDM)
Dry matter in cheese contains proteins, butterfat, minerals, and lactose (milk sugar, although in very small quantities due to lactose fermentation during cheese making). To determine a cheese's fat content, one analyses its dry matter to obtain the fat in dry matter (abbreviated FDM or FiDM) proportion, and then takes into account the water present in the cheese. For example, if a cheese were 50% water and 25% fat, there would be 50% fat in dry matter.
Dry matter can refer to the dry portion of animal feed. A substance in the feed, such as a nutrient or toxin, can be referred to on a dry matter basis (abbreviated DMB) to show its level in the feed (e.g., ppm). Considering nutrient levels in different feeds on a dry matter basis (rather than an as-is basis) makes a comparison easier because feeds contain different percentages of water. This also allows a comparison between the level of a given nutrient in dry matter and the level needed in an animal’s diet. Dry matter intake (DMI) refers to feed intake excluding its water content. The percentage of water is frequently determined by heating the feed on a paper plate in a microwave oven or using the Koster Tester to dry the feed. Ascertaining DMI can be useful for low-energy feeds with a high percentage of water in order to ensure adequate energy intake. Animals eating these kinds of feeds have been shown to consume less dry matter and food energy. A problem called dry matter loss can result from heat generation, as caused by microbial respiration. It decreases the content of nonstructural carbohydrate, protein, and food energy.
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