Volatile and Antioxidant Compounds of Beetroot Powder Obtained by Dehumidified Air Spray Drying of Cloudy Juice

Featured Application

The use of low-temperature spray drying with dehumidified air made it possible to obtain 100% pure powders without the use of carriers. Moreover, powders obtained at a lower temperature (90 °C) without carriers were characterized by the highest share of aromatic volatile compounds, the highest content of betalains and polyphenols and the highest antioxidant activity. The high content of betalains indicates the high coloring ability of the powders. Such high coloring power makes it possible to reduce the dosage of dyes to the product. Due to the current clean label trend, the industry needs natural pure dyes. Additionally, due to the high residue of active substances, low-temperature spray drying using dehumidified air seems to be valuable for the production of dietary supplements and medicines.

Abstract

The aim of this study was to evaluate the quality of cloudy beetroot juice powders with or without a carrier obtained by spray drying using an innovative method of dehumidified air that enabled drying in low temperatures and, consequently, with a reduced carrier content. Phenolic content, betacyanin content, antioxidant activity and the content and types of aromatic compounds of the produced powders were examined. Powders obtained at a lower temperature (90 °C) without carriers were characterized by the highest share of aromatic volatile compounds, the highest content of betalains and polyphenols and the highest antioxidant activity. The addition of carriers (including the variant with added pomace as a natural type of carrier) did not indicate the protection of the active substances present in the juice. The powders obtained with carrier addition compared with those without the carrier addition were characterized by lower antioxidant activity, lower content of betalains and polyphenols and a lower amount of aromatic volatile compounds. No significant differences were found in the content of bioactive and aromatic compounds between powders obtained using different carriers (skim milk powder, Nutriose, maltodextrin and kleptose).

1. Introduction

Beetroot (Beta vulgaris L.) is a part of the family Chenopodiaceae and the color of its root can range from red to yellow. The most commonly used subspecies in the food industry is B. vulgaris ssp. vulgaris. Its root is rich in carotenoids, flavonoids, vitamins, minerals and pigments (betacyanins and betaxanthins) that have antioxidant properties and are widely used in the food industry as food colorants. Beta vulgaris L. is classified as one of ten vegetables that are characterized by the highest antioxidant activity due to its content of polyphenols and pigments. However, these compounds are thermolabile which leads to their degradation during processing, which lowers the final product’s value. Spray drying might be a solution to their loss of value induced by high temperatures because of low drying temperatures and short contact with drying air [1,2].

Spray drying is one of the most common industrial methods to obtain food powders that are used as food concentrates, colorants, flavorings and dietary supplements. This method owes its popularity to cost-effectiveness and simplicity as it is a single-step short operation where the liquid feed is sprayed into the mist in the drying chamber. Therefore, the droplets’ contact time with hot air is no longer than 5–100 s. Moreover, the water evaporation creates a cooling effect that, despite a high inlet drying temperature, makes this method suitable for materials that are thermolabile, such as enzymes or microorganisms. The main stages of this method are preparation of the liquid feed, its atomization, its contact with the drying medium, water evaporation and the powder’s particles’ separation from humid air. However, low-molecular-weight sugars such as glucose and fructose, which are present in a wide range of food materials, cause problems during spray drying due to their low glass transition temperature (T_g; fructose: 5 °C, glucose: 31 °C), which describes the point when material in an amorphous state changes from glassy to rubbery [3]. This phenomenon causes the liquid feed to stick to the walls of the drying chamber in the form of a syrup when the particles’ temperature reaches 10–20 °C above their T_g and in consequence impacts the product’s recovery and the powder’s properties [4,5]. There are multiple approaches that are described in the literature to prevent the problem of stickiness. One of the most common methods is the use of high-molecular-weight sugars or proteins (carrier agents) that have a high T_g [6,7,8]. Another method that is attracting increasing interest, and focuses on the optimization of process parameters such as outlet temperature, is the application of dehumidified air as a drying medium. Jedlińska et al. (2019) used dehumidified air, which enabled them to reduce the carrier content to 20% to produce rapeseed and honeydew honey [9]. As presented by the authors, using dehumidified air enables the lowering of the carrier content used as a drying aid. Samborska et al. (2021) produced white mulberry molasses powders with a carrier content lowered to 10% (solids, w/w) and they were characterized by a highly satisfactory powder recovery (R_p) varying from 64% to 97% [10]. Moreover, the last two years have witnessed a huge growth in the application of dehumidified air as a drying medium in order to completely remove carriers from powder formulations. Barańska et al. (2023) reported that it was possible to produce carrier-free powders from blackcurrant juice concentrate, purple carrot juice concentrate, mango pulp, concentrated sauerkraut juice, tomato pulp and minikiwi pulp [11]. All of the obtained powders were characterized by a water activity (a_w) below 0.2, which ensured their storage stability. Jedlińska et al. (2022) produced minikiwi pulp powders without any additional carrier as a result of dehumidified air application [12]. The authors observed an R_p of obtained powders up to 93%, which signifies a highly satisfactory process of drying.

One of the main causes of the deterioration of food quality is lipid oxidation. This process results in changes in food products that are undesirable for consumers. In recent years, many methods have been developed to control the rate and degree of lipid oxidation in food products. Adding antioxidants is considered one of the most effective methods. They are commonly used in food products as they prevent or delay oxidation processes and extend the shelf life without negatively affecting the sensory and nutritional properties. Due to consumers’ concerns about the use of synthetic food additives, their use is declining. However, interest in natural substances that may act as antioxidants is growing. Most of them occur in plant raw materials and can be found in their leaves, roots, fruits and tubers [13]. Moreover, antioxidants prevent the reactions of free radicals and their derivatives with biologically active compounds and they can interrupt oxidation processes and contribute to the repair of negative changes caused by reactions involving reactive oxygen. Reactive oxygen species are necessary for the proper functioning of some processes. However, their excess may have serious consequences for human health as they lead to oxidative stress, which is the condition where the body is unable to neutralize excess reactive oxygen species. Exposure to too many free radicals may result in the destruction of cell walls and membranes, and consequently lead to DNA damage and cause mutations that may also initiate cancerous changes [14]. As natural alternatives to compounds with antioxidant activity are generating considerable interest, it is important to look for solutions that may respond to consumers’ needs.

Few researchers have addressed the aromatic compounds present in beetroot and available research is quite limited. It is important to determine the volatile aromatic compounds in beetroot products as they are responsible for consumers’ acceptance. Richardson (2013) identified 41 aromatic compounds in canned beetroots [15]. The author found the following as the most potent aromatic compounds: geosmin, 2-isobutyl-isopropyl- and 2-secbutyl -3-methoxypyrazines, 2-acetyl-1-pyrroline, methional, furaneol, p-vinylguaiacol and vanillin. Casciano et al. (2022) analyzed volatile organic compounds (VOCs) in fermented beetroots and found 93 VOCs [16]. Foss et al. (2023) evaluated VOCs in fermented red beetroot juice and noted that fermented juice was characterized by a higher content of VOCs than raw beetroot juice [17].

The aim of this study was to evaluate the quality of cloudy beetroot juice powders with or without a carrier obtained by spray drying using the innovative method of dehumidified air that enabled drying in low temperatures and, consequently, with reduced carrier content. Phenolic content, betacyanin content, antioxidant activity and the content and types of aromatic compounds of the produced powders were examined.

2. Materials and Methods

2.1. Materials

Wodan-variety beetroots prior to squeezing were stored at a temperature of 4–5 °C and at a RH of 80–90%. Beetroots were squeezed on a Kuvings NS-621CES squeezer (Daegu, Republic of Korea) to prepare a cloudy juice that was characterized by an extract of 8 °Brix. Variants of J130 and J90 were obtained.

