CANNING & BOTTLING

Canning Process

Canning high-acid foods such as jams, jellies, sauerkraut, kimchi, pickles, fermented vegetables, chutneys, and relishes is very easy, however, canning low-acid foods such as meat, poultry, fish and vegetables requires more knowledge. Low-acid recipes should be designed by processing authority and must be processed at higher temperatures in pressure canners.

The main steps in canning are:

1) Packing the product into the container.

2) Hermetically sealing the container. Hermetically sealed container means a container that is designed and intended to be secure against the entry of microorganisms and therefore maintains the commercial sterility of its contents after processing.

3) Thermally processing the product and the container together.

High-Acid foods are processed at 212° F, 100° C in water bath canner.

Low-Acid foods must be processed at 240 - 250° F, 116 - 121° C in pressure canner.

4) Cooling foods which were processed in water bath canner is easy: remove the jars from the water bath canner and let them sit undisturbed to cool at room temperature from 12-24 hours. As the temperature of the product drops, a vacuum forms inside and pulls down the lid. This is often accompanied by a popping sound and happens within minutes after removing the jar from the water bath canner. The seal, however, is still soft and the cans must be left undisturbed for the seal to harden. Placing hot jar in cold water will crack the glass.

Cooling low acid-foods such as meat, poultry, fish and vegetables is more involved.

5) Storage.

Packing methods used in canning by commercial packers and home canners vary greatly. Commercial packers use containers of all shapes, sizes and materials. Glass, steel, aluminium, plastic-cardboard-aluminium combinations, plastic containers and all types of closures. Such containers are processed by specialised equipment that is not available to a hobbyist. A home owner will can his products in glass jars or in metal cans, both types of containers are described in detail in Equipment section.

Raw-Packing - is the practice of filling jars tightly with freshly prepared, but unheated food. Such foods, especially fruit, will float in the jars. The entrapped air in and around the food may cause discoloration within 2 to 3 months of storage. Raw-packing is more suitable for vegetables processed in a pressure canner.

Hot-Packing - is the practice of heating freshly prepared food to boiling, simmering it 2 to 5 minutes, and promptly filling jars loosely with the boiled food. Boiling hot liquid is added to the jars.

Canned meat retains flavor and colour better during storage when the meat in each can is entirely covered with liquid. Water or drippings from the pan in which the meat was precooked should be added to the meat after it is packed into the jar or the can. Some juice will be released from meat precooked in cans during exhausting, but if that is not enough to cover the meat, hot water should be added before sealing. Whether food has been hot-packed or raw-packed, the juice, syrup, or water to be added to the foods should also be heated to boiling before adding it to the jars. At first the colour of hot-packed foods may appear no better than that of raw-packed foods, but within a short storage period, both colour and flavor of hot-packed foods will be superior. Pre-shrinking food permits filling more food into each jar.

Removing air - Air bubbles are removed by running a plastic knife or spatula around the inside of the jar.

There should be enough liquid to fill in around the solid food in the jar and to cover the food. The food which is not covered by liquid tends to darken and develop off-flavors. A common example is peeled raw potatoes which will darken unless covered with water.

Glass Jars

Hot-pack - The meats are heated (precooked) before packing into the jars. Pack precooked meats loosely, fill with hot broth or hot water leaving 1 inch head space.

Raw-pack - The raw meats are packed tightly into the jars all the way to the top. When processed in the canner, the meats will shrink and release juice.

Metal Cans

Hot-pack - The meats are precooked and packed into cans hot. Then they are filled with hot liquid (pan drippings, meat broth or hot water) leaving 1/4 inch head space. Seal and process at once.

Raw-pack - The meats are packed into the cans raw to within 1/2 inch of the top. Then they are heated (exhausted) to the temperature at the centre of 170° F, 77° C. If needed, add more hot liquid to within 1/4 inch of the top. Seal and process at once.

