INTRODUCTION
Brassicaceae family comprises a large number
of plant species distributed all over the world except
Antarctica. This family includes approximately 338
genera and 3700 species [1]. Fresh or preserved, cabbage
has been part of human diet since ancient times [2].
Brassica oleracea L. and Brassica rapa L. are the
most popular representatives of Brassica vegetables.
They are almost completely edible, e.g. leaves,
inflorescence, root, stem, and seed. Their excellent
adaptability makes it possible to cultivate them in
different seasons and environments. In the Occident,
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consumers prefer B. oleracea var. capitata, especially
white cabbage and red cabbage. Oriental cuisine features
mostly B. rapa var. glabra Regel (Chinese cabbage)
or B. rapa ssp. chinensis (L.) Hanelt (pak choi) [3].
Brassica vegetables have low concentrations of
protein and fat, which makes them popular low calorie
foods. In addition, they are rich in fiber, such minerals
as calcium and iron, and such bioactive compounds as
polyphenols and glucosinolates [4]. Calcium is essential
for human diet. Dairy products are great sources of
calcium, both qualitatively and quantitatively. However,
people with lactose intolerance and vegans refrain from
dairy products, which makes Brassica vegetables an
excellent source of the recommended daily calcium
intake. Indeed, cabbage has high concentrations of
calcium, iron, selenium, copper, manganese, and zinc.
Unfortunately, it also contains phytates that may form
complexes with calcium, thus reducing its bioavailability
and nutritional value [5].
The past decade has seen an increase in scientific
interest to the antioxidant properties of dietary plant
polyphenols. These secondary metabolites can act
as reducing agents (free radical terminators), metal
chelators, singlet oxygen quenchers, and hydrogen
donors [6]. Furthermore, epidemiological studies
strongly suggest that long term consumption of plant
polyphenols prevents degenerative diseases associated
with oxidative stress [7]. Some recent studies also
showed that cruciferous vegetables decrease the risk
of several types of cancer, which makes cabbage a
functional food [2].
Cabbage can be consumed raw as part of
salads, condiments, or juice. It can be subjected to
thermal processing, e.g. steaming, boiling, roasting,
microwaving, etc., or fermentation (sauerkraut, kimchi,
etc.) [2]. Recent studies demonstrated that Brassica
vegetables lose their nutrient and health-promoting
properties if overheated during domestic cooking [4, 8].
However, fermentation is known to enhance their
nutritional properties [9]. Fermentation is one of the
oldest ways of food processing and preservation. It is
a spontaneous process carried out by lactic bacteria
present in vegetables tissues. Fermentation increases
the safety, sensory properties, and shelf-life of foods. It
also promotes the release of bioactive compounds and
reduces anti-nutritional factors [10].
Food safety and shelf-life are associated with
microbial competition and the synthesis of inhibitory
metabolites, such as lactic acid, acetic acid, hydrogen
peroxide, diacetyl, ethanol, bacteriocins, and biosurfactants
[10]. Lactic fermentation improves the nutritional
value of cabbage, as well as its antioxidant activities.
Lactic fermentation reduces phytates, thus improving
the bioavailability of essential dietary nutrients, such
as minerals, e.g. Ca2+, Zn2+, Mg2+, Mn2+, and Fe2+/3+,
proteins, and amino acids [11].
Different databases feature the same nutritional
data on Brassica vegetables (energy, fat, protein,
mineral content, and carbohydrates) [12]. However, the
situation is very different when it comes to the content of
bioactive compounds [2]. The profile and concentration
of phytochemicals depend on the cultivar, fertilization,
agricultural conditions, environment, sowing season,
and processing [13]. Furthermore, different studies
report different effects of fermentation on the total
phenolic compound and antioxidant activity [4, 9, 10,
14]. So far, no studies have featured the changes in
the total phenolics and antioxidant activity that occur
between cabbage tissue and brine.
