Red Beet and Tarragon Microgreens: Phytochemical Composition, Antioxidant Activity, and Sensory Properties of Cold-Pressed Juices

Abstract

This study investigated the phytochemical composition, antioxidant properties, and sensory characteristics of cold-pressed juices prepared from red beet (Beta vulgaris L.) and tarragon (Artemisia dracunculus L.) microgreens, which remain largely unexplored as raw materials for beverage production. Targeted analyses using spectrophotometric methods and UHPLC-Q-ToF-MS identified betalains as major pigments in beet juice and estragole together with quercetin glycosides in tarragon juice, highlighting their contrasting phytochemical profiles. Beet juice exhibited higher total phenolic 73.48 ± 2.11 mg GAE/100 mL and flavonoid contents 47.26 ± 1.44 mg QE/100 mL, along with betalains 32.85 ± 1.09 mg/100 mL, while tarragon juice contained more chlorophylls 18.73 ± 0.92 mg/100 mL. Antioxidant assays confirmed superior ABTS 132.84 mg TE/100 mL and FRAP 118.42 mg TE/100 mL activities in beet juice, with values strongly correlated to phenolic concentration. Sensory evaluation with trained panelists and a consumer group n = 74 indicated moderate acceptance, with tarragon juice rated slightly higher for taste and overall acceptability despite the stronger visual appeal of beet juice. These findings provide evidence that both beet and tarragon microgreens can serve as complementary sources of bioactive compounds and colorants, supporting their application in the development of cold-pressed functional beverages with distinct nutritional and sensory attributes.

1. Introduction

Microgreens are characterized by exceptionally high concentrations of phytochemicals, which confer pronounced biofunctional potential and health-promoting properties [1]. They represent morphologically immature plants, harvested at the stage of fully expanded cotyledons and the emergence of the first true leaves, and are characterized by exceptionally high concentrations of phytochemicals with recognized biofunctional potential [2,3]. Within this group, Beta vulgaris L. (red beet) microgreens are notable for their intense pigmentation and betalain-rich profile [4,5,6], whereas Artemisia dracunculus L. (tarragon) microgreens are distinguished by a complex phenolic spectrum and unique volatile constituents imparting characteristic aroma and flavor [7,8,9].

To date, the consumption of these microgreens has been primarily limited to fresh form or as specialized culinary garnishes, capitalizing on their high micronutrient density and distinctive organoleptic properties [10,11]. The scientific literature indicates that red beet microgreens accumulate substantial levels of betacyanins, betaxanthins, phenolic acids, and flavonoids [12,13], while tarragon microgreens are rich in phenylpropanoids, flavonoid glycosides, and essential oil components such as estragole and methyl eugenol. Red beet (Beta vulgaris L.) and tarragon (Artemisia dracunculus L.) were selected as target species for this study because they represent contrasting phytochemical reservoirs. Beet microgreens are notable for their betalain-rich pigmentation, phenolic acids, and high radical-scavenging capacity, whereas tarragon provides a unique spectrum of flavonoids and volatile phenylpropanoids such as estragole, which contribute to both antioxidant potential and distinctive herbal aroma [14,15]. Both species exhibit pronounced antioxidant activity; however, systematic comparative studies detailing their phytochemical architecture and linking these profiles to antioxidant mechanisms remain sparse. Cold-pressing is increasingly recognized as a superior extraction technique for plant-based beverages, as it minimizes thermal degradation and oxidation of thermolabile phytochemicals compared to conventional juicing methods [16,17]. This technology ensures higher retention of phenolics, pigments, and vitamins, thereby improving the nutritional and functional quality of juices [18,19]. Their combination therefore offers a model system for evaluating how botanical origin shapes the functional and sensory attributes of cold-pressed juices.

In the realm of product development, microgreens have demonstrated potential as raw materials for health-oriented beverages, particularly cold-pressed juices, owing to minimal thermal degradation of thermolabile bioactives during processing [18,19]. While exploratory work has been conducted on juices derived from broccoli, amaranth, and certain aromatic herbs [20,21], comprehensive analyses of cold-pressed red beet and tarragon microgreen juices-encompassing both targeted metabolite profiling and functional activity assessment-are conspicuously absent.

Furthermore, despite the recognized nutritional and functional merits of microgreens, consumer acceptance remains a decisive factor in their market adoption [22,23]. Existing sensory evaluations have predominantly focused on fresh microgreens, with limited attention given to their juice derivatives. The unique sensory attributes of red beet (earthy-sweet notes, subtle astringency) and tarragon (anise-like sweetness with mild bitterness) may differentially influence hedonic perception and product preference [24,25]. Rigorous sensory characterization of such juices, therefore, is an essential prerequisite for their successful positioning as functional beverages.

We selected red beet and tarragon microgreens as a model complementary pair-betalain and phenolic-rich beet versus chlorophyll- and phenylpropanoid-rich tarragon-hypothesizing additive antioxidant capacity and more balanced sensory attributes in prospective juice formulations. This rationale is supported by our measurements higher TPC/TFC, betalains, ABTS/FRAP in beet; higher chlorophylls and distinct flavonoid/phenylpropanoid signatures in tarragon, as well as divergent sensory strengths.

Against this backdrop, the present study was undertaken to develop cold-pressed juices from red beet and tarragon microgreens and to conduct a comprehensive investigation of their phytochemical composition, antioxidant potential, and sensory acceptance. Additionally, unprocessed microgreens were analyzed to evaluate the retention and changes in bioactive compounds during juice preparation.

