The dry matter or dry weight is a measurement of the
mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...
of something when completely dried.
Analysis of food
The dry matter of plant and animal material consists of all its constituents excluding water. The dry matter of food includes
carbohydrate
In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...
s,
fat
In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food.
The term often refers spec ...
s,
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
s,
vitamin
A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an Nutrient#Essential nutrients, essential micronutrient that an organism needs in small quantities for the proper functioning of its ...
s,
minerals
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
, and
antioxidant
Antioxidants are compounds that inhibit oxidation, a chemical reaction that can produce free radicals. This can lead to polymerization and other chain reactions. They are frequently added to industrial products, such as fuels and lubricant ...
s (e.g.,
thiocyanate
Thiocyanate (also known as rhodanide) is the anion . It is the conjugate base of thiocyanic acid. Common derivatives include the colourless salts potassium thiocyanate and sodium thiocyanate. Mercury(II) thiocyanate was formerly used in pyr ...
,
anthocyanin
Anthocyanins (), also called anthocyans, are water-soluble vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart gave the name Anthokyan to a chemical compo ...
, and
quercetin
Quercetin is a plant flavonol from the flavonoid group of polyphenols. It is found in many fruits, vegetables, leaves, seeds, and grains; capers, red onions, and kale are common foods containing appreciable amounts of it. It has a bitter flavor a ...
). 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 composition
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 and 86% water. Swiss cheese is 37% percent water.
The water content of milk and dairy products varies with the percentage of
butterfat
Butterfat or milkfat is the fatty portion of milk. Milk and cream are often sold according to the amount of butterfat they contain.
Composition
Butterfat is mainly composed of triglycerides. Each triglyceride contains three fatty acids. But ...
so that whole milk has the lowest percentage of water and skimmed milk has the highest.
Dry matter basis
The nutrient or mineral content of foods, animal feeds or plant tissues are often expressed on a dry matter basis, i.e. as a proportion of the total dry matter in the material. For example, a 138-gram apple contains 84% water (116 g water and 22 g dry matter per apple). The potassium content is 0.72% on a dry matter basis, i.e. 0.72% of the dry matter is potassium. The apple, therefore, contains 158 mg potassium (0.72/100 X 22 g). Dried apple contains the same concentration of potassium on a dry matter basis (0.72%), but is only 32% water (68% dry matter). So 138 g of dried apple contains 93.8 g dry matter and 675 mg potassium (0.72/100 x 93.8 g).
When formulating a diet or mixed animal feed, nutrient or mineral concentrations are generally given on a dry matter basis; it is therefore important to consider the moisture content of each constituent when calculating total quantities of the different nutrients supplied.
Fat in dry matter (FDM)
Cheese contains both dry matter and water. The dry matter in cheese contains proteins, butterfat, minerals, and
lactose (milk sugar), although little lactose survives
fermentation
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...
when the cheese is made. A cheese's fat content is expressed as the percentage of fat in the cheese's dry matter (abbreviated FDM or FiDM), which excludes the cheese's water content. For example, if a cheese is 50% water (and, therefore, 50% dry matter) and has 25% fat, its fat content would be 50% fat in dry matter.
Techniques
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.
Animal feed
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.
[Buckmaster, Dennis R]
Indoor Hay Storage: Dry Matter Loss and Quality Changes.
{{webarchive , url=https://web.archive.org/web/20100611205744/http://www.abe.psu.edu/extension/factsheets/i/I102.pdf , date=June 11, 2010
See also
*
Body water
In physiology, body water is the water content of an animal body that is contained in the tissues, the blood, the bones and elsewhere. The percentages of body water contained in various fluid compartments add up to total body water (TBW). This ...
*
Moisture
Moisture is the presence of a liquid, especially water, often in trace amounts. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some commercial products. Moisture also refers to the amount of water vapo ...
References
Solids
Measurement
Food science