Classification of commercial apple juices based on multivariate analysis of their chemical profiles

Figures & data

Table 1. Chemical characteristics of the individual apple juices from five different batches (a–e): total soluble solids (TSS), sucrose, glucose, fructose, pH, titratable acidity (TA), ratio of TSS/TA, total phenolics, total antioxidant capacity, TEAC, and requirements of the AIJN Code of Practice (CoP) developed by the European Fruit Juice Association.

	TSS(°Brix)	Sucrose(g/L)	Glucose(g/L)	Fructose(g/L)	pH	TA(g CA/L)	TSS/TA	Total phenolics(mg GAE/L)	TEAC(mM)
Clear FC
1a	11.5	15.6	26.2	82.2	3.4	5.6	2.1	299	2.3
1b	11.1	17.2	27.9	79.6	3.3	5.8	1.9	398	2.2
1c	10.6	12.9	21.5	58.9	3.4	6.5	1.6	329	2.5
1d	11.4	16.1	18.8	57.1	3.2	5.6	2.0	298	2.9
1e	11.2	11.2	25.1	65.7	3.4	5.8	1.9	295	2.4
2a	11.9	10.5	31.3	78.8	3.4	5.1	2.3	232	1.3
2b	11.3	13.7	23.3	83.3	3.3	5.0	2.3	205	1.4
2c	12.0	17.8	31.3	82.7	3.4	6.0	2.0	193	1.5
2d	11.6	11.1	22.4	57.4	3.2	5.0	2.3	351	2.4
2e	11.1	12.7	22.5	78.9	3.5	4.9	2.3	256	1.9
3a	11.7	6.1	21.0	57.3	3.3	5.2	2.3	171	1.3
3b	11.2	21.6	26.7	74.6	3.3	5.6	2.0	418	2.5
3c	11.3	8.0	20.4	52.9	3.1	5.3	2.1	369	2.1
3d	11.3	18.5	17.3	55.4	3.2	5.0	2.2	425	3.9
3e	11.3	23.3	22.5	63.3	3.4	5.2	2.2	116	1.1
4a	11.8	8.3	27.0	61.2	3.5	4.6	2.6	193	2.3
4b	10.9	13.7	30.0	82.3	3.4	4.7	2.3	297	2.4
4c	11.1	8.8	32.7	87.2	3.4	5.0	2.2	449	2.7
4d	11.3	15.3	20.7	62.7	3.2	4.9	2.3	359	2.7
4e	11.0	10.1	25.4	64.4	3.4	5.2	2.1	280	2.2
5a	11.3	11.1	33.7	68.6	3.4	5.2	2.2	292	2.3
5b	11.1	37.4	25.7	61.9	3.4	5.6	2.0	458	2.8
5c	11.4	7.3	23.8	53.4	3.4	5.8	2.0	602	3.6
5d	11.7	11.4	21.4	49.3	3.2	5.6	2.1	447	4.6
5e	11.1	10.2	16.4	58.0	3.4	5.2	2.1	248	2.0
6a	11.9	21.9	42.4	86.2	3.4	5.8	2.1	467	3.1
6b	10.7	20.8	23.1	64.8	3.3	5.5	1.9	243	1.5
6c	12.6	19.3	24.9	66.3	3.4	6.5	1.9	316	1.5
6d	11.4	5.9	22.1	58.0	3.3	5.6	2.0	249	2.5
6e	11.3	8.8	22.8	59.5	3.4	5.8	2.0	363	2.1
7a	11.5	15.8	28.7	79.0	3.3	5.3	2.2	186	1.3
7b	11.2	13.4	26.2	47.9	3.4	5.7	2.0	399	2.4
7c	11.4	14.7	32.2	81.8	3.3	5.2	2.2	316	2.5
7d	11.5	18.1	20.7	66.8	3.3	5.3	2.2	441	3.4
7e	11.0	13.3	19.6	57.9	3.4	5.4	2.1	304	2.1
Cloudy FC
1a	11.4	8.2	22.0	65.1	3.4	4.4	2.6	490	3.3
1b	11.2	22.1	35.4	104.1	3.4	4.4	2.5	430	4.6
1c	12.1	7.5	19.7	62.5	3.5	5.4	2.2	387	3.4
1d	11.5	16.5	18.8	60.4	3.2	4.5	2.6	640	6.2
1e	11.5	11.6	20.1	60.8	3.5	4.3	2.7	385	3.4