The mixed beetroot liquid feed (MJ130) was prepared with a Termomix TM31 (Wuppertal, Germany) by mixing 330 g of juice with 66 g of beetroot waste left from squeezing. The device worked at the highest speed for 30 s. Concentrated cloudy juice (J90c), which was characterized by an extract of 50 °Brix, was prepared with the addition of an antifoaming agent on a BUCHI Rotavapor R-124 evaporator (Uster, Switzerland) at a bath temperature lower than 70 °C, with an initial pressure of 130 hPa. Carriers in appropriate proportions were added in a ratio of 2:3 to the cloudy juice after squeezing (JM130, JN130, JMD130, JK130).

2.2. Spray Drying

Beetroot juices were spray-dried without a carrier or with skimmed milk powder, Nutriose, maltodextrin and kleptose as carriers using a laboratory spray dryer MOBILE MINOR (GEA, Skanderborg, Denmark) with the rotating disc rotation’s speed set at 26,500 rpm, pump set at 0.20 mL∙s⁻¹, inlet/outlet temperatures set, respectively, at 130/80 °C or 90/55 °C (

Table 1. Liquid feed variants with carrier types and drying parameters.

Variant	Juice Type	Carrier	Inlet/Outlet Temperature [°C]
MJ130	Cloudy juice mixed with beetroot waste	Not added	130/80
J130	Cloudy juice	Not added	130/80
J90	Cloudy juice	Not added	90/55
J90c	Concentrated cloudy juice	Not added	90/55
JM130	Cloudy juice	Milk powder	130/80
JN130	Cloudy juice	Nutriose	130/80
JMD130	Cloudy juice	Maltodextrin	130/80
JK130	Cloudy juice	Kleptose	130/80

). An air-dehumidifying system that consisted of a cooling unit and a condensation–adsorption unit was used for lowering the inlet air’s humidity below 1 g·m⁻³. Powders were spray-dried according to the methodology presented by Jedlińska et al. (2021) [18].

2.3. Analytical Methods

2.3.1. Analysis of Aromatic Compounds

Each sample of 0.75 g of beetroot powder was prepared for head space extraction and dissolved in 4.25 mL of distillated water and then transferred to vials (20 mL) which were closed with a silicone septum. Sampling was performed using DVB/CAR/PDMS fiber (1 cm long) at a 60 °C temperature and the absorption time was 5 min in an SPME system. Before the absorption of volatiles on the SPME fiber, 1 μL of internal standard (1,2-dichlorobenzene, 0.01% solution in methanol) was added to each sample. The fiber was inserted into the GC/S injector, where after 2 min desorption took place. The apparatus used in the experiment was GCMS-QP2010 (Shimadzu Corportion, Kyoto, Japan). The separation of aroma compounds was performed with the use of Stabilwax (30 m × 0.25 mm × 0.25 µm, polyethelene glycol) from Restek. The carrier gas was helium and the column flow was 0.58 mL/min. The column temperature program was as follows: initial temperature 60 °C (for 10 min) at a rate of 5 °C/min to 200 °C, and 200–250 °C at a rate of 20 °C/min (holding time 5 min at 250 °C). The total time of the analysis was 55 min. The interface and injector temperatures were 25 °C. The ion source temperature was 250 °C and the ionization energy 70 eV. The internal standard 1,2-dichlorobenzene was used to semi-quantify volatile compounds. Identification of aroma compounds was made on the basis of mass spectra libraries (NIST, Gaithersburg, USA 2008, Wiley 175) and from literature data. The analysis was conducted twice for each material.

2.3.2. Dry Matter Content

Dry matter content (d.m.) was analyzed using the oven method—1 g of powder was dried at 105 °C/4 h [18].

2.3.3. Phenolic Content

Phenolics were extracted in the dark by shaking 3 g of material with 30 mL of 70% acetone for 1 h at the ambient temperature followed by static extraction at 5 °C for 24 h and shaking again for 30 min at the ambient temperature. Obtained extracts were filtered and frozen at −20 °C. Phenolic content was measured by the original method of Singleton and Rossi (1965), as previously described by Jedlińska et al. (2020) [19]. Appropriate dilutions were pipetted (300 µL) into test tubes, and then 3.7 mL of distilled water and 250 µL of Folin–Ciocalteu reagent were added, and after 4 min 750 µL of 20% sodium carbonate solution was added as well. Absorbance at 750 nm was measured 2 h after the addition of Folin–Ciocalteu reagent. The phenolic content was determined using a standard curve prepared from gallic acid solutions and the results were expressed per 100 g of the tested preparation and 100 g d.m. of the processed material.

2.3.4. Betalain Content

Betalains were extracted in the dark by shaking 3 g of tested material with 30 mL of 0.1 M phosphate buffer (pH 6.5) for 1 h at the ambient temperature. The extracts were filtered and diluted with buffer to obtain the absorbance at 537 nm in the range of 0.3–0.8. Samples were kept in the dark for 20 min and then the absorbance at 537 nm and 600 nm was measured [20]. Betalain content expressed as mg betanin/100 mL of extract was calculated taking into account the dilution factor (D) and betalain absorption coefficient using the following formula:

B = 1.095∙(A538 − A600)∙D/1.12

The results were expressed per 100 g of the tested preparation and 100 g d.m. of the processed material.

2.3.5. Antioxidant Capacity

Antioxidant capacity was determined in the extracts prepared for phenolic or betacyanin content analysis.

CUPRAC Reducing Capacity

The reducing capacity towards copper (II) ions was determined using the CUPRAC method [21]. An amount of 1 mL of copper chloride (1 mM), neocuproin (156 mg/100 mL) and 1 M ammonium acetate buffer (pH 7.0) were successively taken into test tubes. After mixing, appropriately diluted antioxidant extracts in 70% acetone or buffer (1.1 mL) were added. After 30 min, absorbance was measured at 450 nm against a reagent blank. The results were calculated using a standard curve prepared from Trolox solutions (0.02–0.10 mg/1.1 mL).

Antioxidant Activity

Antiradical activity was measured against ABTS radical cations and DPPH stable radicals [22,23]. To prepare radicals, a 7 mM ABTS solution and a 2.45 mM potassium persulfate solution were combined, and after 12 h they were diluted with PBS. An amount of 4 mL of obtained radical solution was added to 40 µL of extracts in 70% acetone or buffer and after 6 min the absorbance was measured at 734 nm. The results were calculated using a standard curve from Trolox solutions (0.08–0.40 mg/mL). A 0.5 M solution of DPPH radicals was prepared. An amount of 4 mL of appropriately diluted extracts in 70% acetone were taken into test tubes and 1 mL of radical solution was added. After 30 min, the absorbance was measured at 562 nm. The standard curve was prepared from Trolox solutions (1–5 µg/4 mL).

CBA Crocine-Bleaching Assay

The ability to inhibit the HAT-based crocin degradation reaction was measured using the crocine-bleaching assay (CBA) according to Bountagkidou et al. (2010) and DiMajo et al. (2011), with modifications [24,25]. Briefly, the crocin stock solution (1 mg/mL methanol) was diluted eight times with PBS buffer before use and 2 mL of such solution was taken into test tubes. Then, 3 mL of extracts appropriately diluted with 70% acetone or buffer was added. Tubes were placed in a shaking water bath (37 °C) for 5 min, and then 1 mL of AAPH solution (8 mg/mL) was added. After 75 min, the absorbance was measured at 443 nm. The results were calculated based on the standard curve from Trolox solutions (7–70 µg/3 mL).