2. Materials and Methods

2.1. Microgreen Samples

Experimental samples of red beet (Beta vulgaris L.) and tarragon (Artemisia dracunculus L.) microgreens were cultivated under controlled environmental conditions at the Food Product Research Laboratory, S. Seifullin Kazakh Agro Technical Research University (Astana, Kazakhstan) (Figure 1). The production system employed a vertical farming configuration with multi-tier growth trays. The growth environment was maintained at 22 ± 1 °C, with 85% relative humidity and a 16 h light/8 h dark photoperiod. Illumination was provided by LED lamps (Philips GreenPower, Eindhoven, The Netherlands) at a photosynthetic photon flux density (PPFD) of 220 μmol m⁻² s⁻¹. The microgreens were harvested 12 days after sowing, when cotyledons were fully expanded and the first pair of true leaves appeared.

The growth substrate consisted of sterilized peat-based mixture, which was pre-treated before sowing. Seeds were evenly distributed over the moistened substrate surface and gently pressed to ensure uniform germination. Irrigation was performed using a fine misting system with deionized water, and no nutrient supplementation was applied during the early developmental stages in order to preserve the intrinsic phytochemical profiles. Harvesting was conducted at 12 days post-germination, coinciding with the emergence of the first pair of true leaves and the complete expansion of cotyledons. Plants were cut manually at approximately 2–3 cm above the substrate level using sterilized stainless-steel scissors to minimize mechanical stress and oxidative degradation of bioactives.

2.2. Preparation of Cold-Pressed Microgreen Juices

Freshly harvested microgreens of red beet (RBM) and tarragon (TRM) were immediately weighed and rinsed with chilled deionized water to remove residual particulates (Figure 2). After blotting to remove surface moisture, the plant material was processed using a slow-masticating cold-press juicer (Angel Juicer 8500, Angel Co., Ltd., Busan, Republic of Korea) operating at 82 rpm to minimize thermal and oxidative degradation of thermolabile compounds. The resulting cold-pressed juices—designated RBJ (red beet juice) and TRJ (tarragon juice)—were collected in sterile, amber polypropylene containers to limit photooxidation. Each batch was divided into two fractions: one stored at 4 °C for immediate sensory evaluation ≤ 24 h, and the other centrifuged at 9000× g for 12 min at 4 °C to remove insoluble material. The clarified supernatants were aliquoted into 50 mL polypropylene tubes and stored at −20 °C until spectrophotometric, chromatographic, and antioxidant analyses. No longitudinal shelf-life or nutrient-stability evaluation was performed in this study.

2.3. Preparation of Microgreens for Chromatographic Analysis

Freshly harvested microgreens of red beet (Beta vulgaris L.) and tarragon (Artemisia dracunculus L.) were cut approximately 2–3 cm above the growth substrate and immediately frozen in liquid nitrogen to arrest enzymatic activity and preserve labile phytochemicals. The frozen material was finely ground in a cryogenic mill to obtain a homogeneous powder.

For the extraction of bioactive compounds, 1 g of powdered microgreens was mixed with 10 mL of 80% methanol acidified with 0.1% HCl (w/v ratio 1:10) and subjected to constant agitation for 1 h on a mechanical shaker (Thys 2, MLW Labortechnik GmbH, Seelbach, Germany) [26]. The suspensions were centrifuged at 4000× g for 10 min at 4 °C, and the supernatants were filtered through 0.22 μm PTFE syringe filters. The resulting extracts—designated RBM (red beet microgreens) and TRM (tarragon microgreens)—were used for subsequent qualitative and quantitative analysis of phenolic compounds, betalains (for red beet), and other secondary metabolites by UHPLC-Q-ToF MS.

The selected extraction solvent system was chosen based on its proven efficiency in recovering a wide spectrum of plant phenolics and pigments. For tarragon microgreens, this protocol was also effective for phenylpropanoid derivatives and flavonoid glycosides, whereas for red beet microgreens it allowed high-yield recovery of betacyanins and betaxanthins [27,28,29,30,31].

2.4. Preparation of Cold-Pressed Microgreen Juices for Chromatographic Analysis

Cold-pressed juices obtained from red beet (RBJ) and tarragon (TRJ) microgreens (as described in Section 2.2) were clarified prior to chromatographic analysis using solid-phase extraction (SPE) to remove sugars and colloidal impurities. SPE was performed with CLEAN-UPR C18 cartridges (Unendcapped-PKG50, UCT, Bristol, UK), preconditioned sequentially with 5 mL of acidified methanol (0.1% HCl) and 5 mL of Milli-Q water.

Juice samples were passed through the cartridges under gravity flow, followed by washing with 5 mL of Milli-Q water to remove residual water-soluble impurities. Adsorbed bioactive compounds were eluted with 1 mL of acidified methanol (0.1% HCl), filtered through 0.45 μm PTFE syringe filters, and analyzed by UHPLC-Q-ToF MS.

2.5. UHPLC-Q-ToF MS Analysis of Microgreens

The phytochemical profiles of microgreen extracts (RBM, TRM) and their respective juices (RBJ, TRJ) were determined using an Agilent 1290 Infinity UHPLC system coupled with a 6530C quadrupole time-of-flight mass spectrometer (Q-ToF MS) (Agilent Technologies, Santa Clara, CA, USA), following the protocol of Kostić and Milinčić. The Q-ToF MS was equipped with a dual Agilent Jet Stream electrospray ionization (ESI) source operating in both positive (ESI⁺) and negative (ESI⁻) ionization modes, with parameters identical to those previously reported [32]. Data acquisition and processing were performed using Agilent MassHunter Workstation software (version 10.0, Agilent Technologies, Santa Clara, CA, USA).

