4 ms·

So cocoa got heavy metals from soil, makes sense. But why does it have significant more concentration than other crops?

zwieback 3y ago
The researchers conclude that while cocoa bean shells may be one source of lead, most contamination occurs during shipping or processing of the beans and in manufacturing. Further research on those stages of the process will help to isolate the source. source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1281312/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1281312/
waveBidder 3y ago
it doesn't really: >The FDA estimated dietary exposure of children to Cd and Pb from 2014 to 2016 based on Cd and Pb concentration data from the FDA Total Diet Study and food consumption data from the National Health and Nutrition Examination Survey and determined that dietary Cd and Pb from all sweets (i.e., candy, gelatin, jelly, sugar, and syrup), including chocolate, comprises 1.2 and 3.5% of total dietary intake, respectively. https://pubmed.ncbi.nlm.nih.gov/32293881/ https://pubmed.ncbi.nlm.nih.gov/32293881/ https://sci-hub.se/10.1021/acs.jafc.9b08295 https://sci-hub.se/10.1021/acs.jafc.9b08295
perihelions 3y ago
From the linked report: - "Excessive nib Cd levels occur due to several main factors: 1) Theobroma cacao is a natural Cd accumulating plant species compared to others grown on the same soils; 2) topsoil Cd increases from deposition of litter and harvest debris on the soil surface; 3) Because cocoa roots remain in the topsoil, tillage to incorporate soil amendments harms the trees; 4) Most cocoa soils in South America and the Caribbean (LAC) are strongly acidic with pH as low as 4.5, so low that soil Cd is highly phytoavailable; 5) Some cocoa soils were historically Cd contaminated by mining wastes (minor part of land in cocoa production); and 6) some cocoa soils are naturally Cd enriched from parent rocks (e.g., marine shale) which makes these have high Cd:Zn ratios and thus have very high Cd phytoavailability. In these soils, beans can reach 10 mg Cd/kg rather than the 0.8 mg Cd/kg limit usually enforced on bean imports in the EU. One location in Colombia has 27 mg Cd/kg topsoil, 100-fold background levels. Other areas with high Cd:Zn problem soils growing cocoa were identified in at least Ecuador, Honduras, Peru and Trinidad & Tobago." - "Cocoa plants absorb Cd into roots on a ZIP-family Zn transporter, not on the NRAMP5 transporter used by rice. Zn2+ in soil solution strongly inhibits Cd2+ uptake; thus higher Zn2+ in soil can reduce Cd in cocoa beans. The Cd:Zn ratio in the soil solution strongly affects Cd accumulation in cocoa trees and beans. Unfortunately, surface applied ZnSO4 does not rapidly leach into the rooting zone soil, and foliar Zn sprays are ineffective in reducing Cd in beans. Surface applied ZnEDTA as a Zn fertilizer could leach Zn into the rooting depth soil. But ZnEDTA costs much more than ZnSO4."

The researchers conclude that while cocoa bean shells may be one source of lead, most contamination occurs during shipping or processing of the beans and in manufacturing. Further research on those stages of the process will help to isolate the source. source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1281312/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1281312/

waveBidder 3y ago

it doesn't really: >The FDA estimated dietary exposure of children to Cd and Pb from 2014 to 2016 based on Cd and Pb concentration data from the FDA Total Diet Study and food consumption data from the National Health and Nutrition Examination Survey and determined that dietary Cd and Pb from all sweets (i.e., candy, gelatin, jelly, sugar, and syrup), including chocolate, comprises 1.2 and 3.5% of total dietary intake, respectively. https://pubmed.ncbi.nlm.nih.gov/32293881/ https://pubmed.ncbi.nlm.nih.gov/32293881/ https://sci-hub.se/10.1021/acs.jafc.9b08295 https://sci-hub.se/10.1021/acs.jafc.9b08295

perihelions 3y ago

From the linked report: - "Excessive nib Cd levels occur due to several main factors: 1) Theobroma cacao is a natural Cd accumulating plant species compared to others grown on the same soils; 2) topsoil Cd increases from deposition of litter and harvest debris on the soil surface; 3) Because cocoa roots remain in the topsoil, tillage to incorporate soil amendments harms the trees; 4) Most cocoa soils in South America and the Caribbean (LAC) are strongly acidic with pH as low as 4.5, so low that soil Cd is highly phytoavailable; 5) Some cocoa soils were historically Cd contaminated by mining wastes (minor part of land in cocoa production); and 6) some cocoa soils are naturally Cd enriched from parent rocks (e.g., marine shale) which makes these have high Cd:Zn ratios and thus have very high Cd phytoavailability. In these soils, beans can reach 10 mg Cd/kg rather than the 0.8 mg Cd/kg limit usually enforced on bean imports in the EU. One location in Colombia has 27 mg Cd/kg topsoil, 100-fold background levels. Other areas with high Cd:Zn problem soils growing cocoa were identified in at least Ecuador, Honduras, Peru and Trinidad & Tobago." - "Cocoa plants absorb Cd into roots on a ZIP-family Zn transporter, not on the NRAMP5 transporter used by rice. Zn2+ in soil solution strongly inhibits Cd2+ uptake; thus higher Zn2+ in soil can reduce Cd in cocoa beans. The Cd:Zn ratio in the soil solution strongly affects Cd accumulation in cocoa trees and beans. Unfortunately, surface applied ZnSO4 does not rapidly leach into the rooting zone soil, and foliar Zn sprays are ineffective in reducing Cd in beans. Surface applied ZnEDTA as a Zn fertilizer could leach Zn into the rooting depth soil. But ZnEDTA costs much more than ZnSO4."