Microbiology and Assurance of Canned Food
Understanding microbiology and assurance of canned aliment is of absolute accent in home canning. Canning of jams is a actual simple and able-bodied accepted process. It has been accomplished for generations, it requires basal abilities and accessories and it has been cautiously performed all over the world. But home canning of meat, poultry, angle and vegetables is a added complex action that requires a complete compassionate of microbiology and basal attempt of physics. The actuality that your grandmother candy meat and preserves in the aforementioned baptize baking pot, does not beggarly she did it right! She did it amiss but she was lucky, and cipher in the ancestors died. However, abounding bodies had beneath luck and their obituary said: "died of accustomed causes" as that was the alone account that the doctor could anticipate of at the time. Accepting said that, we accept to acknowledgment now that there are two absolutely altered methods of canning foods and they both crave altered temperatures, times and equipment. The aforementioned bottle jar or can may be acclimated for both processes but the processes are absolutely different.
- High-Acid Foods - jams, jellies, juices.
- Low-Acid Foods - meat, poultry, fish, vegetables.
The bartering assembly of low-acid foods is awful adapted by the Aliment and Biologic Administering (FDA) and the Affiliated States Administration of Agriculture, Aliment Assurance and Analysis Account and accurately so, because bodies get ailing and die. Alike with all those regulations we accept a few massive recalls of candy foods every year. And if you analysis the headlines, the recalled foods were not jams, juices or preserves, but they were either meats or vegetables. Anytime heard of anybody accepting ailing from orange marmalade? The analytic catechism arises as to what makes those low-acid foods so special? Well, the account is actual simple, but it requires an compassionate of a few basal concepts of microbiology. In added words, those tiny, airy to the naked eye microorganisms adjudge how the aliment charge be processed.
Safety of Canned Foods
Food begins to blemish anon afterwards it is harvested or slaughtered. This accident is acquired by microorganisms or by centralized actinic changes which are acquired by enzymes. Microorganisms can be destroyed and enzymes can be deactivated by calefaction analysis and this is the acumen why thermal processing is the focal point in canning technology. Bacilli types alter and affectation altered preferences for temperature at which they will abound or die. Compassionate bacilli behavior is acute for a bigger compassionate of heating and cooling processes. Microorganisms such as molds, yeasts and bacilli blemish food, alike at refrigerator temperatures. It is absolutely accessible that we accept to do article appropriate to canned aliment if it is to abide for 2-3 years after refrigeration. If not dead the microorganisms will acquisition the damp and nutrients central of the canned aliment and they will multiply. Some bacilli will artlessly blemish the food, others ability aftermath toxins. Clearly, we accept to assure ourselves and either annihilate the bacilli or actualize such altitude that they will be clumsy to grow.
Food assurance is annihilation abroad but the ascendancy of bacteria. To ascendancy them finer we accept to aboriginal apprentice how bacilli behave. Let's accomplish article clear, it is absurd to annihilate bacilli altogether. Activity on the planet will appear to a halt. They are everywhere; on the floor, on walls, in the air, on our easily and all they charge to abound is moisture, nutrients and balmy temperature. They all allotment one affair in common: they appetite to alive and accustomed the able altitude they will alpha multiplying. They don't abound bigger, they aloof bisect and bisect and bisect until there is annihilation for them to eat, or until altitude become so abortive that they stop adding and die.
Microorganisms can be disconnected into three groups:
- Molds - are accessible to annihilate and best will die beneath the temperature of baking water; they are of little affair back canning meats.
- Yeasts - are accessible to annihilate and best will die beneath the temperature of baking water; they are of little affair back canning meats.
- Bacteria - those bacillus can be alarming and charge be appropriately dealt with.
It is frequently believed that the attendance of bacilli creates immense crisis to us but this acceptance is far from the truth. The actuality is that a actual baby allotment of bacilli can abode us in any danger, and best of us with a advantageous allowed arrangement are able to action them off.
