Nutritional Composition and Bioactive Properties of Salicornia brachiata: A Comparison of Drying Methods

Abstract

Objective

Salicornia brachiata, an euhalophyte thriving in saline environments, can be processed into a dried powder (termed bio-salt) from its tender aerial parts. This study aimed to evaluate how three distinct drying methods; freeze-drying (FD), microwave-vacuum drying (MVD) as low temperature drying methods, and heat pump oven drying (HPOD) as a high temperature drying method, affect nutritional composition and bioactivities of S. brachiata. Ultimately, this research aims to identify the most suitable drying approach that retains bioactive and nutritional properties to preserve the health benefits of bio-salt.

Methods

The aerial parts of S. brachiata were washed, air-dried overnight, and then subjected to various drying methods. The proximate composition, colour measurements, mineral composition, and microbial quality of the dried powders were evaluated. The lipid extracts were analyzed using GC-MS and the total phenolic content and antioxidant activity of the resulting powders were assessed.

Results

Among the methods, FD best preserved the plant's color and yielded the highest levels of carbohydrates (42.64%), crude fat (0.88%), and dietary fibers (29.72%). Methanolic extracts of FD powders exhibited the highest phenolic content (43.68 ± 0.04 mg GAE/g DW) and superior antioxidant activity, with IC₅₀ values of 8.72 ± 0.50 µg/mL for the DPPH assay and 19.49 ± 0.76 µg/mL for the ABTS assay, outperforming both MVD and HPOD. The FD extracts contained a higher proportion of unsaturated fatty acids compared to saturated fatty acids. In vitro antibacterial assays revealed that the FD extract at 100 mg/mL demonstrated the strongest inhibition against test bacteria. In an anti-inflammatory assay, FD was identified as the most effective drying method, yielding the lowest IC₅₀ value of 314.78 ± 1.55 µg/mL.

Conclusion

These results suggest that freeze-drying is the most suitable drying method for preserving the bioactive properties and health benefits of bio-salt derived from the aerial parts of S. brachiata.

