Structural and health functionality of dried goji berries as affected by coupled dewaxing pre-treatment and hybrid drying methods

Figures & data

Table 1. Drying conditions of four different drying methods.

Drying Methods^a	Pretreatments^a	Drying Conditions	Drying Time(h)
FD	DW	First drying stage: at temperature −55°C, vacuum pressure 0.37 kPa; Second drying stage: at temperature 25°C	58 h
	SC	The drying conditions of SC pretreatment was the same as DW	58 h
FD-DIC	DW	Freeze drying at temperature −55°C, vacuum pressure 0.37 kPa for 14 h; explosion puffing temperature of 90°C for 15 min, followed by vacuum drying at −0.1 MPa and 60°C for 1.5 h.	15.5 h
	SC	The drying conditions of SC pretreatment was the same as DW	15.5 h
HAD	DW	The drying time and temperature of air drying was 40°C(2 h)-50°C(4 h)-60°C(12 h), air velocity 1.2 m/s, relative humidity 40%	18 h
	SC	The drying time and temperature of air drying was 40°C(2 h)-50°C(4 h)-60°C(8 h), air velocity 1.2 m/s, relative humidity 40%	14 h
HAD-DIC	DW	Hot air drying: 40°C(2 h)-50°C(4 h); explosion puffing temperature at 90°C for 15 min, followed by vacuum drying at −0.1 MPa and 60°C for 1.5 h.	7.5 h
	SC	Hot air drying: 40°C(2 h)-50°C(2.5 h); explosion puffing temperature at 90°C for 15 min, followed by vacuum drying at −0.1 MPa and 60°C for 1.5 h	6 h

^aDW, distilled water; SC, sodium carbonate; FD, freeze drying; FD-DIC, freeze drying combined with instant controlled pressure drop drying; HAD, hot air drying; HAD-DIC, hot air drying combined with instant controlled pressure drop drying.

Figure 1. Typical DSC thermogram of Goji powder (FD(DW), moisture content = 169g/kg solid).

Table 2. Effect of different drying methods and pretreatments on physicochemical properties of Lycium barbarum.

				Texture
Treatments	Pretreatments	Moisture Content (g/kg)	Tg (°C)	Crispness (PC)	Hardness (N)
Fresh		804 ± 2a	-	-	-
FD	DW	169 ± 5b	8.41 ± 0.04d	6 ± 0e	17.4 ± 0.8ef
	SC	165 ± 5b	8.86 ± 0.05d	8 ± 1d	13.5 ± 0.9f
FD-DIC	DW	137 ± 4cd	20.5 ± 0.6b	17 ± 1b	22 ± 1cd
	SC	127 ± 2d	27.8 ± 0.6a	21 ± 2a	19.6 ± 0.7de
HAD	DW	170 ± 1b	4.6 ± 0.3ef	1 ± 0f	115 ± 2a
	SC	166 ± 2b	7.1 ± 0.2e	2 ± 1f	108 ± 6b
HAD-DIC	DW	160 ± 2b	9.6 ± 0.1c	15 ± 1c	24.7 ± 0.8c
	SC	144 ± 4c	20.9 ± 0.3b	18 ± 0b	24 ± 1c

DW, distilled water; SC, sodium carbonate. Moisture content and T_g are expressed as mean value ± SD (n = 3). Texture values are expressed as mean value ± SD (n = 15). Different letters in the same column indicate significant differences at p < 0.05.

Figure 2. Effect of different drying methods and pretreatments on µCT scanning graphic images of Lycium barbarum. a: FD (DW), b: FD (SC), c: FD-DIC (DW), d: FD-DIC (SC), e: HAD (DW), f: HAD (SC), g: HAD-DIC (DW), h: HAD-DIC (SC). DW, distilled water; SC, sodium carbonate; FD, freeze drying; FD-DIC, freeze drying combined with instant controlled pressure drop drying; HAD, hot air drying; HAD-DIC, hot air drying combined with instant controlled pressure drop drying.