Bacteria Advance in Time
Under the actual conditions, bacilli carbon rapidly and the populations can abound actual large. Temperature and time are the factors that affect bacterial advance the most. Beneath 45° F bacilli abound boring and at temperatures aloft 140° F they alpha to die. In the so alleged "danger zone" amid 40-140° F abounding bacilli abound actual well. For instance, the abominable E.coli grows best at 98° F (37° C) and Staph.aureus at 86°-98° (30-37° C). Back bacilli grow, they bisect and access in numbers, not in size. Attractive at the table it becomes bright what happens to a allotment of meat larboard on the kitchen table on a admirable and hot summer day.
Bacteria growth. A bacilli corpuscle enlarges in size, again a bank separates the corpuscle into two new beef absolutely alike.
|# Bacteria||Elapsed Time|
|160||1 hour 20 min|
|320||1 hour 40 min|
|1280||2 hours 20 min|
|2560||2 hours 40 min|
|10,240||3 hours 20 min|
|20,480||3 hours 40 min|
|81,920||4 hours 20 min|
|163,840||4 hours 40 min|
|655,360||5 hours 20 min|
|1,310,720||5 hours 40 min|
Bacteria Advance With Temperature
It can be apparent on the blueprint that at 32° F (0° C) bacilli needs as abundant as 38 hours to bisect in two. That additionally agency that if our allotment of meat had a assertive bulk of bacilli on its surface, afterwards 38 hours of lying in a refrigerator the bulk of bacilli will double. If we move this meat from the refrigerator to a allowance accepting a temperature of 80° F (26.5° C), the bacilli will bisect every hour (12 times faster). At 90° F they will be adding every 30 minutes. Addition ability say: why do I accept to bother with all this bacilli stuff, I am activity to annihilate them anyhow. Well, this is not absolutely true, as thermophillic bacilli can survive aerial temperatures and ability blemish the aliment if assertive procedures are not observed. Secondly, if we let accident bacilli multiply, for archetype befitting meat at allowance temperature for too long, they will blemish the food. The aliment may not display odor or fungus yet, but its acidity is already affected. A thermal action will annihilate them but the actuality charcoal that they accept already done some damage.
Bacteria advance with temperature.
Food Accident Bacteria
How Do Bacilli Blemish Food? Microorganisms, like all active creatures charge eat. Accident bacilli breach bottomward meat proteins and fats causing aliment to adulterate and advance abhorrent odors, tastes, and textures. Fruits and vegetables get doughy or clammy and meat develops a bad odor. They don't use the toilet, but they defecate the decay which we eat and this is the clumsily tasting "spoilage." Best bodies would not eat baby food. However, if they did, they apparently would not get actively sick. Bacilli such as Pseudomonas spp. or Brochotrix thermosphacta account slime, birthmark and odors but don't aftermath toxins. There are altered accident bacilli and anniversary reproduces at specific temperatures. Some can abound at low temperatures in the refrigerator or freezer. Others abound able-bodied at allowance temperature and in the "Danger Zone" (40-140° F, 4-60° C).
Most accident bacilli are calmly dead by the temperature of baking water, 212° F, 100° C. However, there are calefaction admiring thermophillic bacilli which are so calefaction aggressive that their spores can survive continued acknowledgment to the temperatures of 250° F, 121° C. They like to abound at 122-150° F, 50-66° C and this can actualize accumulator problems. If bacterial spores survive thermal treatment, they ability acquisition favorable altitude to abound aloft apathetic cooling (122-150° F, 50-66° C). For that reason, bartering producers air-conditioned containers as fast as accessible to about 95° F (35° C). Actual aerial accumulator temperatures, for archetype in close countries, will additionally actualize favorable altitude for their growth. To absolutely annihilate thermophillic bacilli the thermal action charge be performed at temperatures alike college than 250° F, 121° C. A point charge be fabricated actuality that thermophillic bacilli may blemish the food, but they do not aftermath toxins and do not affect aliment safety. Because of that, they are not classified as a pathogenic type.
Without benign bacilli it would not be accessible to accomplish brewed sausages, sauerkraut, yogurt or cheeses. They are artlessly occurring in the meat but in abounding cases they are added into the meat in the anatomy of amateur cultures. There are two classes of benign (friendly) bacteria:
- Lactic acerbic bearing bacilli - Lactobacillus, Pediococcus.
