Sciencemadness Discussion Board

Washing fruit

Quaff - 2-11-2017 at 07:43

I'm a big fan of raspberries and blackberries. Typically, I'll soak them in water, and add about 100 mg of Dawn dishwash liquid to the soak mixture. I let them soak a few minutes, then quintuple rinse the berries, followed by two more rinses with distilled H2O.

Theory is that by breaking the surface tension with the soap, I'm permitting more of molecules that might be adsorbed on the fruit to be liberated into the water rinses. Maybe I'm right, or maybe I'm wrong but that's what I've been doing. Any and all thoughts on this I appreciate !

hissingnoise - 2-11-2017 at 07:58

Quote:
Any and all thoughts on this I appreciate

Try picking your fruit at sites other than toxic, heavy metal landfills? :D

SWIM - 2-11-2017 at 08:03

Quote: Originally posted by hissingnoise  
Quote:
Any and all thoughts on this I appreciate

Try picking your fruit at sites other than toxic, heavy metal landfills? :D



They don't have toilet facilities in most berry fields.
He could just be trying to limit the urine and feces content of his snacks.

However I think water does that quite well.

hissingnoise - 2-11-2017 at 08:13

Quote:
He could just be trying to limit the urine and feces content of his snacks

Whoops! There goes that outdoor flavour!

Texium - 2-11-2017 at 08:29

Quote: Originally posted by hissingnoise  
Quote:
He could just be trying to limit the urine and feces content of his snacks

Whoops! There goes that outdoor flavour!

As my grandfather says, a little clean dirt never hurt anyone ;)

For real though, rinse your fruit with tap water a couple times and you're good. And if you still feel uncomfortable, spend extra on Organic even though it's kind of a shakedown.

NEMO-Chemistry - 2-11-2017 at 09:34

Milton fluid for babies apparently was used alot to wash salad stuff. I am told it cost a fortune but was the goto stuff for washing food that wasnt going to be cooked.

Found some information on it while looking to see what Clorox was. Turns out that Milton fluid for babies is plain old 3% bleach lol

So you could go weak bleach wash, thiosulphate wash to get rid the bleach, then distilled water a few times.

but flame your knife and fork before eating anything. make sure you eat in an area with a updraft.....

[Edited on 2-11-2017 by NEMO-Chemistry]

hissingnoise - 2-11-2017 at 12:01

And never start a pizza at the crust... :cool:


DraconicAcid - 2-11-2017 at 12:20

Quote: Originally posted by zts16  
Quote: Originally posted by hissingnoise  
Quote:
He could just be trying to limit the urine and feces content of his snacks

Whoops! There goes that outdoor flavour!

As my grandfather says, a little clean dirt never hurt anyone ;)

For real though, rinse your fruit with tap water a couple times and you're good. And if you still feel uncomfortable, spend extra on Organic even though it's kind of a shakedown.


But then you'd get even more organic fertilizer, and have to worry about more E. Coli, etc.

NEMO-Chemistry - 2-11-2017 at 12:39

Quote: Originally posted by hissingnoise  
And never start a pizza at the crust... :cool:




Well thats a given, just like never eat yellow snow :D

AJKOER - 9-11-2017 at 21:45

To remove serious microbes and copper pesticide residue, may I suggest a tap water mixture of dilute H2O2, NaHCO3 and a final touch of vinegar with sea salt.

Let stand in sunlight and then several rinses with distilled water.

In the presence of salts of transition metals found in common tap water (like manganese), this brew is not far removed from a highly regarded chemical/biological warfare decontamination protocol (see "Development of Bicarbonate-Activated Peroxide as a Chemical and Biological Warfare Agent Decontaminant" at https://www.google.com/url?sa=t&source=web&rct=j&... ).

[Edited on 10-11-2017 by AJKOER]

j_sum1 - 10-11-2017 at 01:37

First reference here is relevant - the latest research on washing pezticides from fruit.
www.compoundchem.com/2017/11/05/twic05112017/#more-15390

AJKOER - 11-11-2017 at 04:20

Note, my suggested protocol includes NaHCO3.

However, I suspect the effective pesticides are not easily washed off as they are applied to fruit which can be subject to repeated rain events.

