Understanding the difference between net and drained weight
When you pick up a can of corn at the grocery store, you see a total weight printed on the label, such as 15 ounces or 425 grams. This is the net weight, representing the total mass of all contents inside the can, including the solid corn kernels and the liquid they are packed in, which is typically a brine solution or water. The amount of actual corn you'll use for your recipe is the drained weight, which is the weight of the solid corn once the liquid has been poured off. This drained weight is always significantly less than the net weight.
For a standard 15-ounce (approx. 425g) can, the drained weight typically falls in the range of 8 to 10 ounces (225–285 grams). This means that up to 40% of the contents you paid for could be the non-edible packing liquid. This difference can be a significant surprise for home cooks and chefs who don't read the finer details of the label.
The role of the canning process
The reason for the liquid is integral to the food preservation process. Canned corn production involves several steps to ensure the product remains safe and fresh on the shelf.
The standard canning procedure
- Selection: The process begins with selecting fresh, high-quality sweet corn at the optimal stage of ripeness.
- Husking and Cutting: Cobs are de-husked, and high-tech equipment then cuts the kernels from the cobs.
- Washing and Blanching: The loose kernels are thoroughly washed and then blanched in hot water or steam for a few minutes. This process helps to preserve color, texture, and flavor.
- Filling: The blanched kernels are measured and filled into cans. A brine solution (water, salt, and sometimes sugar) is added to fill the remaining space. Some brands offer vacuum-packed corn, which contains much less liquid.
- Sealing and Sterilizing: The cans are hermetically sealed and then sterilized under high pressure and temperature to kill any bacteria and ensure a long shelf life.
Why the liquid is necessary
The packing liquid serves multiple crucial functions beyond simply filling the can. It protects the delicate kernels from damage during transport, helps to conduct heat during the sterilization process for even cooking, and, importantly, creates the airtight, anaerobic environment necessary to prevent spoilage and extend shelf life.
The numbers behind the can: A comparison
Different can sizes and types will have varying ratios of drained weight to net weight. The following table provides a breakdown based on typical industry standards, though exact figures can differ slightly by brand.
| Can Size (Net Weight) | Typical Drained Weight | Percentage of Drained Corn |
|---|---|---|
| 15 ounces (425g) | 8–10 ounces (225-285g) | ~60-67% |
| 198g (Tesco) | 165g | ~83% |
| 340g (Newman Foods) | 250g or 285g | ~74-84% |
| 2.650 ml (Oh Products) | 1.550g | ~58% |
As you can see, the ratio can vary significantly. The higher percentage for the smaller Tesco can could indicate a vacuum-packed product with minimal liquid, while the larger Oh Products can suggests a standard brine-packed product. Always check the label or use your own measurements for true accuracy.
Factors influencing drained weight
Beyond just the amount of packing liquid, several factors can affect the final drained weight of canned corn:
- Corn Variety and Maturity: Different corn varieties have different kernel sizes and moisture content. The stage of maturity when canned also plays a role. Using corn that is too immature can lead to browning.
- Processing Conditions: As research has shown, slight differences in heating temperature and sterilization time can impact the final product quality and, potentially, the drained weight. The fill weight, which is the pre-processing weight of solids, is controlled by the factory.
- Can Size and Shape: The volume and shape of the can can influence the overall ratio of kernels to liquid. Some smaller cans may be more densely packed or vacuum-sealed, resulting in a higher drained weight percentage.
- Added Ingredients: The amount of salt and sugar in the brine solution can also affect the final weight by drawing moisture out of or into the kernels during storage.
The historical perspective on canned corn
The practice of canning corn has a long history, starting in the United States in the mid-19th century. Brothers J. Winslow Jones and Isaac Winslow pioneered the process in Portland, Maine, and opened the country's first successful corn canning factory in 1852. Their method involved heating corn in a sealed can to kill bacteria, allowing it to remain edible for extended periods. This innovation made corn available year-round and played a significant role in making canned food a household staple. During the Civil War, the Portland Packing Company secured lucrative contracts with the Union Army, further popularizing the practice. The canning process has evolved with technology, but the core principle of using heat and a sterile, sealed environment remains the same.
Conclusion
Understanding the distinction between net and drained weight is essential for any savvy shopper. While the number on the front of the can provides a gross weight, the true, usable quantity of corn is the drained weight, which can be surprisingly less. For those who want more bang for their buck, choosing a vacuum-packed can or comparing labels for the highest drained weight percentage is a wise move. The next time you're preparing a recipe that calls for canned corn, remember to account for the liquid to ensure you have enough kernels. It's a small detail, but one that can significantly impact both your recipe and your grocery budget. For more detailed information on food safety and canning standards, you can refer to resources like the FDA's Guide to Inspections of Low Acid Canned Food.
Note: The weight figures are approximations and can vary between brands and products. Always refer to the specific nutritional information and drained weight (if listed) on the can's label.
