UConn Extension‘s Diane Hirsch held a workshop for 12 students from the UConn Spring Valley Farm and the UConn EcoGarden Club as well as others. The focus was on pressure canning as the Spring Valley Farm students hope to purchase a pressure canner in the near future. Julia Cartabiano, the farm manager, made the arrangements so that we could use the kitchen at the Whitney Dining Hall. We canned applesauce that the students had made.
By Diane Wright Hirsch
UConn Extension Educator/Food Safety
It has been a wonderful year for growing fruits and vegetables in Connecticut. A trip to your backyard vegetable garden, local farmers’ market or maybe the nearby pick-your-own orchard, even late in the season, will attest to this: bins and shelves are still overflowing with beautiful tomatoes, raspberries, green beans and corn. But, soon it will all be gone and we will be wishing that we had stashed some away for the long winter.
There is a way to fix this–without turning to imports from China or Chile or even the well-traveled produce from California, which begins to lose nutritional value as soon as it is picked. Freeze your local produce, whether it is from your garden or the farmer down the road. If done right, freezing can preserve the flavor and health-giving benefits of summer fresh fruits and vegetables. IF DONE RIGHT.
Freezing is easy, requires no special equipment and is often the home food preservation method of choice. Many people do not want to use a canner or pressure canner. It can be a little scary if you do not know what you are doing. Keep in mind, though, that freezing can be a more costly way of preserving than canning. It requires that you have a freezer that can hold all of the food you want to freeze at 0°F and, if you choose single use plastic freezer bags, they can be expensive. But, it is less time consuming and most folks prefer the flavor and texture of frozen foods.
Another thing to keep in mind is that you may not be able to reproduce the commercially frozen products that you are used to. Unless you have a blast freezer in the basement! The frozen foods you buy in the grocery store is often picked and processed the same day. This is always best, though not always possible when you are waiting for your garden to produce enough green beans to make the job worth it. Also, they are freezing food very fast at very low temperatures that create very small crystals and prevent mushiness and texture changes that may occur during home freezing.
Freezing produce at home
You can’t just wash your produce, cut it up and throw it in the freezer without much thought. Well you can, but the result will be just as tasteless as a January tomato. People need to know that while the temperature of a freezer keeps food safe, it will not preserve the quality of your produce without some help.
After harvest, fruits and vegetables undergo chemical changes which can cause spoilage and deterioration of the product. This is why these products should be frozen as soon after harvest as possible and at their peak degree of ripeness. Fresh produce contains chemical compounds called enzymes which can cause flavor, color and texture changes, and the loss of vitamins and minerals even while stored in the freezer. These enzymes must be inactivated to prevent these reactions.
When freezing vegetables, you can inactivate the enzymes by blanching—or dropping them into boiling water or steaming for a short time. Cool the vegetable quickly in ice water to keep it from cooking. Even though blanching can be a bother, in most cases it is absolutely essential for producing quality frozen vegetables. The exceptions to this rule are peppers, onions and herbs, which do not need to be blanched.
Fruits are a bit different. The major problem associated with enzymes in fruits is the development of brown colors and loss of vitamin C. Because fruits are usually served raw, they cannot be blanched like vegetables. Instead, home food preservers control the browning and loss of vitamins with ascorbic acid (vitamin C), an anti-oxidant. Ascorbic acid may be used in its pure form or in commercial mixtures (such as “Fruit Fresh”). This is more effective than the use of lemon juice.
Often you will see recipes that suggest that you freeze fruits with sugar or in a light sugar syrup. Though many folks today are sugar phobic, keep in mind that the quality of many fruits (peaches, apples) is not as good when packed without sugar. Sugar helps to preserve both the flavor and texture of frozen fruits. If you are planning to use the fruits to make jams or preserves later on, or, if there are health concerns such as diabetes, then, of course, freeze in plain water or dry.
Frozen fruits and vegetables can also suffer a variety of changes—flavor and texture—when the product is not well protected from the air. You might have heard it referred to as freezer burn. You can control this problem by using materials for packaging that are made specifically for the freezer—plastic wraps, plastic bags, hard sided plastic containers or even glass. You should not consider this an opportunity to re-use plastic containers that may have once held cottage cheese, yogurt or other non-frozen foods. Economically and environmentally speaking, you may want to invest in re-usable freezer containers that may be found in grocery, farm supply or department stores next to the home canning supplies. Glass works well, too, but special care must be taken to avoid breakage, including leaving enough space for the food to expand while freezing.
Keep in mind also that while freezing preserves safety and quality, there are some foods that will simply be different after you freeze them. Some fruits and vegetables are naturally high in moisture. When frozen, the moisture freezes and causes the cells of the plant to burst. Once thawed, these products will be softer than when fresh—no matter how careful you are. So, tomatoes, many fruits, summer squash and greens once frozen will be better suited to mixed dishes, sauces or soups. It doesn’t make much sense to freeze cabbage (develops off flavors), celery, cucumbers, endive, lettuce, or radishes.
Frozen fruits and vegetables will maintain good quality for one year if packed well and kept in a freezer at 0°F.
Freezing Green or Yellow Beans
Pick young tender beans that snap when broken. Harvest while seeds are small and tender. Wash, snip off tips and sort for size. Cut or break into suitable pieces or freeze small beans whole. Blanch 3½ minutes. Chill in ice water. Drain, pack in freezer container.
