Benefits or effects of salt on fruit fruit cleanliness with regards to wax, pests, pesticides, insecticides, etc?

Question

There's a language barrier here for context.

I have heard from a family relative that they think using salt in the preparation of some fruits to be beneficial from a cleanliness perspective, which they heard from the radio. I inquired about the mechanics of how and why this works and did not receive any sort of explanation that satisfied me (e.g. Kenji J lopez style experiments or references to any scientific models/theories of why)

I understand that not all scientific models/theories work in all cases and some become historical as more cases and knowledge is discovered. However I do enjoy/prefer theories/models with experiments and tests with reproducible and measurable results to help prove things.

In all examples the salt used is normal table salt.

1. Preparing an apple to be eaten raw, putting salt on it first and rubbing. Then washing off the salt and washing like normal. Something about the salt is supposed to do something about insecticides and pesticides? I'm not sure if a case could be made for the salt being used as an abrasive for removing wax?

2. Grapes, Berries (blueberry, raspberry, strawberry) Rinsing them off with water like normal, then briefly soaking them in salt water, then dumping the salt water, then rinsing with water again. The salt water soak is supposed to do something for possible (insect) pests, pesticides, insecticides?

Let me know if these kinds of salt operations have any substantial effects good or bad, with regards to cleanliness, taste, nutritional etc. I have heard of brining meat, but never thought or heard of these kinds of practices.

I would be happy to see this debunked or explained.

Answer 1

According to this article, submerging strawberries in saltwater will make fruitfly larva leave the berries. Apparently the idea was popularized in May 2020 by a TikTok post. But the author goes on to say that it's probably not necessary, that consuming fruitfly eggs or larvae is not harmful (they site USDA for this claim), and soaking your strawberries in saltwater may ruin the flavor. I get the impression that the author of this article didn't actually wash any strawberries in saltwater themselves (given that they only say "may" ruin the taste).

This article cites India's Centre for Environmental Science as recommending washing fruit in 2% saltwater to help remove pesticide residue from the fruit surface. They say that most pesticide residue will be removed by washing with normal cold water, but saltwater removes even more pesticides. Here's an article from the Centre for Environmental Science, which has the information cited in the previous article.

Apparently there is also a myth that washing fruits and vegetables with salt water is a bad idea, that it will make pesticide residues "more durable." That myth is debunked here. This article cites Dr. Jessada Denduangboripant of Chulalongkorn University, as saying “salt water can be used to wash fruit and vegetables” and "Most insecticides come in oil form so salt will make the oil compound separate from each other."

Since point of the salt is to help remove oil-based pesticides, you might think of washing your produce with detergent. The problem with that idea is that detergents are not tested for food safety, and you risk leaving some detergent residue on the produce (or even of the produce absorbing the detergent) which you then eat. Eating detergent is not good for you. The advantage of salt is that if you don't manage to rinse it all off, the remaining traces of salt are non-toxic.

All the sources I found about this mentioned using saltwater, not dry salt. So I don't think the salt is meant as an abrasive. Maybe it would work for that, but I didn't find any references for it.

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You mentioned a language barrier with the relative who told you about using salt to clean vegetables. Given that two of the top search results were from India and Thailand, and that I've never heard this technique recommended here in the US, I wonder if this might be a technique which is more common in southeast Asia, and perhaps originated there. Some of the recent sources referenced Covid, so perhaps the idea came about when everyone was (unnecessarily, as it turns out) trying to sterilize their vegetables in the early stages of the pandemic. Or perhaps the idea already existed, and it had a surge in popularity for the same reason. Pure speculation on my part.

Answer 2

No academic appears to have researched whether washing strawberries with salt water is more efficacious than tap water.

"Staying submerged in water might force a few of them out," said Sriyanka Lahiri[, PhD, an assistant professor at the University of Florida]. Incidentally, Lahiri isn't aware of any benefits of adding salt to the water, as it was in the TikTok video, although Lahiri hasn't conducted any research to that end. "Also, I am not sure the fresh strawberry taste will remain the same after being submerged in saltwater for too long," Lahiri added.

I Googled to find mixed anecdotal feedback online.

The theory behind this method

When salt comes into contact with bugs, it draws out water through osmosis (the same mechanism by which vegetables, like eggplant and tomato slices, and salt-preserved eggs are prepared). As the bugs lose their internal water and several other biological mechanisms begin to take a hit (for example, the proteins that perform important structural and functional roles, like enzymes, stop working), they become uncomfortable and come out of the fruit, in search of a less-salty home. Some of them might perish (depending on how much salt is used and for how long they’re exposed).

Then Nik Sharma concluded

Based on my results, it appears that water by itself is just as good at getting rid of bugs from fruit. At the end of the day, I’m going to stick to washing my strawberries (and other fruit) with tap water.

But Sarra Sedghi concluded

Wash your strawberries! Exactly half of the bowls I tested ended up with bugs in them. While both salt and tap water seem effective, the salt water definitely got the bugs out more quickly.

One interesting thing that I noticed was that the bugs preferred to hide in the leafy part, so you could bypass some bugs by chopping the tops off before washing your strawberries.

Answer 3

Typically in industrial produce wash handling, what is more commonly used is sodium hypochlorite 12.5% at concentration of 200ppm ±15ppm @ 6pH ±0.5pH. I have never heard of using sodium chloride as a wash water additive, but it's possible this is simply due to the cost inhibitive nature of such a practice making it unviable in industrial contexts.

I'll refrain from commenting on its efficacy in removal of pesticides, but I do want to point out that salinity is a legitmate control for food pathogens (specifically, when referencing the ubiquitous mnemonic device FAT TOM, it would apply to "M" for moisture, i.e., water activity, for which salinity is a common control mechanism).