The abundance of a summer tomato harvest often exceeds what can be consumed fresh, making preservation a practical necessity. This process, commonly known as “putting up,” allows you to extend the enjoyment of vine-ripened flavor far beyond the growing season. Preserving tomatoes saves money and ensures you have access to high-quality ingredients throughout the year. Mastering various preservation methods allows you to store a large bounty efficiently, giving you a taste of summer even in the depths of winter.
Essential Preparation and Supplies
Successful preservation, regardless of the method, begins with selecting the best fruit. Choose firm, ripe tomatoes that are free of any blemishes, cracks, or signs of disease, as poor quality fruit can compromise the safety and flavor of the final product. Overripe tomatoes or those from dead or frost-killed vines should be avoided, as their acidity levels may be too low for safe canning.
All tomatoes must be thoroughly washed under cool, running water to remove any dirt or debris from the skins. After washing, the stem scar, or core, should be removed using a sharp knife. Peeling and seeding the tomatoes is an optional step depending on the final use, but it is often done by briefly dipping the fruit in boiling water until the skins split, then immediately transferring them to an ice bath.
Basic kitchen tools like large stockpots, sharp knives, cutting boards, and measuring cups are necessary for processing the harvest. While some preservation methods require specialized equipment, these universal supplies help with the initial steps of washing, coring, and preparing the tomatoes. Utilizing the correct tools ensures a smooth and efficient transition from fresh harvest to preserved product.
Safe Water Bath Canning
Canning tomatoes in a boiling water bath is a popular method that results in a shelf-stable product, but it requires careful attention to safety protocols. Historically, tomatoes were considered naturally high-acid foods, but modern varieties and growing conditions mean that their acidity, or pH, can vary significantly. A pH above 4.6 allows the dangerous bacteria Clostridium botulinum to grow, which produces the toxin responsible for botulism.
Because of this variable acidity, you must add an acidifier to every jar of tomatoes processed in a water bath canner. For a quart jar, two tablespoons of bottled lemon juice or one-half teaspoon of crystalline citric acid must be added directly into the jar before filling. Using bottled lemon juice is recommended over fresh because its acidity level is standardized and reliable for preservation safety.
The canning process begins with preparing your jars and lids; the jars should be sterilized or thoroughly cleaned and kept hot until they are filled. Once the acidifier is added, the tomatoes are packed into the jars, leaving a half-inch of headspace at the top. The filled jars are then sealed with lids and rings, placed on a rack inside a large canning pot, and completely submerged in boiling water.
Processing times vary, but at sea level, whole or crushed tomatoes generally require a 45-minute boil for quart jars, with times increasing for higher altitudes. After the processing time is complete, the canner lid is removed, and the jars should sit for five minutes before being carefully lifted out and allowed to cool undisturbed for 12 to 24 hours. A proper seal is indicated when the center of the lid is concave and does not flex when pressed, which confirms the safety of the product.
Simple Freezing Techniques
Freezing is the fastest and simplest way to preserve tomatoes, requiring less specialized equipment than canning. Unlike canning, freezing does not require the addition of any acid because the low temperature inhibits microbial growth. This method is ideal for preserving whole tomatoes, diced pieces, or purees, which will be used later in cooked applications like sauces and soups.
For freezing whole tomatoes, simply wash, dry, and remove the stem scar, then place the individual fruits on a tray to flash freeze. Once they are solid, the tomatoes can be transferred to a heavy-duty freezer bag or rigid container to save space. This initial flash-freezing prevents the tomatoes from clumping together, allowing you to remove only what is needed later.
You can also process the tomatoes into a puree or crush them before freezing. To do this, blend the prepared tomatoes and pour the resulting product into freezer-safe containers, leaving a one-inch headspace to allow for expansion as the liquid freezes. For any freezing method, removing as much air as possible from the container or bag helps to prevent freezer burn and maintain the quality of the preserved tomatoes.
Dehydrating and Drying
Dehydrating tomatoes involves removing the moisture content, which concentrates the flavor and drastically changes the texture, creating a product similar to sun-dried tomatoes. This preservation method results in a light, shriveled piece of fruit that is shelf-stable. Paste varieties, such as Roma tomatoes, are particularly suited for drying because they have a higher solid content and less water to evaporate.
The tomatoes should be sliced uniformly, typically into quarter-inch thick pieces, or halved if using smaller varieties like cherry or grape tomatoes. A dedicated electric dehydrator provides the most consistent results, with the optimal temperature range set between 135 and 145 degrees Fahrenheit. The slices are placed on the dehydrator trays, ensuring there is a small space between them for air circulation.
Drying times can vary widely, ranging from 6 to 18 hours, depending on the thickness of the slices and the equipment used. The tomatoes are finished when they feel leathery or crisp and brittle to the touch, with no noticeable moisture remaining when a piece is squeezed. Once completely cooled, the dried tomatoes should be stored in an airtight container to prevent reabsorption of moisture from the air.