Compound identification was based on accurate monoisotopic mass measurements, MS/MS fragmentation patterns, and comparison with authentic standards when available. Phenolic derivatives were quantified using calibration curves prepared with gallic acid (for total phenolics) and quercetin or apigenin (for flavonoid derivatives). Betalain pigments in red beet samples were quantified as betanin equivalents, and the relative proportion of individual betalains was calculated as the percentage of peak area relative to the total betalain area in the chromatogram.

2.6. Total Phenolics, Flavonoids, Betalains, and Chlorophyll Content in Microgreen Juices

The total phenolic content (TPC) and total flavonoid content (TFC) of RBJ and TRJ were determined using the Folin–Ciocalteu assay and the aluminum chloride colorimetric method [26], respectively. For TPC determination, 0.5 mL of appropriately diluted juice was mixed with 2.5 mL of Folin–Ciocalteu reagent and 2.5 mL of 7.5% Na₂CO₃ solution. For TFC determination, 2 mL of diluted juice was sequentially mixed with 0.15 mL of 5% NaNO₂, 0.15 mL of 10% AlCl₃, 1 mL of 1 M NaOH, and 1.2 mL of Milli-Q water. After incubation, absorbance was measured at 760 nm (TPC) and 510 nm (TFC) using a UV-Vis spectrophotometer (HALO DB-20S, Dynamica Scientific Ltd., Livingston, UK). TPC results were expressed as mg gallic acid equivalents (mg GAE/100 mL juice) and TFC results as mg quercetin equivalents (mg QE/100 mL juice).

For TPC (Folin–Ciocalteu) and TFC (AlCl₃ colorimetry), calibration curves were prepared with gallic acid (GA) and quercetin (QE), respectively. Eight-point external calibrations were used: 5–200 mg/L GA and 2.5–100 mg/L QE, yielding linearity of R² ≥ 0.998. Limits of detection and quantification, estimated as 3.3 σ/S and 10 σ/S, were 1.1/3.3 mg/L for TPC and 0.8/2.4 mg/L for TFC. Cold-pressed juices were diluted (1:10–1:40) to keep absorbance within the linear range; reagent blanks were run with each batch and a QC check standard was read every ten samples. Method validation for these matrices was performed via standard addition and matrix-matched calibration: spike recoveries were 95–104%, with no significant matrix effect (slope ratios 0.98–1.03). Precision was ≤3% RSD (intra-day) and ≤5% RSD (inter-day, n = 6). Results are expressed as mg GAE/100 mL (TPC) and mg QE/100 mL (TFC).

For red beet juice, total betacyanins and betaxanthins were quantified according to Stintzing and Schieber [33]. The absorbance of appropriately diluted samples was measured at 485 nm (betaxanthins), 536 nm (betacyanins), and 650 nm (background correction). Concentrations were calculated using the formula:

$$\mathrm{Betaxanthins} \left(\mathrm{Betacyanins}\right) {\displaystyle \frac{\mathrm{m}\mathrm{g}}{100 \mathrm{m}\mathrm{L}}}={\displaystyle \frac{A\times DF\times MW\times 100}{\mathsf{\epsilon }\times i}}$$

(1)

where A = A485 − A650 for betaxanthins and A = A536−A650 for betacyanins; DF—dilution factor; MW—molecular weight (339 g/mol for betaxanthins, 550 g/mol for betacyanins); ε—molar extinction coefficient (48,000 for betaxanthins, 60,000 for betacyanins); i—optical path length (cm).

Total chlorophyll a and b in both juices were quantified according to Ali and Popović [34]. Juices were diluted with 80% acetone, and absorbance was recorded at 645 nm and 663 nm. Concentrations were calculated as:

$$\mathrm{Chlorophyll} \mathrm{a} (\mathrm{mg}/100 \mathrm{mL}) = {\displaystyle \frac{\left(12.71\times A_{663}-2.59\times A_{645}\right)\times DF}{10}}$$

(2)

$$\mathrm{Chlorophyll} \mathrm{b} (\mathrm{mg}/100 \mathrm{mL})={\displaystyle \frac{\left(22.9\times A_{645}-4.68\times A_{663}\right)\times DF}{10}}$$

(3)

where DF is the dilution factor, and A refers to the absorbance at the specified wavelengths.

2.7. Antioxidant Properties of Cold-Pressed Microgreen Juices

The antioxidant capacity of RBJ and TRJ was assessed by three complementary spectrophotometric assays: DPPH radical scavenging activity, ABTS radical cation scavenging activity, and ferric reducing antioxidant power (FRAP) [26,35]. For the DPPH assay, 0.1 mL of diluted juice was mixed with 1.9 mL of freshly prepared DPPH methanolic solution and incubated in the dark for 30 min, after which absorbance was measured at 515 nm. For the ABTS assay, 0.03 mL of diluted juice was added to 3 mL of ABTS working solution, incubated for 6 min, and absorbance was read at 734 nm. The FRAP assay was performed by mixing 0.1 mL of juice with 0.3 mL of Milli-Q water and 3 mL of FRAP reagent, followed by incubation at 37 °C for 40 min. Absorbance was measured at 593 nm. In all cases, Trolox was used as the reference standard, and results were expressed as mg Trolox equivalents (TE) per 100 mL juice.

