Food Safety - Vegetables and Fruit
Food Borne Illness and Contamination
June 22, 2011
This is the second in a two-part series on food safety. This article covers fruits and vegetables.
As with meats, fruits and vegetables can be carriers of the four most common types of bacteria implicated in food poisoning. These are Escherichia coli (e. coli), Campylobacter jejuni (c. jejuni), Salmonella enteritis (salmonella) and Listeria monocytogenes or simply listeria.
All of these bacteria tend to emulate a flu infection and all of them are particularly dangerous to the very young, older adults, those with compromised immune systems and the pregnant.
Listera, though the least common type of infective agent, is possibly the most dangerous with a high mortality rate among pregnant women. Listeria if allowed to become advanced, can cause heart infections. Salmonella is almost equally dangerous as it has been linked to reactive arthritis in a small percentage of people recovering from that infection.
Almost all contamination is the direct result of fecal matter dispersion in the field. This is possible if cattle are allowed to roam freely through fruit and vegetable fields and the plant matter is not properly cleaned.
Another source of possible illness is from the use of pesticides.
Bacteria on Plants
Sources of Bacteria on Plants
Because there are so many types of fruit and vegetables (and I'll include nuts in this category) they grow in a wide variety of locations in relation to the ground or soil. Apples, pears, and peaches grow on trees (naturally) so soil bacteria have less chance to get on these fruits; however, birds and rodents that eat these fruits are excellent bacterial vectors. In other words woodland creatures can carry bacteria to tree borne fruit.
Strawberries, melons and peanuts all contact the ground which is laced with bacteria. Bacteria can even be carried by wind and rain.
As mentioned in the Food Safety - Meat article, bacteria need water to multiply. Certain fruit such as melons, banana, and citrus have a thick skin which prevents bacteria from invading into the heart of the fruit. Grapes and strawberries, by contrast, have very thin skins. Regardless the outer surface of the fruit is only a good barrier as long as it is not pierced or cut. Once the outer skin of fruit has been cut bacteria have a ready source of nutrients and water. The two key elements for bacterial growth.
Buying Fruit and Vegetables
Because bacteria linger on the outside of food plants it is important to choose produce that is blemish free. Any fruit or vegetable that has been pierced during harvesting or has worm holes should be rejected; they have already been invaded by bacteria.
However, if the skin is intact it is a very easy matter to rinse away the offending bacteria before consumption.
A Note on Cutting Boards
Despite the fact that I have a granite counter top in my kitchen, I use cutting boards liberally.
I have two wooden ones, four flexible plastic ones (marked 'chicken,' 'beef,' 'vegetable,' and 'fish" as well as four rigid plastic cutting boards for meat (X2) vegetables (X2) and cheese.
Yes, each food type has it's own cutting surface. The reason for this is simple. I like to be able to pick the cutting board up and move it to the pot, pan or grill that I need the prepared food placed in. I have two meat boards, one for raw meat and the other for cooked. They are also far easier to clean than the entire counter-top.
Recent (year 2000) research indicates that the plastic cutting board recommended by the U.S. Department of Agriculture may not be the best surface to work on. Research at the University of California Davis indicates in fact that the wooden cutting board seems to be hostile to bacteria where the plastic board may actually promote bacterial growth.
So if you prefer a wooden board to a plastic one take heart. You may have made the best choice for your health as well as the quality of your meals.
Cleaning Your Produce
Which fruits and vegetables should be cleaned? All of them.
Imagine if you will, all the people who have handled your produce before it got to market. While in the field it was subject to the whims and curiosity of fauna. It was picked by one pair of hands, handled at the warehouse by another pair and yet another pair or two handled it when it went on display.
Then there were all the other shoppers who picked it up and put it back down when choosing for their own meal.
You need to clean your produce!