My advanced oxidation protocol can actually breakdown organics with one source claiming HCO4- and others the carbonate radical formation (from the action of hydroxyl radicals acting on bicarbonate) as possible active agents. See, for example, "Equilibria, Kinetics, and Mechanism in the Bicarbonate Activation of Hydrogen Peroxide:  Oxidation of Sulfides by Peroxymonocarbonate", by David E. Richardson, et al, link: http://pubs.acs.org/doi/abs/10.1021/ja9927467 and also https://www.google.com/url?sa=t&source=web&rct=j&... , and a source for carbonate radical presence see http://www.sciencedirect.com/science/article/pii/S0162013410... . This last reference cites a reaction chain:

Cu(II) + H2O2 → Cu(I) + O2•− +2 H +

2 O2•− + 2 H+ → H2O2 + O2

Cu(I) + H2O2 → Cu(II) + •OH + −OH

With a possible carbonate radical formation from:

•OH + HCO3- → H2O + •CO3-

To quote the author comments:

"Although less oxidizing than the •OH (Eo = 2.3 V, pH 7.0) [5–7], the carbonate radical is a strong one-electron oxidant (Eo = 1.8 V, pH 7.0) [5–7] which, in contrast to the former, does not add to biomolecules. Since the carbonate radical is more specific than the hydroxyl radical, it may increase oxidation/nitration of particular biotargets [11,22,25]."

The precise path to the carbonate radical apparently is not certain. The author comments, for example:

".. it is still unclear whether the immediate precursor of the carbonate radical is bicarbonate [19,26], carbon dioxide [14,30] or peroxymonocarbonate (HCO4−) [27–29]. Strong evidence for the involvement of peroxymonocarbonate in the formation of CO3•− derives from kinetic studies of bovine serum albumin (BSA-cysSH) and glutathione (GSH) peroxidation in the presence of bicarbonate [25], and the demonstration that the formation and reduction of peroxymonocarbonate is facilitated by the many metal centres of xanthine oxidase [31]."

[Edited on 11-11-2017 by AJKOER]

unionised - 11-11-2017 at 05:04

Someone actually did some science about this
https://cen.acs.org/articles/95/web/2017/10/Baking-soda-wash...

AJKOER - 11-11-2017 at 05:47

Quote: Originally posted by unionised  
Someone actually did some science about this
https://cen.acs.org/articles/95/web/2017/10/Baking-soda-wash...


The above protocol in addition to NaHCO3 recommends tap water likely rich in some dissolved O2 (which via transition metal base autooxidation uses oxygen to create in situ H2O2, but not anywhere as efficient as by adding H2O2), and a small amount of transition metals along with a biocide from the action of Cl2 or NH2Cl on the water. This may be a bad idea as a rise in water temperature can largely reduce dissolved oxygen content, so adding H2O2 is a safer and more efficient path. Also, chloramine for sure is destroyed by seating in copper pipes, so run the water to reduce the risk of bio-contamination.
---------------------------

My slightly revised protocol is as follows:

"To remove serious microbes and pesticide residue, may I suggest a 80% tap water mixed with dilute H2O2, NaHCO3 (or better NH4HCO3) followed by a touch of vinegar with sea salt, to generate CO2, and then add more NaHCO3 to make the solution alkaline. Let stand preferably in sunlight followed by rinsing in distilled water.


[Edited on 11-11-2017 by AJKOER]

unionised - 11-11-2017 at 06:18

"The above protocol in addition to NaHCO3 recommends tap water likely rich in some dissolved O2 ".
Not very likely.
Tap water may have dissolved air but it may be scavenged out by reaction with copper pipes or with methane etc in the water.
by he time you have left it open to the air in a bowl for a while it will have plenty of air.
It is interesting that you propose the production of peroxide from air and water in the presence of transition metals.

In practice the reaction is known to go the other way. peroxides are destroyed by metal ions and produce oxygen and water.
Why do you think the reaction goes backwards in this case?
Are you assuming that magic happens?

It may be that adding peroxide would improve the removal of pesticides, but since it's already been shown that soda and tap water works very well, why bother?

In many cases the proposed mechanism for removal of the pesticides was hydrolysis by the base. No need for an oxidant.

AJKOER - 11-11-2017 at 06:29

Unionised:

I completely agree about the dissolved oxygen issue and it is why I recommend the use of H2O2 and not just aerated water. However, the latter is, I suspect, the basis of the so called alluded to 'science', and the O2 presence suggests a possible link to the literature, for the tap water with NaHCO3 only path.

Please read my sources and prior references quoted therein as opposed to no cited source for the tap water/HCO3- only 'science'.

There is a claim that pesticides (two common pesticides, which may be due to the selectivity of the carbonate radical) are broken down into harmless molecules by seemingly just NaHCO3 (see, http://www.dailymail.co.uk/health/article-5020377/Baking-pow... ). No, such reduction is a classic statement as a consequence of an AOP (advanced oxidation process), which can be, at times, effected in the presence of O2, transition metal and bicarbonate as I outlined. Also, the NaHCO3 path was more effective than alkaline NaOCl, which should suggest that there's something more complex is afoot.

With respect to the acidified metal autooxidation path to in situ H2O2 creation, here is a reference: http://pubs.acs.org/doi/abs/10.1021/ja01600a004 .

The tap water/HCO3- only 'science' is, in my assessment, a readable reductionist attempt to explain an AOP protocol to wash fruit for the very largely scientifically unschooled masses. Note my honest presentation that the exact path of carbonate radical creation remains a matter of debate, even among the very schooled.

