White / yellow mustard seed

The mildest mustard, with two names

White mustard and yellow mustard are the same plant, Sinapis alba L., a relative of the cabbage and rapeseed genus Brassica that older books file as Brassica hirta or Brassica alba. White is the name of the species, yellow the colour of the seed that trade and kitchen prefer: the seeds are light straw yellow, yellow to yellowish-brown according to another description, and they give off an odour only when mixed with liquid. They are slightly larger than the seeds of black and brown mustard. Crop guides count about 100,000 seeds to the pound for yellow mustard and about 200,000 for brown and oriental types.

It is the mildest of the three mustards and the lowest in oil. Yellow varieties averaged about 24% oil in North Dakota trials, against about 35% for brown and oriental varieties, and plants are shorter and earlier maturing than brown. The seed is high in protein and low in starch. Lietzow's review calls it milder in taste than the other mustard species, and says its seeds are often used for pickling gherkins or mixed pickles and in sausages. The Agricultural Marketing Resource Center says its major market is the North American condiment industry.

The species is believed to be native to the Mediterranean. In Europe it is the most used mustard species, and in North America it is the only species in commercial production for food processing and condiments. Yellow mustard supplies about 90% of Upper Midwest production, according to the Wisconsin and Minnesota crop manual, which also notes that the plant is called Sinapis alba in Europe. More than 100 varieties are listed in the catalogue of agricultural plant species cited by the toxicology review, differing in earliness, nematode resistance and glucosinolate or erucic acid content.

How the crop spread

Mustard seed has been used since antiquity. The first known cultivation and use of mustard plants is dated by the toxicology review to about 3000 BC, and the Wisconsin and Minnesota manual says ancient Greeks and Romans used the seed as paste and powder. Pliny the Elder, in the first century AD, called mustard the sharpest in taste and the most fiery in effect and said that it needed no cultivation. None of these accounts names the species, so they speak for mustard seed in general.

The North American crop is recent. Mustard supplies from western Europe were disrupted during the Second World War, and California and Montana were the main producers until the early 1950s. Upper Midwest production began in the early 1960s, and Canadian production rose for about twenty years and peaked in the mid-1980s; Alberta, Manitoba and Saskatchewan now grow a large share of the world's crop. The manual lists the yellow varieties that built the trade: Kirby, released in 1970 by Colman Foods, Gisilba and Ochre, and Tilney, released in 1978 and prized by processors for its high mucilage. France was the largest consumer, at 1.5 pounds a year per person, and bought about 70% of the Canadian crop, in the manual's older figures.

The best-known product of the yellow seed is American ballpark-style mustard, made from the white seed blended with vinegar and spices and usually coloured with turmeric. Add vinegar to a ground mixture of black and white seed and the result is a milder German-style blend. White mustard seed is also pressed for oil, which has served as a lubricant and for lighting, and more recently as a feedstock for biodiesel.

Why the sting is mild

Every mustard seed keeps a glucosinolate and an enzyme apart until the seed is crushed. Black and brown seed hold sinigrin, which becomes the sharp, volatile allyl isothiocyanate. White mustard holds sinalbin instead, which myrosinase turns into 4-hydroxybenzyl isothiocyanate. That isothiocyanate contributes to the irritating odour and sharp flavour of the seed, but in water it is hydrolysed to 4-hydroxybenzyl alcohol, so the sting does not last. At physiological pH, between 5 and 7, sinalbin decomposes mainly to 4-hydroxybenzyl alcohol and the thiocyanate ion; in acid conditions a nitrile, 4-hydroxybenzyl cyanide, forms as well. A study of mild yellow mustard found 2-(4-hydroxyphenyl)acetonitrile as the main degradation product in ground seed and 4-(hydroxymethyl)phenol the most abundant in the finished paste.

The seed holds plenty of sinalbin: reports range from 165 to 250 micromoles per gram, and another gives 16.6 to 46.2 grams per kilogram of fresh seed within a glucosinolate total of 45.4 to 61.9. Its myrosinase is the least active of the three mustards, at 0.63 units per millilitre in one comparison, against 1.50 for black and 2.75 for brown. Research on white mustard seed myrosinase found an optimum temperature near 60 degrees Celsius, with activity falling at higher temperatures and depending on pH and ascorbic acid.

Binder, emulsifier and pickling seed

The yellow seed does work that has little to do with heat. North Dakota extension guidance says yellow mustard is used mainly in the meat packing industry as an aid to flavour, emulsification and texture in processed meats such as hot dogs and bologna. The Wisconsin and Minnesota manual says yellow mustard flour serves as an emulsifier and stabilizer in sausage, and that dry mustard seasons mayonnaise, salad dressings and sauces. A review of white mustard describes it as widely used as a binding agent and protein extender in meat processing and for hot dog mustard, mayonnaise and salad dressings. Its seed has a high protein and oil content and low starch, and its amino acid profile is described as well balanced.

The seed coat carries mucilage, a gel-forming carbohydrate, and processors have bred for it: the variety Tilney was released in 1978 and valued for high mucilage. Seed oil from white mustard is rich in erucic acid, at 32.8 to 60.3% of fatty acids in the range reported, a high content that the review calls a property of white mustards particularly from Europe, while the highest oleic acid content is found in oils from North and South America.

