Mustard can be processed into several forms ranging from whole seed in spice blends to finely ground defatted and/or deheated powders. Food manufacturers process mustard in several different forms depending on what component of the seed is important to them. Mustard seed has many different fractions or components including: glucosinolates, mucilage, oil, meal and protein.
An enzyme, active in the presence of water, hydrolyses glucosinolates to give rise to subsidiary compounds that actually impart mustard’s characteristic pungent flavour. The compounds, isothiocyanates, are different depending on the type of mustard. Yellow mustard contains hydroxybenzyl isothiocyanate (derived from sinalbin), while oriental and brown contain allyl isothiocyanate (derived from sinigrin). The allyl form is much hotter than the hydroxybenzyl form and is responsible for the hot taste of Dijon style mustard.
Medical researchers have tested glucosinolates for benefits such as decreasing blood cholesterol and blood glucose levels as well as having antioxidant properties. In addition, researchers have identified insecticidal properties that affect roundworm species (nematodes).
Mucilage is the outermost coating of yellow mustard seeds. Mucilage gives yellow mustard its thickening, water binding and emulsifying properties that are important in the making of salad dressings, mayonnaise and prepared meats.
Mustard is considered a spice crop, however, mustard seed contains approximately 30% – 40% oil content. Mustard oil is not considered fit for human consumption in North America because of the relatively high concentration of erucic acid, the monounsaturated omega-9 fatty acid that was removed from canola cooking oil.
However, many cultures in Asia use high erucic acid oils for cooking. Mustard oil is also suitable for industrial applications like biodiesel and other lubricants.
Meal is the largest percentage of the mustard seed and contains both glucosinolates and mucilage which have applications as a food ingredient. Heated mustard meal also has antimicrobial properties and can be incorporated into food packaging or used as natural pest control agent (biofumigant).
Mustard seed has a relatively high protein content that makes it an attractive potential source of food-grade vegetable protein. The balance of amino acids found within the seeds also compares favourably with that required for human nutrition. Mustard protein production has not yet been commercialized and so it is not widely available.
The Canadian Grain Commission classes domestic mustard seed as yellow, brown or oriental, or mixed.