Monday, February 10, 2014

Is Pre-washed Salad Safe?

 

is-pre-washed-salad-safe

Pre-washed Salad is a Dirty Trick

Pre-washed salads are typically washed in chlorine solution twenty times stronger than that in a swimming pool. Sales of salads in developed countries are almost double what they were a decade ago. It’s not that we have become so enamored with healthy, low-calorie living that we are actually eating that much more – rather that supermarkets have found a way of adding value to this simplest and freshest of foods, by providing it in pre-washed form. It seems a wonderfully convenient way of eating healthily.

When you see a salad inside its clear sealed plastic bag, you might think that the bag contains just air and salad. In fact, it’s not air in the bag, but a modified form in which levels of oxygen have been reduced from the normal 21% to just 3% and carbon dioxide levels have been raised. Oxygen is the gas that makes fruit and vegetables go brown and limp after they are picked. So reducing the oxygen keeps the salad fresh much longer. In fact, salads kept in this modified-atmosphere packaging (MAP) can stay looking fresh for up to a month.

Despite their apparent freshness, however, MAP wrapped salads may not be quite as healthy as they look. Research by Italian scientists at the Rome Institute of Food and Nutrition suggests that MAP packed lettuces lose many of their nutrients. Indeed, many of the antioxidant nutrients that make green salad vegetables good for health, such as vitamins C and E and poly - phenols, all seem to be reduced. The problem is not that the MAP process actually robs salads of their nutrients; unwrapped salads also lose their nutrients quickly after they are picked. But you can tell the nutrients are gone in an unwrapped salad because it goes limp. With MAP, it stays looking fresh after its nutrient value has diminished.

The nutrient content of packed salad may be further reduced by the way it’s washed. Supermarkets are very conscious of the possibility of food-poisoning from packaged salad. Because salads are typically neither cooked nor washed by consumers, they have to be free from contamination if they are not to cause outbreaks of E. coli or salmonella illnesses. Rather than take any risk of causing such an outbreak, supermarkets insist that their salads are carefully washed in what is effectively disinfectant. According to one food company boss, salads are typically soaked in a bath which contains 50mg of chlorine in every liter of water – that’s twenty times the concentration of chlorine in an average swimming pool. Whether this heavy chlorination does anyone any harm no one knows, but many people think it at least kills some of the salad’s taste.

Dilute mixtures of chlorine bleach and water are a common and cost-effective method for sanitizing equipment in food processing  operations. When used properly, chlorine bleach can be a very effective method of killing undesirable microorganisms. Processors  should be aware, however, that there are regulations concerning  the use of this sanitizer. The germ-killing effect in a solution of  chlorine bleach and water is due to available chlorine, present as  hypochlorite and hypochlorous acid. United States Federal regulations (21 CFR  Part 178) permit the use of sanitizing solutions containing sodium hypochlorite on food processing equipment and food contact articles  with the following provisions:

1) Equipment or articles sanitized with the solution must be  allowed to drain adequately before contact with food.

2) Solutions used for sanitizing equipment shall not exceed  200 parts per million (ppm) available chlorine.




In addition to sanitizing food contact surfaces, chlorine bleach solutions may be used for sanitizing raw fruits and vegetables during  the washing or peeling process. The U.S. federal regulations that apply  differ slightly from those for sanitizing solutions given above. The  regulations (21 CFR Part 173) specify two conditions for the permitted use of hypochlorite solutions in washing produce:

1) The concentration of sanitizer in the wash water must not  exceed 2000 ppm hypochlorite.

2) The produce must be rinsed with potable water following  the chlorine treatment.

Most operations, unless the produce is very dirty, will not need a  sanitizer concentration greater than 200 ppm total chlorine to achieve  the desired sanitizing effect. Contact times of one minute or greater  are typically sufficient to achieve a thorough kill.

The regulations do not specify a permissible residual level of  chlorine. Presumably, the fresh water rinse eliminates any potential problem with residual chlorine. As a practical matter, residual  chlorine would in most foods produce highly objectionable flavors  and odors well before becoming a safety hazard. Food processing  in-plant chlorination systems typically produce water for processing  with residual available chlorine levels of no more than 0.5 ppm. For  container cooling or general washing, residual available chlorine  levels of 2 to 7 ppm are commonly used. Typical municipal water  systems produce potable water with a residual available chlorine  level of 0.25 to 2 ppm.


Try this healthy recipe... Eggless Egg-Salad


Are you into modernist cuisine? You should know this... Molecular Gastronomy at Home: Taking Culinary Physics Out of the Lab and Into Your Kitchen

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