Materials

Figure 1.
*Salicornia brachiata* plants in the salt marshes of Puttalam, Sri Lanka.
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Figure 2.
Dried powders of *S. brachiata*; (a) MVD, (b) FD, and (c) HPOD.
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Figure 3.
Effect of different drying method on proximate composition of *S. brachiata*. Each bar represents mean ± standard deviation of 3 replicates.
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Figure 4.
Effect of different drying methods on the level of Sodium (Na), Calcium (Ca), Magnesium (Mg), Phosphorous (P), and Potassium (K) in *S. brachiata*. MVD - microwave-vacuum drying, FD - freeze-drying, HPOD - heat pump oven drying. Each bar represents mean ± standard deviation of 3 replicates.
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Figure 5.
Effect of different drying methods on the level of Copper (Cu), Zinc (Zn), Iron (Fe), Arsenic (As), Cadmium (Cd), and Lead (Pb) in *S. brachiata*. MVD - microwave-vacuum drying, FD - freeze-drying, HPOD - heat pump oven drying. Each bar represents mean ± standard deviation of 3 replicates. * < detection limit (0.1 µg/g).
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Figure 6.
Effect of different drying methods on the level of amino acids in *S. brachiata*. MVD - microwave-vacuum drying, FD - freeze-drying, HPOD - heat pump oven drying. Each bar represents mean value of 3 replicates.
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Figure 7.
Effect of different drying methods on total phenolic content (A), total flavonoid content (B), and condensed tannin content (C) in extracts of *S. brachiata*. MVD - microwave-vacuum drying, FD - freeze-drying, HPOD - heat pump oven drying. Each bar represents mean ± standard deviation of 3 replicates.
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Figure 8.
Effect of different drying methods on DPPH (A) and ABTS (B) radical scavenging activity of methanolic extracts of *S. brachiata*. MVD - microwave-vacuum drying, FD - freeze-drying, HPOD - heat pump oven drying, Standard - Butylated hydroxytoluene (BHT). Each bar represents mean ± standard deviation of 3 replicates.
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Figure 9.
Effect of different drying methods on ferric reducing absorbance power values (A) and anti-inflammatory activity (B) of methanolic extracts of *S. brachiata*. MVD - microwave-vacuum drying, FD - freeze-drying, HPOD - heat pump oven drying, Standard - Butylated hydroxytoluene (BHT). Each bar represents mean ± standard deviation of 3 replicates.
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		MVD^†	FD^‡	HPOD^§
Proximate composition (g per 100 g of dry matter)
Moisture		5.23 ± 0.12^b	6.62 ± 0.09^a	4.74 ± 0.10^c
Total ash		38.6 ± 0.19^b	32.9 ± 0.15^c	41.5 ± 0.23^a
Crude protein		9.53 ± 0.09^a	9.55 ± 0.09^a	9.24 ± 0.12^b
Crude fat		0.81 ± 0.06^{a, b}	0.88 ± 0.07^a	0.75 ± 0.02^b
Crude fiber		5.74 ± 0.10^b	7.41 ± 0.14^a	4.85 ± 0.11^c
Total carbohydrate		40.06 ± 0.13^b	42.64 ± 0.13^a	38.90 ± 0.11^c
Total dietary fiber		23.75 ± 0.57^c	29.72 ± 0.50^a	25.57 ± 0.07^b
Salt (as NaCl)		40.30 ± 0.02^a	39.25 ± 0.11^a	41.25 ± 0.11^a
Color measurements
L*		39.74 ± 0.42^c	67.22 ± 0.30^a	41.18 ± 0.20^b
a*		−6.08 ± 0.09^b	−11.72 ± 0.06^c	−0.35 ± 0.11^a
b*		20.48 ± 0.47^b	24.31 ± 0.13^a	17.67 ± 0.32^c
Minerals
Sodium (Na)	mg/g	129.73 ± 0.15^c	143.70 ± 0.44^b	150.20 ± 0.53^a
Calcium (Ca)		2.92 ± 0.05^c	3.39 ± 0.09^a	3.18 ± 0.01^b
Magnesium (Mg)		9.47 ± 0.06^a	9.00 ± 0.03^b	9.40 ± 0.05^a
Phosphorous (P)		16.43 ± 0.31^{a, b}	16.10 ± 0.36^b	17.00 ± 0.30^a
Potassium (K)		14.43 ± 0.06^a	14.57 ± 0.12^a	12.56 ± 0.05^b
Copper (Cu)	µg/g	5.02 ± 0.11^b	5.75 ± 0.20^a	5.88 ± 0.06^a
Zinc (Zn)		7.25 ± 0.08^c	14.69 ± 0.61^a	10.63 ± 0.34^b
Iron (Fe)		38.10 ± 0.61^c	206.23 ± 5.20^a	63.74 ± 1.36^b
Arsenic (As)		0.27 ± 0.61^c	0.31 ± 0.01^b	0.39 ± 0.01^a
Cadmium (Cd)		0.49 ± 0.01^a	0.16 ± 0.00^b	0.15 ± 0.00^b
Lead (Pb)		<0.1 *	<0.1 *	<0.1 *
Microbial quality
Aerobic mesophilic bacteria	CFU/g	1.2 × 10³	2.4 × 10⁴	1.6 × 10⁴
Escherichia coli	MPN/g	n. d	n. d	n. d
Yeast and molds	CFU/g	50	4.5 × 10²	1.5 × 10²
Salmonella spp.	Per 25 g	Absent	Absent	Absent

The Proximate Composition, Color Measurements, Mineral Composition and Microbial Quality of S. brachiata Subjected to Different Drying Treatments.