The research objective was to evaluate the effect
of spontaneous fermentation on: 1) phytase activity,
calcium, and phytic acid concentrations; 2) total phenolic
content and antioxidants activity of methanol extracts,
water extracts, and brine throughout the fermentation
of three Brassicaceae cabbages harvested in Patagonia
(Argentina).
STUDY OBJECTS AND METHODS
Preparing the ferments. Chinese cabbage (Brassica
rapa var. glabra Regel), white cabbage (Brassica
oleracea var. capitate f. alba), and red cabbage
(B. oleracea var. capitata f. rubra) were obtained from
a local farm of Valle Inferior del Río Chubut located
in Patagonia, Argentina. The cabbages were planted
in March 2020 and harvested in June 2020. Before the
fermentation, each cabbage head was stripped of dry
outer leaves. The cleaned cabbage heads were chopped
in a shredder into 2 mm thick strips and mixed with
3.0 % (w/w) of salt. Sterile water homogenized the
medium (5 mL/100 g of cabbage). Each cabbage was
spontaneously fermented at 18°C for 30 days. The
fermentation was performed in duplicate.
Fermentation parameters. The total content of
lactic bacteria and pH were monitored during the
fermentation process on days 0, 1, 2, 3, 4, 5, 10, 15,
20, 25, and 30. At the beginning of the process, these
parameters were examined after 6 and 12 h. The pH of
the ferments was measured using a pH meter (model
Orion 410A). The lactic bacteria count was monitored
by incubating on MRS agar at 30°C for 48 h [15]. The
results were expressed as colony forming units per
milliliter of experimental sample (CFU/mL).
Preparing the solvent extracts and brine. During
fermentations, the solid and liquid samples were
withdrawn on days 0, 1, 3, 5, 10, 15, 20, 25, and 30. To
prepare the solvent extracts, solid samples were dried
at 37°C until constant weight to avoid degradation of
thermal-sensitive compounds. After that, they were
ground. Methanol and distilled water (1:10 m/V dilution)
were used to prepare the extracts. For the methanol
extract, the mixes were incubated for 3 h at 37°C under
stirring. For the water extract, they were autoclaved
for 15 min at 120°C. Both extracts were centrifuged at
13,000×g for 15 min at 25°C. The supernatants were
stored at –20°C, while the brine samples (liquid
material) were stored at –20°C.
Measuring calcium. The o-cresolftaleín complexone
colorimetric method was used to determine the
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amount of calcium in the cabbage brines. Briefly,
50 μL of sample were mixed with 950 μL of reaction
mix composed by 3.7 mM of cresolphtalein complexone
and 0.2 mM of amino methyl propanol solution (pH 11).
The calcium content in the brines was determined
against the calcium standard curve (0–55 μg Ca/mL).
The absorbance was measured at 570 nm using a Jenway
spectrophotometer (UK). The results were expressed as
mg calcium per 100 mL brine (mg Ca/100 mL).
Phytic acid determination. The content of phytic
acid was evaluated using an enzymatic method kit
(Megazyme International, Ireland), based on its
hydrolysis and further determination of free phosphorus.
The procedure followed the manufacturer’s instructions.
The phosphate released from phytic acid was measured
using a modified colorimetric molybdenum blue assay
described by McKie et al. [11]. The color reagent
was prepared with a solution of 0.6 M sulfuric acid
(32 mL/L), ammonium molybdate (5 g/L), and ascorbic
acid (20 g/L). After enzymatic treatment, 1.0 mL of
color reagent was added to 50 μL of supernatant. The
system was incubated for 30 min at 50°C, and the
absorbance was measured at 820 nm. A standard curve
was constructed with dipotassium phosphate (K2HPO4)
(0–0.4 μg/mL). The results were expressed as mg
K2HPO4/100 mL brine. The concentration of phytic acid
was calculated on the basis of free phosphorus using the
formula suggested by McKie et al. [11].