NOTE Filled containers should be sealed as soon as possible when still hot and placed in hot water in the canner. Then they should be immediately processed. The higher the filling temperature, the less pressure will be generated in the container by heating the contents. As a result a stronger vacuum forms in the container after thermal processing and cooling. Salt does not preserve meat in canning and is added for flavouring. It can even be left out altogether. If used, place salt in the container before putting in the meat.

Head Space

The unfilled space above the food in a sealed container and below its lid is termed head space. The amount of head space required depends on the type of food being canned. For example, starchy foods tend to expand when heated and therefore require more head space. Head space is of lesser importance in metal cans because the cans withstand the inside pressure quite well and allow the food to expand without spreading the seams. It is, however, accepted trade practice to reserve about 6% of the volume of the can for head space. The meats packed in cans in home production are usually filled with hot broth or hot water leaving about 1/4 inch head space. Heating air is a slow process so any additional volume of air will adversely affect the heat transfer.

Leaving the specified amount of head space in a jar is important to assure a vacuum seal. If too little head space is present the food may expand and bubble out when air is being forced out from under the lid during processing. The bubbling food, especially fat, may leave a deposit on the rim of the jar or the seal of the lid and prevent the jar from sealing properly. If too much head space is present, the food at the top is likely to discolour. Also, the jar may not seal properly because there will not be enough processing time to drive all the air out of the jar. And more air means more oxygen available to discolour the food and promote rancidity in fats

Headspace is needed for the expansion of food as jars are processed and for forming vacuums upon cooling. The extent of the expansion is determined by the air content in the food and by the processing temperature. Air expands greatly when heated to high temperatures; the higher the temperature the greater the expansion. Foods expand less than air when heated.

The headspace for most products processed in cans at 240-250° F, 116-121° C, should be no less than 6% and no more than 10%. The proper amount of headspace contributes to the formation of a vacuum inside a can and is needed to accommodate the expanding food and gasses.

Headspace in Glass Jars:

Jams and jellies - 1/4 inch

Fruits and tomatoes - 1/2 inch

Meats, poultry, fish - 1 - 1-1/4 inch

Headspace in Metal Cans:

Meats, poultry, fish - No. 2 can (307 x 409) - 1/2 inch

No. 3 can (404 x 414) - 3/4 inch

Vacuum and Exhausting

In canning process vacuum is needed to provide a strong closure. Vacuum is a measure of the extent to which air has been eliminated from the container. The amount of air that is left in the container after filling and the amount of vacuum are closely interrelated.

The container is filled with hot food and sealed. A little air remains inside after sealing which is an indication of a strong vacuum. The container is ready for thermal treatment..

Heat has been applied and the amount of air molecules remains the same. However, the molecules start to move faster and collide with the sides, the lid and each other. They start to exert pressure on the body of the container. As more heat is applied, the air molecules move even faster causing the pressure and temperature to increase.

The same container filled with cold food and sealed. As a result more air remains inside and the vacuum is weak. Heat is applied and the air molecules start moving around building up the pressure. The can contains plenty of molecules of air which have no place to go. They start to exert a lot of pressure on the lid and the seams of the can. This may weaken the seam and even deform the can.

Glass jars do not face seaming or cover deforming problems as the accumulating pressure (air molecules) can escape through the still soft sealing compound.

A strong vacuum provides the following benefits:

It reduces stress to the can and its seams during thermal processing.

It maintains the can ends or jar lids in a concave position giving a visual indication to the conditions of the container.It reduces the quantity of oxygen in the container. Fats are not going rancid, the food maintains its quality longer.

In food containers a vacuum is produced by the following methods:

Thermal exhaust

Steam displacement

Mechanical action

Exhausting

Exhausting is allowing air or similar gases to escape from the food. In a sealed container oxygen is undesirable, whether it is released from food cells or is present in the form of entrapped air. Oxygen may react with the food and the interior of the can and affect the quality and nutritive value of the canned food. Other gasses, for example, carbon dioxide, should also be exhausted as much as possible. They may place undue strain on the container during the heat process as they will expand. This will be more of a concern in metal cans, where the gases will be hermetically trapped and have no means to escape.