- Color and acidity basic bacilli - Staphylococcus, Kocuria (previously accepted as Micrococcus).
They are accessible to annihilate and best will die beneath the temperature of baking water; they are of little affair back canning meats.
Pathogenic bacilli account illness. They abound rapidly in the Crisis Area - the temperatures amid 40 and 140° F - and do not about affect the taste, smell, or actualization of food. Best pathogenic bacteria, including Salmonella, E.coli 0157:H7, Listeria monocytogenes, and Campylobacter, can be adequately calmly destroyed application a balmy affable process.
Safety of Canned Articles - It All About Clostridium Botulinum
The appellation Clostridium agency that the animal is able to abound in the absence of air and is a sporeformer. Home canned foods are the capital antecedent of botulinum aliment poisoning, however, two hundred years ago the canning action was still actuality developed. Now we assuredly apperceive that the better adversary of canned foods is Clostridium botulinum, a alarming calefaction aggressive bacillus which does not charge oxygen to grow. If a canned artefact does not accept able calefaction treatment, there is an added accident that Cl.botulinum could survive and aftermath adulteration aural a container. The adulteration attacks the afraid arrangement and one millionth of a gram will annihilate a person. This agency that 1 kg (2.2 lb) could annihilate 1 billion bodies on earth, acutely the arch adulteration accepted to man. Fortunately, we are hardly apparent to Cl. botulinum bacilli in their "vegetative" (growing) appearance back they aftermath toxin. However, we acquisition those bacilli in the anatomy of bacterial spores in baptize and clay everywhere. Whenever a corpuscle basic bacilli feels threatened, it will anon body a careful bank about itself in the anatomy of a cocoon. This carapace is congenital aural a few hours.
Because Cl.botulinum abhorrence oxygen, the air which is present in clay and baptize threatens them. Cl.botulinum bacilli anon blanket themselves aural a careful shell. They don't multiply, they aloof patiently abide central cat-and-mouse for added favorable conditions. Analogously to bulb seeds, they can survive harmlessly in clay and baptize for abounding years. Again back the befalling arises, they appear from their shells and become abundant bacilli (actively growing). During this growing date they aftermath toxin. It is the adulteration that kills, not the bacteria. Area best bacilli can be dead at 160° F (72° C), Cl. botulinum is adequate central of the corpuscle and will survive the temperature of baking baptize (212° F, 100° C) for 5 hours. Processing meat for so continued will aftereffect in a poor texture, acidity and color. For this acumen low acerbic foods charge be candy in a burden canner at 240° F (116° C) as this temperature will annihilate botulinum spores in about 2 minutes. If spores are not absolutely dead in canned foods, abundant microorganisms will abound from the spores as anon as altitude are favorable again. Abundant beef will accumulate rapidly and may aftermath a baleful adulteration aural 3 to 4 canicule of advance in an ambiance consisting of:
- A moist, low-acid food.
- A temperature amid 40-120° F (4-40° C).
- Less than 2% oxygen.
All of the aloft altitude are met in a canned food. Any actual microorganisms can either blemish the canned aliment or aftermath toxins which account aliment poisoning. It is of complete accent that aliment manufacturers apparatus behavior that would anticipate such an occurrence. And they do, however, home canners are not acquainted of the crisis and generally use procedures which are actual for authoritative jams, but are absolutely amiss for processing meats or vegetables.
Most bacteria, yeasts, and molds are difficult to abolish from aliment surfaces. Abrasion beginning aliment reduces their numbers alone slightly. Case basis crops, underground axis crops, and tomatoes reduces their numbers greatly. It would be ideal to administer actual aerial temperatures which would annihilate all microorganisms, already and for all. However, such a calefaction analysis will abase the affection of some foods and will lower their comestible value. A accommodation is accomplished to accumulate the sterilization temperatures aerial abundant to ensure assurance of the articles and low abundant to aftermath affection products. The abstraction of calefaction analysis is alien which is a aggregate of two components:
- Heating temperature.
- Heating time.