†

microwave-vacuum drying, ^‡freeze-drying, ^§heat pump oven drying. L* (lightness), a* (green-red), and b* (blue-yellow). The values are the means ± standard deviations for three replicates and those in the same row not sharing the same superscript letter are significantly different from each other (p < 0.05). * Limit of detection µg/g, n. d: not detected.

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Amino acid (AA)*	MVD^†	FD^‡	HPOD^§
Non-essential amino acids (NEAA)
Aspartic acid	61.60 ± 1.50^c	129.47 ± 0.65^a	96.40 ± 1.21^b
Glutamic acid	60.73 ± 1.27^b	71.13 ± 0.40^a	49.97 ± 0.06^c
Serine	81.73 ± 1.01^a	80.40 ± 1.35^a	64.27 ± 1.04^b
Glycine	55.80 ± 1.51^a	47.57 ± 1.27^b	22.73 ± 0.76^c
Arginine	64.90 ± 2.00^b	76.17 ± 0.97^a	51.00 ± 0.46^c
Alanine	43.27 ± 1.31^a	34.80 ± 0.90^c	37.23 ± 1.91^b
Proline	457.13 ± 2.00^a	93.17 ± 1.03^c	322.80 ± 0.36^b
Tyrosine	131.60 ± 1.31^a	106.40 ± 1.25^c	109.63 ± 0.64^b
Cystine	302.20 ± 1.90^a	294.43 ± 1.58^b	271.57 ± 0.87^c
Essential amino acids (EAA)
Histidine	125.47 ± 1.27^b	422.77 ± 2.61^a	97.63 ± 1.16^c
Valine	139.43 ± 1.00^b	112.37 ± 1.66^c	189.23 ± 1.08^a
Methionine	59.90 ± 0.50^a	56.30 ± 1.71^b	49.77 ± 1.50^c
Phenylalanine	90.00 ± 1.28^b	91.50 ± 1.25^b	111.37 ± 1.25^a
Threonine	587.67 ± 3.23^a	78.80 ± 0.60^c	215.53 ± 0.80^b
Isoleucine	166.70 ± 1.00^b	154.43 ± 1.22^c	189.43 ± 0.76^a
Leucine	168.93 ± 1.45^b	121.90 ± 1.51^c	192.40 ± 1.55^a
Lysine	118.60 ± 0.66^a	69.43 ± 1.03^c	107.37 ± 1.37^b
∑ EAA	1456.70	1107.50	1152.73
∑ NEAA	1258.96	933.54	1025.60
EAA/NEAA	1.16	1.19	1.12
EAA/AA	0.54	0.54	0.53

Amino Acid Composition (mg/kg) of S. brachiata Subjected to Different Drying Treatments.

†

microwave-vacuum drying, ^‡freeze-drying, ^§heat pump oven drying. The values are the means ± standard deviations for three replicates and those in the same row not sharing the same superscript letter are significantly different from each other (p < 0.05). * Tryptophan has not been measured.

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Compound name	Common name	Retention time (min)	[% FA/total FA]
			Drying methods
			MVD^†	FD^‡	HPOD^§
Tetradecene		19.5	tr	tr	tr
Hexadecene		22.6	tr	tr	tr
Tridecanoic acid	Myristic acid	22.61	n.d.	n.d.	0.41 ± 0.01
Hexadecanoic acid	Palmitic acid	25.25	18.74 ± 1.71	36.61 ± 6.92	36.27 ± 2.80
Octadecanoic acid	Stearic acid	26.65	2.16 ± 0.38	2.18 ± 0.48	3.47 ± 2.01
Docosanoic acid	Behenic acid	32.17	3.42 ± 1.48	n.d.	n.d.
Tricosanoic acid	Lignoceric acid	35.70	4.13	1.17	tr
∑SFA %			31.26	38.79	40.15
9,12-Octadecadienoic acid	Linoleic acid	27.28	10.59± 1.78	19.13 ± 4.74	17.04 ± 2.46
9,12,15-Octadecatrienoic acid	α-Linolenic acid	27.59	41.21 ± 4.08	40.89 ± 3.84	48.73 ± 9.94
∑USFA %			51.80	60.02	65.77
ω-6/ω-3			0.25	0.47	0.35

GC-MS Analysis of the Lipid Extract Obtained from Dried Powders of S. brachiata Tender Aerial Parts.