For picklers the seed is a classic. The toxicology review says white mustard seeds are often used for pickling gherkins or mixed pickles and for making sausages. The same review notes that unprocessed whole seed is also used as a seasoning in several dishes, and that mustard flour is made from ground, peeled, non-degreased seed.

A seed with a part in fermentation

Sinalbin's breakdown products are antimicrobial, and the white mustard literature says the seeds have strong disinfectant properties and can serve as a food preservative, and that the essential oil is antimicrobial. That is a statement about extracts and concentrations, not about a spoonful in a jar, but studies have started to show what mustard seed does inside living ferments.

The processing review reports that white mustard powder scored better in sensory evaluation than black or brown when added to meat products, and that in fermented sausage mustard seed improved storage stability by promoting phenolic acid production, lowering the redox potential and raising antioxidant activity. A study of nitrite-free organic fermented sausage found that native or autoclaved mustard seed combined with acid whey lowered the pH during fermentation and kept lipid oxidation over 90 days of vacuum storage similar to a nitrite-cured control; the abstract does not name the species. The review also reports that mustard seed extract promoted growth of lactic acid bacteria while reducing undesirable microorganisms, and that mustard seed extract improved storage stability and colour of dry-aged pork loin ham.

A Greek household tradition shows the same effect with a related plant. Pears kept in water with seeds of the wild mustard Sinapis arvensis developed more lactic acid bacteria, mainly Leuconostoc mesenteroides, and a lower pH, while Enterobacteriaceae declined. The fruit had higher titratable acidity and phenolic content than pears kept in water alone, and tasters preferred it. The authors suspect oxalic acid. The seed was wild mustard, not white mustard, so the result illustrates what a mustard seed can do in a water-based ferment and does not establish a method for white seed.

Growing and harvesting

White mustard is an annual, cool-season plant with yellow four-petalled flowers that grows up to 100 cm high. It matures in 80 to 95 days depending on the guide, shorter than brown mustard. It tolerates drought and heat well enough for drier soils, is grown in rotation with cereals, and also serves as green manure and fodder. In the Upper Midwest it is seeded at 8 to 14 pounds an acre in spring, and a good small-grain crop follows it. It should not follow other crops that share its diseases, and the manual advises waiting at least four years between mustard crops.

Yellow mustard resists shattering better than brown. Growers straight-combine when maturity is uniform and the crop is free of green weeds, at 12 to 13% seed moisture, and dry the seed artificially; otherwise they swath when 60 to 70% of the seed has turned yellow-green. Seed is stored at 10% moisture or less in one guide and 9% or less in another, with drying air under 150 degrees Fahrenheit. North Dakota trials gave yellow varieties average yields of 1,279 to 1,507 pounds an acre. Old Upper Midwest guidance expected 800 to 900 pounds an acre from growers. Large-seeded yellow mustard has one advantage: wild mustard seed can be separated from it mechanically, which is not possible with brown or oriental seed.

World cultivation of white mustard is estimated at 60,000 to 80,000 hectares a year, producing up to 685,000 tonnes of seed, according to the white mustard review, which puts average yields at 770 to 930 kg per hectare worldwide and 1,500 to 1,800 kg in Serbia. Nepal and Canada led world mustard seed production of all species in 2017.

Allergy and food-safety notes

White mustard is the species with the best-documented allergens. Its 2S albumin Sin a 1 is the major allergen and the best marker for diagnosing sensitisation, and three more are known: Sin a 2, an 11S globulin called cruciferin, Sin a 3, a lipid transfer protein, and Sin a 4, a profilin. Sin a 1 is closely related to Bra j 1 of brown mustard, so people allergic to one mustard are likely to react to another. The proteins resist heat and trypsin digestion, which means cooking and making table mustard do not reduce the allergenic potential. About half the mustard-allergic patients in one report were sensitised to mugwort pollen and to some plant foods.

Mustard made from white seed also contains bisphenol F, a compound structurally similar to bisphenol A. It has been detected in mustard made from Sinapis alba but not in mustard made from Brassica juncea or Brassica nigra, nor in mustard flour. Researchers consider that it forms from sinalbin, which is hydrolysed to 4-hydroxybenzyl alcohol that can dimerise, rather than coming from packaging, and mild mustards had the highest levels: a mean of 3.2 mg per kilogram in 19 mild commercial mustards, against a mean of 1.84 mg per kilogram and a maximum of 8.4 across 61 commercial table mustards. The Swiss food safety office made a rudimentary assessment and found a daily intake of 0.67 mg tolerable for a 60 kg person. No health-based guidance values or legal limits for bisphenol F in food exist, and the review notes that no comprehensive evaluation of risk to humans is available.

Notes and open questions

The sources read do not date the first cultivation of Sinapis alba, and the Roman mustard they describe is not tied to a species. The white mustard review gives world area and yield figures that cover a mix of mustard in some tables and white mustard in others, so they are indicative only. The Upper Midwest manual dates from the early 1990s. No source gives a shelf life for the whole seed.