Evaluation of the quality attributes of Ghanaian Robusta coffee subjected to different degrees of roasting

Figures (4) Tables (3)

Figure 1.
Green and roasted Robusta coffee samples: whole beans and ground (image by Emmanuel Duah Osei).
Figure 2.
Map showing the cultivation and processing location of the coffee (image by Emmanuel Duah Osei).
Figure 3.
Phytochemical and antioxidant activity of green, light, medium, and dark roasted robusta coffee beans. (a) Total phenolic content. (b) Total phenolic acids. (c) Total flavonoid content. (d) DPPH radical scavenging activity. Results are expressed as means (n = 3). Error bars represent standard deviation. Different capital letters (A, B, C) above the bars represent significant differences (p ≤ 0.05).
Figure 4.
Oxidative stability of green, light, medium, and dark roasted robusta coffee beans. Results are expressed as means (n = 3). Error bars represent standard deviation. Different capital letters (A, B, C) above the bars represent significant differences (p ≤ 0.05).

Robusta coffee	Proximate composition (g/100 g)
Robusta coffee	Moisture	Ash	Protein	Fat	CHO	Energy (kcal)
Green	9.81 ± 0.02^c	3.27 ± 0.09^a	14.70 ± 1.26^a	2.48 ± 0.24^a	69.74 ± 1.445^a	360.1 ± 1.480^a
Light roast	3.32 ± 0.04^b	3.28 ± 0.02^a	18.05 ± 0.32^b	5.94 ± 0.05^b	69.40 ± 0.350^a	403.3 ± 0.336^b
Medium roast	1.84 ± 0.28^a	3.69 ± 0.06^b	20.70 ± 1.56^b	7.40 ± 0.68^bc	66.37 ± 2.468^a	414.9 ± 2.530^c
Dark roast	1.92 ± 0.08^a	4.11 ± 0.12^c	18.06 ± 1.15^b	8.60 ± 0.33^c	67.31 ± 1.279^a	418.9 ± 2.452^c
p-value	< 0.001	0.001	0.030	< 0.001	0.239	< 0.001
Values are means ± standard deviation (n = 3). Means along the same row with different superscripts are significantly different (p ≤ 0.05). CHO, total carbohydrates.

Table 1.

Effect of roasting on the proximate composition of Robusta coffee.

Elements (mg/kg)	Robusta coffee beans
Elements (mg/kg)	Green	Light roast	Medium roast	Dark roast
Cobalt (Co)	nd	nd	nd	nd
Calcium (Ca)	193 ± 9.53^d	1,726 ± 6.90^b	1,631 ± 3.55^a	1,790 ± 8.42^c
Sodium (Na)	454.0 ± 4.09^d	384.3 ± 1.20^c	373.2 ± 0.38^b	325.8 ± 1.71^a
Potassium (K)	17,480 ± 4.03^d	15,848.7 ± 2.71^c	14,690 ± 3.03^a	15,062 ± 1.77^b
Aluminium (Al)	0.95 ± 0.77^a	8.66 ± 1.04^c	2.89 ± 0.46^b	2.72 ± 0.38^ab
Silver (Ag)	0.08 ± 0.03^b	0.01 ± 0.02^a	0.02 ± 0.01^a	0.01 ± 0.017^a
Magnesium (Mg)	245.8 ± 0.84^d	235.8 ± 0.48^c	225.9 ± 0.07^b	204.7 ± 0.61^a
Barium (Ba)	5.37 ± 0.01^d	4.33 ± 0.01^b	3.60 ± 0.00^a	4.84 ± 0.03^c
Cadmium (Cd)	nd	nd	nd	nd
Chromium (Cr)	nd	nd	nd	nd
Copper (Cu)	17.63 ± 0.09^c	14.03 ± 0.01^a	17.69 ± 0.03^c	15.62 ± 0.12^b
Iron (Fe)	42.29 ± 0.24^bc	41.74 ± 0.23^b	42.61 ± 0.19^c	35.70 ± 0.42^a
Lithium (Li)	0.09 ± 0.02^b	0.03 ± 0.00^a	0.03 ± 0.00^a	0.02 ± 0.00^a
Manganese (Mn)	13.08 ± 0.05^d	12.81 ± 0.07^c	11.46 ± 0.02^a	11.76 ± 0.02^b
Nickel (Ni)	nd	2.29 ± 0.21^a	2.53 ± 0.04^b	3.14 ± 0.14^c
Strontium (Sr)	7.85 ± 0.05^d	6.63 ± 0.02^b	6.22 ± 0.01^a	7.07 ± 0.05^c
Lead (Pb)	nd	nd	nd	nd
Zinc (Zn)	5.90 ± 0.62^b	4.70 ± 0.53^b	2.49 ± 0.58^a	3.01 ± 0.80^a
Antimony (Sb)	0.32 ± 0.60^a	0.49 ± 0.10^a	nd	0.21 ± 0.52^a
Arsenic (As)	nd	nd	nd	nd
Mercury (Hg)	nd	nd	nd	nd
Selenium (Se)	nd	nd	nd	nd
Values are means ± standard deviation (n = 3). Means along the same row with different superscripts are significantly different (p ≤ 0.05). nd, not detected.

Table 2.

Impact of roasting on minerals, including risk elements of coffee beans.

Microorganism	Zone of inhibition (mm)
Microorganism	Green coffee	Light roast coffee	Medium roast coffee	Dark roast coffee
CCM 8270	3.58 ± 0.71^b	3.84 ± 0.87^a	3.58 ± 0.72^b	3.04 ± 0.44^c
CCM 8186	3.84 ± 0.87^a	2.78 ± 0.29^c	2.78 ± 0.29^c	3.58 ± 0.72^b
CCM 8223	3.04 ± 0.44^a	3.04 ± 0.44^a	3.04 ± 0.44^a	2.78 ± 0.29^b
CCM 4224	7.58 ± 0.93^a	5.18 ± 0.60^b	5.18 ± 0.60^b	2.78 ± 0.29^a
CCM 3954	4.38 ± 0.16^d	5.44 ± 0.75^a	4.64 ± 0.31^c	5.18 ± 0.60^b
CCM 4699	5.98 ± 0.04^a	3.84 ± 0.87^b	3.84 ± 0.87^b	5.98 ± 0.04^a
CCM 1959	5.18 ± 0.60^a	4.38 ± 0.16^b	3.85 ± 0.87^c	3.85 ± 0.87^c
CCM 3807	4.64 ± 0.31^b	5.44 ± 0.75^a	4.38 ± 0.16^c	3.84 ± 0.87^d
CCM 2461	6.78 ± 0.49^a	3.84 ± 0.87	3.84 ± 0.87	5.98 ± 0.04^b
Candida glabrata CCM 8270, Candida albicans CCM 8186, Candida tropicalis CCM 8223, Enterococcus faecalis CCM 4224, Escherichia coli CCM 3954, Listeria monocytogenes CCM 4699, Pseudomonas aeruginosa CCM 1959, Salmonella enterica subs. Enterica CCM 3807, Staphylococcus aureus subs. aureus CCM 2461. Values are means ± standard deviation (n = 3). Means along the same row with different superscripts are significantly different (p ≤ 0.05). nd, not detected.

Table 3.

Antimicrobial activity of green, light, medium, and dark roasted robusta coffee.