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I often like to make smoothies where I among other things add frozen berries. I boil some water in my tea-boiler and pour it over the berries before I add them to the smoothie mix. Is this enough to get rid of the dangerous bacteria, especially found in raspberries?

Ps. Recipe is: Vanilla soy-milk . Banana . Berries . Orange (to keep the banana from turning brown)

Blend until smooth.

Aaronut
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Stella
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    What dangerous bacteria? – Aaronut Aug 01 '11 at 21:53
  • I do not know. But I remembered a news program where they warned that raspberries contained some kind of germs/bacteria that could be dangerous. Also I've been raised with the "need to pour boiling water over" frozen berries. The question is an aim to clarify the risk of not fully boiling the berries before blending, if any. – Stella Aug 01 '11 at 22:06
  • What country are you in. Berry bacteria is not a common problem? Freezing stops bacteria multiplication, and since you normally consume smoothies immediately after making them there should be no problem even IF dangerous bacteria was present? – TFD Aug 01 '11 at 22:10
  • I live in Denmark, though the berries can often be from other countries as we import a lot. But say the berries DO have bacteria, would the washing in boiling water be enough? – Stella Aug 01 '11 at 22:18
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    Hard to say without knowing what kind of bacteria, and how much. Cooking almost never kills every single individual bacterium, it's a question of safety thresholds. If you have reason to believe that the fruit is contaminated, but don't know any more details, then nothing short of boiling it into purée is truly safe. On the other hand, if it's safe to eat right out of the bag (which is normally guaranteed and enforced by government food agencies) then boiling water is just a waste of time, water, and perfectly good fruit. – Aaronut Aug 01 '11 at 23:07
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    What do you do when you get fresh berries? Presumably you wash them and eat them, right? Are you assuming that these frozen berries are somehow more contaminated? – Cascabel Aug 01 '11 at 23:46
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    I'd also suggest that, in general, *NO*, pouring boiling water over them wouldn't kill the bacteria (if present) for the following reasons: 1) would be surface-only, 2) would rapidly chill below the kill zone due to the temperature of the berries, and 3) would not be in contact long enough at a high enough temperature. Look at pasteurization (which doesn't actually sterilize, it only kills off enough pathogens to make the food "safe") - it requires a temperature of 275 degrees F (135C) for at least one second. That's well above the boiling point. At 160F (71C) you need at least 15-20 sec. – GalacticCowboy Aug 02 '11 at 03:00
  • Thank you Galactic Cowboy, that was pretty much what I wanted to know. This is my first post here and I realize that I should have formulated the question like this: IF berries have a health issue through bacteria or the like, is pouring boiling water over them enough, or do I need to boil them through. :) – Stella Aug 02 '11 at 04:20
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    Recently in Sweden there has been a lot of talk about the parasite "Dvärgbandmask" (sorry, don't know the English name). It is a small worm carried by foxes and such. Berries picked in the woods can be contaminated, even though it is highly unusual. The disease that this parasite can cause in humans is *extremely* dangerous, and there is no cure. In the past these worms did not exist in Sweden, only further south in Europe (Denmark?) but last year they started appearing in Sweden too. Anyway, if you want to be 100% safe from these guys you have to cook the berries properly. – Henrik Söderlund Aug 02 '11 at 08:17
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    I've always been quite happy picking raspberries in the hills and eating on the spot (Scotland). If I had some bough from a shop, I'd wash in cold water to clean of any pesticides and insects. Frozen and packeted fruit should have been washed and be sterilised so I wouldn't bother washing them at all. I doubt hot water rinse would kill any bacteria. In fact I'd suspect it would be just the thing to encourage them to grow. Bacteria often love warm water. You have to use high temperatures for several minutes to kill most bacteria. – Rincewind42 Aug 02 '11 at 14:10
  • @Henrik Söderlund: Easy way to find the English name: Look it up on your local Wikipedia, then use the English interwiki link. It seems that gives http://sv.wikipedia.org/wiki/Echinokockinfektion with an English name of echinococcosis. I'm not completely sure of this since I can't read Swedish. – derobert Aug 03 '11 at 22:16
  • Even in the US we have to worry about contaminants in our raw and cooked foods. Organic is actually more apt to be a carrier of e coli, etc (i.e. 2013 Oregon Organic frozen Berries were contaminated with hep A, 2011 Colorado Antelopes had outbreak of Listeria, Hawaii, man gets sick from his veggies in garden because of a snail that eats contaminated rat droppings) Washing all raw foods will eliminate most problems - I do a soak of 10 parts water 1 part vinegar and that will help even more (about 5-10 minutes)- It removes the wax trapping human ick and kills bacteria. –  Jun 26 '13 at 19:06
  • @Rama Washing your veggies is prudent, but I highly doubt that a soak in such a diluted vinegar solution kills bacteria in noticeable amounts. – rumtscho Jun 26 '13 at 21:32

4 Answers4

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From the comments, Henrik noted that there is a parasite in Sweden (called "Dvärgbandmask" in Swedish) that contaminates wild fruit. This is a type of tapeworm called "Echinococcus" in English. Its eggs can cause a parasitic disease called Echinococcosis or hydatid disease. According to this article, freezing the eggs to very low temperatures and/or freezing the eggs very rapidly is fatal to them. Given that modern "IQF" freezing methods for berries bring the fruit very quickly to below -20°C, I'd say that the danger from echinococcosis is very low (much lower than eating unwashed fresh fruit).

As for risks from bacteria, these are also very low because the process of preparing the fruit for freezing and then subsequently freezing them kills the majority of any present bacteria.

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ESultanik
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Raspberries seem fairly acidic, and many bacteria don't stand up well to acid. Here's one article that says raspberry juice kills bacteria. If you're worried, then, you might consider pureeing the raspberries in your blender and letting them sit for a minute before adding the yogurt, banana, or whatever else you put in your smoothies.

Caleb
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No, you should boil for at least 1 Minute.

Food Safety Authority of Ireland states the following in May 2017, especially for imported berries:

As a result of outbreaks of norovirus and hepatitis A virus in imported frozen berries across Europe in recent years, the FSAI recommends boiling imported frozen berries for one minute before consumption.

See FSAI : Berries - Advice to boil imported frozen berries (May 2017)

NotIrish
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McGee has an article for conserving fresh berries for some days longer. He talks about molds, not bacteria...

Frozen berries should be alright as your country's health regulations will not allow dangerous foods to be imported or produced or sold.

BaffledCook
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    The goal of health regulations is to not allow them ... but many countries have had problems with pathogens that were believed to be *in* the items (eg, tainted water used to grow spinich in the U.S, the bean sprout incident in Germany where they think it might've been in the seeds). The only advantage to frozen over fresh in this case is that if it's sold frozen, it's packaged with tracking numbers, so it's easier to identify the source if there's a recall. – Joe Aug 03 '11 at 14:03
  • The number of cases is so small you should ignore the risk. Tons of food, frozen, fresh, dehydrated, you name it, is sold around the world and less then 100 people have died of one localized incident. Not that that's not serious, but you really should consider food bought in shops as safe. – BaffledCook Aug 03 '11 at 16:13