Thermal Exhaust - This is a typical home production method.

Cans: contents of the container are heated to 170° F, 77° C, prior to sealing the container. As the contents contract during the cooling step, a vacuum is produced inside.

Jars: The same effect is produced by filling jars with hot food, and adding boiling water, broth, syrup or brine to the container.

Air bubbles may be trapped inside the jar and will raise to the top during processing, increasing head space. This may adversely affect the closure of the jar. Run a plastic utensil (knife, spatula) around the jar, moving it up and down, so that any trapped air is released.

In commercial applications exhausting is accomplished by:

Steam Displacement - Steam is introduced into the headspace where it forces air out. When the container cools down, the steam condenses and a vacuum is produced. Filled with food, open containers are passed through an 'exhaust box' in which steam is used to expand the food by heat and expel air and other gasses.

Obtaining a vacuum by injecting steam into head space. The steam pushes the air out, then the can is immediately sealed. When the steam condenses, a vacuum is formed

Mechanical - A commercial method. A portion of the air in the container head space is removed with a pump. Regardless of the exhausting method used, the container must be immediately sealed while it is still hot.

NOTE After exhausting the metal cans should be processed at once, while still hot. Cans are never sealed cold.

Canning at Altitude

Using the process time for canning food at sea level may result in spoilage if you live at altitudes of 1,000 feet or more. Water boils at lower temperatures as altitude increases. Increasing the process time or canner pressure compensates for lower boiling temperatures. Therefore, select the proper time and pressure for the altitude where you are canning.

Canning food altitude.

The following table can be used for pressure and temperature conversion for canners that use the metric system.

A weighted gauge comes in three pressure settings: 5, 10 and 15 lbs. After the canner is being vented, the pressure inside is 14.69 psi and the temperature at 212° F, 100° C.

Adding a 5 lb weighted gauge increases pressure to 14.69 + 5 = 19.69 lb of pressure which corresponds to about 227° F, 108.5° C.

Adding a 10 lb weighted gauge increases pressure to 14.69 + 10 = 24.69 lb of pressure which corresponds to about 240° F, 116° C.

Adding a 15 lb weighted gauge increases pressure to: 14.69 + 15 = 29.69 psi. This corresponds to 250° F, 121° C

.Recipes usually list processing times and pressures for altitudes of 0-1000 feet for dial type and weighted gauge pressure canners. If you are canning at higher altitudes, follow the USDA altitude adjustments listed below.

NOTE make sure you know the type of your pressure canner.

If your recipe calls for 15 lbs. pressure at the sea level increase the pressure 1 lb. for each 2000 feet altitude. Thus at an altitude of 4000 feet, process food at 17 lbs. of pressure instead of 15 lbs. pressure. If you canner will not allow you to increase the pressure over 15 lbs., increase processing time 20% for each 1,000 ft. rise in altitude.

Microbiology and Safety of Canned Food

Understanding microbiology and safety of canned food is of utmost importance in home canning. Canning of jams is a very simple and well known process. It has been practised for generations, it requires basic skills and equipment and it has been safely performed all over the world. But home canning of meat, poultry, fish and vegetables is a more involved process that requires a sound understanding of microbiology and basic principles of physics. The fact that your grandmother processed meat and preserves in the same water boiling pot, does not mean she did it right! She did it wrong but she was lucky, and nobody in the family died. However, many people had less luck and their obituary said: "died of natural causes" as that was the only explanation that the doctor could think of at the time. Having said that, we have to mention now that there are two completely different methods of canning foods and they both require different temperatures, times and equipment. The same glass jar or can may be used for both processes but the processes are entirely different.

• High-Acid Foods - jams, jellies, juices.

• Low-Acid Foods - meat, poultry, fish, vegetables.