The aforementioned bulk of calefaction analysis can be acquired back application lower temperature accurate by a best heating time OR college temperature accurate by a beneath heating time. It is easier to annihilate bacterial spores back the canning temperature is increased. The advertence temperature of 250° F (121° C) and advertence time of one minute is chosen. The bulk of calefaction which is delivered at 250° F (121° C), during one minute is authentic as F-value-1. F-value for killing Cl. botulinum spores is 2.52, which agency that the spores are deactivated back submitted to 2.52 account of heating time at 250° F (121° C). This F-value of 2.5 for C. botulinum spores is accepted as "botulinum cook."
|Time and Temperature Bare to Conciliate Cl. botulinum Spores|
|214° F, 101° C||232° F, 111° C||250° F, 121° C|
|250 min||25 min||2.5 min|
Temperatures for aliment preservation.
We ensure aliment assurance with:
- Pasteurization, 149-203° F (65-95° C). Pasteurization kills pathogenic bacilli and is able for foods that would be refrigerated. Typically, aerial acerbic foods or acidified foods (added vinegar, auto juice) with a pH
- Sterilization, 221-266° F (105-130° C). Sterilization adjustment makes broad artefact activity at ambient temperatures. Typically, low acerbic foods with a pH > 4.5 are sterilized.
- Blanching additionally helps, but the basic controls are the adjustment of canning and authoritative abiding the recommended heating temperatures and times are used. The processing times in USDA guides ensure abolition of the better accepted cardinal of heat-resistant microorganisms. Appropriately antibacterial canned aliment will be chargeless of accident if lids allowance and jars are stored beneath 95° F (35° C). Autumn jars at 50-70° F (10-21° C) enhances the assimilation of quality.
Why Canned Foods Action Favorable Altitude for the Advance of Cl. botulinum?
Cl.botulinum do not abound in the attendance of air, so we are not at accident back affable meats with accepted affable methods. However, bacterial spores do not die, they abide in a abeyant stage, belted in their careful shells until altitude become favorable for their growth. This happens back there is no added oxygen (air) and this is absolutely what happens during canning back best of the accessible air is beat from the container. In adjustment to anatomy a able exhaustion central of the container, as abundant air as accessible is removed. This creates a stronger allowance and leaves allowance for the amplification of gasses. After a vacuum, the cans will catch and the capacity of a jar may abscess over through the seal. In a hermetically closed alembic bacterial spores acquisition the appropriate temperature, affluence of damp and nutrients, and the absence of air. Bacilli leave the corpuscle and germinate. They alpha growing and aftermath toxin.
Control of Cl. botulinum
There are two means of authoritative Cl. botulinum:
- Killing spores.
- Preventing spores from beginning and growing.
Spores of Cl.botulinum are present in both acerbic and low-acid foods. In low acid-foods such as meats and vegetables, Cl.botulinum spores can alone be dead at 240° F, 116° C or higher. However, the aerial acidity (pH Cl.botulinum is inhibited at 10% alkali absorption which is agnate to a baptize action of about 0.93. Obviously, such aerial alkali percentages will not be acceptable by a consumer.
The adulteration is not calefaction resistant; it can be inactivated by baking in baptize (212° F 100° C) for 10 minutes. Old canning manuals generally asked for baking home canned meats and vegetables for 10-15 account in an accessible vessel. This action was meant to abort any bacilli or toxins that ability accept survived the incorrect canning process.
pH Acidity and Processing Methods
The capital cold of thermal processing is ascendancy of Cl.botulinum bacteria. Whether aliment should be candy in a burden canner or boiling-water canner depends on the acidity of the food. The appellation "pH" is a admeasurement of acidity; the lower its value, the added acerb the food. Bacilli abhorrence acidity, this actuality works to our advantage. Acidity may be natural, as in best fruits, or added, as in pickled food. The acidity akin in foods can be added by abacus auto juice, citric acid, or vinegar. All bacilli accept their own adopted acidity akin for growth, about about aloof pH (7.0). Bacilli will not abound back the pH is beneath the minimum or aloft the best absolute for a accurate bacilli strain. As the pH of foods can be adjusted, this action becomes a almighty weapon for the ascendancy of Cl.botulinum. The thermal attrition of microorganisms decreases as the pH of their average is lowered. As explained earlier, best bacteria, decidedly Cl. botulinum, will not abound beneath pH 4.6. Accordingly acerb foods accepting pH beneath 4.6 do not crave as astringent calefaction analysis as those with pH aloft 4.6 (low acid) to accomplish microbiological safety. The pH amount of 4.6 is the analysis amid aerial acerbic foods and low acerbic foods. Low-acid foods accept pH ethics college than 4.6. They accommodate red meats, seafood, poultry, milk, and all beginning vegetables except for best tomatoes.
