Microbes and Food Preservation. 1. Why study how certain microbes cause disease in animals and humans? Because the safety of your food and products used to make it affects you every day!.
Why study how certain microbes cause disease in animals and humans? Because the safety of your food and products used to make it affects you every day!
March 2013: Food Safety & Inspection Services finds E. Coli bacteria in many frozen foods (e.g. pizzas, quesadillas) made by Rich Products. The company recalls 10.5 million pounds of its foods after 24 people in 15 states are sickened…
May 2013: U.S. Food and Drug Administration (FDA) investigates an outbreak of hepatitis A virus linked to a frozen organic berry mix. 30 illnesses so far reported in CO, NM, NV, AZ and CA. The disease is contagious, and usually spread by poor hygiene.
October 2012: Major outbreak of fungal meningitis linked to injectable steroids made by New England Compounding Center (MA) used to treat arthritis/pain. At least 620 cases of patients with evidence of infection, with 39 people dead.
May 2012: Dimond pet food company expands recall of pet food possibly contaminated with Salmonella bacteria. Deaths of pets have been noted in many states, including CT!!
September 2011: Centers of Disease Control (CDC) confirm outbreak of Listeria food poisoning in cantaloup spreading to 18 states & leading to at least 30 dead, hundreds sick, mostly young and elderly.
Food can become contaminated by microbes, a general term for very small organisms that are found nearly everywhere (air, soil, water). Microbes include…
Salmonella bacteria (causes food poisoning)
Plasmodium (causes malaria)
Mold that caused Potato Famine (1845) in Ireland
Microbes are a vital part of any ecosystem!
Used to make food (e.g. cheese, yogurt, beer…)
Used to decompose sewage, break down toxins in soil, even oil floating in water
Bacteria Streptomycin have been engineered to produce antibiotics such as Bacitracin and Erythromycin.
But You Don’t Need Us!
Still, when people think of bacteria, they think harmful.
Tetanus, typhoid fever, pneumonia, syphilis, cholera, and tuberculosis are all caused by bacteria.
Bacteria and molds release toxins (poisonous substances) as they grow which is actually what cause the illness.
Don’t mess with me!
E. Coli is normally found in stomachs of animals. So, the likely source of E. Coli poisoning is feces from animals, possibly as manure used as fertilizer.
Bacteria cause other “everyday” problems such as body odor and bad breath!
A variety of methods to prevent microbes from contaminating food have been developed, and depend on giving microbes a poor environment to grow and live in…
Dehydration: removing water under vacuum or by heating it (sun drying). Good for many foods, including vegetables.
Salting: adding salt not only sucks water out of food and microbes, but most organisms cannot live in a high salt environment. Good for fish & meats, changes the taste of the food.
Sea salt being added to ham to remove water
Methods of Food Preservation - remove oxygen
Vacuum packing: get rid of oxygen by sucking it out under a vacuum. Good for many kinds of foods, and lasts as long as the vacuum is good.
Inert gas: storing food under an inert gas like nitrogen prevents many microbes from growing.
Vegetables stored in vacuum sealed bags
Inert: something that has no ability to react
Refrigeration or freezing: very common & easy, lasts as long as food stays frozen. Some microbes can survive freezer temperatures, so freezing should be used in combination with another method.
Fruit & veggies stored in a freezer
Supermarket frozen food section
Methods of Food Preservation - heating
Cooking & boiling: one of most effect methods. Often changes taste of food, destroys or removes nutrients. Must be done long enough to ensure microbes are killed, but once done, you don’t have to keep heating.
Pasteurisation is the process of heating foods hot enough to kill bacteria, but not so long that you ruin the taste (e.g. milk & juice)
Milk being pasteurised at a factory
Pork needs to be cooked at a high enough temperature and long enough
A pH of 7 is called neutral. Pure water has pH of 7.
A pH lower than 7 is said to be acidic (there’s lots of H+ around)
A pH above 7 is said to be basic (there’s not a lot of H+ around).
Methods of Food Preservation - irradiation
Irradiated foods such as meat, grains, fruits & vegetables with the international symbol for irradiated food
Left: factory where peanuts are irradiated. Right: protest to stop irradiated food from being used in school lunches
Organisms pass their resistance to chemicals on to offspring through DNA and genes.
Other Methods - chemicals
In the end…
The best techniques to keep food safe are the easiest…