The commercial production of low-acid foods is highly regulated because people get sick and die. Even with all those regulations we have a few massive recalls of processed foods every year. And if you check the headlines, the recalled foods were not jams, juices or preserves, but they were either meats or vegetables. Ever heard of anybody getting sick from orange marmalade? The logical question arises as to what makes those low-acid foods so special? Well, the explanation is very simple, but it requires an understanding of a few basic concepts of microbiology. In other words, those tiny, invisible to the naked eye microorganisms decide how the food must be processed.

Safety of Canned Foods

Food begins to spoil soon after it is harvested or slaughtered. This spoilage is caused by microorganisms or by internal chemical changes which are caused by enzymes. Microorganisms can be destroyed and enzymes can be deactivated by heat treatment and this is the reason why thermal processing is the focal point in canning technology. Bacteria types vary and display different preferences for temperature at which they will grow or die. Understanding bacteria behaviour is crucial for a better understanding of heating and cooling processes. Microorganisms such as molds, yeasts and bacteria spoil food, even at refrigerator temperatures. It is quite obvious that we have to do something special to canned food if it is to remain for 2-3 years without refrigeration. If not killed the microorganisms will find the moisture and nutrients inside of the canned food and they will multiply. Some bacteria will simply spoil the food, others might produce toxins. Clearly, we have to protect ourselves and either kill the bacteria or create such conditions that they will be unable to grow.

Food safety is nothing else but the control of bacteria. To control them effectively we have to first learn how bacteria behave. Let's make something clear, it is impossible to eliminate bacteria altogether. Life on the planet will come to a halt. They are everywhere; on the floor, on walls, in the air, on our hands and all they need to grow is moisture, nutrients and warm temperature. They all share one thing in common: they want to live and given the proper conditions they will start multiplying. They don't grow bigger, they just divide and divide and divide until there is nothing for them to eat, or until conditions become so unfavourable that they stop multiplying and die.

Microorganisms can be divided into three groups:

• Molds - are easy to kill and most will die below the temperature of boiling water; they are of little concern when canning meats.

• Yeasts - are easy to kill and most will die below the temperature of boiling water; they are of little concern when canning meats.

• Bacteria - those microorganism can be dangerous and must be properly dealt with.

It is commonly believed that the presence of bacteria creates immense danger to us but this belief is far from the truth. The fact is that a very small percentage of bacteria can place us in any danger, and most of us with a healthy immune system are able to fight them off.

Bacteria Growth in Time

Under the correct conditions, bacteria reproduce rapidly and the populations can grow very large. Temperature and time are the factors that affect bacterial growth the most. Below 45° F bacteria grow slowly and at temperatures above 140° F they start to die. In the so called "danger zone" between 40-140° F many bacteria grow very well. For instance, the infamous E.coli grows best at 98° F (37° C) and Staph.aureus at 86°-98° (30-37° C). When bacteria grow, they divide and increase in numbers, not in size. Looking at the table it becomes clear what happens to a piece of meat left on the kitchen table on a beautiful and hot summer day.

Canning food safety microbiology bacteria division.

Bacteria growth. A bacteria cell enlarges in size, then a wall separates the cell into two new cells exactly alike.

Bacteria Growth With Temperature

It can be seen on the graph that at 32° F (0° C) bacteria needs as much as 38 hours to divide in two. That also means that if our piece of meat had a certain amount of bacteria on its surface, after 38 hours of lying in a refrigerator the amount of bacteria will double. If we move this meat from the refrigerator to a room having a temperature of 80° F (26.5° C), the bacteria will divide every hour (12 times faster). At 90° F they will be dividing every 30 minutes. Someone might say: why do I have to bother with all this bacteria stuff, I am going to kill them anyhow. Well, this is not entirely true, as thermophillic bacteria can survive high temperatures and might spoil the food if certain procedures are not observed. Secondly, if we let spoilage bacteria multiply, for example keeping meat at room temperature for too long, they will spoil the food. The food may not exhibit odor or slime yet, but its flavor is already affected. A thermal process will kill them but the fact remains that they have already done some damage.