Fe (II) Chelating Activity

The chelating ability of Fe (II) ions was determined using the method described by Lai et al. (2001) [26]. An amount of 2.5 mL of appropriately diluted extracts and 250 µL of 0.2 mM FeCl₂ were taken into test tubes, and the contents were mixed and then left for 20 min. After this time, 0.5 mL of 0.25 mM ferrozine solution was added and after 10 min a spectrophotometric measurement was performed at 562 nm. The amount of iron bound by the extract components was determined using a standard curve obtained as a result of decreasing additions of FeCl₂. The determined activity (with the exception of chelating ability) was expressed in mg of Trolox per 100 g of the tested material used for extraction. The activity obtained by the extraction of the carrier material (skim milk powder, Nutriose, maltodextrin, kleptose) was also determined and consequently the activity of the products converted into 100 g d.m. of the material subjected to drying was calculated. Also, the share of the carrier in the antioxidant activity of the entire product was determined where applicable. In the case of chelating ability, the results were given in mg of Fe ions bound by active ingredients contained in 100 g of the tested material or 100 g d.m. of the processed material.

2.4. Statistical Methods

STATISTICA 13.1 program was used to perform a one-way analysis of variance (ANOVA) at a significance level of α = 0.05 and Tukey’s test to determine homogeneous groups.

3. Results and Discussion

3.1. Analysis of Aromatic Compounds

Table 2. Identification of volatile aroma compounds and their content in cloudy beetroot juice powders obtained without additional carriers (nd—no data).

Group of Compounds	Compound Name	MJ130 mg/100 g Solids	J130 mg/100 g Solids	J90 mg/100 g Solids	J90c mg/100 g Solids
Aldehydes	Pentanal	16.89 ± 0.19 a	12.23 ± 3.52 a	4.91 ± 0.19 a	nd
	Nonanal	32.22 ± 1.09 b	nd	12.74 ± 1.09 a	8.95 ± 1.88 a
	Octanal	nd	nd	nd	1.43 ± 0.35 a
	Decanal	nd	nd	nd	4.72 ± 0.42 a
	Benzene	nd	nd	2.39 ± 0.12 b	1.02 ± 0.21 a
	acetaldehyde
	3-furaldehyde	nd	142.79 ± 36.63 a	nd	nd
	2-furan	37.44 ± 3.72 b	nd	6.69 ± 1.23 a	nd
	carboxaldehyde
	5-methyl furfural	5.59 ± 1.55 a	nd	2.27 ± 0.20 a	nd
	5-methyl-2-furancarboxaldehyde	9.24 ± 0.55 a	104.23 ± 14.24 b	nd	nd
	5-(hydroxymethyl)-2-furancarboxaldehyde	77.28 ± 10.74 b	175.10 ± 12.93 a	20.37 ± 0.57 c	nd
	Total aldehydes	178.66 ± 11.41 b	434.35 ± 67.32 c	54.01 ± 5.33 a	16.12 ± 2.86 a
Alcohols	1-hydroxy-2-propanone	29.53 ± 0.36 a	93.27 ± 13.95 b	11.47 ± 0.51 a	nd
	2-furanmethano	17.33 ± 3.64 b	57.82 ± 1.56 a	3.89 ± 0.18 c	0.87 ± 0.05 d
	cis-1,2-cyclohexanediol	nd	7.08 ± 0.46 a	nd	nd
	5-methyl-2-furanmethanol	17.31 ± 1.16 a	nd	nd	nd
	2-cyclohexen-1-ol	6.79 ± 1.74 a	nd	nd	nd
	E-11,13-tetradecadien-1-ol	9.45 ± 2.47 a	nd	nd	nd
	1,4-butanediol	3.53 ± 0.43 a	3.08 ± 0.82 a	nd	nd
	6-methyl-2-pyrazinylmethanol	22.04 ± 0.22 b	nd	nd	1.58 ± 0.07 a
	2,4-dimethyl-3-pentanol	nd	nd	nd	9.23 ± 1.58 a
	1-hexanol	nd	nd	nd	0.84 ± 0.04 a
	1-octanol	nd	nd	nd	0.31 ± 0.02 a
	1-nonanol	nd	nd	nd	0.49 ± 0.10 a
	1-hexadecanol	nd	nd	nd	0.35 ± 0.09 a
	Phenol	nd	nd	6.02 ± 0.07 b	0.65 ± 0.02 a
	Cyclopropyl carbinol	nd	nd	nd	0.90 ± 0.04 a
	2-phenoxy- ethanol	nd	nd	nd	0.66 ± 0.03 a
	Total alcohols	105.98 ± 7.01 b	161.25 ± 20.13 c	21.39 ± 0.57 a	15.05 ± 2.16 a
Esters	N-hydroxy-Benzenecarboximidic acid methyl ester	22.06 ± 1.52 b	32.44 ± 2.36 c	15.19 ± 0.23 b	3.40 ± 0.08 a
	Isopropyl myristate	6.52 ± 0.23 a	nd	nd	nd
	Hexadecanoic acid methyl ester	10.47 ± 1.71 a	nd	5.63 ± 0,11 a	nd
	Hexadecanoic acid ethyl ester	nd	nd	nd	1.27 ± 0.15 a
	2-oxo-Propanoic acid methyl ester	nd	nd	1.33 ± 0.20 a	nd
	oxiranyl 2-Propenoic acid methyl ester	nd	13.04 ± 1.58 a	nd	nd
	4-methyl-2,3-Pentanedione	nd	11.23 ± 0.59 a	nd	nd
	9-oxo-Nonanoic acid methyl ester	nd	nd	nd	1.00 ± 0.08 a
	Total esters	39.05 ± 0.60 c	56.70 ± 4.73 d	22.15 ± 0.77 b	5.67 ± 0.22 a
Lactones	Butyrolactone	7.45 ± 1.42 a	15.61 ± 0.61 b	4.94 ± 0.03 a	nd
	2-hydroxy-gamma-butyrolactone	12.22 ± 0.33 bc	17.28 ± 3.97 c	4.23 ± 0.60 ab	0.55 ± 0.08 a
	Total lactones	19.67 ± 2.47 bc	32.89 ± 6.47 c	9.17 ± 0.80 ab	0.55 ± 0.08 a
Hydrocarbones	2-methyl-Cyclopentanone,	nd	nd	1.71 ± 0.15 a	nd
	Total hydrocarbones	nd	nd	1.71 ± 0.15 a	nd
Ketones	6-oxa-bicyclo [3.1.0]hexan-3-one	16.49 ± 1.08 b	12.77 ± 0.61 b	2.26 ± 0.12 a	nd
	2,5-dimethyl-4-hydroxy-3(2H)-furanone	1.42 ± 0.32 a	12.03 ± 0.62 a	1.02 ± 0.04 b	nd
	2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one	5.59 ± 0.58 b	81.79 ± 20.00 a	nd	nd
	3,4-octanedione	nd	7.51 ± 3.03 a	nd	nd
	3-penten-2-one, 3-(2-furanyl) (3Z)-3-(2-Furyl)-3-penten-2-one	nd	3.86 ± 1.86 a	nd	nd
	dihydro-2(3H)-furanone	nd	nd	nd	1.64 ± 0.00 a
	Total ketones	23.51 ± 1.16 a	117.97 ± 35.18 b	3.29 ± 0.23 a	1.64 ± 0.00 a
Acids	Trans 2-hexenoic acid	nd	14.82 ± 6.11 a	nd	nd
	Total acids	nd	14.82 ± 6.11 a	nd	nd
Others	Dimethyl sulfoxide	nd	nd	3.99 ± 0.38 b	0.72 ± 0.10 a
	Methanesulfonyl chloride	nd	5.57 ± 1.43 a	nd	nd
	2-formyl-5-hydroxypyridine	nd	4.19 ± 0.29 a	4.65 ± 0.37 a	nd
	Borane, chlorodipropyl-	nd	nd	nd	2.44 ± 0.03 a
	Total others	nd	9.76 ± 1.72 b	8.64 ± 0.75 b	3.16 ± 0.11 a
Total		366.86 ± 5.12 b	827.74 ± 2.89 c	120.36 ± 8.6 a	42.19 ± 5.43 a

