Characterisation of cellulose from coffee silverskin

Figures & data

Figure 1. The schematic diagram of different protocols performed to extract cellulose from coffee silverskin.

Table 1. Influence of different treatment methods on the physicochemical properties of cellulose extracted from coffee silverskin.

Sample	WL (%)	CC (%)	R10 (%)	L*	a*	b*	WI	C (%)
A	15 ± 2^a	38 ± 1^a	83.1 ± 0.9^a	41 ± 1^b	3.9 ± 0.8^de	15 ± 2^a	39 ± 1^b	40 ± 1^a
B	46 ± 3^b	50.4 ± 0.9^c	87 ± 2^bc	40 ± 2^b	4.8 ± 0.9^e	15 ± 1^a	38 ± 3^ab	54.4 ± 0.6^c
C	46 ± 4^b	50.0 ± 0.6^c	85 ± 2^ab	36.8 ± 0.7^a	4.9 ± 0.4^e	14 ± 2^a	35 ± 2^a	54.0 ± 0.5^c
D	52.6 ± 0.3^c	44 ± 2^b	88.3 ± 0.7^cd	77 ± 1^h	0.12 ± 0.02^a	20 ± 1^bc	69 ± 2^e	51.6 ±0.8^b
E	58 ± 3^c	59.0 ± 0.5^d	93 ± 1^e	67± 1^c	0.6 ± 0.1^a	21 ± 2^c	61 ± 2^c	56.0 ± 0.3^c
F	68 ± 4^de	75.0 ± 0.7^f	90 ± 2^d	70 ± 1^d	1.13 ± 0.05^ab	24 ± 1^d	61 ± 2 ^c	64.4 ± 0.8^e
G	64 ± 3^d	72.1 ± 0.6^e	93 ± 2^e	71.9 ± 0.7^ef	0.7 ± 0.1^a	24 ± 2^d	63 ± 2^cd	66.8 ± 0.7^f
H	65 ± 2^d	73.6 ± 0.7^e	92 ± 1^e	76 ± 1	2.0 ± 0.4^bc	17.7 ± 0.9^b	70 ± 1^e	64.0 ± 0.5^e
I	70 ± 2^ef	75 ± 1^f	96 ± 1^f	73.5 ± 0.9^f	5 ± 1^e	25 ± 2^d	66 ± 1^d	59.2 ± 0.4^d
J	78 ± 4^g	82.2 ± 0.5^g	96.0 ± 0.8^f	71 ± 1^de	2.4 ± 0.4^c	24 ± 1^d	62 ± 2^c	68.4 ± 0.5^f
K	74 ± 4^fg	85.5 ± 0.3^h	95 ± 1^f	66 ± 2^c	3.4 ± 0.5^d	18 ± 2^bc	61 ± 2^c	70.0 ±0 .4^g

WL: weight loss; C_C: cellulose content; R₁₀: alkaline resistance; WI: whiteness index, and C: crystallinity.

Means followed by the same letters in the same column are not significantly different (p > 0.05).

Figure 2. FTIR spectra of the extracted cellulosic materials from coffee silverskin (samples A–K obtained by various procedures shown in Fig. 1)

Figure 3. Evolution of peak height at 707 cm⁻¹ as a function of extraction procedure.

Figure 4. X-ray diffraction patterns of the extracted cellulosic materials from coffee silverskin (samples A–K obtained by various procedures shown in Fig. 1)

Table 2. Influence of different treatment methods on the thermal stability of cellulose extracted from coffee silverskin.

Sample	Ti (°C)	TMDP (°C)	S	AMDP (%)	ADTG	WL (%)
A	231 ± 2^f	305 ± 2^e	1.61 ± 0.09^e	66 ± 2^b	423 ± 3^f	41 ± 1^fg
B	228 ± 3^ef	299 ± 3^d	0.9 ± 0.2^d	72 ± 2^c	455 ± 3^g	42 ± 2^g
C	229 ± 3^ef	307 ± 3^e	0.88 ± 0.08^d	70 ± 2^c	419 ± 4^f	39 ± 1^f
D	226 ± 2^e	310 ± 2^e	0.8 ± 0.1^cd	64± 1^b	378 ± 4^e	42± 2^g
E	211 ± 3^d	321± 3^f	0.7 ± 0.1^cd	50.8 ± 0.8^a	93 ± 2^c	31 ± 2^e
F	206 ± 3^c	340 ± 4^g	0.66 ± 0.07^bc	50 ± 1^a	102 ± 3^d	27.8 ± 0.9^d
G	207 ± 1^cd	338 ± 3^g	0.65 ± 0.09^bc	52 ± 2^a	107 ± 3^d	25.4 ± 0.9^c
H	190 ± 2^b	236 ± 2^b	0.51 ± 0.05^ab	77 ± 2^de	75 ± 2^b	18.2 ± 0.8^b
I	188 ± 2^ab	241 ± 2^c	0.7 ± 0.1^cd	80 ± 1^e	67 ± 2^a	20.2 ± 1.2^b
J	185 ± 2^a	235 ± 2^b	0.51 ± 0.06^ab	76 ± 2^d	67 ± 2^a	15.2 ± 0.9^a
K	188 ± 1^ab	229 ± 2^a	0.46 ± 0.08^a	78 ± 2^de	68 ± 2^a	13 ± 1^a

T_i: initial decomposition temperature; T_MDP: the main decomposition temperature; S: slope of TGA at 280°C; A_MDP: percentage of the area under the main decomposition temperature peak; A_DTG: total area under DTG curves; WL: extent of weight loss obtained from TGA in the range of 280–360°C.

Means followed by the same letters in the same column are not significantly different (p > 0.05).

Figure 5. TGA curves of the extracted cellulosic materials from coffee silverskin (samples A–K obtained by various procedures shown in Fig. 1)