Degradation of carotenoids in pumpkin (Cucurbita maxima L.) slices as influenced by microwave vacuum drying

Figures & data

Table 1. Color of pumpkin slices by different drying methods.

Color index	FD	HD	MVD
L*	80.1 ± 0.7^a	73.1 ± 0.4^b	78.5 ± 0.4^a
a*	21 ± 1^b	28 ± 2^a	22.0 ± 0.4^b
b*	55.4 ± 1.1^b	57.3 ± 0.3^a	56.4 ± 0.5^ab
C	59.4 ± 1.5^b	64 ± 1^a	60.6 ± 0.4^ab
H	69.0 ± 0.6^a	64 ± 1^b	68.7 ± 0.5^a
ΔE	—	10 ± 1^a	2.1 ± 0.2^b

Figure 1. Dried pumpkin chips after A: freeze drying; B: hot air drying; and C: microwave vacuum drying.

Figure 2. Effect of different drying methods on total carotenoid contents.

Figure 3. HPLC chromatograms of carotenoids in pumpkin slices under microwave vacuum drying (MVD). Peak identification: 1. neoxanthin, 2. neochrome, 3. violaxanthin, 4. all-trans-lutein, 5. 9-cis-lutein, 6. β-carotene-5, 6-epoxide, 7. α-cryptoxanthin, 8. β-cryptoxanthin, 9. 15-cis-β-carotene, 10. 13-cis-β-carotene, 11. all-trans-α-carotene, 12. 9-cis-α-carotene, 13. all-trans-β-carotene, and 14. 9-β-carotene.

Table 2. Quantitative changes in the carotenoid composition of MVD pumpkin slices under different microwave powers (μg/gDW).

Carotenoid	Microwave power (W/g)
	4	5	6	7	8
Neoxanthin	0.62 ± 0.06^b	0.50 ± 0.05^c	0.9 ± 0.1^a	0.69 ± 0.04^b	0.55 ± 0.02^c
Neochrome	0.54 ± 0.06^c	0.72 ± 0.02^b	0.8 ± 0.1^b	1.14 ± 0.03^a	1.2 ± 0.1^a
Violaxanthin	0.4 ± 0.1^b	0.6 ± 0.2^a	0.56 ± 0.03^a	0.44 ± 0.07^b	0.56 ± 0.06^a
all-trans-lutein	47 ± 1^a	42 ± 3^a	36 ± 3^b	32 ± 4^c	30 ± 4^c
9-cis-lutein	2.2 ± 0.1^b	2.2 ± 0.2^b	2.42 ± 0.05^a	2.18 ± 0.06^b	1.61 ± 0.07^c
β-carotene-5,6-epoxide	1.21 ± 0.01^c	1.63 ± 0.09^c	0.98 ± 0.06^d	2.7 ± 0.1^b	2.9 ± 0.4^a
α-cryptoxanthin	2.12 ± 0.09^b	1.6 ± 0.3^d	2.54 ± 0.06^a	2.0 ± 0.2^b	1.78 ± 0.08^c
β-cryptoxanthin	2.3 ± 0.2^c	2.6 ± 0.1^b	2.58 ± 0.06^b	2.5 ± 0.4^b	2.87 ± 0.08^a
15-cis-β-carotene	6.3 ± 0.3^c	6.5 ± 0.6^c	6.4 ± 0.1^c	9.6 ± 0.2^b	17.0 ± 0.6^a
13-cis-β-carotene	6 ± 1^c	6.8 ± 0.3^c	6.68 ± 0.06^c	17.1 ± 0.3^b	23.1 ± 0.4^a
all-trans-α-carotene	382 ± 19^a	374 ± 2^a	341 ± 10^b	314 ± 4^c	301 ± 1^d
9-cis-α-carotene	2.17 ± 0.05^b	1.58 ± 0.03^c	1.7 ± 0.1^c	2.8 ± 0.3^a	2.7 ± 0.6^a
all-trans-β-carotene	265 ± 20^a	260 ± 5^a	229 ± 16^b	205 ± 10^c	168 ± 12^d
9-cis-β-carotene	5.0 ± 0.2^c	4.5 ± 0.3^d	3.7 ± 0.2^e	7.5 ± 0.1^a	7.0 ± 0.8^b
Total carotenoids	702 ± 24^a	691 ± 13^a	632 ± 34^b	603 ± 7^c	564 ± 14^d

Table 3. Quantitative changes in the carotenoid composition of MVD pumpkin slices under different vacuum levels (μg/g DW).

Carotenoid	Vacuum level (KPa)
	–50	–60	–70	–80	–90
Neoxanthin	0.53 ± 0.03^c	1.21 ± 0.04^a	1.2 ± 0.1^a	0.84 ± 0.06^b	0.89 ± 0.07^b
Neochrome	0.87 ± 0.01^b	0.87 ± 0.07^b	0.94 ± 0.01^b	1.07 ± 0.08^a	1.11 ± 0.06^a
Violaxanthin	0.80 ± 0.00^a	0.7 ± 0.1^b	0.74 ± 0.06^a	0.45 ± 0.08^c	0.42 ± 0.04^c
All-trans-lutein	38 ± 3^b	38 ± 3^b	40 ± 5^a	38 ± 1^b	35.4 ± 0.5^c
9-cis-lutein	2.7 ± 0.2^a	2.36 ± 0.08^b	2.4 ± 0.1^b	0.5 ± 0.1^c	0.47 ± 0.06^c
β-carotene-5,6-epoxide	3.25 ± 0.01^a	2.6 ± 0.2^c	3.0 ± 0.2^b	1.23 ± 0.01^d	2.93 ± 0.04^b
α-cryptoxanthin	1.5 ± 0.3^b	1.56 ± 0.02^b	1.61 ± 0.01^b	1.65 ± 0.01^b	1.84 ± 0.03^a
β-cryptoxanthin	2.0 ± 0.1^b	1.7 ± 0.2^c	1.6 ± 0.2^c	2.14 ± 0.06^b	2.65 ± 0.05^a
15-cis-β-carotene	9.0 ± 0.2^b	9.6 ± 0.6^a	8.3 ± 0.2^c	7.13 ± 0.08^d	7.30 ± 0.06^d
13-cis-β-carotene	10.9 ± 0.3^a	11.1 ± 0.5^a	9.2 ± 0.2^b	7.4 ± 0.4^c	7.50 ± 0.08^c
All-trans-α-carotene	348 ± 3^b	333 ± 11^c	342 ± 7^b	368 ± 6^a	373.1 ± 0.1^a
9-cis-α-carotene	1.20 ± 0.04^c	1.69 ± 0.08^b	1.5 ± 0.2^b	1.60 ± 0.05^b	2.01 ± 0.01^a
All-trans-β-carotene	223 ± 11^a	218 ± 6^ab	218 ± 4^ab	213 ± 3^b	213 ± 4^b
9-cis-β-carotene	5.6 ± 0.3^a	6.1 ± 0.5^a	4.7 ± 0.1^b	3.9 ± 0.2^c	4.6 ± 0.2^b
Total carotenoids	638 ± 11^a	642 ± 12^a	645 ± 4^a	650 ± 11^a	652 ± 3^a