Temperatures for food preservation.

We ensure food safety with:

Pasteurization, 149-203° F (65-95° C). Pasteurization kills pathogenic bacteria and is adequate for foods that would be refrigerated. Typically, high acid foods or acidified foods (added vinegar, lemon juice) with a pH < 4.5 are pasteurized.

Sterilization, 221-266° F (105-130° C). Sterilization method makes indefinite product life at ambient temperatures. Typically, low acid foods with a pH > 4.5 are sterilized.

Blanching also helps, but the vital controls are the method of canning and making sure the recommended heating temperatures and times are used. The processing times in USDA guides ensure destruction of the largest expected number of heat-resistant microorganisms. Properly sterilized canned food will be free of spoilage if lids seal and jars are stored below 95° F (35° C). Storing jars at 50-70° F (10-21° C) enhances the retention of quality.

Why Canned Foods Offer Favorable Conditions for the Growth of Cl. botulinum?

Cl.botulinum do not grow in the presence of air, so we are not at risk when cooking meats with usual cooking methods. However, bacterial spores do not die, they remain in a dormant stage, enveloped in their protective shells until conditions become favorable for their growth. This happens when there is no more oxygen (air) and this is exactly what happens during canning when most of the available air is exhausted from the container. In order to form a strong vacuum inside of the container, as much air as possible is removed. This creates a stronger seal and leaves room for the expansion of gasses. Without a vacuum, the cans will buckle and the contents of a jar may boil over through the seal. In a hermetically sealed container bacterial spores find the right temperature, plenty of moisture and nutrients, and the absence of air. Bacteria leave the spore and germinate. They start growing and produce toxin.

Control of Cl. botulinum

There are two ways of controlling Cl. botulinum:

Killing spores.

Preventing spores from germinating and growing.

Spores of Cl.botulinum are present in both acid and low-acid foods. In low acid-foods such as meats and vegetables, Cl.botulinum spores can only be killed at 240° F, 116° C or higher. However, the high acidity (pH < 4.6) prevents botulinum bacteria from leaving the spores. This prevents them from germinating and growing, and of course no toxin is produced. For this reason high-acid foods such as fruits or juices can be processed at 212° F, (100° C) as this temperature will kill all bacteria in vegetative form and bacterial spores are prevented from germinating by high acidity. The growth of Cl.botulinum is inhibited at 10% salt concentration which is equivalent to a water activity of around 0.93. Obviously, such high salt percentages will not be tolerated by a consumer.

Inactivating Toxin

The toxin is not heat resistant; it can be inactivated by boiling in water (212° F 100° C) for 10 minutes. Old canning manuals often asked for boiling home canned meats and vegetables for 10-15 minutes in an open vessel. This procedure was meant to destroy any bacteria or toxins that might have survived the incorrect canning process.

pH Acidity and Processing Methods

The main objective of thermal processing is control of Cl.botulinum bacteria. Whether food should be processed in a pressure canner or boiling-water canner depends on the acidity of the food. The term "pH" is a measure of acidity; the lower its value, the more acidic the food. Bacteria hate acidity, this fact works to our advantage. Acidity may be natural, as in most fruits, or added, as in pickled food. The acidity level in foods can be increased by adding lemon juice, citric acid, or vinegar. All bacteria have their own preferred acidity level for growth, generally around neutral pH (7.0). Bacteria will not grow when the pH is below the minimum or above the maximum limit for a particular bacteria strain. As the pH of foods can be adjusted, this procedure becomes a potent weapon for the control of Cl.botulinum. The thermal resistance of microorganisms decreases as the pH of their medium is lowered. As explained earlier, most bacteria, particularly Cl. botulinum, will not grow below pH 4.6. Therefore acidic foods having pH below 4.6 do not require as severe heat treatment as those with pH above 4.6 (low acid) to achieve microbiological safety. The pH value of 4.6 is the division between high acid foods and low acid foods. Low-acid foods have pH values higher than 4.6. They include red meats, seafood, poultry, milk, and all fresh vegetables except for most tomatoes.