2a	11.6	20.5	21.3	68.4	3.4	4.9	2.4	557	3.4
2b	11.3	26.6	35.1	60.7	3.4	4.7	2.4	490	5.1
2c	11.6	10.8	26.8	65.3	3.4	5.7	2.0	464	2.8
2d	11.7	11.8	20.7	52.9	3.2	5.0	2.3	757	7.1
2e	11.4	10.9	24.1	63.7	3.4	5.4	2.1	633	6.2
Cloudy NFC
1a	11.5	13.0	25.9	76.3	3.3	5.8	2.0	553	3.1
1b	11.2	16.5	24.6	71.4	3.3	5.4	2.1	630	6.4
1c	12.0	10.8	21.3	60.1	3.4	6.4	1.9	1071	7.1
1d	10.8	18.7	19.1	52.2	3.3	5.1	2.1	761	8.4
1e	11.7	11.7	23.9	62.6	3.4	5.4	2.2	648	9.5
2a	11.4	14.8	20.5	70.1	3.4	6.0	1.9	896	11.9
2b	10.7	14.2	15.8	61.5	3.3	5.5	1.9	1169	17.0
2c	10.9	12.6	17.6	63.1	3.3	5.3	2.0	1925	14.9
2d	10.8	15.9	16.5	54.4	3.3	5.0	2.2	1382	16.4
2e	12.1	21.8	24.2	76.6	3.4	4.9	2.5	1026	9.8
3a	11.7	1.8	23.9	70.8	3.3	6.1	1.9	419	3.2
3b	13.7	5.0	33.4	72.1	3.2	7.8	1.8	647	5.7
3c	14.2	3.8	35.7	78.8	3.2	9.5	1.5	666	5.4
3d	13.6	3.9	32.1	77.2	3.4	8.7	1.6	759	6.8
3e	13.3	5.0	31.3	83.6	3.2	9.1	1.5	619	7.7
4a	11.0	3.3	22.2	69.7	3.6	3.5	3.1	380	2.9
4b	11.5	3.0	28.9	84.9	3.6	3.0	3.8	235	1.9
4c	11.3	4.0	31.7	92.1	3.7	3.2	3.6	183	2.1
4d	12.2	5.5	31.8	86.9	3.6	3.5	3.5	341	3.2
4e	13.6	4.9	35.0	83.5	3.5	4.9	2.8	258	2.4
5a	10.6	0.8	24.9	68.8	3.4	4.3	2.5	393	3.5
5b	11.8	4.0	35.8	90.2	3.3	5.2	2.3	686	4.4
5c	13.5	4.1	32.2	76.9	3.3	8.1	1.7	738	4.8
5d	14.9	6.3	38.1	91.2	3.4	5.0	3.0	717	7.4
5e	12.8	4.3	27.5	67.1	3.5	4.8	2.6	290	3.0
6a	11.2	4.2	24.7	69.1	3.5	4.7	2.4	290	2.2
6b	12.2	5.6	25.4	61.6	3.3	5.5	2.2	171	1.4
6c	13.1	3.1	33.9	60.2	3.5	5.1	2.6	274	1.7
6d	12.8	2.0	29.2	77.7	3.1	6.4	2.0	200	2.1
6e	12.9	5.2	31.4	79.5	3.4	5.0	2.6	196	2.1
7a	11.2	22.8	19.0	70.5	3.5	4.8	2.3	522	5.8
7b	11.2	11.9	33.3	95.7	3.5	3.5	3.2	551	6.0
7c	11.4	23.1	24.4	76.2	3.4	4.3	2.7	567	4.0
7d	11.6	11.3	24.7	71.8	3.3	5.3	2.2	648	6.9
7e	12.2	9.9	21.1	74.6	3.7	4.3	2.8	687	8.4
Fresh
1a	11.4	39.6	20.0	80.4	3.4	4.4	2.6	507	3.4
1b	11.7	19.2	13.6	60.3	3.3	6.1	1.9	278	2.7
1c	10.5	14.7	17.6	57.9	3.5	3.7	2.9	360	0.8
1d	11.4	17.8	15.8	67.9	3.4	4.0	2.9	430	4.9
1e	11.1	27.3	16.6	57.6	3.4	4.6	2.4	481	5.1
2a	10.6	19.8	18.3	59.3	3.4	4.4	2.4	483	2.8
2b	10.9	22.1	14.7	52.1	3.4	4.5	2.4	391	3.0
2c	10.9	22.7	14.5	55.5	3.4	4.2	2.6	415	2.0
2d	10.4	18.7	15.3	57.1	3.5	3.0	3.5	437	5.1
2e	11.3	12.2	11.6	63.0	3.4	4.4	2.5	403	4.6
AIJN	min.	5–30	15–35	45–85	—	2.2–7.5	—	—	—
Code of	10.0/	g/L	g/L	g/L		g CA/L
Practice	min.
limits	11.2*

*Minimum TSS limit for NFC juices: 10.0, for FC juices: 11.2.