Processing methods for low and aerial acerbic foods.
Most mixtures of low-acid and acerbic foods additionally accept pH ethics aloft 4.6 unless their recipes accommodate abundant auto juice, citric acid, or alkali to accomplish them acerbic foods. Acerbic foods accept a pH of 4.6 or lower. They accommodate fruits, pickles, sauerkraut, jams, jellies, marmalades, and bake-apple butters.
pH of assorted foods and materials. A lower pH amount indicates college acidity.
Although tomatoes about abatement on the pH adding band at 4.6, there are varieties that accept a lower pH akin and there are varieties which additionally accept a college pH level. Tomatoes are usually advised an acerbic food. Figs additionally accept pH ethics hardly aloft 4.6. Therefore, if they are to be canned as acerbic foods, these articles charge be acidified to a pH of 4.6 or lower with auto juice, citric acerbic or vinegar. Appropriately acidified tomatoes and figs are acerbic foods and can be cautiously candy in a boiling-water canner. However, alteration acidity levels requires a acceptable compassionate of aliment technology and should be larboard to professionals. In addition, not all foods will address to a customer back their acidity is ever acidic.
There are abounding companies authoritative pH barometer equipment. Ample bank models are big-ticket and will be acclimated by the professionals who authorize thermal processes for canned foods. We accept been application the Hanna Instruments HI 99163 Meat pH Beat with abundant achievement for authoritative brewed sausages. The apparatus is of abundant amount for the pH assay of meat products. This pH beat is simple to use with alone two buttons. The dispensable assimilation brand allows the user to admeasurement not alone the surface, but additionally the centralized pH of the meat. The assemblage is actual authentic and the account is acquired aural seconds.
- Range pH - 2.00 to 16.00 pH
- Range Temperature - 5.0 to 105.0° C / 23.0 to 221.0° F
- Resolution pH 0.01 pH
- Resolution Temperature 0.1° C / 0.1° F
- Accuracy pH ± 0.02 pH
Control of Bacilli by Baptize Activity
In adjustment to abide animate the microorganisms charge nutrients and moisture. How do bacilli eat? Brainstorm some sugar, abrade or aliment crumbs agitated on the table. Abode a dry blot on top of the amoroso and you will see that the blot will not aces up any of the ingredients. Cascade some baptize over the capacity and echo the blot procedure. The blot will blot the band-aid after any difficulty. Bacilli are like a sponge, they blot aliment through the wall, but the aliment charge be in a anatomy of a solution. It charge accommodate water. Back baptize is eliminated, bacilli cannot eat.
All microorganisms charge baptize and the bulk of baptize accessible to them is authentic as baptize activity. Baptize action (Aw) is an adumbration of how deeply baptize is "bound" central of a product. It does not say how abundant baptize is there, but how abundant baptize is accessible to abutment the advance of bacteria, yeasts or molds. Abacus alkali or amoroso "binds" some of this chargeless baptize central of the artefact and lowers the bulk of accessible baptize to bacilli which inhibits their growth. The best applied access for blurred baptize action is drying, although it is a apathetic action which charge be anxiously monitored, contrarily it may backlash and ruin the product. A simple calibration is acclimated to allocate foods by their baptize action and it starts at 0 (bone dry) and ends on 1 (pure water).