[Edited on 11-11-2017 by AJKOER]

unionised - 11-11-2017 at 09:50

You do realise that he paper you cited doesn't actually show that H2O2 is produced, don't you?

the experiments show that bicarbonate works, and that it works better than the readily available oxidant; bleach.
Why do you think adding peroxide is going to improve it?

AJKOER - 11-11-2017 at 10:07

Here is an extract on one of my prior discussion of Fenton-type reactions proceeding from in situ formed H2O2, to quote:

"Well, let's start with some possible Fenton based reactions creating the hydroxyl radicals, .OH and the superoxide anion, .O2- . As a reference, see, for example, "Generation of Hydroxyl Radicals from Dissolved Transition Metals in Surrogate Lung Fluid Solutions" by Edgar Vidrio, et al at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2626252/ . Cited reactions :

Cu(l)/Fe(II) + O2(aq) → Cu(ll)/Fe(III) + .O2-

As an alternate reference for the above reaction (which I have personally performed on Cuprous citrate using an air pump from an old fish tank), see for example, https://books.google.com/books?id=WjReuSXxl4YC&pg=PA17&a...

The reaction chain continues as:

Cu(l)/Fe(II) + .O2- +2 H+ → Cu(ll)/Fe(III) + HOOH

Cu(l)/Fe(II) + HOOH → Cu(ll)/Fe(III) + .OH + OH-

Net of the last three reactions:

3 Cu(l)/Fe(II) + O2(aq) +2 H+ → 3 Cu(ll)/Fe(III) + .OH + OH-

And, in the presence of sunlight (or a reductant like Citric or Ascorbic acid), a cyclic reaction could ensue in the case of sunlight:

Cu(ll)/Fe(lll) (aq) + hv → Cu(l)/Fe(ll) (aq) + HO• + H+ "

In my opinion, a process that requires first the formation of in situ H2O2 or HO2-, is slower than one that starts with some H2O2. Also, the hydrogen peroxide serves as a backup in case your safe tap water isn't safe for various possible reasons (storms, human error,...).
----------------------------

If your tap water is strongly chlorinated, the mechanics of the fenton-type reaction will proceed (actually per my recollection much faster, several orders of magnitude) with hypochlorous acid in place of H2O2 as follows, especially in sunlight:

Cu(l)/Fe(II) + HOCl → Cu(ll)/Fe(III) + .OH + Cl- (source: see Eq 5 at https://www.researchgate.net/publication/259648754_Hypochlor... )

Cu(ll)/Fe(lll) (aq) + hv → Cu(l)/Fe(ll) (aq) + HO• + H+

where the created hydroxyl radical could react with bicarbonate forming the carbonate radical:

•OH + HCO3- → H2O + •CO3-

As the reported time frame to remove pesticides was 15 minutes, this strongly suggests that the underlying AOP was via transition metal(s) (likely sourced from the vegetable) activated hypochlorous acid with subsequent possible formation of the carbonate radical in the presence of bicarbonate.

[Edited on 11-11-2017 by AJKOER]

happyfooddance - 12-11-2017 at 07:59

I would advise against using dish soap directly on berries. The detergents and fragrances are designed to rinse easily from materials with low surface reactivity such as glass, ceramic, or plastic. Fruits have many more reactive functional groups (ketones, etc.) and a complex surface landscape which can serve to trap or complex with your soap. I have a very sensitive palate, and I find it nearly impossible to satisfactorily rinse commercial dish soap (I use dawn) from most fruits and veggies.

The general consensus among chefs with regards to rinsing berries is: one rinse, before serving. Never rinse berries before storing, it increases the chance for mold growth.

I use a little dish soap when washing fruits with a thick rind, such as melons, avocado, pineapple... People often don't think to wash these fruits, but because the rind isn't eaten, growers can (and do) legally put significantly higher concentrations of pesticide on them. They should be washed thoroughly, and cut with a non-serrated knife.

AJKOER, I like the idea about the HOOH and sunlight, I would leave out the salt, though.

feacetech - 12-11-2017 at 14:55

Quote: Originally posted by DraconicAcid  
Quote: Originally posted by zts16  
Quote: Originally posted by hissingnoise  
Quote:
He could just be trying to limit the urine and feces content of his snacks

Whoops! There goes that outdoor flavour!

As my grandfather says, a little clean dirt never hurt anyone ;)

For real though, rinse your fruit with tap water a couple times and you're good. And if you still feel uncomfortable, spend extra on Organic even though it's kind of a shakedown.


But then you'd get even more organic fertilizer, and have to worry about more E. Coli, etc.


Dont forget the heavy metal content of "organic" mineral fertilisers like RPR. Or the asbestos content of "organic" magnesium ferlisers based around serpentine or olivine, not a worry unless you are grinding your berries up and inhaling them