Chapter 3
IN THIS CHAPTER
Putting your fears of home-canned food to rest
Determining your processing method by your food’s acidity
Making the acquaintance of food-spoiling microorganisms and enzymes
Recognizing the signs of food spoilage
The desire and determination to produce a delicious, safe-to-eat product without the risk of food poisoning is one thing longtime canners and people new to canning have in common. The canning and preserving techniques used today provide you with these results as long as you follow the proper steps and procedures for preparing, processing, and storing your food.
Before you begin your canning and preserving journey, take a stroll through this chapter, which introduces you to microorganisms, enzymes, and other potentially dangerous situations that cause food spoilage. You can also find information on how to prevent and identify food spoilage. The technical portion of this chapter shouldn’t deter you from canning. Rest assured, after reading this information, you’ll have no fear about preparing and serving your home-canned and home-preserved food.
Preventing food spoilage is the key to safe canning. Over the years, home-canning has become safer and better. Scientists have standardized processing methods, and home-canners know more about using these methods. When you follow up-to-date guidelines exactly, you’ll experience little concern about the quality and safety of your home-canned and home-preserved food.
The following sections offer some tips for safely handling, preparing, and processing your food.
Prepping to start canning and preserving can sometimes feel daunting and keep you from starting. The truth is, getting your food ready is only a matter of basic science and common sense. None of these steps are difficult. For example, use fresh, firm (not overripe) food. Wash and prepare your food well to remove any dirt and bacteria: Wash it in a large bowl filled with room temperature water and a few drops of dish detergent, and then rinse it in a separate bowl of fresh water (see Figure 3-1). Can your fruit and vegetables as soon as possible after they’re picked. Wash only the type of food you are going to be preserving each time. To avoid cross contamination, do not mix different foods during this step.
FIGURE 3-1: How to wash fruit and vegetables well.
You have picked your food and washed it carefully. Now, you are in the home stretch, and the way you fill the canning jars is super important:
FIGURE 3-2: Headspace.
When you’re canning food, too little headspace in your canning jars restricts your food from expanding as it boils. Inadequate space for the expanding food may force some of it out of the jar and under the lid, leaving particles of food between the seal and the jar rim. If this occurs, your jar won’t produce a vacuum seal.
Leaving too much headspace may cause discoloration in the top portion of your food. Excess headspace can keep your jar from producing a vacuum seal if the processing time isn’t long enough to exhaust the excess air in the jar.
Always use the headspace stated in your recipe. If your recipe doesn’t give you a headspace allowance, use these guidelines:
The most important thing to do when you’re filling your jars is to release trapped air bubbles between the food pieces. This may seem unimportant, but air bubbles can play havoc with your final product.
FIGURE 3-3: Releasing air bubbles from your filled jars.
Always use the correct processing method for your food. Process all high-acid and pickled food in a water-bath canner. Process all low-acid food in a pressure canner. To find out how to determine whether a food has a low or high acidity level, head to the next section. (You can find out about the different canning methods in Chapters 4 and 9.)
In addition to choosing the right canning method, follow these guidelines to guard against food spoilage:
To prevent spoilage, your equipment must be in good shape and working properly:
Knowing the acidity level of the food you’re processing is important because the pH, the measure of acidity, determines which canning method you use: water-bath or pressure canning.
For canning purposes, food is divided into two categories based on the amount of acid the food registers:
High-acid foods include fruits and pickled foods. (For detailed information on identifying and processing high-acid food, refer to Chapter 4.) Foods in this group have a pH of 4.6 or lower. Processing them in a water-bath canner destroys harmful microorganisms.
Tomatoes are considered a low-high acid food (or in the low range of high-acid foods). With all of the new varieties of tomatoes, it is now recommended that the home canner add an acid to the canning process, to ensure that the proper acidity is reached every time.
Properly processing your home-canned foods destroys microorganisms. Knowing your altitude is important because the boiling point of water and pressure in a pressure canner changes at altitudes over 1,000 feet above sea level. This occurs because the air is thinner at higher elevations. With less air resistance, water boils at a temperature below 212 degrees.
To produce food free from microorganisms at higher elevations, adjust your processing time and pressure to compensate for your altitude. Use the altitude adjustment charts in Chapter 4 (for water-bath canning) and in Chapter 9 (for pressure canning). These adjustments ensure that your food is heated to the correct temperature for destroying microorganisms.