Antioxidant assays (DPPH, ABTS, FRAP) were performed on three independent juice batches per microgreen (biological replicates), each measured in triplicate. Reagent blanks were used for background correction. Trolox was used to construct multi-point calibration curves in each run and as a positive control; results are expressed as mg TE/100 mL. Precision across triplicates was ≤5% RSD.

2.8. Sensory Properties of Cold-Pressed Microgreen Juices

The sensory study was approved by the Ethics Committee of the Faculty of Technology, S. Seifullin Kazakh Agro Technical Research University (Approval No. 1, 30 July 2025) and conducted in accordance with the Declaration of Helsinki and relevant ISO standards. Testing took place in an ISO 8589:2007 [36]-compliant facility (individual booths, standardized white illumination, odor-free, noise-controlled). Fresh RBJ and TRJ were served (20 mL, 8 ± 1 °C) in identical odorless glassware, coded with random three-digit identifiers, and presented monadically in randomized, counterbalanced order (AB/BA); palate cleansing (room-temperature water, unsalted crackers) and rest intervals minimized carry-over. The trained panel comprised 10 assessors selected and trained per ISO 8586:2023 [37] after a 3-week calibration (1 × 2 h/week). Assessors, blinded to identity, rated appearance, odor, mouthfeel (texture), and taste on a 0–5 category scale (0 = unsatisfactory; 5 = excellent). Overall quality was calculated as a weighted index using importance coefficients (appearance = 1, odor = 6, mouthfeel = 5, taste = 8); results are mean ± SD. A consumer test (ISO 11136:2014 [38]) assessed overall acceptability under equivalent serving and blinding conditions; the panel comprised 74 regular consumers of vegetable-based beverages (57% male, 43% female; mean age 29 years). Inclusion criteria were habitual consumption of vegetable beverages and absence of sensory impairments, oral dysfunction, or relevant health issues; all participants were ≥18 years, provided written informed consent, no personally identifiable information was collected, and data were analyzed in aggregate. Trained-panel data were analyzed by repeated-measures ANOVA (product fixed; assessor random), consumer scores by one-way ANOVA; assumptions were checked (Shapiro–Wilk, Levene), p < 0.05, with Duncan’s post hoc where appropriate.

2.9. Physicochemical Analyses

Moisture content. Moisture was determined by the oven-drying method to constant weight according to AOAC 934.06 (AOAC, 2005). Approximately 5 g of juice sample was dried at 105 °C for 24 h, and the results were expressed as percentage moisture content.

Total soluble solids (TSS). TSS was measured using a digital refractometer (Atago PAL-1, Tokyo, Japan) at 20 °C, and the values were reported in degrees (°).

pH. The pH was determined directly in fresh juice using a calibrated digital pH meter (Mettler Toledo, Greifensee, Switzerland) at room temperature following AOAC 981.12.

Titratable acidity. Titratable acidity was measured by titrating juice samples with standardized 0.1 N NaOH solution using phenolphthalein as an indicator until a faint pink endpoint was reached (AOAC 942.15). Results were expressed as grams of citric acid per 100 mL of juice.

Total and individual sugars. Total sugars were quantified using the phenol–sulfuric acid method, with glucose as a standard, and results were expressed as g/100 mL. Individual sugars (glucose and fructose) were determined by high-performance liquid chromatography (HPLC, Agilent 1260 Infinity, Santa Clara, CA, USA) equipped with a refractive index detector and a Rezex RCM-Monosaccharide Ca²⁺ column (300 × 7.8 mm, Phenomenex, Torrance, CA, USA). Deionized water was used as the mobile phase at a flow rate of 0.6 mL/min, with the column maintained at 80 °C. Identification and quantification were performed by comparison with authentic glucose and fructose standards.

All experiments were conducted on three independent biological replicates per species. For each biological replicate, spectrophotometric assays TPC, TFC, betalains, chlorophylls, DPPH, ABTS, FRAP and physicochemical measurements were performed in technical triplicate. UHPLC-Q-ToF-MS analyses were run for each biological replicate with duplicate injections, using external calibration with authentic standards where available and pooled QC injections at regular intervals.

The analytical part followed a randomized complete block design (RCBD) with species beet, tarragon as the fixed factor and batch as the blocking factor. Sensory testing used the procedures described in Section 2.8; samples were presented monadically in randomized, counterbalanced order (AB/BA) to minimize positional effects. These procedures ensured statistical robustness for both analytical and sensory datasets.

2.10. Statistical Analysis

Data from proximate composition, spectrophotometric assays, chromatographic quantifications, and antioxidant tests are reported as mean ± SD with n = 3 biological replicates per species; within each biological replicate, technical triplicates were averaged. RCBD one-way ANOVA was applied with species as the fixed factor and batch as the blocking factor. Assumptions were checked by Shapiro–Wilk (normality) and Levene’s test (homoscedasticity). When the block term was not significant, it was removed and a fixed-effects one-way ANOVA was reported. Post hoc comparisons used Duncan’s multiple range test at p < 0.05. Pearson’s correlations (p < 0.05) were computed between phytochemical metrics and antioxidant outcomes.

For sensory data, trained-panel attribute scores were analyzed by repeated-measures ANOVA (product as fixed effect; assessor as random effect). Consumer hedonic scores (n = 74) were analyzed by one-way ANOVA (product as fixed effect); linear mixed models with participant as a random effect were used as a robustness check. Statistical analyses were performed in IBM SPSS Statistics v25.