^a–d The differences between the mean values with the same letter in the rows are statistically insignificant (p < 0.05).

describes the content of aromatic compounds in the powders obtained without carriers. Analyzing the total content of aromatic compounds in the powders without carriers, the highest amount was for the powder obtained at a temperature of 130 °C from the pure juice (J130). A significantly lower total content of aromatic compounds was observed for the powder obtained at the same temperature with the addition of pomace (MJ130). Other powders obtained at a temperature of 90 °C (J90, J90c) did not differ in terms of the content of all aromatic compounds. It is worth emphasizing that the total content of all aromatic compounds in the powder from the pure juice at a temperature of 130 °C was a few times higher compared to the amount of aromatic compounds in other powders from this group. The total contents of aromatic compounds in the powders without carriers were as follows: 827.74 ± 2.89 mg/100 g solids (J130), 366.86 ± 5.12 mg/100 g solids (MJ130), 120.36 ± 8.6 mg/100 g solids (J90), 42.19 ± 5.43 mg/100 g solids (J90c).

A significant effect of the drying temperature on the total content of aromatic compounds in the tested powders without carriers was noted. A higher drying temperature (130 °C) led to the formation of a high amount of volatile compounds. However, more volatile compounds in the powder from the pure juice (J130) were found than in the juice with the addition of pomace (MJ130). Presumably, a high amount of low-molecular compounds, such as simple sugars, in the case of pure juice powder resulted in more reactions and consequently the formation of more volatile compounds. The pure juice powder (J130) was characterized by a high amount of 2-furancarboxaldehyde (HMF), which is a product of the Maillard reaction with low-molecular-weight sugars present in the juice formed at a high temperature. Perusko et al. (2021) observed a higher content of products of the Maillard reaction in camel milk powders spray-dried at a high temperature than in the variant produced at a reduced temperature [27]. Moreover, it seems likely that volatile compounds that are closely related to the structure of the pomace matrix made it more difficult for the volatile compounds to penetrate into the headspace of the sample. In the case of the powders without carriers, obtained at a temperature of 90 °C, it was observed that fewer aromatic compounds were in the powders from concentrated juice, as aromatic compounds were lost during the thickening process. Alcohols and ketones were present in the largest amounts in this group. The powder obtained from the pure juice at a temperature of 130 °C contained an exceptionally high amount of ketones.

Analyzing the content of aromatic compounds in the powders with the addition of carriers (

Table 3. Identification of volatile aroma compounds and their content in cloudy beetroot juice powders obtained with carriers (M—skimmed milk powder; N—Nutriose; MD—maltodextrin; K—kleptose).

Group of Compounds	Compound Name	JM130 mg/100 g Honey Solids	JN130 mg/100 g Solids	JMD130 mg/100 g Solids	JK130 mg/100 g Solids
Aldehydes	Pentanal	nd	34.72 ± 2.16 a	73.60 ± 8.22 b	nd
	Hexanal	266.98 ± 19.62 c	120.06 ± 16.62 b	35.38 ± 0.87 a	24.14 ± 0.35 a
	Octanal	19.25 ± 2.05 a	nd	nd	nd
	Nonanal	18.42 ± 0.12 b	36.25 ± 0.70 c	9.22 ± 1.16 a	nd
	5-methyl furfural	2.00 ± 0.31 a	nd	nd	5.93 ± 0.14 b
	2-furancarboxaldehyde	nd	21.09 ± 0.47 a	nd	nd
	5-methyl-2-furancarboxaldehyde,	nd	nd	36.95 ± 31.42 a	nd
	5-(hydroxymethyl)-2-furancarboxaldehyde	28.13 ± 6.07 a	nd	54.57 ± 11.52 b	nd
	Total aldehydes	334.78 ± 28.00 b	212.13 ± 19.96 ab	209.72 ± 53.19 ab	97.42 ± 0.52 a
Alcohols	1-hydroxy-2-propanone	7.74 ± 1.36 a	42.88 ± 5.49 b	83.78 ± 5.49 c	66.62 ± 1.36 bc
	2-amino-1,3-propanediol	nd	nd	nd	2.48 ± 0.28 a
	2-furanmethanol	6.00 ± 0.30 a	14.79 ± 1.79 a	25.13 ± 1.29 b	59.29 ± 3.30 c
	Cyclopropyl carbinol	5.19 ± 1.11 a	nd	nd	64.40 ± 2.46 b
	4H-pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl-	nd	nd	nd	14.72 ± 1.17 a
	4H-pyran-4-one, 3-hydroxy-2-methyl-	1.93 ± 0.37 a	nd	nd	nd
	1-hexanol	8.36 ± 0.40 a	25.07 ± 2.20 b	nd	nd
	1-heptanol	2.59 ± 0.31 a	nd	nd	nd
	1-octanol	7.03 ± 0.00 a	nd	7.39 ± 0.54 a	nd
	3-octanol, 2-methyl-	nd	nd	4.64 ± 0.57 a	nd
	1,4-pentanediol	nd	4.75 ± 1.07 a	nd	nd
	1-octen-3-ol	4.85 ± 0.19 a	nd	nd	nd
	Total alcohols	43.69 ± 4.03 a	87.50 ± 11.26 b	124.42 ± 8.79 c	209.60 ± 8.27 d
Esters	oxiranyl-2-propenoic acid methyl ester	nd	nd	nd	3.69 ± 0.44 a
	Isopropyl myristate	4.49 ± 0.71 a	2.44 ± 0.40 a	3.05 ± 1.01 a	10.56 ± 0.89 b
	Octadecanoic acid methyl ester	7.12 ± 0.72 b	nd	4.70 ± 0.69 a	3.13 ± 0.43 a
	Tetradecanoic acid methyl ester	nd	nd	0.49 ± 0.16 a	nd
	Hexadecanoic acid methyl ester	14.71 ± 2.94 b	nd	5.56 ± 0.18 a	nd
	Total esters	26.32 ± 4.37 c	2.44 ± 0.40 a	13.8 ± 2.04 b	17.38 ± 1.76 b
Lactones	Butyrolactone	2.76 ± 1.87 a	11.90 ± 0.22 b	8.09 ± 0.92 ab	8.63 ± 1.57 ab
	2-hydroxy-gamma-butyrolactone	1.29 ± 0.11 a	13.09 ± 1.86 ab	18.31 ± 3.56 b	14.31 ± 2.27 b
	Total lactones	4.05 ± 1.98 a	24.99 ± 2.08 b	26.40 ± 4.48 b	22.94 ± 0.70 b
Hydrocarbones	2-methyl-Cyclopentanon	nd	nd	nd	15.30 ± 2.26 a
	Total hydrocarbones	nd	nd	nd	15.30 ± 2.26 a
Ketones	2(5H)-Furanone	0.90 ± 0.20 a	nd	nd	13.31 ± 3.12 b
	1-(1H-pyrrol-2-yl)- Ethanone	nd	nd	nd	1.08 ± 0.06 a
	3-hydroxy-2-methyl-4H-Pyran-4-one	nd	nd	nd	2.23 ± 0.05 a
	dihydro-4-hydroxy-2(3H)-Furanone	nd	nd	nd	17.46 ± 3.31 a
	-(2-furanyl)-1-Propanone	5.45 ± 1.55 a	nd	nd	8.31 ± 0.41 a
	2(3H)-Furanone, 5-ethyldihydro-	nd	nd	nd	13.52 ± 2.11 a
	-(2-furanyl)-3-Penten-2-one	nd	nd	nd	1.08 ± 0.11 a
	6-Oxa-bicyclo [3.1.0]hexan-3-one	2.36 ± 0.28	14.12 ± 3.13	32.42 ± 4.14	nd
	2-Furyl ethyl ketone	nd	nd	7.25 ± 0.51 a	nd
	4-Hepten-3-one, 4-methyl-	nd	93.39 ± 5.65 a	nd	nd
	Total ketones	8.71 ± 2.03 a	107.51 ± 8.78 c	39.67 ± 4.65 b	56.99 ± 9.17 b
Acids	4-oxo-Pentanoic acid	nd	nd	nd	1.76 ± 0.07 a
	Acetic acid	8.73 ± 1.17 a	nd	29.16 ± 0.02 b	85.14 ± 8.07 c
	3-hydroxy- Butanoic acid	nd	nd	13.51 ± 0.76 a	nd
	3,4-dyhydroxymandelic acid-tetrams	nd	nd	4.68 ± 1.01 a	nd
	9-oxo-Nonanoic acid methyl ester	nd	nd	3.25 ± 0.63 a	nd
	Total acids	8.73 ± 1.17 a	nd	50.60 ± 2.43 b	86.90 ± 8.14 c
Others	1-methylpentyl Hydroperoxide	nd	nd	nd	4.27 ± 0.33 a
	Methane, sulfinylbis	nd	nd	nd	10.53 ± 0.72 a
	2-methyl-, oxime Propanal	nd	7.67 ± 1.37 a	nd	11.74 ± 0.95 a
	2-Pyrrolidinone	6.44 ± 0.76 a	nd	nd	7.09 ± 0.68 a
	Dimethyl sulfoxide	5.01 ± 0.67 a	nd	16.28 ± 2.23 b	nd
	methoxy-phenyl-Oxime	nd	55.30 ± 2.01 a	44.94 ± 1.44 a	nd
	1-(dimethoxymethyl)-4-(1-methoxy-1-methylethyl)-Benzene	nd	12.55 ± 1.27 a	nd	nd
	6,10-dimethyl-5,9-Undecadien-2-one	0.49 ± 0.09 a	nd	nd	nd
	2,3-dihydro-3,5-dihydroxy-6-methyl-4H-Pyran-4-one-	6.90 ± 0.10 a	nd	nd	nd
	[(2-fluorophenyl)methyl]-1H-Purin-6-amine,	0.69 ± 0.01 a	nd	nd	nd
	Total others	19.54 ± 0.14 a	53.88 ± 2.14 bc	61.23 ± 1.12 c	47.23 ± 4.22 b
Total		445.82 ± 41.72 a	488.45 ± 44.62 a	525.83 ± 61.87 a	553.77 ± 21.89 a

