Photo from Adobe Stock/Mat Hayward
Molds and yeasts are fungi that can affect meat quality, although their effect is far less significant than toxins or bacteria. Molds typically cause spoilage in grains, cereals, flour, and nuts that have low moisture content and in fruits that have a low pH. Yeasts are generally involved when a food product contains high amounts of sugar. Yeasts that affect meat are usually not a problem because of the low sugar or carbohydrate content of muscle.
While viruses have the potential to cause foodborne diseases, they generally only affect raw or uncooked shellfish. Viruses are inert and unable to multiply outside a host cell. However, avian influenza (or bird flu as it is commonly known) is of some concern to hunters. Avian influenza is an illness caused by several different strains of influenza viruses that have adapted to a specific host. All known viruses that cause influenza in birds belong to the influenza A virus. If humans contract bird flu, it is usually a result of either handling infected dead birds or from contact with infected fluids. Although it is easy for humans to become infected by birds, it is much more difficult for humans to pass the virus to each other without close and lasting contact. The last recorded incident of bird flu affecting humans in the United States occurred in New York in 2003.
A parasite infection will occur in the live animal before it occurs in a human. There are three parasites that are of major concern to humans: Trichinella spiralis, or trichinosis; Toxoplasma gondii, or toxoplasma; and Anisakis marina, or anisakis. Trichinosis has long been identified as a parasite that can live in swine muscle and be transferred to humans through raw or uncooked pork. Toxoplasma is a small protozoan that exists throughout the world and has been observed in a wide range of birds and mammals. Anisakis is a roundworm parasite found only in fish. Using adequate or recommended cooking temperatures and times will destroy parasites.
Trichinella spiralis photo from Adobe Stock/Caroline K Smith MD
Chronic wasting disease (CWD) is a progressive fatal illness of deer, elk, and moose. It has gained national attention after being discovered in animals from fifteen states and two Canadian provinces.
CWD damages portions of the brain and causes progressive loss of body condition, behavioral changes, excessive salivation, and ultimately death. It is believed to be caused by a prion protein that has been found in the brains of similarly affected animals.
Although the mode of transmission is not fully understood, it is thought that the disease is spread through direct animal-to-animal contact or exposure to contaminated feed and water. To date, no strong evidence of CWD transmission to humans has been reported.
Precautions can be taken against CWD, such as not shooting, handling, or eating any deer, elk, or moose that appears sick or decimated, or tests positive for CWD. Hunters harvesting animals in a known CWD-positive area may wish to have their animal tested for CWD before consuming any of the meat. Information about testing is available from most state wildlife agencies.
If you field dress any deer, elk, or moose, it is a good precaution to wear gloves, bone-out the meat from the animal, and minimize handling of the brain and spinal cord tissues. Also, avoid eating the brain, spinal cord, eyes, spleen, and lymph nodes.
Photo from Adobe Stock/Wildlife World
Temperature and Time Effects on Meat Quality
Mismanagement of temperature is one of the most common reasons for outbreaks of foodborne diseases, as is the amount of time food spends at a critical temperature — for example, the correct temperature is either used too late or for too short a period.
Meat can generally be kept safe from harmful bacteria if stored under 40 degrees Fahrenheit. Cooking prevents most microorganisms from growing, but does not kill them. Some parasites can be killed if kept in a frozen state for various lengths of time, but most microorganisms merely go dormant and can revive when thawed. If meat is thawed from a frozen state it should be used as soon as possible and not refrozen.
To kill microorganisms with heat, you must maintain a recommended temperature for a minimum period of time. You will damage or kill microorganisms more effectively by reaching a given temperature and holding it for a period of time rather than reaching a higher temperature but holding it for a shorter period.
Meat can be kept safe when it is hot or cold, but not in between. If meat is being cooked, it should pass between 40 to 140 degrees Fahrenheit in four hours or less. If it is being cooled, it should pass from 140 to 40 degrees Fahrenheit within the same amount of time.
Photo from Adobe Stock/Bill
Most microorganisms are killed at 140 degrees Fahrenheit, but not all. The outside of a piece of meat may have become contaminated during your processing, but the interior can be considered sterile, or nearly so, unless it has been cut into. When a piece of meat is cooked by conventional methods (except with a microwave oven), the outside cooks first and reaches a higher end temperature than the inside. Recent recommendations state that meat should be cooked to 160 degrees Fahrenheit, since some microorganisms can survive a 140 degrees Fahrenheit temperature. Poultry meat is more alkaline and should be cooked to 180 degrees Fahrenheit; if red meat is to be reheated it should reach 165 degrees Fahrenheit for optimum safety. If you are grinding meat, be aware that it can become contaminated more easily than whole cuts because more of the meat particle surface areas are exposed and more processing and handling steps are involved.
Moisture in meat is essential for palatability but is also a medium for microbial growth. The level of moisture in fresh meat is high enough to provide spoilage organ-isms with an ideal environment for growth. Researchers have found that moisture levels of at least 18 percent will allow molds to grow in meat. Drying meat through a smoking process will typically eliminate any moisture concerns.
Oxygen is necessary for any living animal to survive, but it is not a welcome agent when processing meat. Aerobic microbes need oxy-gen to grow. These include yeasts, molds, and many bacteria. Microbes that cannot grow when oxygen is present are called anaerobic. This group of microbes can be deadly because they include clostridium, which produces a toxin, and a group called putrifiers, which degrade proteins and produce foul-smelling gases. Preventing the growth of anaerobic microbes is essential if your food preservation plan includes canning.
Photo from Adobe Stock/santypan
Soon after an animal is harvested, the muscle undergoes a gradual change in pH, declining from about 7.0 to 5.5. This decline results from the loss of glycogen held within the muscle and its conversion to lactic acid. The degree of acidity or alkalinity (pH) will influence the growth of microorganisms. More will thrive at a point that is nearly neutral — a pH of 7.0 — than at any other level above or below. Although meat pH ranges from about 4.8 to 6.8, microorganisms generally grow more slowly at a pH of 5.0 or below. This acidity level helps preserve many sausages and acts as a flavor enhancer. Acidity levels are not a concern unless there is a long delay in processing the carcass at room temperatures.
A whole carcass has the minimum amount of exposed surface area. As large cuts are made, more area is exposed. When it is cut into smaller pieces, still more area is exposed. If the meat is ground, this exposes the most area for possible contamination. Simply put, the more the meat is processed, the more it may be exposed to microorganisms. To help reduce microbial activity, use clean, sanitary equipment and table surfaces and keep work area temperatures low while working as quickly as possible.