3. Results and Discussion

3.1. UHPLC-Q-ToF MS Profile of Bioactive Compounds of Beet and Tarragon Microgreens

The comprehensive profiling of secondary metabolites in Beta vulgaris (beet) and Artemisia dracunculus (tarragon) microgreens was performed using ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QToF-MS) [39,40]. The analysis enabled the identification of key phenolic acids, flavonoid glycosides, and species-specific phytoconstituents based on retention time (RT), molecular formula, calculated and exact masses, and fragmentation patterns. The extraction conditions were optimized for each species to ensure maximum recovery of thermolabile and polar compounds-acidified 80% methanol at room temperature for beet microgreens [41] and 70% boiling methanol under thermoshaker agitation for tarragon microgreens [15,42].

Table 1. Characterization and quantification (mg/100 g FW) of phenolic and other bioactive compounds detected in beet and tarragon microgreens by UHPLC-QToF-MS.

No	Compound Name	RT	Formula	Calculated Mass	m/z	Exact Mass	mDa	MS Fragments (% Base Peak)	Beet (mg/100 g)	Tarragon (mg/100 g)
1	Betanin (betacyanin)	2.15	C24H26N2O13	562.1379	551.1502	562.1427	−4.80	389 (100), 307, 345, 178	82.45 ± 1.12	-
2	Caffeic acid hexoside	2.83	C15H14O9	354.0583	355.0667	354.0615	−3.20	179 (100), 161, 135, 119	12.34 ± 0.26	8.91 ± 0.15
3	Ferulic acid hexoside	3.47	C16H18O9	370.0896	371.0979	370.0924	−2.75	193 (100), 178, 149	7.84 ± 0.19	6.12 ± 0.14
4	p-Coumaric acid	4.12	C9H8O4	180.0423	181.0506	180.0450	−3.95	163 (100), 145, 119	4.65 ± 0.08	5.03 ± 0.11
5	Quercetin-3-O-glucoside	4.76	C21H20O12	464.0955	463.0882	464.0955	−4.22	301 (100), 179, 151	9.44 ± 0.16	11.02 ± 0.22
6	Kaempferol-3-O-rutinoside	5.54	C27H30O15	594.1587	593.1512	594.1587	−4.60	285 (100), 255, 227	6.25 ± 0.13	4.92 ± 0.10
7	Estragole (methyl chavicol)	6.02	C10H12O	164.0837	149.0969	178.0990	−2.90	164 (100), 149, 135	-	34.18 ± 0.54
8	Chlorogenic acid	6.45	C16H18O9	354.0951	197.0818	196.0770	−3.30	179 (100), 161, 135	10.91 ± 0.17	7.45 ± 0.14
9	Isorhamnetin-3-O-glucoside	5.89	C22H22O12	478.1112	479.1195	478.1112	−3.10	315 (100), 300, 271	3.87 ± 0.06	2.45 ± 0.05
10	Rutin (quercetin-3-O-rutinoside)	5.72	C27H30O16	610.1536	611.1609	610.1536	−2.85	301 (100), 271, 179	5.63 ± 0.12	8.32 ± 0.16
11	Apigenin-7-O-glucoside	4.88	C21H20O10	432.1056	433.1139	432.1056	−3.00	271 (100), 253, 151	2.94 ± 0.05	6.15 ± 0.11
12	Luteolin-7-O-glucoside	4.94	C21H20O11	448.1005	449.1088	448.1005	−3.40	285 (100), 255, 151	3.18 ± 0.06	4.09 ± 0.07
13	Gallic acid	3.12	C7H6O5	170.0215	171.0298	170.0215	−3.70	125 (100), 107, 79	1.86 ± 0.03	2.11 ± 0.04
14	Syringic acid	3.26	C9H10O5	198.0520	199.0603	198.0520	−3.60	183 (100), 155, 127	1.94 ± 0.03	2.68 ± 0.05
15	Sinapic acid	3.78	C11H12O5	224.0630	225.0713	224.0630	−3.25	209 (100), 181, 153	2.55 ± 0.04	2.13 ± 0.04
16	Vanillic acid	3.08	C8H8O4	168.0423	169.0506	168.0423	−3.80	153 (100), 125, 97	2.21 ± 0.04	3.02 ± 0.05
17	Myricetin-3-O-glucoside	4.84	C21H20O13	480.0853	481.0936	480.0853	−3.15	317 (100), 299, 271	2.12 ± 0.04	3.45 ± 0.06
18	Naringenin	4.66	C15H12O5	272.0685	273.0768	272.0685	−3.50	153 (100), 119, 93	1.45 ± 0.03	2.74 ± 0.05
19	Rosmarinic acid	5.02	C18H16O8	360.0846	361.0929	360.0846	−3.40	179 (100), 161, 135	1.98 ± 0.03	7.92 ± 0.12
20	Diosmetin-7-O-glucoside	5.31	C22H22O11	462.1163	463.1246	462.1163	−3.20	301 (100), 286, 258	1.22 ± 0.02	2.54 ± 0.04
21	Vitexin (apigenin-8-C-glucoside)	4.43	C21H20O10	432.1056	433.1139	432.1056	−3.00	311 (100), 283, 255	2.84 ± 0.05	3.62 ± 0.07
22	Isovitexin (apigenin-6-C-glucoside)	4.39	C21H20O10	432.1056	433.1139	432.1056	−3.00	311 (100), 283, 255	2.41 ± 0.05	3.11 ± 0.06

summarizes the identified compounds, highlighting their distribution between the two species. Notably, beet microgreens exhibited betalain pigments such as betanin, while tarragon microgreens were distinguished by estragole, a major volatile phenylpropanoid [43,44]. Both species shared several phenolic acids and flavonoid derivatives, suggesting overlapping yet distinct phytochemical profiles that may contribute synergistically to their functional properties.

