Major and Minor Element Concentrations in Fermented Shalgam Beverage

Abstract

The concentrations of sodium, potassium, calcium, magnesium, and phosphorus (major elements) and iron, manganese, tin, copper, nickel, zinc, lead, and cadmium (minor elements) were determined in fermented shalgam beverage samples of different brands randomly collected from domestic markets in Bursa province, Turkey, using inductively coupled plasma optical-emission spectrometry technique. The elements with the highest frequency were Na, K, Ca, Mg, and P and the range of these elements were 4.52–6.15 g L⁻¹, 0.27–0.72 g L⁻¹, 34.02–148.30 mg L⁻¹, 30.61–75.38 mg L⁻¹ and 8.72–82.96 mg L⁻¹, respectively. The concentrations of heavy metals, such as Cd, Ni, Sn, and Pb, found in shalgam beverage were below 1 mg L⁻¹ in almost all of the samples.

Keywords:

• Mineral elements
• Shalgam beverage
• ICP–OES

INTRODUCTION

The mineral elements play an important role in human nutrition because they are not synthesized in the body. They can be divided into macro minerals (major elements), such as sodium, potassium, magnesium, calcium, and phosphorus; micro minerals (trace elements), such as iron, copper, zinc, and manganese; and ultra trace elements, such as aluminum, bromine, and cadmium. While these elements are essential nutrients, some elements like lead, cadmium, and mercury can also produce toxic effects at high concentrations. In recent years, there has been growing interest in the evaluation of the macro- and microelements in a variety of food samples.[1–4

Fermented shalgam beverage, literally meaning “turnip juice,” is a traditional Turkish beverage produced by the fermentation of the black/purple carrot (Daucus carota L. spp. sativus), aromatic turnip (Brassica rapa L.), and/or red chili powder, yeast, sourdough, salt, wheat, or bulgur flour and adequate water. The fermentation is a spontaneous fermentation involving a mixed culture of lactic acid bacteria and yeasts, which give the drink its characteristic taste and flavor by producing lactic acid, ethanol, and other organic compounds. It is turbid, dark red or purple color, and has a very strong sour taste. Though being popular particularly in southern parts of Turkey, the consumption of shalgam beverage is increasing due to high levels of amino acids, water-soluble vitamins (B₁, B₂, and C), natural antioxidants, and phenolics. Shalgam beverage has also been reported as having therapeutic properties, such as improving the immune system and preventing digestion disorders, mainly due to its mineral composition.[5–11

Shalgam beverage has been reported to be a good source of minerals; however, the levels of essential minerals in shalgam may vary for many different reasons. The mineral composition of shalgam beverage is affected by cultivar, degree of maturity, harvesting methods, and postharvest handling procedures of the raw materials used in its production, processing technologies, the ingredients used, storage conditions, brand, and packaging material.[1,8,11–13

Although the consumer demand for shalgam beverage has increased due to its beneficial health effects, there have been relatively few scientific studies characterizing the elemental content of this product. The present study was carried out to assess the levels of several major and minor elements in shalgam beverage consumed in Turkey in order to bring into focus the contribution of this traditional fermented drink to the mineral intake of consumers. In this work, the concentrations of the major elements Na, K, Ca, Mg, and P and of the minor elements Fe, Cu, Zn, Ni, Mn, Pb, and Sn were determined in various brands of shalgam beverage samples by inductively coupled plasma optical-emission spectrometry (ICP–OES). Moreover, due to the importance of mineral elements in the human diet, combined with the nutritional density of this drink with respect to several minerals, this report could motivate a demand for better and more marketable shalgam beverages.

MATERIALS AND METHODS

Sampling

Fourteen different shalgam beverage samples were purchased from local markets in Bursa, Turkey in 2008. Seven samples of spicy (hot) shalgam beverage (flavored with red chili) and seven samples of plain shalgam beverage (without red chili) were analyzed. Sample containers were of the same capacity (500 mL) of either plastic or glass bottles. The samples were stored at 4 ± 1°C. The products were selected in two stages: (1) one sample of each product was obtained from the supermarkets; and (2) after 1 month a second visit was made to the same supermarkets to obtain a second sample of each. This procedure was applied to include samples of different lots for each product. The numbers of samples of each product depended on the numbers of brands available in the market.

Reagents

Nitric acid (65%; Merck, Darmstadt, Germany) of analytical grade was used for the mineralization of the samples. Analytical standard solutions used for calibration were prepared by dilution of each pure element standards obtained from Merck (Darmstadt, Germany). All aqueous solutions and dilutions were prepared with ultrapure water (Milli-Q; Millipore, Bedford, MA, USA).