Table 3. Effect of different drying methods and pretreatments on colour values of Lycium barbarum.

		color
Treatments	Pretreatments	L	a	b	ΔE
Fresh		28.26 ± 0.06d	27.8 ± 0.5a	12.3 ± 0.2b
FD	DW	33.0 ± 0.1b	25.7 ± 0.8b	13.0 ± 0.1a	5.3 ± 0.2e
	SC	33.5 ± 0.3a	26.1 ± 0.2b	13.0 ± 0.1a	5.6 ± 0.2e
FD-DIC	DW	28.23 ± 0.04d	19.2 ± 0.2c	9.48 ± 0.06d	9.1 ± 0.2d
	SC	28.7 ± 0.2c	18.9 ± 0.1c	9.7 ± 0.1c	9.3 ± 0.1d
HAD	DW	24.5 ± 0.1f	12.5 ± 0.2f	5.82 ± 0.08g	17.1 ± 0.2a
	SC	25.28 ± 0.07e	13.4 ± 0.2e	6.22 ± 0.02f	15.9 ± 0.1b
HAD-DIC	DW	24.81 ± 0.07f	13.49 ± 0.09e	6.03 ± 0.05f	16.0 ± 0.1b
	SC	25.6 ± 0.2e	14.5 ± 0.3d	6.8 ± 0.2e	14.7 ± 0.4c

DW, distilled water; SC, sodium carbonate. Dates are expressed as mean value ± SD (n = 3). Different letters in the same column indicate significant differences at p < 0.05.

Table 4. Different drying methods and pretreatments on nutritional components and antioxidant activities of Lycium barbarum.

Treatments	Pretreatments	Total carotenoids content (g/kg)	Total Lycium barbarum Polysaccharide content (g/kg)	Total phenolic content (mg GAE/g)	Total flavonoid content (mg RE/g)	DPPH (μmol TE/g)	FRAP (μmol TE/g)	ABTS (μmol TE/g)
Fresh		3.64 ± 0.06a	169 ± 6a	6.7 ± 0.1e	1.78 ± 0.01f	5.8 ± 0.6f	24 ± 1f	28 ± 1g
FD	DW	2.46 ± 0.00c	105 ± 7c	8.2 ± 0.5d	2.2 ± 0.2e	8.5 ± 0.1e	30 ± 3e	50 ± 1c
	SC	2.60 ± 0.05b	107 ± 1c	8.4 ± 0.1d	3.3 ± 0.4d	8.9 ± 0.2e	30 ± 2e	51.8 ± 0.9bc
FD-DIC	DW	2.34 ± 0.06d	135 ± 9b	10.48 ± 0.06bc	3.84 ± 0.04c	11.8 ± 0.6d	39 ± 2bc	53.3 ± 0.8b
	SC	2.43 ± 0.04cd	139.8 ± 0.3b	11.3 ± 0.3a	4.13 ± 0.05b	12.7 ± 0.4c	44 ± 1a	57.6 ± 0.5a
HAD	DW	1.60 ± 0.08g	90 ± 3d	8.1 ± 0.3d	3.2 ± 0.1d	11.8 ± 0.4d	34 ± 1d	40 ± 2f
	SC	1.74 ± 0.07f	91 ± 4d	10.1 ± 0.4c	3.8 ± 0.1c	13.2 ± 0.5c	38 ± 2c	43 ± 2e
HAD-DIC	DW	2.07 ± 0.08e	94.5 ± 0.8d	11.0 ± 0.4ab	4.6 ± 0.2a	14.1 ± 0.3b	41 ± 2abc	45.1 ± 0.4de
	SC	2.32 ± 0.05d	110 ± 1c	11.4 ± 0.3a	4.8 ± 0.1a	15.1 ± 0.2a	42 ± 2ab	45.7 ± 0.8d

DW, distilled water; SC, sodium carbonate. Dates are expressed as dry base. Each value is expressed as mean value ± SD (n = 3). Different letters in the same column indicate significant differences at p < 0.05. GAE: gallic acid equivalent; RE: rutin equivalent; TE: trolox equivalent

Table 5. Correlation analysis on the colour, nutritional properties, and antioxidant activity.

	L	a	b	TCC	LBP	TPC	TFC	DPPH	FRAP	ABTS
L	1	0.996**	0.995**	0.776	0.324	−0.473	−0.618	−0.857**	−0.609	0.634
a		1	0.997**	0.801**	0.358	−0.449	−0.598	−0.845**	−0.595	0.656
b			1	0.804**	0.402	−0.430	−0.597	−0.841**	−0.568	0.687
TCC				1	0.605	0.093	−0.049	−0.396	−0.124	0.812**
LBP					1	0.401	0.170	−0.45	0.351	0.859**
TPC						1	0.865**	0.800**	0.876**	0.228
TFC							1	0.870**	0.815**	−0.0285
DPPH								1	0.807**	−0.328
FRAP									1	0.120
ABTS										1

Note: TCC: total carotenoid content; LBP: total Lycium barbarum polysaccharide (LBP) content; TPC: total phenolic content; TFC: total flavonoid content; **and* mean significant level at 0.01 and 0.05, respectively.