Dry matter

Analysis of food

The dry matter of plant and animal material consists of all its constituents excluding water. The dry matter of food includes 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 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 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 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.