Sweet corn, or corn on the cob, is a delicious summer treat during barbecue season. Sweet corn is the result of a gene mutation in field or grain corn, which is corn that is traditionally grown for animal feed or processed corn products (corn starch, corn meal, corn flour, etc.). The first sweet corn was discovered in the mid 1700s in the United States with a mutation that stopped the sugars in the kernels from being converted to starch right away, extending the period where the corn stays sweet.
The three most common types of sweet corn are normal, sugar-enhanced and supersweet and each comes with yellow, white or bicolour (yellow and white) kernels.
The natural sugars in normal and sugar-enhanced corns eventually convert to starch, causing the kernels to lose sweetness and become tough over time. But that doesn’t happen with supersweet corn, making it particularly desirable when there’s a delay between harvest and consumption.
Only about a quarter of the sweet corn grown in Canada is sold fresh. The majority of it is frozen or canned and immature cobs can be purchased as ‘baby corn’ which is usually canned or frozen.
How to Buy:
Fully ripe sweet corn has bright green, moist husks. The silk should be stiff and moist. You should also be able to feel individual kernels by pressing gently against the husk.
How to Store:
Corn is at its best when it is cooked and eaten immediately after picking since its natural sugar begins to decline as soon as it is picked. It is recommended to keep corn moist and cool between harvest or purchase and cooking and use it within two or three days.
There are a number of ways to freeze corn including:
- Uncooked, whole ears of corn: Shuck, place in freezer bags, extract air by using a straw, and place in the freezer.
- Uncooked kernels: Shuck and cut the kernels off the cob into a large bowl. Spoon kernels into freezer bags, remove as much air as possible (again using a straw), seal and freeze.
- Blanched kernels: Bring a large pot of water to boil. Drop shucked ears into boiling water and cook for 2-3 minutes. Remove from water to a large bowl and rinse in cool water. Towel dry and cut kernels off of cobs, spoon into freezer bags, remove as much air as possible (again using a straw), seal and freeze.
How to Prepare:
Before boiling or steaming sweet corn, remove the husk (outer leaves) and any remaining bits of silk. Trim the cobs and remove undeveloped tip ends or any disfigured kernels. If boiling fresh corn, cook for 3 to 4 minutes for young cobs or 5 to 7 minutes for mature cobs. Alternatively, place cobs in a large pot of salted water and bring it to boiling point. Once the water hits a rapid boil, turn off the burner, add a dash of milk to the water, cover and let sit for 30 minutes. If steaming, cook corn for 7 to 11 minutes, depending on size (small cobs, 7 minutes; medium, 9 minutes; large, 11 minutes).
To barbecue, trim off any loose strands of husks and soak cobs, with green husks, in cold water for at least 30 minutes. Place on grill over medium-high heat; close lid and grill, turning frequently, for about 20 minutes or until husks are charred and corn is tender. Let cool slightly, then cut kernels off the cobs. For charred marks, place the stripped cobs on the grill for a few minutes until brown on all sides.
To microwave, remove husks and silk and place cobs in a microwaveable baking dish, and cover with plastic wrap. If cooking only 1 or 2 cobs, wrap individually. Microwave on High power 2 minutes per cob or just until tender. Let stand 2 minutes before unwrapping.
Corn is a good source of folate and contains fibre, Vitamin C, vitamin B6, niacin, potassium, magnesium and thiamine. Sweet corn also has high levels of the phytochemicals lutein and zeaxanthin, which helps promote healthy vision by preventing cataracts and age-related macular degeneration. An average ear of corn has 85-90 calories.
How They Are Grown:
Most of the field corn grown in Canada is used for animal feed; however, sweet corn is used for human consumption and available in stores, markets and roadside stands for you to enjoy over the summer months.
Sweet corn is one of the most widely planted vegetable crops in Canada and, although the majority of Canada’s production comes from Ontario (53%), Quebec (36%), and Alberta (7%), it is grown in all provinces. However, heat is crucial for corn to thrive, so much so that a standardized unit of measurement was developed called Corn Heat Units that measures temperature and hours of sunlight.
Corn seeds (called kernels) are planted in the ground starting in late spring to avoid damage by frost. However, because they only take about 3 weeks to mature, more corn is planted throughout the summer to ensure a steady supply and multiple harvests over the summer and into fall. The stalks grow quickly in the heat and can reach heights of 1.5 to 2.5 meters. The plant sends up tassels at the top where pollen is produced and the corn relies on wind for pollination. The corn cobs grow out of the sides of the stalks and the silk is visible at the top of the leaves. Each strand of silk represents a kernel on a cob of sweet corn. Once the silk starts to turn brown and the cobs have filled out, the cobs are ready for harvest.
Sweet corn for fresh consumption is often picked by hand to reduce damage. Teams of trained pickers walk through the field and place the corn onto a conveyor belt that moves it onto a flatbed trailer pulled by a tractor. More workers on the trailer pick out the immature or small cobs, remove loose or extra leaves and stack the corn in boxes or bags. The bulk containers are later moved to a packing house for further processing and grading and sold to the consumer within one or two days before the sugars can start to convert to starch and kernels start to dry out.
Sweet corn can also be picked by special harvesting machines and loaded into trailers. It is then sorted and packaged and shipped for processing into corn ingredients, frozen or canned products. Special production lines remove the outer leaves on the corn and clean the cobs before lining them up and sending them through a ‘kernel stripper’. This is a rotating set of knives that separates the kernels from the cobs and moves them down separate processing lines. Larger pieces and leftover chunks of the cob are screened out of the kernels and the cobs, leaves and leftover pieces are sent for animal feed. The kernels are then canned and pasteurized or flash frozen and packaged for retail sale.
Canadian Crop is Available: July – October
Grown in: Ontario, Quebec, Alberta
For More Information:
- BC Vegetable Marketing Commission
- Ontario Farm Fresh
- Ontario Processing Vegetable Growers
- Ontario Fruit and Vegetable Growers Association
- Quebec Federation of Producers of Processing Fruits and Vegetables