Processing methods for low and high acid foods.

Most mixtures of low-acid and acid foods also have pH values above 4.6 unless their recipes include enough lemon juice, citric acid, or vinegar to make them acid foods. Acid foods have a pH of 4.6 or lower. They include fruits, pickles, sauerkraut, jams, jellies, marmalades, and fruit butters.

pH of various foods and materials. A lower pH value indicates higher acidity.

Although tomatoes generally fall on the pH dividing line at 4.6, there are varieties that have a lower pH level and there are varieties which also have a higher pH level. Tomatoes are usually considered an acid food. Figs also have pH values slightly above 4.6. Therefore, if they are to be canned as acid foods, these products must be acidified to a pH of 4.6 or lower with lemon juice, citric acid or vinegar. Properly acidified tomatoes and figs are acid foods and can be safely processed in a boiling-water canner. However, changing acidity levels requires a good understanding of food technology and should be left to professionals. In addition, not all foods will appeal to a consumer when their flavor is overly acidic.

pH Meters

There are many companies making pH measuring equipment. Large bench models are expensive and will be used by the professionals who establish thermal processes for canned foods. We have been using the Hanna Instruments HI 99163 Meat pH Meter with much satisfaction for making fermented sausages. The instrument is of great value for the pH analysis of meat products. This pH meter is simple to use with only two buttons. The replaceable penetration blade allows the user to measure not only the surface, but also the internal pH of the meat. The unit is very accurate and the reading is obtained within seconds.

Control of Bacteria by Water Activity

In order to remain alive the microorganisms need nutrients and moisture. How do bacteria eat? Imagine some sugar, flour or bread crumbs spilled on the table. Place a dry sponge on top of the sugar and you will see that the sponge will not pick up any of the ingredients. Pour some water over the ingredients and repeat the sponge procedure. The sponge will absorb the solution without any difficulty. Bacteria are like a sponge, they absorb food through the wall, but the food must be in a form of a solution. It must contain water. When water is eliminated, bacteria cannot eat.

Sponge will not pick up food particles from a dry surface.

Sponge easily picks up food particles that dissolved in water.

All microorganisms need water and the amount of water available to them is defined as water activity. Water activity (Aw) is an indication of how tightly water is "bound" inside of a product. It does not say how much water is there, but how much water is available to support the growth of bacteria, yeasts or molds. Adding salt or sugar "binds" some of this free water inside of the product and lowers the amount of available water to bacteria which inhibits their growth. The most practical approach for lowering water activity is drying, although it is a slow process which must be carefully monitored, otherwise it may backfire and ruin the product. A simple scale is used to classify foods by their water activity and it starts at 0 (bone dry) and ends on 1 (pure water).

Below certain Aw levels, microbes can not grow. USDA guidelines state: "A potentially hazardous food does not include... a food with a water activity value of 0.85 or less."

Meats, dried fruits and vegetables were preserved throughout our history and the technology was based on simple techniques of salting and drying. It was also discovered that the addition of sugar would preserve foods such as candies and jellies. Both factors contribute to lowering the water activity of the meat. Freshly minced meat possesses a very high water activity level around 0.99, which is a breeding ground for bacteria. Adding salt to meat drops this value immediately to 0.96-0.98 (depending on the amount of salt), and this already creates a hurdle against the growth of bacteria. This may be hard to comprehend as we know that water does not suddenly evaporate when salt is added to meat. Well, this is where the concept of water activity becomes useful.