The comprehensive chemical profiling of beet (Beta vulgaris L.) and tarragon (Artemisia dracunculus L.) microgreens was carried out using UHPLC-QToF-MS to identify and quantify the principal phenolic acids, flavonoids, and other bioactive metabolites [2]. This approach enables high-resolution separation and precise mass detection, allowing the differentiation of structurally similar compounds and the assessment of their relative abundance in fresh plant material. The analysis revealed a diverse phytochemical spectrum, including betalains (specific to beet), hydroxycinnamic acid derivatives, flavonoid glycosides, and unique volatile phenylpropanoids such as estragole in tarragon. For each compound, retention time (RT), molecular formula, calculated and exact mass, mass deviation (mDa), and characteristic MS fragmentation patterns were recorded, providing reliable identification supported by the literature and spectral libraries. The quantification, expressed as mg per 100 g fresh weight (FW), highlights marked differences between the two microgreen species, reflecting their distinct biosynthetic pathways and potential functional properties relevant to antioxidant, anti-inflammatory, and organoleptic characteristics.

As expected, betanin (betacyanin) was exclusively detected in beet microgreens (RT 2.15 min), with a characteristic m/z 551.1502 and dominant fragment at m/z 389, confirming its identity. This compound is responsible for the intense red-violet pigmentation and is well-documented for potent radical scavenging and anti-inflammatory activities [33,45]. Its absence in tarragon underscores the taxonomic specificity of betalain biosynthesis to the Caryophyllales order [46].

Both species shared caffeic acid hexoside (RT 2.83 min) and ferulic acid hexoside (RT 3.47 min), with similar fragmentation patterns (base peaks at m/z 179 and m/z 193, respectively). However, beet microgreens exhibited slightly higher estimated concentrations, suggesting an active phenylpropanoid pathway complementing betalain synthesis. The presence of p-coumaric acid (RT 4.12 min) in both species, with base peak at m/z 163, indicates a shared biosynthetic precursor role in lignin, flavonoid, and hydroxycinnamate ester production [4].

Quercetin-3-O-glucoside (RT 4.76 min) and kaempferol-3-O-rutinoside (RT 5.54 min) were present in both microgreens, although fragmentation data (m/z 301 and m/z 285 as base peaks, respectively) suggested variable glycosylation patterns influencing their solubility and bioavailability. These flavonol glycosides contribute significantly to antioxidant capacity, vascular protection, and modulation of inflammatory signaling pathways [47].

A notable difference was the exclusive detection of estragole (methyl chavicol, RT 6.02 min) in tarragon microgreens, characterized by its base peak at m/z 164, a hallmark of its methoxy-substituted phenylpropanoid structure. Estragole contributes to the characteristic anise-like aroma of tarragon and exhibits antimicrobial and potential chemopreventive properties, although its toxicological profile warrants controlled intake [48].

Both species contained chlorogenic acid (RT 6.45 min, m/z 197.0818), a well-recognized phenolic ester with documented antioxidant, antidiabetic, and neuroprotective functions. Its presence in both microgreens enhances their functional food potential, particularly in mitigating oxidative stress-related pathologies [49].

Overall, beet microgreens displayed a broader diversity of water-soluble pigments and hydroxycinnamic acid derivatives, aligning with their betalain-rich metabolic background. In contrast, tarragon microgreens presented a more specialized profile featuring volatile phenylpropanoids, which may impart stronger aromatic qualities and antimicrobial action but lower pigment-driven antioxidant activity.

The integration of these phytochemicals contributes to the overall nutraceutical value of both species, suggesting complementary applications in functional food formulations: beet microgreens as a pigment- and polyphenol-rich antioxidant source, and tarragon microgreens as a flavor-enhancing, antimicrobial, and bioactive additive.

3.2. Total Phenolic, Flavonoid, Betalain, and Chlorophyll Content in Cold-Pressed Microgreen Juices

Figure 3 presents the spectrophotometrically determined total phenolic content (TPC, expressed as mg gallic acid equivalents [GAE]/100 mL) and total flavonoid content (TFC, expressed as mg quercetin equivalents [QE]/100 mL) [4]. Figure 4 shows the quantification of betalain pigments, including betacyanins and betaxanthins (mg/100 mL), which are responsible for the characteristic red-purple and yellow coloration, respectively [50]. Figure 5 illustrates the levels of total chlorophylls, chlorophyll a, and chlorophyll b (mg/100 mL), which contribute to the green pigmentation and photosynthetic capacity of the microgreens. Values represent means ± standard deviations (n = 3) [51]. Different lowercase letters indicate significant differences between microgreen juices according to Duncan’s test (p < 0.05).

The cold-pressed beet microgreen juice (BMJ) and tarragon microgreen juice (TMJ) demonstrated distinct phenolic profiles. The total phenolic content (TPC) of BMJ reached 73.48 ± 2.11 mg GAE/100 mL, significantly higher (p < 0.05) than that of TMJ (59.12 ± 1.87 mg GAE/100 mL) [2]. This difference is consistent with the chromatographic results showing higher concentrations of phenolic acids, particularly caffeic and ferulic acid derivatives, in beet microgreens. The total flavonoid content (TFC) followed a similar trend, with BMJ exhibiting 47.26 ± 1.44 mg QE/100 mL compared to 39.84 ± 1.27 mg QE/100 mL in TMJ [22]. Despite both species containing flavonoid glycosides, the higher quercetin and kaempferol derivatives in BMJ likely account for its superior TFC values.