^a–d The differences between the mean values with the same letter in the rows are statistically insignificant (p < 0.05).

), no statistically significant differences were found in the total content of aromatic compounds, and their content was noted from 445.82 ± 41.72 to 553.77 ± 21.89 mg/100 g solids.

The content of aromatic compounds in the powders with carriers (JM130, JN130, JMD130 and JK130) was lower than in the powders obtained without carriers (J130), but significantly higher compared to the other powders without carriers (MJ130, J90 and J90c). It is worth noting that the powders without carriers had the same overall content of aromatic compounds. However, the content of individual groups of aromatic compounds was significantly different depending on the type of carrier used. Therefore, the type of carrier influenced the fragrance profile. For example, the powder with the addition of skimmed milk powder (JM130) had a significantly higher content of aldehydes and the kleptose-based powder had a significantly higher amount of alcohol. Carrier-based powders had a higher amount of acids compared to those from pure juice. Foss et al. (2023) found in beetroot juice the following groups of compounds: alcohols, acids, aldehydes, ketones, lactones and esters [17]. Moreover, Geosmine is found to be the most associated volatile for beetroot smell, but it was not identified in the beetroot powders. This substance has an earthy or musty odor, and people can easily smell it in the beetroot aroma. The absence of this volatile in beetroot powder is a positive observation because it means that the analyzed powders do not have an unpleasant odor. Another compound which can be detected in beetroot aroma is furaneol and it was found in our study, but the given name is 2,5-dimethyl-4-hydroxy-3(2H)-furanone. Other characteristic volatiles that are found in beetroot products are as follows: octanal, nonanal and butanediols [15].

3.2. Phenolic Content

The cloudy beetroot juice obtained in this study had the lowest phenolic content (less than 50 mg GAE/100 g). Among the tested beetroot powders, the highest content of total phenols was found in the beetroot juice dried at a reduced temperature and concentrated (J90c), and not subjected to pre-concentration (J90) (

Table 4. Phenolic content, betalain content, Fe (II), antioxidant activity (as CUPRAC, DPPH, ABTS and CBA) and Fe (II) chelating activity of cloudy beetroot juice and cloudy beetroot juice powders without carries.

