Coffee Silverskin: Chemical and Biological Risk Assessment and Health Profile for Its Potential Use in Functional Foods

Abstract

The coffee supply chain is characterized by a complex network with many critical and unsustainable points producing a huge amount of waste products. Among these, coffee silverskin (CS), the only by-product of the coffee roasting phase, has an interesting chemical profile that suggests potential use as a food ingredient. However, few data on its safety are available. For this reason, the purpose of the study was to assess the occurrence of chemical and biological contaminants in CS, and the resulting risk due to its potential consumption. Essential, toxic, and rare earth elements, polycyclic aromatic hydrocarbons (PAHs), process contaminants, ochratoxin A (OTA), and pesticides residues were analyzed in three classes of samples (Coffea arabica CS, Coffea robusta CS, and their blend). Furthermore, total mesophilic bacteria count (TMBC) at 30 °C, Enterobacteriaceae, yeasts, and molds was evaluated. The risk assessment was based upon the hazard index (HI) and lifetime cancer risk (LTCR). In all varieties and blends, rare earth elements, pesticides, process contaminants, OTA, and PAHs were not detected except for chrysene, phenanthrene, and fluoranthene, which were reported at low concentrations only in the arabica CS sample. Among essential and toxic elements, As was usually the most representative in all samples. Microorganisms reported a low load, although arabica and robusta CS showed lower contamination than mixed CS. Instead, the risk assessment based on the potential consumption of CS as a food ingredient did not show either non-carcinogenic or carcinogenic risk. Overall, this study provides adequate evidence to support the safety of this by-product for its potential use in functional foods.

Toxicological Assessment of Roasted Coffee Silver Skin (Testa of Coffea sp.) as Novel Food Ingredient

“…Minerals were widely analyzed in coffee silver skin. Potassium is present with about 5000 mg/100 g, magnesium with 200–2000 mg/100 g, calcium with 500–1000 mg/100 g and iron with 18–80 mg/100 g, zinc with 0.7–2.2 mg/100 g [ 29 , 35 , 36 , 44 ]. That are in 26 g of estimated daily intake of silver skin 32% of daily dose for potassium, 14–140% for magnesium, 13–26% for calcium, 50–200% of iron and around 5% for zinc.…”

“…Ubiquitous contaminants are heavy metals, mainly lead, mercury, and cadmium. In silver skin mercury and cadmium were found to be 0.05 mg/kg and 0.07 mg/kg respectively, lead content is up to 0.36 mg/kg with big differences between the samples from different sources ranging from <1 to 0.36 mg/kg [ 42 , 44 ]. A further study reports a lead content of 2.63 mg/kg [ 35 ].…”

“…Furfuryl alcohol was not detected [ 3 ], polycyclic aromatic hydrocarbons were only detected in traces, furan, methylfuran, and pesticides were also below the detection limit [ 44 ]. Nolasco et al [ 35 ] fount dibenzo-pyrene to be the main polycyclic aromatic hydrocarbon with 0.86 mg/kg, all other polycyclic aromatic hydrocarbon were found to be below 0.1 mg/kg.…”

“…Acrylamide was found in silver skin with <20–161 g/kg [ 3 , 44 ] as well as with 720 g/kg [ 40 ]. One of the benchmark levels in Regulation (EU) No.…”

“…Cadmium was found with 0.07 mg/kg [ 42 ] which is in accordance with the limits for wheat and therefore also not of concern. The content of lead with up to 0.36 mg/kg [ 42 , 44 ] or even 2.63 mg/kg [ 35 ] is over the limit for grain which is 0.2 mg/kg. The value of 2.63 mg/kg is clearly too high for food use and therefore not included in further consideration.…”