Betalains were a major pigment group in BMJ, with total concentrations of 32.85 ± 1.09 mg/100 mL, predominantly composed of betacyanins (23.61 ± 0.87 mg/100 mL) and betaxanthins (9.24 ± 0.36 mg/100 mL). As expected, betalains were absent in TMJ, reflecting its botanical composition [50]. The betalain levels in BMJ align with the literature values reported for young Beta vulgaris tissues and confirm that beet microgreens can be considered a concentrated dietary source of these nitrogen-containing pigments known for antioxidant, anti-inflammatory, and potential chemopreventive properties.

In contrast, TMJ exhibited a markedly higher total chlorophyll content (18.73 ± 0.92 mg/100 mL) compared to BMJ (12.46 ± 0.64 mg/100 mL), with chlorophyll a being the dominant form in both samples. The chlorophyll a:b ratio was approximately 2.5 in both microgreen juices, consistent with actively photosynthesizing young plant tissues. The higher chlorophyll levels in TMJ may be attributed to its lighter pigmentation from phenolic and aromatic compounds, which allows for more efficient light absorption by chlorophylls [52].

The colorimetric differences between the two juices are clearly associated with pigment composition: BMJ’s intense red-purple hue is driven by betalains, while TMJ’s vivid green shade is due to its higher chlorophyll content [53]. This pigment-specific profile has implications not only for sensory appeal but also for functional food development, as these pigment classes provide distinct antioxidant and bioactive contributions [41].

From a nutritional and functional standpoint, both beet and tarragon microgreen juices present valuable phytochemical profiles, but with complementary bioactive profiles. BMJ is more suitable as a natural source of betalains and phenolic acids, potentially enhancing antioxidant and anti-inflammatory capacity. TMJ, on the other hand, offers higher chlorophyll content alongside moderate phenolic and flavonoid levels, which may contribute to detoxification and photoprotective effects. Combining these microgreen juices could yield a product with a balanced phytochemical spectrum and a visually appealing color blend.

3.3. Antioxidant Properties of the Cold-Pressed Microgreen Juices

The antioxidant assays revealed distinct differences in the radical scavenging and reducing power of beet microgreen juice (BMJ) and tarragon microgreen juice (TMJ). In the ABTS assay, BMJ demonstrated significantly higher activity (132.84 mg TE/100 mL) compared to TMJ (109.47 mg TE/100 mL, p < 0.05) [28]. This suggests that beet microgreens possess a greater abundance of hydrophilic antioxidants, likely due to their high betalain and phenolic content, which efficiently react with the polar ABTS radical cation [4].

In contrast, the DPPH scavenging values were markedly lower for both juices-18.94 mg TE/100 mL for BMJ and 15.82 mg TE/100 mL for TMJ-corresponding to approximately a seven-fold reduction compared to ABTS values. This trend is consistent with the higher polarity of the bioactive compounds present, which display limited reactivity toward the more hydrophobic DPPH radical [54]. These findings align with previous reports on microgreens such as wheatgrass and amaranth, where ABTS activity consistently exceeded DPPH values due to the predominance of water-soluble antioxidants.

The FRAP assay further emphasized the strong reducing potential of BMJ (118.42 mg TE/100 mL) relative to TMJ (102.16 mg TE/100 mL) [55]. The correlation analysis revealed that FRAP values were positively associated with total phenolic content (r = 0.97) and total flavonoid content (r = 0.94), suggesting that phenolic compounds were the principal contributors to electron-donating capacity [56].

Overall, beet microgreen juice exhibited superior antioxidant activity in all assays, likely reflecting its higher betalain and phenolic acid concentrations. Tarragon microgreen juice, while exhibiting comparatively lower values, still demonstrated considerable antioxidant potential, which may be attributed to its unique flavonoid profile, particularly apigenin derivatives and hydroxycinnamic acids [49]. These results underscore the potential of both microgreens as functional ingredients for health-promoting beverages, with beet microgreens offering stronger radical scavenging capacity and reducing power. The elevated ABTS scavenging activity and FRAP values observed in beet microgreen juice are in strong agreement with its higher total phenolic content and the presence of betalain pigments, particularly betanin. These compounds are well documented for their high electron-donating capacity and radical neutralization potential, which explains the superior antioxidant performance of beet compared to tarragon.

3.4. Sensory Properties of Cold-Pressed Microgreen Juices

The results of the sensory evaluation of beet and tarragon microgreen juices are presented in

Table 2. Sensory quality attributes and overall consumer acceptability of cold-pressed beet (BMJ) and tarragon (TMJ) microgreen juices.

Attribute	Beet (BMJ)	Tarragon (TMJ)
Appearance	4.9 ± 0.3	4.1 ± 0.4
Odor	4.2 ± 0.2	4.4 ± 0.3
Texture	4.3 ± 0.2	4.8 ± 0.2
Taste	3.4 ± 0.3	3.9 ± 0.3
Overall quality	3.6 ± 0.2	4.3 ± 0.3
Overall acceptability (hedonic)	5.2 ± 0.4	6.1 ± 0.3

. The mean scores for odor and texture did not differ significantly between the two juices. Tarragon juice achieved the highest score for texture (4.8), mainly due to its clear appearance and lack of colloidal turbidity, whereas beet juice scored slightly lower (4.3). The odor of both juices was evaluated as characteristic of the corresponding plant species, with beet juice described as earthy and slightly sweet, and tarragon juice as herbal and anise-like [57].

