Brown: Canning on smooth-top stoves not smooth

A flat-bottomed canner alone would not solve this problem for all stove tops. If your stove has the sensor, the heat will still fluctuate and it won’t get hot enough to get the big canner full of water to a full boil. If you can confirm with your stove’s manufacturer that a flat-bottomed canner will work, here are some tips to help you while canning:

• The pot must not be more than 1 inch wider that the heating element. Canners that exceed the burner diameter by more than 1 inch can trap and reflect heat to surfaces of the stove that are not intended to get that hot, and thus crack the stove top. The damage can range from discoloration of white tops, burner damage, cracking of the smooth tops, or even fusion of the metal pot to the glass top.

• Avoid dragging. Scratching of the stove surface can occur if the canner is slid or pulled across the cook top. This often happens with large, heavy canners, so people need to be careful.

• Auto-shutoffs prevent sufficient heating. As mentioned above, many of these cook tops have automatic shutoffs on their burners when heat gets excessive. If that option is built in, and the burner under a canner shuts off during the process time, then the product will be under processed and cannot be salvaged as a canned food. If the pressure drops quickly liquid and maybe even food could be lost from the jar during the canning process.

• You must use a flat-bottom canner. Even if boiling water canning is approved by the manufacturer, it may be necessary to fashion your own canner out of a very large flat-bottom stock pot with a bottom rack inserted. Many canners are not flat enough to work well on a smooth cook top, and therefore not able to maintain a full boil over the tops of the jars. The pot used as a canner must also be large enough to have plenty of water boiling freely around the jars, and at least 1 to 2 inches over the tops of jars. If the canner is too small, then it starts boiling faster than expected and the total required heat the jars receive in the canner, even before the process time begins, can be too short.

Most pressure canners manufacturers do not recommend the use of a smooth-top stove. The weight, along with the diameter of them, prevents them from safe use on a smooth-top stove. There is one brand of pressure canner that does state it is safe for smooth-top stove use. Most of all, if you plan to use a smooth-top range for canning, check with the manufacturer for its guidelines and follow them. If there are no recommendations, then be cautious.

Alternative burners

So what are the choices if the smooth-top stoves can’t be used? Well, there are some options.

There are a couple of canning systems or electric canners that work on your countertop. You also could purchase a portable electric coil burner, a gas burner system or an outdoor gas burner.

Electric portable burners may be an option at least for boiling water bath canning. All portable burners are not the same, and not all portable burners are appropriate for canning. Check the burner manufacturer’s specifications and directions for canning. Some basic guidelines for selecting a portable burner for canning are:

• The burner must be level, sturdy and secure. Look for enough height to allow air to flow under the burner, but not so much that it becomes unsteady with a full, heavy canner resting on it. One that is about 4 inches off the counter works well.

• Find a burner diameter that is no more than 4 inches smaller than the diameter of the canner.

• Find a wattage that will bring the large pot of water to a boil fairly quickly. I recommend a wattage of about 1,500 watts. If you can find one at 1,750 watts it would be better, and similar to an electric range.

• The burner must be able to hold up to high heat under the canner for long heating periods and not damage the counter tops with the reflected heat. It may be wise to put a cutting board or something under the burner that wouldn’t be damaged by the reflected heat.

For pressure canning, a choice may be to use an outdoor low-pressure gas burner or outdoor gas burner. Recommendations for use of outdoor gas burners are:

• Do not use a gas burner that is over 12,000 BTUs (British thermal units). Any higher, and pressure canners and boiling water bath canners could warp easily under the high heat. The other concern is that water will boil more quickly, which during pressure canning alters the total processing time and causes the food to be under processed and unsafe to eat.

If you are considering preserving food outdoors with a portable gas burner, also consider these points:

• Is the area free from wind and cool air? If air temperature is too cool, there is a chance of jar breakage when taking the jars out of the canner.

• Where are you filling the jars before putting them in the canner? If done inside and then taken outside, the jars will cool before going in the canner. Consider putting them in a sturdy box or pan and covered with a towel.

• Where are you putting them when taking them out of the canner? Is the air temperature such that the jars could break?

• Are you moving the jars long distances before they are completely cooled? If so be careful not to disturb the lids and risk a seal failure.

When considering any of these alternative heat sources or considering using the smooth top ranges for canning, always check the manufacturers’ directions or contact them for information about their specific canning recommendations. If you follow its instructions and a canning problem occurs, alert the manufacturer.

Have more questions about canning? Don’t forget to use the Washington State University Food Preservation Hotline: 360-307-6060, ext. 5366, Monday through Friday.

Sandra Brown is the food safety and nutrition expert for the Washington State University Cooperative Extension in Clark, Cowlitz and Wahkiakum counties. Reach her at 360-397-6060, ext. 5700, or browns@wsu.edu. The WSU Cooperative Extension in Clark County is at 11104 N.E. 149th St., Building C-100, Brush Prairie, WA 98606.