Choose well ripened fruit of good quality. Wash in cold water and sort. Dip 3 or 4 peaches into boiling water until skins loosen—15-20 seconds. Peel and slice peaches into containers one-third full of syrup (3 cups sugar to 1 quart water with 1⁄2 teaspoon ascorbic acid). Make sure to leave a head-space of at least ½ inch to allow for expansion of the liquid during freezing.
For specific instructions for freezing fruits and vegetables, contact the UConn Home and Garden Education Center by phone at (877) 486-6271 or by email to firstname.lastname@example.org contact the National Center for Home Food Preparation at: http://www.uga.edu/nchfp.
By Diane Wright Hirsch, MPH, RD
UConn Extension Educator – Food Safety
In the recent past, the tomato crop has not been so great, but thankfully, this year looks like a winner. The tomato plants in my garden are pulling the stakes over; they are so laden with fruit. Next year, it will be back to cages, I think!
An abundant harvest may mean that you want to can some of your tomatoes this year. If you are new to the task (or maybe even more importantly, if you are a long time tomato canner), it is essential that you learn the safest techniques for canning. Over the thirty plus years that I have been canning, recommendations for the safe home canning of tomatoes have evolved. Here is what you should NOT be doing anymore:
- Canning tomatoes without processing them in a water bath or pressure canner
- Processing tomatoes without adding lemon juice to each jar as added “safety insurance”
- Processing quarts of tomatoes in a water bath canner for 30 minutes
So, what are the safety concerns related to home preservation of tomatoes? They include the possibility of spoilage and even botulism poisoning. “But aren’t tomatoes acidic?” you might ask. “Doesn’t that mean that you do not have to worry about botulism?”
Well, the answer is yes and no. It depends on the tomatoes. The pH of tomato varieties can range from an acidic low of 3.8 to a much less acidic pH of 4.7. The story goes that as the consumer has demanded a less acidic tomato, hybrids have been developed that taste less acidic—but some argue that this is due to more sugar in the tomato, not less acid. Would that mean that older heirloom varieties are likely to be more acidic? Not necessarily.
A study by Heflebower and Washburn at Utah State in 2010 looked at hybrid varieties, open pollinated and heirloom varieties. The results indicated that the average pH was 3.92 for the hybrids they tested, 4.03 for open pollinated and 4.16 for the heirloom. Of course all of these are below the 4.6 borderline. The authors still recommend the addition of acid to ensure that the final product remains below 4.6. In a bulletin from the North Dakota Extension Service regarding the use of lemon juice in canned tomatoes and salsa (Garden-Robinson, Houge, & Smith, 2004), the pH of 15 different tomato varieties were tested. The pH readings were taken from the pure tomato pulp prior to canning and again after lemon juice was added and the tomatoes were made into salsa. In this particular study, all of the raw tomatoes tested had a pH from 4.8 to 5.2 prior to canning.
In your home garden, a number of factors can influence the pH of even the more acidic tomatoes: these include soil, vine health, ripeness.
When using a water bath canner we caution home canners to be mindful of the pH of the food you are canning. As a general rule of thumb, if the pH is 4.6 or higher, the food is considered to be “low acid” and should be canned in a pressure canner. If the pH of a tomato product is below 4.6, there is the chance that if clostridium botulinum is present when processed in a water bath canner, that the bacteria will develop the spore form during the heating process, protecting it from destruction. Once the tomatoes are stored at room temperature, the spore can germinate and allow the production of toxin by the bacteria. This generally happens at room temperatures when the environment is moist, low in acid and free of oxygen. A pressure canner can reach temperatures well above the boiling point of water achieved in a boiling water bath canner. These temperatures (240 degrees F) will destroy botulism spores.
So rather than risk the chance of botulism at worst or spoilage, a less ominous outcome, but still one that results in the waste of food and a lot of hard work, why not just learn to can tomatoes using tested, safe methods? The go-to source for up to date information on canning tomatoes is the National Center for Home Food Preservation (www.uga.edu/nchfp). You will find directions for canning tomatoes and tomato products in a water bath canner and a pressure canner. For any tomato products, be sure to add a tablespoon of lemon juice or ¼ teaspoon of citric acid to pints and two tablespoons of lemon juice or ½ teaspoon of citric acid to quart jars.
Some folks are nervous about using the pressure canner. New pressure canners are easy to use and have many built in safety features. And using one makes sense for canning tomatoes. If you want to can tomatoes using no added water, you will need to process quarts in a water bath canner for 85 minutes. If you have lots of tomatoes, that’s a lot of minutes! And a lot of electricity or gas is used in the process. The same tomatoes will only take 25 minutes in a pressure canner at 11 pounds of pressure. It just makes sense to consider the pressure canner in this case.
In addition, if you want to make tomato products that contain significant amounts of low-acid ingredients such as meat, garlic, onions, peppers, or mushrooms, the pressure canner is essential for producing a safe product. All of these low-acid ingredients will surely bring the pH of your sauce or other tomato mixture well above 4.6 even if you start with acidic tomatoes.
The National Center also has tested recipes for canning some tomato products that have a lesser amount of low-acid ingredients. There are recipes for salsa, a tomato-vegetable juice, ketchup, and barbecue sauce. For each of these products, vinegar or lemon juice are important ingredients, adding the acidity needed to safely can in a water bath canner. Never add any additional ingredients or an extra pepper or two as this will likely make these products unsafe to can in the water bath canner.