Although the addition of salt to meat does not force water to evaporate, it does something similar: it immobilizes free water and prevents it from reacting with anything else, including bacteria. It is like stealing food from the bacteria, the salt locks up the water creating less favorable conditions for bacteria to grow and prosper. As we add more salt, more free water is immobilized but a compromise must be reached, as adding too much salt will make the product unpalatable. It may also impede the growth of friendly bacteria, the ones which work with us to ferment the sausage. The same happens when we freeze meat though we never think of it. Frozen water takes the shape of solid ice crystals and is not free anymore. Water exists in meat as:

• Bound (restricted or immobilized water) - structurally associated with meat proteins, membranes and connective tissues. This water (3-5% of total water) can only be removed by high heat and is not available for microbial activities.

• Free or bulk water - held only by weak forces such as capillary action. This free water is available for microorganisms for growth.

Removing water content by drying food has been practiced for centuries. As the process proceeds, water starts to evaporate (water activity decreases), making meat stronger against spoilage and pathogenic bacteria. There eventually comes a point where there are no bacteria present and the meat is microbiologically stable. It will not spoil, as long as it is kept at low temperatures and at low humidity levels. If the temperature and humidity go up, new bacteria will establish a colony on the surface and will start moving towards the inside of the sausage. The mold will then immediately appear on the surface. Microbial spoilage is a frequent cause of spoiled foods or defective containers. It may result from:

• Holding containers too long before processing.

• Contamination after processing.

• Inadequate thermal process.

• Inadequate cooling of the containers or storage at high temperatures.

• Spoilage due to survival of acid-tolerant spores (flat sour).

Botulism

Botulism was discovered and explained by Emile Pierre van Ermengem in 1895. Since the dawn of civilization, man has dealt with food poisoning. It has led to a number of deaths, but in most cases it was blamed on natural causes. There are very few historical sources and documents on the subject prior to the 19th century. In the 10th century Emperor Leo VI of Byzantium prohibited the manufacturing of blood sausage. At the end of the 18th century, there were documented outbreaks of ìsausage poisoningî in Wurttemberg, Southern Germany. The biggest one occurred in 1793 in Wildbad where 13 people became ill (6 of whom died) after eating a locally produced blood sausage. The above incident motivated the German poet and district medical officer Justinus Kerner (1786-1862) to investigate the problem. Although he did not succeed in discovering the bacteria that caused it, he was the first to publish detailed and complete descriptions of food poisoning between 1817-1822. He described 230 cases, most of which were linked to the consumption of sausages. He called it "sausage" or "fatty" poison. In time it became known as "botulism" after "botulus", the Latin word for sausage. Eighty years after Kernerís work, in 1895, a botulism outbreak affected 34 people. After a funeral dinner in the small Belgian village of Ellezelles, a group of local musicians consumed smoked ham. That led to the discovery of the pathogen Clostridium botulinum by Emile Pierre van Ermengem, Professor of bacteriology at the University of Ghent who investigated the incident. Van Ermengen discovered that botulism was intoxication, not infection, and that the toxin was produced by a spore-forming obligate anaerobic bacterium, "Clostridium botulinum."

Ensuring High-Quality Canned Foods

Canning is a method of food preservation and its primary aim is to prevent the growth of microorganisms that would spoil the food and create danger to consumers. Canning does not create super quality canned food, it simply preserves the food that we make. If we prepare a good dish, canning will definitely preserve its quality for a long time. If we simply throw in some meat without spices, salt or broth, we would preserve it, but it would hardly be a culinary masterpiece. In other words, all good cooking principles should be applied not only for the safety of the product, but also for its taste and flavor. Begin with good-quality fresh foods suitable for canning. Quality varies among varieties of fruits and vegetables. Discard diseased and moldy food. Trim small diseased lesions or spots from food. Can fruits and vegetables picked from your garden or purchased from nearby farmers when the products are at their peak of quality-within 6 to 12 hours after harvest for most vegetables. For best quality, apricots, nectarines, peaches, pears, and plums should be ripened 1 or more days between harvest and canning. If you must delay the canning of other fresh produce, keep in a shady, cool place. Many fresh foods contain from 10 percent to more than 30 percent air. How long canned food retains high quality depends on how much air is removed from food before jars are sealed.