Phytase activity of the brine. Phytase activity
was determined by measuring the amount of inorganic
phosphate released from sodium phytate as proposed
by De Angelisa et al. [16]. Briefly, 180 μL of reactive
contained 5 mM of sodium phytate and 200 mM of
sodium acetate buffer (pH 5.0). This amount was added
to 20 μL of brine. After 15 min of incubation at 37°C,
the reaction was stopped by adding an equal volume
of 15% trichloroacetic acid. Afterward, the phosphate
released was determined by the previously described
ammonium molybdate method. One unit of phytase
activity was defined as 1 μmol of phosphate produced
per min per mL of brine under the assay conditions. The
results were expressed as milli-units (mU).
Measuring the total phenolics. The total phenolic
content was determined using the Folin-Ciocalteau
reagent according to previously published procedures,
with minor modifications [17]. An aliquot of 50 μL of
extract was mixed with 100 μL of Folin-Ciocalteu´s
phenol reagent and kept for 10 min. Then, Na2CO3
(1.0% m/V; 1.0 mL) was added and kept for 90 min
at 25°C. The absorbance was measured at 750 nm.
A calibration curve was based on gallic acid as
standard. The results were expressed as milligram
gallic acid equivalents per 100 g of dry weight
(mg GAE/100 g DW).
Determination the antioxidant activity. Diphenyl-
1-picrylhydrazyl (DPPH) radical scavenging assay.
The free radical scavenging activity of the samples
was evaluated by 1, 1-diphenyl-2-picryl-hydrazyl
(DPPH) method as described by Chen et al., with some
modifications [18]. Briefly, 900 μL of an ethanolic DPPH
solution (100 μM) was added to 100 μL of sample at
various concentrations. After 30 min of incubation
in the dark at 25°C, the absorbance was measured at
517 nm using a spectrophotometer. A standard curve
was constructed with Trolox as a reducing agent
(15–250 μg/mL). The results were expressed as
milligram Trolox equivalents per 100 g of dry weight
(mg TE/100 g DW).
Cupric reducing antioxidant capacity (CUPRAC)
assay. Cupric reducing antioxidant power (CUPRAC)
was used to determine the antioxidant capacity of
the sample as described by Gouda et al., with minor
modifications [19]. An aliquot of 100 μL of sample was
mixed with 900 μL of reaction mix. The reaction mix
consisted of 2 mL of Neocuproine solution (5 mM),
1 mL of Cl2Cu (0.01 M), and 3 mL of acetate buffer
(50 mM, pH 5.0). After shaking and incubating for
1 h in the dark, the mix was tested for absorbance at
450 nm. A calibration curve was prepared using Trolox
as standard (15–250 μg/mL). The results were expressed
as mg of Trolox equivalent per 100 g of dry weight
(mg TE/100 g DW).
Total antioxidant capacity. The total antioxidant
capacity of the ferments was calculated by adding partial
antioxidant activity of extracts and liquid phase (brine)
contained in 100 g of edible material to simulate the
antioxidant activity per sample. The same procedure was
repeated for each vegetable and antioxidant parameter,
i.e. DPPH, CUPRAC, and total phenolics. The results
were expressed as milligram Trolox equivalents per
100 g of fresh weight ferment (mg TE/100 g FW).
Statistical analysis. All assays were carried out in
duplicate, unless mentioned otherwise. The data were
analyzed by ANOVA, and the means were compared
by the minimum significant difference test at P < 0.05,
using the Statgraphics Centurion XVI software.
RESULTS AND DISCUSSION
Fermentation parameters. Lactic bacteria and
pH helped monitor the evolution of the fermentation
process. Spontaneous fermentation of cabbage relies
on autochthonous lactic bacteria present on the raw
substrate. Organic acids decrease pH and increase the
titratable acidity of the raw material.
The pH of raw white cabbage, red cabbage, and
Chinese cabbage were 6.0, 5.9, and 6.1, respectively
(Fig. 1). The samples of red and Chinese cabbage
demonstrated a similar decrease in pH. In both cultivars,
the lowest values were observed on day 4 and remained
stable over 30 days (Figs. 1b and 1c). The white cabbage
showed no sharp decrease of pH during fermentation.
