Coffee Silver Skin-Health Safety, Nutritional Value, and Microwave Extraction of Proteins

Overview

Biondic Fuckar and colleagues evaluated coffee silverskin, the thin tegument removed during coffee roasting, for food-safety contaminants and nutritional composition. The source reports one homogenized coffee-silverskin by-product sample with six parallel analyses; nickel (Ni), lead (Pb), total arsenic (As), cadmium (Cd), and chromium (Cr) were measurable, but the matrix is a roasting by-product rather than brewed coffee or ground coffee as sold. The paper is useful for coffee by-product and potential nutraceutical/supplement routing, with a clear matrix firewall.

Key numbers

Table 4 reports the detected heavy metals in coffee silverskin as Ni 2.495 +/- 0.055 mg/kg, Pb 0.249 +/- 0.077 mg/kg, As 0.107 +/- 0.018 mg/kg, and Cd 0.106 +/- 0.002 mg/kg. The paper does not speciate arsenic, so this page treats it as total arsenic rather than inorganic arsenic.

Section 3.2 also reports nutritional and trace-element values in the same silverskin sample: K 24,311 +/- 764 mg/kg, Ca 10,569 +/- 210 mg/kg, Mg 4672.5 +/- 88.5 mg/kg, Na 329 +/- 79 mg/kg, Fe 567.50 +/- 12.50 mg/kg, Cu 74.90 +/- 0.60 mg/kg, Mn 37.55 +/- 0.45 mg/kg, Zn 16.80 +/- 0.70 mg/kg, and Cr 1.53 +/- 0.04 mg/kg.

The authors compare the measured Pb and Cd values to European contaminant limits for food additives and supplements. They state that Pb at 0.249 +/- 0.077 mg/kg is below a 3.0 mg/kg food-additive maximum and that Cd at 0.106 +/- 0.002 mg/kg is below a 1.0 mg/kg food-supplement maximum.

The abstract states that 265 pesticides were analyzed and three were detected at small quantities. Those pesticide results are outside the heavy-metal scope of this source page except as context for the authors’ broader health-safety framing.

Methods (brief)

The coffee-silverskin sample was ground and homogenized before analysis. For metals, 0.5 g of crushed homogenized sample was hydrated, digested with concentrated nitric acid and 30% hydrogen peroxide in microwave decomposition, transferred to 25 mL, and measured by ICP-MS. The paper reports calibration linearity of at least 0.999 for each element and use of Bi, Sc, Y, and Ge internal standards.

The reported heavy-metal results are averages of six parallel analyses. The sample combined Arabica and Robusta roasting by-products, so it should not be interpreted as a varietal comparison.

Related evidence

• Coffee
• Coffee
• Dietary Supplements
• Nickel
• Lead
• Arsenic, Total
• Cadmium
• Chromium
• Copper
• Zinc
• Manganese
• Iron

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git.