When in doubt throw it out


Wednesday, 20 January, 2016


When in doubt throw it out

In spite of advances in modern technology and efforts to provide safe food, foodborne diseases remain a major public health concern. The reality is that there is always some risk of toxicity from eating any food.

Many consumers are convinced that they will avoid any foodborne illnesses by avoiding processed foods and conventionally farmed produce and relying on fresh organically grown produce. However, all produce including organically grown produce, contains naturally present toxic substances, for example:

  • Members of the Brassica genus (which include broccoli, brussels sprouts, cabbage, cauliflower, mustard greens and radishes) also contain goitrogens, substances that suppress the function of the thyroid gland.
  • Teratogenic glycoalkaloids (α-solanine and α-chaconine) are found in potatoes, particularly the peels, sprouts and sun-greened areas.
  • Lectins, substances which bind to and agglutinate red blood cells, are present in lima beans, kidney beans, peas and lentils.
  • Almost every fruit and vegetable contains natural pesticides that are rodent carcinogens, some at orders of magnitude higher levels than synthetic pesticides.

In truth, there is no escaping exposure to microorganisms, mycotoxins, heavy metals, bioactive substances and pesticides from food. Some of the most potent toxins known are produced from bacteria and fungi.

Good condition is the best start

One of the simplest and most effective ways of minimising exposure to toxic substances in food is to ensure produce is in good condition and to use it before it spoils.

Plants that are stressed contain more toxins than healthy plants; for example, concentrations of furocoumarins (substances with phototoxic and photomutagenic properties) in spoiled and diseased parsnips may be up to 2500% higher than fresh parsnips. Infection with fungal pathogens induces production of the furocoumarins timethylpsoralen and 8-methoxypsoralen in celery, increasing the potential for photodermatitis from celery handling. Synthesis of α-chaconine and α-solanine in potatoes is stimulated by light or mechanical injury, and concentrations of solanine in green or blighted potatoes are increased sevenfold. Bruised or soft fruits and vegetables can be contaminated with mould below the surface and should be discarded.

Washing helps

Wash produce thoroughly to remove toxins and pathogens that may be present on the surface of food. In the US the FDA recommends washing all produce thoroughly under running water before eating, cutting or cooking, even if the produce will be peeled before eating. Produce with rinds, grooves or waxy skin like cucumbers, citrus, melons and potatoes should be scrubbed with a brush.

Heat is an effective kill step

High temperature will kill most pathogens and inactivate heat-sensitive toxins — temperatures between 70 and 100°C kill most bacteria. High-temperature cooking destroys goitrogens in Brassica vegetables and lectins in beans. Cooking temperatures under 80°C do not destroy lectin so slow cooking is not advised for cooking beans.

Be cool with your storage

Contamination with pathogens is possible, even in foods that have been cooked at high enough temperatures to kill bacteria. Cooked food can become contaminated with bacteria from food handlers, uncooked or undercooked food or utensils. Bacteria grow most rapidly in the range of temperatures between 4 and 60°C, doubling in number in as little as 20 minutes. Cases of botulism have occurred in people consuming salads prepared from foil-wrapped baked potatoes and sautéed onions stored at room temperature.

The USDA recommends that food should not be left out of refrigeration for more than two hours and leftovers should be transferred to shallow containers for quick cooling and refrigeration within two hours.

To sum it up, the best way to reduce the potential for poisoning from a meal is to use good quality produce and wash it before use, cook food at temperatures necessary to kill pathogens and inactivate toxins, and to keep perishable food at room temperature for less than two hours. A little common sense goes a long way in reducing the potential for poisoning from food.

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