	Juice	MJ130	J130	J90	J90c
Phenolic content
mg GAE/100 g	48.88 ± 2.82 a	178.97 ± 5.75 b	236.79 ± 9.03 c	249.551 ± 6.67 cd	257.67 ± 9.23 d
mg GAE/100 g d.m. of dried material	495.40 ± 28.62 c	187.93 ± 6.04 a	246.62 ± 9.40 b	258.98 ± 17.29 b	266.21 ± 9.54 b
Betalain content
mg betalain/100 g	28.59 ± 0.30 a	307.48 ± 16.41 b	352.99 ± 14.26 c	677.31 ± 9.72 e	551.17 ± 11.85 d
mg betalain/100 g d.m. of dried material	289.75 ± 3.00 a	322.87 ± 17.23 b	367.64 ± 14.85 c	702.90 ± 10.08 e	569.42 ± 12.24 d
CUPRAC
mg Trx/100 g in 70% acetone	121.99 ± 4.53 a	287.31 ± 9.40 b	406.42 ± 17.23 c	517.58 ± 15.43 d	544.43 ± 15.98 d
mg Trx/100 g in buffer	274.53 ± 3.34 a	1324.50 ± 22.20 b	2263.60 ± 182.32 c	2907.14 ± 204.98 d	3310.76 ± 263.27 e
mg Trx/100 g d.m. of dried material in 70% acetone	1236.36 ± 45.93 d	301.70 ± 9.87 a	423.29 ± 17.94 b	537.13 ± 16.01 c	562.47 ± 16.51 c
mg Trx/100 g d.m. of dried material in buffer	2782.45 ± 27.60 c	1390.80 ± 23.31 a	2357.55 ± 189.89 b	3016.95 ± 212.73 c	3420.42 ± 271.99 d
DPPH
mg Trx/100 g in 70% acetone	32.43 ± 0.98 a	192.31 ± 4.87 b	219.06 ± 5.72 b	218.76 ± 38.12 b	300.43 ± 10.61 c
mg Trx/100 g d.m. of dried material in 70% acetone	328.70 ± 9.96 b	201.94 ± 5.11 a	228.16 ± 5.96 a	227.02 ± 39.56 a	310.38 ± 10.96 b
ABTS
mg Trx/100 g in 70% acetone	155.46 ± 4.70 a	554.83 ± 12.80 b	618.35 ± 12.03 c	634.78 ± 17.24 cd	661.77 ± 9.86 d
mg Trx/100 g in buffer	1755.69 ± 76.16 a	1558.04 ± 145.05 a	2006.53 ± 339.51 a	2805.99 ± 163.44 b	2497.44 ± 144.20 b
mg Trx/100 g d.m. of dried material in 70% acetone	1575.66 ± 47.60 c	582.60 ± 13.44 a	644.02 ± 12.53 b	658.76 ± 17.89 b	683.69 ± 10.19 b
mg Trx/100 g d.m. of dried material in buffer	1,7794.47 ± 771.86 d	1636.03 ± 152.31 a	2089.81 ± 353.61 ab	2911.98 ± 169.61 c	2580.16 ± 148.98 bc
CBA
mg Trx/100 g in 70% acetone	46.85 ± 0.67 a	153.52 ± 8.04 a	226.97 ± 10.59 c	281.69 ± 10.24 d	325.61 ± 17.72 e
mg Trx/100 g in buffer	26.17 ± 0.78 a	272.48 ± 4.77 b	310.15 ± 10.36 b	456.93 ± 18.62 c	546.19 ± 34.16 d
mg Trx/100 g d.m. of dried material 70% acetone	474.86 ± 6.76 e	161.21 ± 8.45 a	236.39 ± 11.03 b	292.33 ± 10.63 c	336.40 ± 18.30 d
mg Trx/100 g d.m. of dried material in buffer	265.24 ± 7.89 a	286.12 ± 5.00 ab	323.02 ± 10.79 b	474.19 ± 19.32 c	564.28 ± 35.29 d
Chelating FE (II)
mg Fe/100 g	56.41 ± 0.73 d	32.60 ± 0.78 a	44.47 ± 4.36 b	49.59 ± 1.02 c	49.34 ± 1.34 bc
mg Fe/100 g d.m. of dried material	571.77 ± 7.45 c	34.23 ± 0.82 a	46.31 ± 4.54 b	51.46 ± 1.06 b	50.97 ± 1.39 b

^a–e The differences between the mean values with the same letter in the rows are statistically insignificant (p < 0.05).

). A similar phenolic content was determined in the powder obtained under typical conditions using traditional spray drying (J130). The powders produced with carriers were characterized by a lower phenol content due to the presence of a carrier (

Table 5. Phenolic content, betalain content, Fe (II), antioxidant activity (as CUPRAC, DPPH, ABTS and CBA) and Fe (II) chelating activity of cloudy beetroot juice powders obtained with carriers (M—skimmed milk powder; N—Nutriose; MD—maltodextrin; K—kleptose).

	JM130	JN130	JMD130	JK130
Phenolic content
mg GAE/100 g	151.09 ± 2.18 b	156.74 ± 3.90 b	137.65 ± 5.46 a	153.30 ± 6.75 b
mg GAE/100 g d.m. of dried material	203.82 ± 3.08 a	214.97 ± 5.39 a	189.54 ± 7.54 a	212.94 ± 9.40 a
Betalain content
mg betalain/100 g	229.51 ± 8.12 a	250.43 ± 7.42 b	235.08 ± 2.56 a	240.51 ± 9.14 ab
mg betalain/100 g d.m. of dried material	182.23 ± 6.44 a	194.72 ± 5.77 b	182.48 ± 1.99 a	188.44 ± 7.16 ab
CUPRAC
mg Trx/100 g in 70% acetone	224.23 ± 7.78 a	254.89 ± 8.38 b	216.44 ± 1.92 a	242.33 ± 11.52 b
mg Trx/100 g in buffer	2648.88 ± 169.71 b	1431.17 ± 142.91 a	1292.96 ± 288.88 a	1326.77 ± 17.34 a
mg Trx/100 g d.m. of dried material in 70% acetone	291.17 ± 10.98 a	351.07 ± 11.58 b	297.67 ± 2.65 a	335.93 ± 16.05 b
mg Trx/100 g d.m. of dried material in buffer	3739.08 ± 239.55 b	1978.36 ± 197.55 a	1784.23 ± 398.65 a	1848.06 ± 24.15 a
share of carrier activity in 70% acetone [%]	6.89	0.36	0.34	0.48
share of carrier activity in buffer [%]	nd	nd	nd	nd
DPPH
mg Trx/100 g in 70% acetone	118.11 ± 2.60 a	138.45 ± 4.12 b	118.59 ± 4.62 a	126.14 ± 6.62 a
mg Trx/100 g d.m. of dried material in 70% acetone	161.95 ± 3.68 a	191.39 ± 5.69 b	162.86 ± 6.38 a	174.86 ± 9.22 a
share of carrier activity [%]	2.86	nd	0.48	0.48
ABTS
mg Trx/100 g in 70% acetone	362.81 ± 15.39 a	364.67 ± 10.90 a	348.24 ± 16.05 a	350.43 ± 13.19 a
mg Trx/100 g in buffer	2179.75 ± 44.28 b	1421.78 ± 97.43 a	1534.14 ± 29.49 a	1380.41 ± 129.90 a
mg Trx/100 g d.m. of dried material in 70% acetone	466.01 ± 21.73 a	486.94 ± 15.06 a	461.66 ± 22.15 a	470.98 ± 18.37 a
mg Trx/100 g d.m. of dried material in buffer	3076.87 ± 62.50 b	1965.38 ± 134.69 a	2117.04 ± 40.69 a	1922.77 ± 180.94 a
share of carrier activity in 70% acetone [%]	7.71	3.40	3.93	3.51
share of carrier activity in buffer [%]	6.75	0.73	0.61	0.75
CBA
mg Trx/100 g in 70% acetone	138.56 ± 2.65 a	120.05 ± 22.36 a	133.22 ± 8.29 a	137.39 ± 4.80 a
mg Trx/100 g in buffer	288.34 ± 1.73 b	248.00 ± 4.99 a	235.22 ± 7.43 a	230.81 ± 20.15 a
mg Trx/100 g d.m. of dried material in 70% acetone	185.59 ± 3.73 a	162.71 ± 30.91 a	180.30 ± 11.44 a	187.74 ± 6.68 a
mg Trx/100 g d.m. of dried material in buffer	298.00 ± 2.45 a	342.82 ± 6.90 b	324.60 ± 10.25 ab	321.49 ± 28.07 ab
share of carrier activity in 70% acetone [%]	5.11	1.95	1.92	1.90
share of carrier activity in buffer [%]	26.79	nd	nd	nd
Chelating Fe (II)
mg Fe/100 g	37.19 ± 0.40 a	33.98 ± 1.18 a	33.90 ± 1.43 a	35.09 ± 4.68 a
mg Fe/100 g d.m. of dried material	31.09 ± 0.56 a	46.97 ± 1.63 b	46.78 ± 1.98 b	48.87 ± 6.52 b

^a,b The differences between the mean values with the same letter in the rows are statistically insignificant (p < 0.05).