Maintaining Color and Flavor in Canned Food

To maintain good natural colour and flavor in stored canned food, you must:

• Remove oxygen from food tissues and jars.

• Quickly destroy the food enzymes.

• Obtain high jar vacuums and airtight jar seals.

Follow these guidelines to ensure that your canned foods retain optimum colors and flavors during processing and storage:

• Use only high-quality foods which are at the proper maturity and are free of diseases and bruises. Use the hot-pack method, especially with acid foods to be processed in boiling water. Don't unnecessarily expose prepared foods to air. Can them as soon as possible. While preparing a canner load of jars, keep peeled, halved, quartered, sliced, or diced apples, apricots, nectarines, peaches, and pears in a solution of 3 grams (3,000 milligrams) ascorbic acid* to 1 gallon of cold water. This procedure is also useful in maintaining the natural color of mushrooms and potatoes, and for preventing stem-end discoloration in cherries and grapes. Fill hot foods into jars and adjust headspace as specified in recipes. Tighten screw bands securely, but if you are especially strong, not as tightly as possible. Process and cool jars. Store the jars in a relatively cool, dark place, preferably between 50-70° F (10-21° C). Can no more food than you will use within a year. You can get ascorbic acid* in several forms:

• Pure powdered form - seasonally available among cannersí supplies in supermarkets. One level teaspoon of pure powder weighs about 3 grams. Use 1 teaspoon per gallon of water as a treatment solution.

• Vitamin C tablets - economical and available year-round in many stores. Buy 500 - milligram tablets; crush and dissolve six tablets per gallon of water as a treatment solution.

• Commercially prepared mixes of ascorbic and citric acid - seasonally available among cannersí supplies in supermarkets. Sometimes citric acid powder is sold in supermarkets, but it is less effective in controlling discoloration. If you choose to use these products, follow the manufacturer's directions.

Storage of Canned Food

Canned food should be stored in a dry, cool place. Ideally, the storage area should have some air circulation, otherwise molds might grow on the outside of jars, screwbands, and metal cans might start to rust. Correct processing will kill spoilage bacteria and foods will not spoil, unless kept at temperatures over 95° F (35° C). At these temperatures certain heat loving microorganisms, which could have survived the canning process, might start growing again. Nevertheless, certain chemical reactions which affect fat rancidity, food texture, color and nutritional value may occur when proper storage conditions are not met. The best storage temperature is about 35-59° F (2-15° C), and the higher it is, the more unwelcome changes will occur in stored foods. As explained earlier, extremely high temperatures may create favorable conditions for thermophillic bacteria that survived heat treatment to grow and spoil the food. Freezing will affect texture quality due to water crystal formation inside of the food. This will make frozen food less palatable than properly stored canned food. Besides, this expansion of water may break glass jars and weaken the seals. Glass jars should be protected from light otherwise fats will develop rancidity and the quality of the product will suffer. At proper conditions meat and fish will keep well for 2-3 years. If jars must be kept in a very cold place, just insulate them by any practical means, for example, wrapping them in newspapers or keeping them in boxes covered with more newspapers or blankets. Store cans at room temperature. What we want to mention is that in many cases, for example in tropical countries, canned products might be kept at temperatures higher than 77° F (25° C). Although bacterial spores will be eliminated during proper processing times at 240° F (116° C), there are certain bacteria (thermophillic bacillus strains) which are extremely heat resistant and they will survive. They normally donít grow below 77° F (25° C), even if present in a sealed container. However, when storage temperatures will reach 95° F (35° C) or higher, those bacteria will grow and given time will spoil the food. To eliminate this possibility, the processing times and temperatures must be increased even more. It should be noted that those bacteria spoil the food only and donít pose grave risks to our safety.