Truzzi et al. 2020 - potentially toxic elements in insect biomass and coffee-silverskin substrates

Truzzi et al. tested whether black soldier fly prepupae grown on coffee-silverskin substrates enriched with microalgae could remain chemically suitable as feed or food biomass. The study measured Cd, Pb, total Hg, total As, and Ni in substrate ingredients, formulated growth substrates, prepupae, and frass. Coffee silverskin had low Cd, Pb, total As, and total Hg, while black soldier fly prepupae bioaccumulated Cd, Pb, and total Hg but remained within the EU undesirable-substance limits evaluated by the authors.

Key numbers

• Experimental design: nine growth substrates were tested, each with five replicate groups of 150 larvae. The control substrate was 100% coffee silverskin; the other substrates added 5%, 10%, 20%, or 25% Schizochytrium sp. or Isochrysis sp.
• Coffee silverskin ingredient concentrations, dry weight: Cd 0.053 +/- 0.008 mg/kg, Pb 0.032 +/- 0.002 mg/kg, total Hg 0.027 +/- 0.001 mg/kg, total As 0.147 +/- 0.006 mg/kg, and Ni 3.5 +/- 0.2 mg/kg.
• Microalgae ingredient concentrations, dry weight: Schizochytrium sp. had Cd 0.0025 +/- 0.0002 mg/kg, Pb 0.065 +/- 0.003 mg/kg, total Hg 0.009 +/- 0.002 mg/kg, total As 0.184 +/- 0.002 mg/kg, and Ni 3.6 +/- 0.1 mg/kg. Isochrysis sp. had Cd 0.0020 +/- 0.0005 mg/kg, Pb 0.084 +/- 0.009 mg/kg, total Hg 0.0016 +/- 0.0004 mg/kg, total As 0.153 +/- 0.001 mg/kg, and Ni 1.18 +/- 0.03 mg/kg.
• Growth-substrate concentrations, dry weight: Cd ranged from 0.037 to 0.050 mg/kg, Pb from 0.032 to 0.045 mg/kg, total Hg from 0.020 to 0.027 mg/kg, and total As from 0.139 to 0.154 mg/kg.
• Prepupae concentrations, dry weight: Cd ranged from 0.19 to 0.24 mg/kg, Pb from 0.063 to 0.075 mg/kg, total Hg from 0.029 to 0.112 mg/kg, and total As from 0.123 to 0.138 mg/kg.
• Prepupae concentrations, wet weight, from the abstract: Cd 0.072 to 0.084 mg/kg, Pb 0.018 to 0.026 mg/kg, total Hg 0.010 to 0.032 mg/kg, total As 0.036 to 0.047 mg/kg, and Ni 0.18 to 0.76 mg/kg.
• Bioaccumulation: Cd BAF was greater than 1 for all groups, with mean +/- SD 5.6 +/- 0.8; Pb BAF ranged from 1.6 to 2.3, mean 1.9 +/- 0.3; total Hg BAF was greater than 1 for all groups and ranged from 1.4 to 4.5. Total As BAF was near 1, ranging from 0.82 to 0.99.

Methods (brief)

The authors analyzed coffee silverskin, microalgae, formulated substrates, black soldier fly prepupae, and frass. Cd, Pb, Ni, and As were measured by graphite furnace atomic absorption spectrometry after nitric acid and hydrogen peroxide microwave digestion. Total Hg was measured by thermal decomposition amalgamation atomic absorption spectrometry using a direct mercury analyzer. Analytical quality control used DORM-2 dogfish muscle certified reference material.

Implications

Certification: This is supply-chain and feed-ingredient evidence, not consumer-product occurrence evidence for coffee beverages. It should inform insect-protein, feed, and circular-substrate risk review without entering coffee occurrence percentiles.

Courses: The study provides a concrete example of how upcycled food-industry by-products can be screened before use as insect-rearing substrates, and why bioaccumulation factors matter even when substrate concentrations are low.

App: The paper supports supply-chain context around coffee silverskin and insect biomass, not a direct consumer coffee contamination estimate.

Wiki pages this source may touch

• coffee
• cadmium
• lead
• mercury-total
• arsenic-total
• nickel

Verification notes

• The paper reports arsenic as total As and mercury as total Hg; this page uses tAs and tHg and does not infer inorganic arsenic or methylmercury.
• The auto-fetched filename is a coffee gap hit, but the routeable matrix is coffee silverskin as an insect-rearing substrate plus insect biomass, not brewed coffee.
• Products are intentionally empty because this source does not measure a named consumer product row; it is supply-chain/feed-ingredient evidence.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.