NaHCO3 aka Baking Soda Washes All Pesticides Off Your Fruits & Veggies | 100% Pesticide Removal From Surface

Simply rinsing produce with tap water will not remove any relevant amount of pesticides.

SuppVersity veterans will remember the 2013 installment of "True or False" discussing whether "Washing Your Fruit and Veggies is Useless" (re-read it). The bottom line back then was: it's well worth spending the inconvenient extra-minute it takes to prepare warm water (28-32 °C), put your foods in, scrub a little with your hand and then continue processing them.

Now, after the publication of a recent study in the Journal of Agricultural and Food Chemistry (ahead of print | Yang 2017), I will probably have to update this article.

The authors, scientists from the University of Massachusetts were, after all, able to prove that baking soda, sodium bicarbonate or NaHCO3 comes close to peeling with respect to its ability to reduce the pesticide load from conventional and organic produce.
In the 20th century, both, use and concerns about concerns about potential hazards of pesticides to food safety and human health have increased significantly. Water, alone, will - as previously discussed - not get rid of all the pesticide residues on your fruits and veggies.

Voilá: Pesticide + clorox = main constituents of your 'healthy' smoothie

Moreover, fresh produce is commercially processed using sanitizers in the postharvest washing process to remove visible soil or organic matter residues as well as to reduce the microbial contamination found on the surface (Akgun 2001; Batzer 2002) - usually with Clorox Germicidal bleach, which is approved by the United States Environmental Protection Agency (U.S. EPA).

In their latest paper, Yang et al. wanted to figure out if this practice would also contribute to a reduction in pesticide residues and/or simply lead to the accumulation of a cocktail of potentially hazardous chemicals on our fruits and veggies.
As the authors point out, their own previous studies have shown that pesticides, which are applied to the produce surface, can penetrate into the produce over time (Yang 2016a,b, 2017b). In that, systemic pesticides can penetrate more rapidly and deeper compared to non-systemic pesticides. The objective of the study under review was to

"investigate the effectiveness of commercial (Clorox Germicidal bleach) and homemade (tap water and NaHCO3) washing agents to remove surface and internalized pesticide residues on and in apples, respectively" (Yang 2017a).

In that, Yang et al. hypothesized that systemic pesticides will be more difficult to remove from whole apples as a result of their greater penetrating abilities. After application and washing, the scientists monitored the amount of each pesticide or its degradation products that remained on the surface and penetrated into the apple over time using the surface-enhanced Raman spectroscopy (SERS) mapping method (according to the authors this is the first time it was used in this context). If pesticides degraded to other molecules but were still left on the surface, SERS would be able to detect some signals.

Figure 1: Schematic Illustration of the SERS Mapping Method for Evaluation of Removal Effectiveness of Pesticide Residues on and in Apples with Commercial and Homemade Washing Agents (Yang 2017a).

For the study, the scientists used organic apples to which they applied a standardized amount of pesticides (see Figure 1) before they were washed using three different washing agents/methods:

• Clorox Germicidal bleach (25 mg/L available chlorine, pH 8.05), 
• 10 mg/mL NaHCO3 (pH 9.12), and 
• tap water (pH 6.85). 

The actual procedure of washing is described by Yang et al. (2017a) as follows:

• For Clorox and NaHCO3 solutions, the treated apples were first immersed into 200 mL of a washing solution for 2 or 8 min and then gently rinsed with 150 mL of deionized water for 10 s. 
• The tap water washing method, which was intended to imitate how people washed their apples at home, was applied by rinsing treated apples with approximately 1.8 L of tap water for 2 min at a flow rate of 15 mL/s. 

All washed apples were air-dried at room temperature for 10 min before the analysis of pesticide residues was conducted. In that, the SERS spectra collected from 25 locations in each mapping image were averaged.

Figure 2: SERS surface mapping images of the apple surface with thiabendazole after different washing treatments: (a) without washing, (b) tap water washing for 2 min, (c) Clorox solution washing for 2 min, (d) NaHCO3 solution washing for washing 2 min, (e) Clorox solution washing for 8 min, (f) NaHCO3 solution washing 8 min, (g) NaHCO3 solution washing 12 min, (h) AuNPs on the apple surface, and (i) apple surface alone for comparisons (Yang 2017a).

Figure 2 shows the resulting SERS surface mapping images of the apple surface with thiabendazole after different washing treatment. Figure 3 gives you an idea of the of how deep the pesticides penetrated the skin of the apples.