†

microwave-vacuum drying, ^‡freeze-drying, ^§heat pump oven drying. Unless otherwise indicated, the match factor for the identified compounds was > 80%. Results are given as [% FA/total FA]. tr: trace amount, n.d.: not detected. Values represent the mean in triplicate (n = 3).

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	MVD^‡	FD^‡	HPOD^§
TPC (mg GAE/g DW)	38.00 ± 0.07^c	43.68 ± 0.04^a	42.86 ± 0.01^b
TFC (mg CE/g DW)	33.78 ± 0.00^c	72.44 ± 0.01^a	52.00 ± 0.00^b
CTC (mg CE/g DW)	14.44 ± 0.15^a	14.32 ± 0.19^a	14.32 ± 0.24^a

Total Phenolic Content (TPC), Total Flavonoid Content (TFC), and Condensed Tannin Content (CTC) in Extracts of S. brachiata Obtained Using Three Drying Methods.

†

microwave-vacuum drying, ^‡freeze-drying, ^§heat pump oven drying. Values represent the mean ± SD in triplicate (n = 3) and those in the same row not sharing the same superscript letter are significantly different from each other (p < 0.05).

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Methanol Extract	DPPH	ABTS	Anti-inflammatory activity (50% stability dose)
	IC₅₀ values (µg/mL)
MVD^†	24.27 ± 1.065^b	32.867 ± 0.42^b	394.36 ± 3.96^b
FD^‡	8.717 ± 0.501^c	19.49 ± 0.76^c	314.78 ± 1.55^c
HPOD^§	39.40 ± 0.13^a	51.75 ± 0.641^a	493.52 ± 1.97^a
Standard	5.29 ± 1.04	37.37 ± 4.87	106.57 ± 9.32

Anti-Inflammatory Activity and Antioxidant Activity (IC₅₀ Values, µg/mL) of Methanol Extracts of S. brachiata Obtained from MVD, FD, and HPOD.

†

microwave-vacuum drying, ^‡freeze-drying, ^§heat pump oven drying. BHT was used as the positive control for DPPH and ABTS assays and Aspirin was used for anti-inflammatory assay. Values represent the mean ± SD in triplicate (n = 3). In each column, different letters indicate significant differences.

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Bacteria strain	Standard (Amoxicillin) 500 µg/mL		S. brachiata aerial parts extracts (mg/mL)				Standard (azithromycin) 0.1 mg/mL
Bacteria strain	Standard (Amoxicillin) 500 µg/mL	Extract	100	50	25	12.5
Escherichia coli	3.00	MVD	3.33	2.44	1.99	1.94	3.10
		FD	3.55	2.51	2.05	1.98
		HPOD	3.53	1.97	1.98	1.98
Staphylococcus aureus	3.10	MVD	2.94	2.38	1.90	1.55	4.00
		FD	3.03	2.54	1.97	1.94
		HPOD	3.02	2.04	1.96	1.33
Bacillus subtilis	1.41	MVD	3.06	2.35	2.00	1.94	4.20
		FD	3.13	2.29	2.07	1.57
		HPOD	3.05	1.98	1.87	1.21
Pseudomonas aeruginosa	1.73	MVD	2.92	2.00	1.55	1.38	4.00
		FD	3.06	2.35	1.96	1.51
		HPOD	3.00	2.05	1.99	1.30

Antibacterial Activity of S. brachiata Extracts Evaluated by Well Diffusion Method.

NS: No sensitivity. Values represent the mean in triplicate (n = 3).

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