Hot and dry summers lead to spicier mustard seeds

As summers on the Canadian Prairies get hotter and drier, the seeds used to make the mustard for our hotdogs, sandwiches and dressings are getting spicier.

The Canadian Grain Commission’s Oilseeds Program analyzes the quality of the mustard seed samples submitted each year to our Harvest Sample Program from Saskatchewan and Alberta. One characteristic of mustard seeds that we have tracked for more than 15 years is glucosinolate content.

Glucosinolates are naturally occurring compounds found in mustard and other related plants, such as horseradish, arugula and Brussels sprouts. When these plants are physically damaged through actions like chewing, the glucosinolates break down and the by-products produce a spicy or pungent taste.

Different types and amounts of glucosinolates are found in different plant species, and this contributes to the diversity of plant flavours. Glucosinolate content can also vary between parts of a plant. In mustard plants, glucosinolates occur in high concentrations in the seeds.

The different kinds of prepared mustard that we find in stores are made by crushing, breaking or milling mustard seeds and mixing them with water, wine or other liquids. Hot dog mustard is made from yellow mustard seeds, while Dijon mustard is made from brown mustard seeds. The by-products produced by the processing of mustard seeds slowly lose their flavour over time and freshly made mustard will have the strongest taste.

A variety of glucosinolates are found in mustard seeds and each type contributes to the flavour of mustard, so our Oilseeds Program assesses total glucosinolate content in the samples we receive. This data helps food manufactures better understand how end-use products like prepared mustard will be affected by a crop from a specific growing year.

Results from our Oilseeds Program show that since 2020, there has been a notable increase in total glucosinolate content for all types of Canadian mustard seeds. During that time, Canadian mustard growing regions have experienced persistent heat and drought. As there has been no change in the varieties of mustard grown, our research team’s results show an association between environmental stress and higher levels of glucosinolates. This observation has also been reported from scientific studies of other plants in the mustard family.

Canada is one of the top producers of mustard seeds, with an estimated 139,802 metric tonnes of yellow, brown and oriental mustard seeds grown in 2025. Results from our quality monitoring provides valuable information to mustard seed buyers and mustard manufacturers. If drought-like conditions persist and the glucosinolate content in mustard seeds continues to increase, the taste of mustard seeds will be further affected, and food manufacturers may need to adjust their recipes.

The full 2025 mustard seed quality report is available at https://www.grainscanada.gc.ca/en/grain-research/grain-harvest-export-quality/mustard/2025/harvest-quality-report-mustard-2025.html.

Quote:

“Canadian mustard growing regions have experienced high temperatures and drought since 2020. Our monitoring of mustard seed quality shows that levels of glucosinolates, the compounds responsible for mustard’s spicy flavour, have been increasing under these conditions.”