Figure 3: SERS depth mapping images of apples with thiabendazole after different washing treatments (Yang 2017a).

As you can see, the scientists' analysis showed that the systemic pesticide thiabendazole was able to penetrate into the apple peel following the 2 min wash and the amount of residue decreased following the 8 min washing (panels b–g of Figure 3).

After washing with a NaHCO3 solution for 12 min, the amount of pesticides on the apples was reduced below the detection limit of this method (Figure 3, panel g).

The problem of residues in the apple peel, on the other hand, persisted. Similar results were obtained using the non-systemic pesticide, phosmet. In that, it's worth noting that the NaHCO3 solution was more efficient than tap water and Clorox solution in all conditions. Even with baking soda in the water, the washing time was yet the crucial determinant of pesticide removal - with 12 minutes in the NaHCO3 bath yielding by far the best results.

Even with bicarbonate, buying organic may still be worth it!

One thing this article should not be abused is as evidence in an argument against buying organic. Yes, you can reduce the pesticide load on the peel of your favorite produce to almost zero and yes, even the latest (highly pro-organic) review of the literature highlights that pesticides are where the major differences are, but you're (a) still left with the pesticides beneath the skin and will (b) not benefit from the other potential benefits Tiziano Gomiero highlights in his latest paper in Applied Soil Ecology (see Figure 4).

Figure 4: Benefits of organic agriculture compared to conventional practices (Gomiero 2017).

The X-axis of Gomiero's graphical illustration of his comprehensive evaluation of the proven benefits of organic agriculture lists, among others, effects on the environment, antibacterial resistance, potentially increased nutritive value, and often lower heavy metal concentrations as additional benefits. It does yet also show that there's some truth to the notion that organic produce ain't immune to natural toxins and bacteria... the good news, however, is that the nine pertitent studies didn't find disadvantages, either.
References:

• Akgun Karabulut, O.; Lurie, S.; Droby, S. Evaluation of the use of sodium bicarbonate, potassium sorbate and yeast antagonists for decreasing postharvest decay of sweet cherries Postharvest Biol. Technol. 2001, 23 (3) 233– 236 DOI: 10.1016/S0925-5214(01)00151-X 
• Batzer, J. C.; Gleason, M. L.; Weldon, B.; Dixon, P. M.; Nutter, F. W. J. Evaluation of postharvest removal of sooty blotch and flyspeck on apples using sodium hypochlorite, hydrogen peroxide with peroxyacetic acid, and soap Plant Dis. 2002, 86 (12) 1325– 1332 DOI: 10.1094/PDIS.2002.86.12.1325.
• Gomiero T. Food quality assessment in organic vs. conventional agricultural produce: Findings and issues. Applied Soil Ecology. 2017 Oct 21. 
• Guardia-Rubio, M.; Ayora-Cañada, M. J.; Ruiz-Medina, A. Effect of washing on pesticide residues in olives J. Food Sci. 2007, 72 (2) C139– C143 DOI: 10.1111/j.1750-3841.2006.00252.x 
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• Yang, T.; Zhang, Z.; Zhao, B.; Hou, R.; Kinchla, A.; Clark, J. M.; He, L. Real-Time and in Situ Monitoring of Pesticide Penetration in Edible Leaves by Surface-Enhanced Raman Scattering Mapping Anal. Chem. 2016a, 88 (10) 5243– 5250 DOI: 10.1021/acs.analchem.6b00320 
• Yang, T.; Zhao, B.; Hou, R.; Zhang, Z.; Kinchla, A. J.; Clark, J. M.; He, L. Evaluation of the Penetration of Multiple Classes of Pesticides in Fresh Produce Using Surface-Enhanced Raman Scattering Mapping J. Food Sci. 2016b, 81 (11) T2891– T2901 DOI: 10.1111/1750-3841.13520
• Yang, T.; Zhao, B.; Kinchla, A. J.; Clark, J. M.; He, L. J.  Effectiveness of Commercial and Homemade Washing Agents in Removing Pesticide Residues on and in Apples. Agric. Food Chem. 2017a, Article ASAP DOI: 10.1021/acs.jafc.7b03118
• Yang, T.; Zhao, B.; Kinchla, A. J.; Clark, J. M.; He, L. Investigation of Pesticide Penetration and Persistence on Harvested and Live Basil Leaves Using Surface-Enhanced Raman Scattering Mapping J. Agric. Food Chem. 2017b, 65, 3541– 3550 DOI: 10.1021/acs.jafc.7b00548