Unveiling the Compositional Analysis of Green Coffee Beans with and without Silver Skin

Green Coffee Bean (GCB) is covered with silver skin that is shed as a by-product of the roasting process. For the first time, a comparative study was conducted to differentiate the compositional analysis of green coffee beans with silver skin and without silver skin.

The study aims comparatively assessing nutritional, anti-nutritional and fatty acids composition of green coffee beans with silver skin and without silver skin. The present study is also intended to find out various organic compounds of green coffee beans.

The proximate analysis was used to study nutritional composition. Mineral analysis was assessed by atomic absorption spectroscopy. The antinutrients like phytic acid and tannin were assessed by UV-visible spectroscopy whereas volumetric and gravimetric analysis was used to determine oxalates and alkaloids. Gas chromatography and Fourier Transform Infra-Red spectroscopy were used for studying fatty acids and organic compounds, respectively.

Protein content was significantly (p<0.05) high in green coffee beans with silver skin, indicating 15% higher protein. Macro mineral content was also found significantly (p<0.05 and p<0.01) high in green coffee beans with silver skin, whereby 5.11% higher Phosphorus and 24.12% higher Calcium content was observed. However, iron content was 68.10% lower in green coffee beans with silver skin which might be due to its higher tannin content. Trace minerals zinc and copper were also found to contain 57.18% to 18.11% higher concentrations respectively in silver skin. Anti-nutritional analysis revealed the content of phytic acid and tannin as 161 and 77.29 mg/100g, respectively in green coffee beans with silver skin. The percentages of oxalates and alkaloids were found to be 0.64 and 14.30. These anti-nutritional compounds were significantly (p<0.05 and p<0.01) higher from green coffee beans without silver skin. Green coffee beans have been found with an utmost number of saturated fatty acids having palmitic acid as the most abundant. The unsaturated part is mainly composed of linoleic and oleic acid. Chlorogenic acid isomers and caffeine were the organic compounds detected through Fourier transform infrared spectroscopy.

These findings reveal the presence of both nutritional and anti-nutritional components in Coffee silver skin, with significantly higher levels of anti-nutritional factors in green coffee with silver skin, emphasizing the need for caution in the consumption of green coffee and utilization of coffee silver skin as a valuable bioresource.