The lowest value was achieved on day 10 and remained
stable (Figs. 1a vs 1b and 1c).
The initial population of lactic bacteria was
2.1, 2.1, and 2.5 log CFU/mL in the white, red,
and Chinese cabbages, respectively (Fig. 1). This
trend confirms previous reports by R. Di Cagno
et al. and J. Beganović et al. [10, 20]. While the
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highest count was observed on day 5 (9.9 log
CFU/mL), the red cabbage sample approached
its maximal counts on day 3 (9.4 log CFU/mL)
(Fig. 1b). A similar curve was observed for the Chinese
cabbage fermentation; however, the maximal counts
were detected after day 4 (9.7 log CFU/mL) (Fig. 1c).
Regarding the white cabbage, lactic bacteria population
increased slower than in other samples and reached
its maximum (9.2 log CFU/mL) on day 5 (Fig. 1a). In
all the cases, once the peak was reached, the bacteria
populations began to decrease. On day 30, the lactic
bacteria cell counts were 5.0, 5.9, and 5.7 log CFU/mL
for red cabbage, white cabbage, and Chinese cabbage,
respectively (Fig. 1).
Calcium, phytic acid, and phytase activity.
Figure 2 shows the changes in the phytase activity and
calcium and phytic acid concentrations that occurred in
the brine during fermentation. The raw samples of red
and Chinese cabbage (Figs. 2b and 2c, respectively)
contained comparable amounts of water-soluble calcium,
whereas the white cabbage appeared to have a much
lower concentration (Fig. 2a).
The initial level of phytic acid was almost the same
for all three cultivars. The raw sample of Chinese
cabbage showed the highest phytase activity (Fig. 2c).
The initial specific activities of white and red cabbages
were 39.54 ± 18.67 (Fig. 2a) and 56.71 ± 8.20 mU
(Fig. 2b), respectively. The enzymatic activity was
supplied exclusively by vegetal tissue during early
Figure 1 pH and total lactic acid bacteria counts grown
on MRS agar in sauerkraut brine during spontaneous
fermentation for white cabbage (а), red cabbage (b),
and Chinese cabbage (c). Each value is mean ± SD of two
measurements
log CFU/mL
(а)
(b)
(c)
log CFU/mL log CFU/mL
log CFU/mL
Figure 2 Calcium, phytic acid, and phytase activity during
fermentation for white cabbage (а), red cabbage (b),
and Chinese cabbage (c). Each value is mean ± SD of two
measurements
mg/100 mL mg/100 mL mg/100 mL
(а)
(b)
(c)
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fermentation, and then bacterial phytase brought about
phytate hydrolysis [21].
The highest phytase activity was detected between
days 5 and 10 in the samples of white and red cabbage,
when the population of lactic bacteria reached its
maximum (Figs. 2a and 2b). After that, the values
remained constant. In the sample of Chinese cabbage,
the maximal activity was detected on day 10 (Fig. 2c),
which coincided with the maximal viable cell count of
lactic bacteria.
As the fermentation process advanced, the
phytate concentration decreased and the amount of
soluble calcium increased in all the samples. This
phenomenon was more pronounced in Chinese cabbage
when the phytase activity had its highest value. The
lowest phytate concentration and the highest calcium
concentration were achieved on day 30. The assays for
all the samples proved that the highest phytase activity
occurred under acidic conditions.
Phytic acid (myo-inositol-6-phosphate) is the major
storage form of phosphorous and represents 50–85%
of total phosphorous in plants [21]. This compound
and its derivatives are the main inhibitors of divalent
mineral absorption in the gastrointestinal tract due to the
formation of insoluble and indigestible complexes [22].
Hence, it may decrease the calcium bioavailability
in cabbage [21]. However, this point of view is now
controversial since several studies demonstrated that
the myo-inositol-6-phosphate consumption may be
associated with some health benefits. The antinutrient
effect of phytic acid has not been fully demonstrated
in vivo. On the other hand, phytic acid exerts antiinflammatory
and anticancer activities and diminishes
the risk of osteoporosis [23].