Melon and Citrus
Once you pierce the skin of a melon your knife will introduce bacteria into the fruit. For that reason, all melon, regardless of type, should be thoroughly washed before being sliced or cut into serving sizes. Once you have prepared melon you should refrigerate or serve immediately. Refrigeration will retard the growth of bacteria.
Cantaloupe are a real problem. The highly textured skin is very difficult to clean. Much as I hate to say this (and I love the flavor of this melon) I rarely eat it due to this problem.
Berries, particularly grape and strawberry should be washed just prior to serving. The skin of these fruits are very thin. Once they have been washed any protective coating has also likely been washed away. Serve immediately or refrigerate to retard bacterial growth.
All leafy produce should be thoroughly washed, even the prepackaged salads that claim to be pre-washed. For that reason I highly recommend a vegetable spinner.
If cleaning lettuce, celery, onions or other layered produce remove the outer leaves or layers and discard them. Then separate each layer and rinse them thoroughly under running water. This applies to fresh herbs as well such as basil, thyme, etc.
Do not use detergents or other cleaning solutions. These can add their own level of contamination so clear running water alone is best.
Corn Potatoes Apples
Fruit and vegetables with firmer skins should be washed with the aid of a vegetable brush. These brushes should be dishwasher safe or be capable of immersion in a disinfecting solution.
Prepare Your Produce for Cooking
You should always segregate the work surface you prepare your fruit and vegetables on from the work surface you use to prepare meat. Cross-contamination is a major problem in the kitchen and it is very easy to contaminate clean veggies with the juices from raw meat.
All it takes is a momentary lapse of touching one thing and then another. For that reason you should prepare one food item at a time until you have completed the task, wash your hands thoroughly, dry them, and them move on to the next item.
Since the same knives are usually used no matter what item is being prepared be sure to wash the knife (tip to tail) in warm soapy water with a hot water rinse. Knives are a prime source of cross-contamination too.
Cooking and Serviing
Most fruit is not cooked prior to serving. For those items make it the last thing you prepare. Wash them carefully in cool water, let drain in a colander for a few minutes, and then serve. The longer fruit sits out the more likely a bacterial colony can form.
If you can't serve the fruit immediately then refrigerate it. Temperatures at or below (4° C) or 40 ° F will inhibit the growth of most bacteria.
If cooking fruit or vegetables be certain that the water reaches boiling. Steaming is also a viable option as steam is usually hotter than boiling water. You can also saute your veggies. You know the right internal temperature has been reached if they are greener than when raw, have caramelized slightly or are clearly softened by the process of cooking.
The use of pesticides to protect and preserve crops prior to harvest is still quite common. So it isn't just bacteria that can make you ill.
The produce with the highest incidence of pesticide residue is:
- bell peppers
- kale and collard
- imported grapes
- green beans (U.S. grown and imported)
- imported plums
- hot pepper
Washing these particular fruits and vegetables then is vitally important.
Produce with the least pesticide residue include:
- Frozen sweet corn
- Frozen sweet peas
So substituting from the list above for any item in the "heavy pesticide use" list will virtually insure that the buyer will consume fourteen less pesticides per day.
Pesticides and Bacteria
A study in Canada conducted in 2000 found that some pesticides actually enhance the growth of bacteria a thousand fold. One fungicide in particular, chlorothalonil, seemed to enhance the reproductive rates of both e. coli and salmonella.
Though organic fruit and vegetables are more expensive, they are, by their very nature, largely free of pesticides, fungicides, and insecticides.
The good news is that produce is very easy to clean when compared to meats. Much less special handling is required; most of the time, if not all of the time, a good rinsing in clean water is all that is required.
However, I would limit or completely avoid the high pesticide use items.
The author was not compensated in any way, either monetarily, with discounts, or freebies by any of the companies mentioned.
Though the author does make a small profit for the word count of this article none of that comes directly from the manufacturers mentioned. The author also stands to make a small profit from advertising attached to this article.
The author has no control over either the advertising or the contents of those ads.