Table 2. Chemical characteristics of the apple juices in each of the four categories.

	TSS (°Brix)	Sucrose (g/L)	Glucose (g/L)	Fructose (g/L)	pH	TA (g CA/L)	TSS/TA	Total phenolic (mg GAE/L)	TEAC (mM)
Clear FC	11.4^b ± 0.4	14.3^a ± 6.1	25.1^a ± 5.3	67.0^a ± 11.6	3.3^b ± 0.1	5.4^a ± 0.4	2.1^b ± 0.2	322^b ± 104	2.3^b ± 0.7
n = 35	10.6–12.6	5.9–37.4	16.4–42.4	47.9–87.2	3.1–3.5	4.6–6.5	1.6–2.6	116–602	1.1–4.6
Cloudy FC	11.5^ab ± 0.2	14.6^ab ± 6.4	24.4^a ± 6.2	66.4^a ± 13.9	3.4^ab ± 0.1	4.9^a ± 0.5	2.4^ab ± 0.2	523^ab ± 122	4.6^ab ± 1.5
n = 10	11.2–12.1	7.5–26.5	18.8–35.4	52.9–104.1	3.2–3.5	4.3–5.7	2.0–2.7	385–757	2.8–7.1
Cloudy NFC	12.1^a ± 1.1	8.82^b ± 6.4	26.9^a ± 6.1	73.7^a ± 10.7	3.4^a ± 0.1	5.4^a ± 1.6	2.4^ab ± 0.6	614^a ± 372	6.0^a ± 4.1
n = 35	10.6–14.9	0.8–23.1	15.8–38.1	52.2–95.7	3.1–3.7	3.1–9.5	1.5–3.8	171–1925	1.4–17.0
Fresh	11.0^b ± 0.4	21.4^a ± 7.6	15.8^b ± 2.4	61.1^a ± 8.0	3.4^ab ± 0.1	4.3^a ± 0.8	2.6^a ± 0.4	418^ab ± 67	3.4^ab ± 1.4
n = 10	10.4–11.7	12.2–39.6	11.6–20.0	52.1–80.4	3.3–3.5	3.0–6.1	1.9–3.5	278–507	0.8–5.1

TSS: total soluble solids, TA: titratable acidity, TEAC: Trolox equivalent antioxidant capacity.

Different superscripts in the same column indicate significant difference between samples (p ≤ 0.05), determined by Tukey’s test.

Table 3. Loadings for the first four principal components for apple juice samples.

	PC1	PC2	PC3	PC4
TSS	0.479	0.675*	–0.158	–0.177
Sucrose	–0.160	–0.529	0.104	0.754*
Glucose	0.182	0.857*	–0.113	0.275
Fructose	–0.070	0.731*	–0.326	0.473
pH	–0.667*	0.295	–0.394	–0.126
TA	0.922*	0.189	0.191	–0.0004
TSS/TA	–0.849*	0.167	–0.361	–0.114
Total phenolic	0.454	–0.413	–0.755*	0.029
TEAC	0.393	–0.409	–0.794*	–0.013

*Significant loadings.

TSS: total soluble solids, TA: titratable acidity, TEAC: Trolox equivalent antioxidant capacity.

Figure 1. Principal component analysis of the chemical profiles of 90 apple juices, scores plots A: PC1 versus PC2; and B: PC3 versus PC4.

Figure 2. Hierarchical cluster analysis of the chemical profiles of 90 apple juices. Juices: clear FC (red), cloudy FC (green), cloudy NFC (blue), fresh (cyan).

Table 4. Characteristic of the kNN classification model.

	Sensitivity (%)	Specificity (%)	Classification error (%)
Clear FC	91	76	17
Cloudy FC	0	98	51
Cloudy NFC	81	85	17
Fresh	50	100	25

Table 5. Prediction results for the test set samples using kNN classification model.

Actual	Clear FC	Cloudy FC	Cloudy NFC	Fresh
Predicted as
Clear FC	13	4	2	0
Cloudy FC	0	0	0	0
Cloudy NFC	0	1	6	0
Fresh	0	0	0	4