Phenolic compounds. Phenolic composition and
antioxidant activity depend mainly on the type of
extraction solvent. The choice of solvent depends mainly
on the chemical nature and polarity of the compounds
to be extracted. Methanol and water are widely used
as solvents in vegetable and plant tissues [14]. In this
study, methanol and water helped measure phenolic
compounds and antioxidant activity in the cabbage
samples during fermentation.
Figure 3 shows the total phenolic content in the
extracts (methanol and water) and brines of white, red,
and Chinese cabbages. Regarding the white cabbage
sample, the water and methanol extracts exhibited
a similar total phenolic content. However, the total
phenolic content in the water extracts of red and Chinese
cabbages was much higher than in the methanolic
extract (Figs. 3b and 3c). Probably, the solubility of
phenolic compounds depended on extraction conditions,
e.g. the chemical structure of solvents, dielectric
constant, time, temperature, phytochemical properties,
etc. However, thermal treatment is known to damage
some phenolics [24].
The total phenolic content in the extracts and brine
of red cabbage was higher than in the samples of white
and Chinese cabbage. This trend was in agreement with
previous studies. For instance, Tabart et al. [25] reported
1851 mg GAE/100 g DW in red cabbage; Vicas et al.
[26] – 980–1220 mg GAE/100 g DW in white cabbage;
Seong et al. [27] – 347.46 ± 32.17 mg GAE/100 g DW in
Chinese cabbage. In vegetables, phenolics exist mostly
in conjugated forms through hydroxyl groups with sugar
as glycosides. Lactic bacteria possess an enzymatic
battery that can convert phenolics to aglycone forms,
which are simpler and biologically more active [28].
Furthermore, during fermentation, pectic enzymes
may soften cabbage texture, thus releasing phenolics
compounds from the solid to the liquid phase [27].
Lactic fermentation promoted a significant
decreased in the total phenolic content in the red
and white cabbage extracts (methanol and water)
after 3–5 days of incubation (Figs. 3a and 3b).
Figure 3 Total phenolic content in methanol extract (ME),
water extract (WE), and brine during fermentation for white
cabbage (а), red cabbage (b), and Chinese cabbage (c). Each
value is mean ± SD of two measurements
(а)
(b)
(c)
mg GAE/100 mL mg GAE/100 mL mg GAE/100 mL
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Afterward, the total phenolic content dropped
slowly and remained almost constant until the end
of lactic fermentation. The total phenolic content
in the methanol and water extracts decreased
almost by half. On the contrary, the brine samples
demonstrated a significant increase between days 3
and 5, and then the concentration remained almost
stable until the end of storage. The Chinese cabbage
sample showed a slight decrease in the total phenolic
content in methanol and water extracts throughout the
fermentation (Fig. 3c).
Antioxidant activity. The antioxidant activity
was evaluated by DPPH radical scavenging assay and
CUPRAC reduction assay. Both are electron transferbased
methods, frequently used to determine the
antioxidant activities of phenolic compounds [6].
Figure 4 illustrates the antiradical activity of methanol
and water extracts against DPPH radical. The methanol
extract contained significantly less reduction power than
the water extract in all the cabbage samples. Probably,
this solvent failed to provide efficient extraction
of compounds with antioxidant activity. The raw
Figure 4 Antioxidant activity (DPPH assay) in methanol
extract (ME), water extract (WE), and brine during
fermentation for white cabbage (а), red cabbage (b),
and Chinese cabbage (c). Each value is mean ± SD of two
measurements
Figure 5 Antioxidant activity (CUPRAC assay) in
methanol extract (ME), water extract (WE), and brine
during fermentation for white cabbage (а), red cabbage (b),
and Chinese cabbage (c). Each value is mean ± SD of two
measurements
mg TE/100 mL mg TE/100 mL mg TE/100 mL
(а)
(b)
(c)
mg TE/100 mL mg TE/100 mL mg TE/100 mL
(а)
(b)
(c)
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sample of red cabbage showed the highest antioxidant
capacity with 1050.44 ± 71.33 TE/100 g DW and
616.63 ± 49.80 mg TE/100 g DW in water and methanol
extracts, respectively (Fig. 4b). Afterwards, these values
declined until the end of fermentation.