). The content of polyphenols in the spray-dried beetroot juice mixed with waste (MJ130) was higher than in the powders with carriers (JM130, JN130, JMD130 and JK130), but lower than in the case of juice dried without their addition (J130, J90 and J90c). After converting the amount of phenolics per dry matter of pure beet material used in the process, the highest phenolic content was found in the cloudy juice not subjected to further treatment. The results for the powders obtained with carriers and the powder without a carrier but produced from juice mixed with beetroot waste (MJ130) did not differ significantly (188–215 mg GAE/100 g d.m.) and were lower than the content of phenols in the powder dried without carrier (J130, J90 and J90c), statistically insignificant due to applied conditions (247–266 mg GAE/100 g d.m.). An even smaller content of phenolic compounds was found in the research of Vasconcellosa et al. (2016) [28]. They investigated the total phenolic content in various beetroot products, including beetroot juice and spray-dried powders. They observed a decrease in the phenolic content from around 380 mg (beetroot juice) to around 90 mg of gallic acid/100 g of d.m. in beetroot powders. It is important to underline that the differences noted by the authors could have resulted from different drying parameters used and the assay conditions that contributed to a greater retention of the components, such as the optimal selection of the solvent used for sample extraction.

3.3. Betalain Content

The betalain content in the produced powders ranged from 29 to 677 mg/100 g (Table 4 and Table 5). The lowest betalain content was determined in raw juice (29 mg/100 g), while the highest in the powder dried at a reduced temperature (J90, 677 mg/100 g). The content in this sample was significantly higher than in the product derived from concentrated juice (J90c), despite the same drying conditions. This discrepancy was probably due to the possible degradation of these compounds during juice concentration, which was not observed in the case of more stable phenolic compounds. Cloudy juice dried at an elevated temperature, both alone (J130) and with beetroot waste (MJ130), contained a similar content of betalains (353 and 307 mg/100 g, respectively). Products dried at the same temperature (130/80 °C), but using carriers, contained significantly lower amounts of these pigments (230–250 mg/100 g). Interactions between carriers and beetroot juice ingredients are possible, as a result of which betalains are transformed into compounds with different absorption spectra or are not fully extracted under the conditions used. Castellanos-Santiago and Yahia (2008) determined the content of betalains in the freeze-dried pulp of prickly pears as almost 500 mg/100 g [29], which is the same degree of magnitude but a higher value than the dried material obtained in the study using pomace that can be compared with this research. This difference may result from many factors, such as a different composition of the raw material, a different drying method in the cited work (lyophilization) or different light exposure times, which significantly affect the content of betalains in dried powders [30].

Considering the results converted into the dry matter of processed beetroot material, it can be observed that the powders obtained as a result of drying without carriers (J130, J90 and J90c: 368–703 mg/100 g d.m.) and the drying of juice with beetroot waste (MJ130, 322 mg/100 g d.m.) have a considerably higher betalain content than the powders obtained with carriers (182–195 mg/100 g d.m.) and unprocessed juice (290 mg/100 g d.m.). The determined amount of betalains in the powders with carriers is very similar, which clearly distinguishes them from the powders without their addition, where the amounts of compounds from this group were determined to be up to six times higher. Research conducted by Guldiken et al. (2016) showed that part of the betalains in beetroot juice degrade under the influence of thermal treatment [31]. However, the content of isobetanins, compounds that are formed from betanins as a result of high temperature, increased several times. A similar tendency was demonstrated by Herbach et al. (2004), who noticed an increase in the amount of isobetanins with increasing heating time [32]. This phenomenon may result in a higher content of determined betalains in thermally treated products.

3.4. Antioxidant Activity

Various methods were used to examine the antioxidant activity of the obtained powders and to compare it with the activity of the cloudy juice used to produce them. Two of them are used to measure the basic mechanisms of breaking the free radical reactions, i.e., single-electron transfer, SET (reducing capacity measured at pH 7 with the CUPRAC method) and hydrogen atom transfer, HAT (measured at physiological pH using the crocine-bleaching assay, CBA). Methods utilizing ABTS cation radicals and DPPH radicals are based on mixed mechanisms, and the ability to chelate Fe (II) ions determines the supporting effect by removing pro-oxidant Fe (II) ions from the reaction environment. The tests were carried out using extracts in 70% acetone and in phosphate buffer pH 6.5, applied also to determine the content of phenolics and betalains. Most studies do not focus on the antioxidant properties of beetroot powders. However, Vasconcellos et al. (2016) analyzed the total antioxidant potential (TAP) in beetroot juice and powder [28]. The authors noted the powder’s TAP of 95.31 ± 0.68%, which was significantly higher than for raw beetroot juice (80.48 ± 0.25%). The authors concluded that this phenomenon resulted from drying, as it concentrated bioactive compounds in the product which resulted in a higher antioxidant activity.

Compounds extracted from the cloudy juice with buffer had more than twice the reducing capacity (CUPRAC) of the compounds extracted with 70% acetone. Even greater differences were found when comparing the extracts from dried material (Table 4 and Table 5). The highest reducing capacity was detected in the powders obtained by drying concentrated and raw juice at a reduced temperature (J90c and J90: 2907–3311 mg Trolox/100 g in buffer and 518–544 mg/100 g in 70% acetone). The activity detected in both extracts in the powders obtained with carriers (JMD130, JN130 and JK130) and from the juice with beetroot waste (MJ130) was the most suppressed, except for the high reducing capacity of the compounds extracted with the buffer in JM130. After converting the activity into d.m. of the material originated from beetroot, there was a clear decrease in the reducing capacity of the compounds extracted from juice dried with carriers (approximately 300 mg Trolox/100 g d.m.) in relation to the raw juice before drying (1236 mg Trolox/100 g d.m.) and this was slightly lower in juice dried without a carrier at the temperature of 130C (J130: 423 mg Trolox/100 g d.m.), and especially in juice dried at a reduced temperature (J90: 537–562 mg Trolox/100 g d.m.). A different situation was observed in the case of the extracts in buffer, because the compounds isolated from the material dried without carriers and using powdered milk as a carrier (JM130) had similar or greater activity (2358–3739 mg Trolox/100 g d.m.) than compounds isolated from juice (2782 mg/100 g d.m.), and slightly lower for other powders with carriers (1391–1978 mg/100 g d.m.). This suggests that phenolic compounds present primarily in acetone extracts were less important in terms of reducing capacity and that the transformations occurring during contact with oxygen at a high temperature (during drying) had a clearly unfavorable effect on this property, unlike water-soluble compounds such as betalains.

Brzezińska-Rojek et al. (2023) [33] determined a similar or greater reducing activity in a CUPRAC assay (2300–9100 mg Trolox/100 g d.m.) after the extraction of conventional beetroots with 50% acidic methanol. The extractant can be to some extent treated as a combination of the two solutions applied in our study, taking into consideration its properties. The most important factor influencing the results was the investigated material—the whole tissue in the aforementioned study vs. cloudy juice in our research. The activity of commercial beetroot products tested by these authors was also similar (325–7800 mg Trolox/100 g).

In contrast to the reducing capacity, compounds isolated with 70% acetone (47 mg Trolox/100 g) had a greater activity using the hydrogen atom transfer deactivation mechanism than those with buffer (26 mg Trolox/100 g) in the juice, used for drying. However, in powders, similarly to the CUPRAC method, a greater activity was recorded in the case of compounds isolated with buffer, which were almost twice as effective each time (Table 4 and Table 5). The highest activity was achieved by powders dried at a lower temperature: concentrated before drying (J90c; 546 mg Trolox/100 g) and unconcentrated (J90; 457 mg Trolox/100 g). The lowest activity was again found in the extracts from products dried with carriers (120–139 mg Trolox/100 g in 70% acetone and 231–288 mg Trolox/100 g in buffer). The product dried with added waste (MJ130) had a similar activity and the juice dried without any carrier at the standard temperature (J130) had an intermediate activity.