Food spoilage is the unwanted deterioration in canned or preserved food that makes your food unsafe for eating. Ingesting spoiled food causes a wide range of ailments, depending on the type of spoilage and the amount of food consumed. Symptoms vary from mild, flu-like aches and pains to more-serious illnesses or even death.
But having said that, the potential for spoiled food shouldn’t stop you from canning. When you understand the workings of these microscopic organisms and enzymes, you’ll know why using the correct processing method for the correct amount of time destroys these potentially dangerous food spoilers. And you’ll have nothing to worry about.
Mold, yeast, bacteria, and enzymes are the four spoilers. Microorganisms (mold, yeast, and bacteria) are independent organisms of microscopic size. Enzymes are proteins that exist in plants and animals. When one or more of these spoilers have a suitable environment, they grow rapidly and divide or reproduce every 10 to 30 minutes! With this high-speed development, it’s obvious how quickly food can spoil. Some of these create spoilage that can’t be seen with the naked eye (like botulism), while others (like mold) make their presence known visually.
Mold is a fungus with dry spores. Poorly sealed jars of high-acid or pickled foods are perfect locations for these spores to set up housekeeping. After the spores float through the air and settle on one of their favorite foods, they start growing. At first you see what looks like silken threads, then streaks of color, and finally fuzz, which covers the food. Processing high-acid and pickled food in a water-bath canner destroys mold spores.
Yeast spores are much less colorful, and grow in food in the same way as mold spores. They’re particularly fond of high-acid food that contains lots of sugar, like jam or jelly. They grow as a dry film on the surface of your food, more commonly inside the food, creating an off flavor and fermentation. Prevent yeast spores from fermenting in your food by destroying them in a water-bath canner.
Bacteria are a large group of single-celled microorganisms. Common bacteria are staphylococcus and salmonella. Botulism, the one to be most concerned with in canning, is the most dangerous form of bacteria and can be deadly. It’s almost undetectable because it’s odorless and colorless. Botulism spores are deadly but can be easily destroyed by heating the food to an internal temperature of 180 degrees Fahrenheit (85 degrees Celsius) for at least 5 minutes. Boiling occurs at 212 degrees Fahrenheit (100 degrees Celsius) and is the safest and easiest way to protect yourself from becoming ill.
Botulism spores hate high-acid and pickled foods, but they love low-acid foods. When you provide these spores with an airless environment containing low-acid food, like a jar of green beans, the spores produce a toxin in the food that can kill anyone who eats it. The only way to destroy them in low-acid food is by pressure canning.
No matter how long you boil your jars, they will never reach a higher temperature than that of boiling water. This is why water-bath canning and pressure canning are not interchangeable.
Enzymes are proteins that occur naturally in plants and animals. They encourage growth and ripening in food, which affects the flavor, color, texture, and nutritional value. Enzymes are more active at temperatures of 85 to 120 degrees Fahrenheit than they are at colder temperatures. They’re not harmful, but they can make your food overripe and unattractive, while opening the door for other microorganisms.
An example of enzymes in action occurs when you cut or peel an apple. After a few minutes, the apple starts to brown. Stop this browning by treating the cut apple with an antioxidant solution (see Chapter 5). Other methods for halting the enzymatic action in your food are blanching (see Chapter 15) and hot packing (see Chapter 5).
No one can promise you that your home-canned foods will always be free from spoilage, but you can rest assured that your chances for spoiled food are greatly reduced when you follow the precise guidelines for each preserving method. However, if you suspect, for any reason, that your food is spoiled or just isn’t right, don’t taste it. Instead, take a time-out to better evaluate the contents. For starters, the best way to detect food spoilage is by visually examining your jars. Review the following checklist. If you can answer “true” for each of the following statements, then your food should be safe for eating:
After your food has passed this preliminary checklist, examine your jars more closely. Truth is, just because your food doesn’t look spoiled doesn’t mean that it’s not. If you discover any spoilage during any step of this process, don’t continue your search, but properly dispose of your product.
Check the contents for any rising air bubbles or unnatural color.
The food and liquid should be clear, not cloudy.
Open the jar.
There shouldn’t be any spurting liquid.
Smell the contents of the jar.
Take note of any unnatural or unusual odors.