In terms of appearance, beet juice received a significantly higher score (4.9, p < 0.05) than tarragon juice (4.1). Evaluators highlighted the attractive red-violet coloration of beet juice, attributed to its high betalain content, while the greenish-brown hue of tarragon juice was considered less appealing. Taste scores were somewhat lower: beet juice received 3.4, largely due to its earthy and slightly bitter aftertaste, while tarragon juice received 3.9, with comments pointing to mild astringency and herbal sharpness [7].

The overall quality scores ranged between 3.6 (beet juice) and 4.3 (tarragon juice), indicating moderate acceptability. According to evaluator comments, the color of beet juice enhanced its visual appeal, but its taste limited consumer acceptance. Conversely, tarragon juice benefited from a more pleasant mouthfeel and herbal aroma, but was penalized for less attractive coloration.

The results of consumer acceptance testing are presented in Table 2. The overall acceptability of the juices ranged from 5.2 (“neither like nor dislike”) for beet to 6.1 (“slightly like”) for tarragon. The hedonic test showed that overall acceptability was most strongly correlated with taste (r = 0.764) and odor (r = 0.623), suggesting that these sensory attributes had the greatest influence on consumer preference. Similarly to previous reports on microgreen-based juices, the intense red color of beet juice contributed positively to appearance scores, while the herbal notes of tarragon were favored in overall consumer acceptance.

In addition to phytochemical and antioxidant characterization, the basic physicochemical properties of cold-pressed beet and tarragon microgreen juices were determined (

Table 3. Physicochemical properties of cold-pressed beet (BMJ) and tarragon (TMJ) microgreen juices.

Parameter	Beet (BMJ)	Tarragon (TMJ)	p-Value
Moisture (%)	91.2 ± 0.4	89.5 ± 0.5	0.012
TSS (°Brix)	6.8 ± 0.2	7.3 ± 0.3	0.021
pH	5.42 ± 0.05	5.18 ± 0.04	0.009
Titratable acidity (g citric acid/100 mL)	0.34 ± 0.02	0.41 ± 0.03	0.033
Total sugars (g/100 mL)	5.8 ± 0.2	6.2 ± 0.3	0.087
Glucose (g/100 mL)	2.1 ± 0.1	2.4 ± 0.1	0.041
Fructose (g/100 mL)	1.9 ± 0.1	2.0 ± 0.1	0.164

).

Moisture content was slightly higher in BMJ 91.2 ± 0.4% compared to TMJ 89.5 ± 0.5%, which is consistent with the general range reported for vegetable-based juices 90–92% [58]. Conversely, the total soluble solids (TSS) were marginally higher in TMJ 7.3 ± 0.3° than in BMJ 6.8 ± 0.2°, indicating a slightly greater accumulation of soluble metabolites in tarragon juice, which could influence both taste and potential concentration yield during processing. Both juices exhibited mildly acidic pH values BMJ 5.42 ± 0.05; TMJ 5.18 ± 0.04, falling within the expected range of 5.0–5.6 for vegetable-based beverages [16]. The titratable acidity was somewhat higher in TMJ 0.41 ± 0.03 g citric acid/100 mL than in BMJ 0.34 ± 0.02 g citric acid/100 mL, suggesting that tarragon juice may provide a sharper taste perception, consistent with its characteristic herbal profile. Total sugar concentration was 5.8 ± 0.2 g/100 mL for BMJ and 6.2 ± 0.3 g/100 mL for TMJ, aligning with previously reported sugar levels in cold-pressed leafy vegetable juices 5–7 g/100 mL [53]. In both juices, glucose and fructose contributed in nearly equal proportions, which indicates balanced sweetness without dominance of a single monosaccharide. From a technological perspective, these parameters are valuable for industrial applications. Moisture and TSS content are critical determinants for juice concentration and storage stability, while acidity and sugar profiles directly affect flavor balance, consumer perception, and microbial safety.

4. Conclusions

In summary, the cold-pressed juices obtained from beet and tarragon microgreens demonstrated distinct phytochemical and functional characteristics. Beet microgreens and their juices were particularly rich in betalains, mainly betanin and decarboxy-betanin, which contributed to the intense red coloration and high antioxidant activity. In addition, beet juice contained higher levels of phenolic acids such as caffeic and ferulic acid derivatives, which supported its radical scavenging and reducing capacities. Tarragon microgreen juice, in contrast, was devoid of betalains but exhibited higher chlorophyll levels and a unique profile of flavonoids and hydroxycinnamic acid derivatives. Estragole and quercetin glycosides were detected as key bioactive compounds in tarragon, providing characteristic herbal and anise-like sensory notes. Although the phenolic content of tarragon juice was lower than that of beet, its antioxidant potential remained considerable, reflecting the contribution of flavonoids and chlorophylls. Both juices exhibited strong ABTS scavenging activity and moderate ferric reducing antioxidant power (FRAP), indicating their potential as functional beverages with health-promoting properties. However, differences in sensory attributes affected consumer perception. Beet juice scored highly for appearance due to its vibrant color but received lower ratings for taste owing to its earthy and slightly bitter flavor. Tarragon juice was judged more favorably in terms of texture and overall acceptability, although its greenish hue was less attractive to some evaluators. Taken together, these findings suggest that beet and tarragon microgreens can serve as complementary raw materials for the development of novel cold-pressed functional beverages. Future research should expand comparative analyses across microgreens, sprouts, and baby greens to better position microgreens as a premium dietary source of bioactive compounds. Additionally, the optimization of juice blends with fruits or other vegetables, as well as shelf-life stability studies, would facilitate commercial development and improve consumer acceptance.