Below assertive Aw levels, bacilli can not grow. USDA guidelines state: "A potentially chancy aliment does not include... a aliment with a baptize action amount of 0.85 or less."
|Water action (Aw) of some foods|
|Fresh meat & fish||0.99|
|Jams & jellies||0.80|
Meats, broiled fruits and vegetables were preserved throughout our history and the technology was based on simple techniques of salting and drying. It was additionally apparent that the accession of amoroso would bottle foods such as candies and jellies. Both factors accord to blurred the baptize action of the meat. Afresh minced meat possesses a actual aerial baptize action akin about 0.99, which is a ancestry arena for bacteria. Abacus alkali to meat drops this bulk anon to 0.96-0.98 (depending on the bulk of salt), and this already creates a hurdle adjoin the advance of bacteria. This may be adamantine to appreciate as we apperceive that baptize does not aback clear back alkali is added to meat. Well, this is area the abstraction of baptize action becomes useful.
Although the accession of alkali to meat does not force baptize to evaporate, it does article similar: it immobilizes chargeless baptize and prevents it from reacting with annihilation else, including bacteria. It is like burglary aliment from the bacteria, the alkali locks up the baptize creating beneath favorable altitude for bacilli to abound and prosper. As we add added salt, added chargeless baptize is anchored but a accommodation charge be reached, as abacus too abundant alkali will accomplish the artefact unpalatable. It may additionally impede the advance of affable bacteria, the ones which assignment with us to agitate the sausage. The aforementioned happens back we benumb meat admitting we never anticipate of it. Arctic baptize takes the appearance of solid ice crystals and is not chargeless anymore. Baptize exists in meat as:
- Bound (restricted or anchored water) - structurally associated with meat proteins, membranes and affiliation tissues. This baptize (3-5% of absolute water) can alone be removed by aerial calefaction and is not accessible for microbial activities.
- Free or aggregate baptize - captivated alone by anemic armament such as capillary action. This chargeless baptize is accessible for microorganisms for growth.
Removing baptize agreeable by dehydration aliment has been accomplished for centuries. As the action proceeds, baptize starts to clear (water action decreases), authoritative meat stronger adjoin accident and pathogenic bacteria. There eventually comes a point area there are no bacilli present and the meat is microbiologically stable. It will not spoil, as continued as it is kept at low temperatures and at low clamminess levels. If the temperature and clamminess go up, new bacilli will authorize a antecedents on the apparent and will alpha affective arise the central of the sausage. The cast will again anon arise on the surface. Microbial accident is a common account of baby foods or abnormal containers. It may aftereffect from:
- Holding containers too continued afore processing.
- Contamination afterwards processing.
- Inadequate thermal process.
- Inadequate cooling of the containers or accumulator at aerial temperatures.
- Spoilage due to adaptation of acid-tolerant spores (flat sour).
|Minimum Aw requirements for bacillus growth|
Water Action Meters
- Resolution: plus, bare 0.01 Aw.
- Accuracy: plus, bare 0.02 Aw.
- Case dimensions: 3.5" x 4"
- Weight: 115 g (4 oz).
- Photo address Decagon Accessories Inc.
Botulinum spores are actual adamantine to abort at boiling-water temperatures; the college the canner temperature, the added calmly they are destroyed. Therefore, all low-acid foods should be antibacterial at temperatures of 240-250° F, 116-121° C, accessible with burden canners operated at 10 to 15 PSIG (PSI). PSIG agency pounds per aboveboard inch of burden as abstinent by gauge. At temperatures of 240-250° F, 116-121° C, the time bare to abort bacilli in low-acid canned aliment ranges from 20 to 100 minutes. The exact time depends on the affectionate of aliment actuality canned, the way it is arranged into jars, and the admeasurement of the jars. The time bare to cautiously action low-acid foods in a boiling-water canner ranges from 7 to 11 hours; the time bare to action acerbic foods in baking baptize varies from 5 to 85 minutes.
The USDA recommends that best meats are adapted to 160° F, 72° C centralized temperature so a catechism may be accustomed why canned meats charge be candy to 240-250° F, 116-121° C. Well, affable meats to 160° F, 72° C centralized meat temperature kills accustomed bacilli so the meat is advised safe to eat, but be acquainted that bacterial spores will survive. Because they are in connected acquaintance with air, they will not germinate and will not aftermath toxin. You ability eat them, but that will not actualize danger, afterwards all we eat bacilli in sauerkraut, salami, cheese and yoghurt all the time.