After converting the activity into 100 g d.m. of the material from beetroot, it was found that the high activity of compounds extracted with 70% acetone from juice (475 mg Trolox/100 g d.m.) was reduced to approximately 300 mg (powders obtained at a lower temperature: J90 and J90c) and 161–188 mg Trolox/100 g d.m. (powders obtained with carriers; Table 5). In the case of the extracts in buffer, the trend was maintained at higher values: juice activity (265 mg Trolox/100 g d.m.) slightly increased after obtaining products with and without carriers at higher temperature (286–343 mg Trolox/100 g d.m.) and up to 474–564 mg Trolox/100 g d.m. in products obtained under reduced drying temperatures. These trends (with slightly changed proportions of the obtained values) are therefore consistent with the observations regarding the reducing capacity.

The antiradical activity against DPPH^• could only be determined in the extracts in 70% acetone (due to the presence of opalization-forming phosphate buffer salts in the remaining extracts) and could be compared to the activity of analogous extracts against ABTS⁺. First of all, the activity of the extracts against DPPH^• radicals was clearly lower than that detected with respect to ABTS radical cations (Table 4 and Table 5). These methods accept both mechanisms; however, one is often preferred. Antioxidants against ABTS•+ under these conditions are more effective using the SET mechanism (buffered environment with increased pH), and against DPPH• ather the HAT mechanism (aprotic solvent containing water), which was confirmed in this study [30]. The activity against DPPH^• radicals was similar in all of the produced powders (118–126 mg Trolox/100 g d.m. with carriers: JM130, JN130, JMD130 and JK130; 192 mg Trolox/100 g d.m. from juice with added beetroot waste: MJ130; 219 mg Trolox/100 g d.m. dried without carrier and without preliminary concentration: J90; and the highest value of 300 mg Trolox/100 g d.m. dried at a low temperature after preliminary concentration: J90c). In the case of ABTS^•+, the powders with carriers had very similar activity: 348–365 mg Trolox/100 g d.m. (Table 5), and the powder obtained from juice with a carrier had an activity much closer to the high activity obtained without carriers (618–662 mg Trolox/100 g d.m.). After taking into account only the activity originating from the beetroot material, even more balanced values were found (462–684 mg Trolox/100 g d.m.), although clearly lower than the activity of compounds in the juice before drying (1576 mg Trolox/100 g d.m.), which is characteristic of the HAT mechanism.

However, the antiradical activity of the cloudy juice extract in the buffer against ABTS^•+ was over ten times higher (1756 vs. 155 mg/100 g), which indicated the involvement of the SET mechanism, and in the obtained powders it was equal and close to that detected in the juice (1380–2806 mg/100 g). However, such a phenomenon did not occur in the previously discussed methods. This can point to a significant loss of activity for the component derived from the raw material (1636–3077 mg Trolox/100 g d.m.) in relation to the juice activity obtained in the buffer and similarly calculated (1,7794 mg Trolox/100 g d.m.), which was the highest activity value obtained in this work. Decreased values instead of an increased activity proves greater participation of the HAT mechanism in the action of tested compounds.

Contrary to our study, Ravichandran et al. (2012) [34] found no effect or an elevated activity against ABTS^•+ and DPPH^• in beetroots after different kinds of thermal treatment. These authors, however, investigated the antioxidant activity in thermally processed beetroot tissue (chopped into pieces), not in beetroot processed into a very new product with the addition of other material (carriers) and with access to large quantities of oxygen, as in our study. The results of Ravichandran et al. can be explained by the easier extraction of bioactive compounds from the tissue as a consequence of its loosening during heat treatment. This may result in easier access for the extractant and the release of some compounds from the matrix. Such processes would not have been so important during the processing of cloudy beetroot juice. Honey and apple concentrate processed in a similar way gave analogous effects to those obtained in this study (similar or reduced activity towards ABTS^•+ and DPPH^•) [35].

HAT antiradical activity signifies a greater probability of effectiveness in interrupting the chain reaction of the oxidation of unsaturated fatty acids [36]. This may, therefore, suggest a satisfying effectiveness of the obtained beetroot juice preparations in products containing lipids, which are easily subject to radical reactions in the presence of oxygen.

In the case of interrupting lipid autoxidation, an effective strategy will also be the binding of transition metal ions, which cause the decomposition of the initially formed hydroperoxides, making the process violent. This study examined the ability to bind one of the most effective ions and one of the most common transition metals found in food—iron (II). The obtained powders had a constant and high ability to remove iron ions from the reaction medium. The powders produced with carriers were characterized by a similar activity (34–37 mg Fe/100 g), and the powders without carriers were again more active (45–50 mg Fe/100 g), approaching the activity of juice (56 mg Fe/100 g). After the conversion to 100 g d.m. of the dried material, the activities determined in the powders did not change significantly, while the ability of the ingredients to bind the dry substance of the juice increased tenfold (572 mg Fe/100 g d.m.). This points to a significant loss of this property during juice processing, but despite this, the final activity is still high and comparable with spray-dried apple concentrate and honey from the study of Samborska et al. (2020) [35].

Using the activity results also determined for the ingredients constituting the carrier material, the share of the activity of the carriers themselves in the activity of the entire powder was calculated (in addition to the activity of the dried ingredients from beets converted into dry matter and discussed above). In the case of reducing power (CUPRAC), the activity of carrier components was detected only in extracts in 70% acetone (Table 5). Its share was negligible (less than 0.5%), except for powdered milk, which was responsible for almost 7% of the activity of the entire product. In the case of the CBA method and the HAT mechanism, relatively small shares in 70% acetone were noted, apart from powdered milk. Powdered milk was the only carrier from which active substances were also isolated in the buffer, and their contribution accounted for a significant part of the powder activity (27%). In the case of free radical methods and extracts in 70% acetone, the above trends were maintained, and in the case of ABTS radical cations and extracts in buffer, a trace share (less than 1%) was observed in all carriers except milk (almost 7%). To sum up, if it is necessary to use a carrier, the use of powdered milk as a carrier will likely increase the antioxidant activity of the dried powder.

The tests almost always showed a lower activity for the powders obtained with carriers. It seems likely that the effective binding of some of the active ingredients under the used conditions prevented complete extraction. However, transformations of compounds exposed to oxygen due to the formation of an additional, possibly open, structure of powder particles by the carrier cannot be ruled out. Such characteristic change, limited to a certain group of products, was supported by a targeted, unusual change in antioxidant activity, measured in particular in one of the extracts and one of the methods (reducing capacity of ingredients obtained in the buffer).

4. Conclusions

• The powders obtained at a lower temperature (90 °C) without carriers were characterized by the highest share of aromatic volatile compounds, the highest content of betalains and polyphenols and the highest antioxidant activity.
• The addition of carriers (including the variant with added pomace as a natural type of carrier) did not indicate the protection of the active substances present in the juice. The powders obtained with carrier addition compared with those without the carrier addition were characterized by a lower antioxidant activity, lower content of betalains and polyphenols and a lower amount of aromatic volatile compounds.
• No significant differences were found in the content of bioactive and aromatic compounds between powders obtained using different carriers (skim milk powder, Nutriose, maltodextrin and kleptose).
• The high content of betalains indicates the high coloring ability of the powders obtained at a lower temperature (90 °C). Such high coloring power makes it possible to reduce the dosage of dyes to the product. Due to the current clean label trend, the industry needs natural pure dyes.
• Due to the high residue of active substances, low-temperature spray drying using dehumidified air seems to be valuable for the production of dietary supplements and medicines.