On the contrary, in the brine, the values kept rising
until day 5 and then remained stable. The extracts of
white and Chinese cabbages displayed a significantly
lower DPPH radical scavenging activity than the extracts
of red cabbage (Figs. 4a and 4c). These trends confirmed
previous reports [29]. The methanol and water extracts
of white cabbage exhibited a slight decrease in the
antiradical activity, while its brine demonstrated an
increase during the first 5 days of fermentation (Fig. 4a).
However, no significant differences in the antioxidant
activities were observed in the Chinese cabbage extracts.
A significant increase was detected in the brine during
the first 10 days of fermentation, but it remained
constant until the end of fermentation (Fig. 4c).
Table 1 Contribution of water extract and brine to the total
phenolic content of each individually fermented cabbage
Total phenolic content, mgGAE/100 mL
Time,
days
White cabbage Red cabbage Chinese cabbage
0 36.27 ± 2.26 24.35 ± 10.82 51.88 ± 2.01
1 35.57 ± 2.13 32.17 ± 9.00 68.31 ± 4.09
3 40.41 ± 3.18 92.95 ± 10.05 69.78 ± 4.77
5 42.24 ± 2.34 161.45 ± 9.83 70.30 ± 5.46
10 40.48 ± 2.21 161.23 ± 15.23 71.81 ± 7.81
15 33.67 ± 1.99 159.73 ± 11.67 70.85 ± 6.24
20 33.74 ± 1.72 168.33 ± 12.43 71.48 ± 1.96
25 35.09 ± 3.25 173.17 ± 7.98 73.77 ± 2.15
30 36.21 ± 1.85 184.75 ± 11.90 76.51 ± 1.75
*Each value is mean ± standard deviation of three measurements
The values were expressed in mg of Gallic Acid Equivalents
(GAE)/100 g of fresh weight
In all the cases, the values of antioxidant capacity
obtained with CUPRAC assay (Fig. 5) were higher than
those obtained with DPPH method. This trend could be
explained by the ability of CUPRAC method to measure
hydrophilic and lipophilic antioxidants simultaneously,
while DPPH detects only those molecules that are
soluble in organic solvents, particularly in alcohols [30].
The antioxidant capacity of the red and white
cabbages decreased significantly in the methanol and
water extracts during day 1 and increased significantly
in the brine (Figs. 5a and 5b). In the white cabbage,
these changes occurred between days 5 and 10. For the
red cabbage, the decrease was observed on day 5 in the
methanol extract and on day 15 in the water extracts.
The maximal value in brine was achieved after 5 days.
Regarding the Chinese cabbage samples, a
comparable trend could be observed between the
values obtained with DPPH radical scavenging assay
and CUPRAC method. The concentration of reducing
agents in dry matter decreased slowly in the water
extract, while the methanol extract showed no significant
differences. A slight but significant increase in the
concentration was detected in the brine (Fig. 5c).
The antioxidant capacity presented a sharp increase
on day 1 (Figs. 4 and 5). This trend was due to the high
driving force produced by concentration gradients of the
substance that tends to equilibrate the medium. In this
process, water flows from the solid phase to the liquid
phase and brings some solutes from the vegetables. This
phenomenon is due to transfer rates that increase or
decrease until equilibrium is reached [31].
Overall evaluation of total phenolics and
antioxidant activity. The total phenolic content and
antioxidant activity in the white and red cabbage
samples decreased in the dry matter and increased in the
liquid phase. This phenomenon was less pronounced in
the Chinese cabbage sample. However, these data alone
cannot estimate the total variation of the antioxidant
capacity throughout the process: both phases contributed
to the phenolic content and scavenging activity since the
cabbages were not to be consumed dry.
Table 2 Contribution of water extract and brine to the total antioxidant capacity (DPPH and CUPRAC) of each individually
fermented cabbage
DPPH assay, mgTE/100 mL CUPRAC assay, mgTE/100 mL
Time, days White cabbage Red cabbage Chinese cabbage White cabbage Red cabbage Chinese cabbage
0 13.04 ± 0.79 52.15 ± 4.85 6.44 ± 0.52 15.01 ± 1.04 104.94 ± 2.13 16.84 ± 0.36
1 14.10 ± 1.01 64.27 ± 2.32 8.86 ± 0.19 18.66 ± 0.80 122.38 ± 12.63 26.46 ± 0.62
3 11.94 ± 1.56 80.45 ± 6.05 8.28 ± 0.65 20.94 ± 0.12 166.01 ± 6.19 25.24 ± 1.03
5 11.37 ± 0.68 97.98 ± 6.88 8.44 ± 0.46 22.20 ± 0.93 213.06 ± 7.82 22.23 ± 2.01
10 11.04 ± 1.17 89.93 ± 6.61 9.28 ± 0.16 19.60 ± 1.80 231.88 ± 15.18 23.92 ± 1.21
15 9.64 ± 0.55 81.44 ± 0.41 10.24 ± 1.17 16.70 ± 1.70 193.52 ± 20.26 24.59 ± 2.92
20 9.79 ± 1.11 81.32 ± 5.57 10.21 ± 0.91 17.99 ± 0.28 194.01 ± 15.47 24.30 ± 0.01
25 10.07 ± 0.43 78.42 ± 5.80 10.29 ± 0.01 16.26 ± 0.05 187.33 ± 13.73 23.69 ± 2.62
30 8.68 ± 0.91 66.81 ± 0.85 9.98 ± 0.00 15.08 ± 1.87 176.77 ± 4.79 24.48 ± 3.11
* Each value is mean ± SD of three measurements
The values were expressed in mg of Trolox Equivalents (TE)/100 g of fresh weight
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Tables 1 and 2 show the results obtained by adding
the values of dry matter and brine. These results can
be considered the total polyphenol content and the
total antioxidant activity of the fermented cabbages.
Regarding the samples of red and Chinese cabbages, the
total phenolic content and the total scavenging activity
in the water extracts and brine gradually increased and
reached plateau after about 5–10 days, which coincided
with the highest population of lactic bacteria. In the
white cabbage samples, the total phenolic content
and the total antioxidant capacity in the water extract
and liquid phase exhibited slight changes. By the end
of fermentation, the total phenolic content and the
antioxidant activity were similar or smaller, in the case
of radical scavenging activity measured by DPPH.
To sum up, the fermentation increased the total
phenolic content and the antioxidant activity in the
liquid phases of red and Chinese cabbages. The red
cabbage sample had the highest total phenolic content.
CONCLUSION
Fermentation was able to significantly improve the
quality and functionality of Brassica L. cabbages. The
test samples showed a significant increase in phytase
activity, which promoted the decrease of phytic acid
and the increase of free calcium. Fermentation raised
the total phenolic content and the antioxidant activity
because of the individual contribution of the solid and
liquid phases to total scavenging capacity.
CONTRIBUTION
Romina Parada is responsible for conceptualization,
methodology, software, validation, formal analysis,
investigation, reviewing, proofreading, and visualization.
Emilio Marguet is responsible for conceptualization,
methodology, formal analysis, investigation,
and drafting. Carmen Campos is responsible for
conceptualization, software, formal analysis, writingreviewing,
and editing. Marisol Vallejo participated in
conceptualization, methodology, writing, reviewing,
editing, and visualization.
CONFLICT OF INTEREST
The authors declare that there is no conflict of
interests regarding the publication of this article.

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