Sample Preparation

Prior to analysis, the samples were thoroughly mixed and analyzed directly by ICP-OES without a previous digestion treatment. The shalgam beverage samples were diluted 1:1 with 0.2% (v/v) HNO₃ and centrifuged for 20 min at 2000 rpm (approximately 630 × g) (Hettich Universal 30F; Andreas Hettich GmbH & Co., KG, Tuttlingen, Germany). All sample vials, sampler cups, and glassware materials were cleaned by soaking in 10% (v/v) HNO₃ and rinsed in deionized water before use. The appropriate standards for each evaluated element were made within the concentration range of the elements in the samples. The results were obtained from triplicate measurements.

Instrumentation

Elemental analysis was carried out with an OPTIMA™ 2100 DV inductively coupled plasma–optical-emission spectrometry (ICP-OES) (Dual View; Perkin Elmer Life and Analytical Sciences, Waltham, MA, USA). The operational conditions, the analytical lines used, measurement parameters, and the wavelengths of the elements are shown in Table 1.

Table 1 Operating parameters for ICP-OES

Nebulization gas flow rate	0.55 L min^−1
Auxiliary gas flow rate	0.2 L min^−1
Plasma gas flow rate	17 L min^−1
Sample flow rate	1.5 mL min^−1
Operating power	1450 W
View	Axial
Interface	Shear gas
Sample uptake rate	1.0 mL min^−1
Spray chamber	Cyclonic
Nebulizer type	Meinhard
Nebulizer set up	Instant
Replicates	3
Detection wavelengths (λ/nm)
P	214.914
Na	589.592
K	766.490
Ca	393.366
Mg	279.553
Fe	259.940
Cu	324.754
Zn	213.857
Mn	257.610
Ni	221.647
Pb	220.353
Sn	235.485
Cd	214.440

RESULTS AND DISCUSSION

The results of analysis of shalgam beverage samples were treated in two separate parts, one for major elements in Table 2 and another for minor and ultra trace elements in Table 3, which show the averages of the amounts and the relative standard deviation from the triplicate determinations. Sodium, the principal cation in the extracellular fluid, is known to be involved in nerve and muscle function, the regulation of plasma volume, and the acid-base balance.[14,15] Continuous overconsumption of sodium has been found to hasten the onset of hypertension and to worsen an existing hypertensive condition;[2] hence, there is a need to limit sodium intake. Shalgam beverage is observed as a rich source of sodium, a consequence of salt incorporation (sodium chloride) for production. The lowest and highest contents of sodium were found to be 4.52 g L⁻¹ for I sample and 6.15 g L⁻¹ for N sample, respectively. The lowest and highest levels of potassium were found to be 0.27 g L⁻¹ for F and 0.72 g L⁻¹ for E and I shalgam beverage samples, respectively. Brand N seems to be the best source of sodium, and when potassium is under consideration, brand I is the best. Potassium, the major cation in the intracellular fluid, plays a role in the regulation of osmotic pressure, blood pressure, and acid-base balance.[14, 16] Despite the fact that there has been no study up to date on the daily intake of shalgam beverage by Turkish people, it is reasonable to estimate that it corresponds to ∼200 mL, which is an adequate amount to supply the adequate ingestion of Na and K considering the recommended dietary allowance values (>100 mg per day).[17]

Table 2 Major element composition of shalgam beverage samples (Mean ± Standard Deviation)

Code	Sample information	Na (g L^−1)	K (g L^−1)	Ca (mg L^−1)	Mg (mg L^−1)	P (mg L^−1)	Mn (mg L^−1)	Fe (mg L^−1)
A	Deionized water, purple carrot, turnip, salt, red chili powder, bulgur flour, sodium benzoate	5.71 ± 0.071	0.50 ± 0.154	34.49 ± 0.602	38.76 ± 0.482	43.75 ± 0.778	0.32 ± 0.028	0.45 ± 0.052
B	Deionized water, purple carrot, turnip, salt, bulgur flour, sodium benzoate	5.80 ± 0.556	0.46 ± 0.236	47.07 ± 0.979	30.61 ± 0.414	36.73 ± 1.403	0.34 ± 0.034	0.64 ± 0.025
C	Water, purple carrot, turnip, salt, bulgur flour	4.77 ± 0.067	0.68 ±0.440	92.29 ± 1.350	48.08 ± 0.144	42.14 ± 0.926	0.12 ± 006	0.35 ± 0.032
D	Water, purple carrot, turnip, salt, red chili powder, bulgur flour, sodium benzoate	5.20 ± 0.357	0.64 ± 0.031	88.10 ± 1.039	50.03 ± 1.328	42.71 ± 0.669	0.32 ± 0.002	0.61 ± 0.023
E	Water, purple carrot, turnip, salt, bulgur flour, sodium benzoate	4.99 ± 0.408	0.72 ± 0.137	88.68 ± 0.174	51.70 ± 0.671	54.64 ± 1.266	0.11 ± 0.003	0.36 ± 0.041
F	Water, black carrot, turnip, salt, red chili powder, bulgur flour	5.29 ± 0.016	0.27 ± 0.194	124.60 ± 0.784	57.66 ± 0.538	51.23 ± 0.915	0.28 ± 0.065	0.45 ± 0.043
G	Water, black carrot, turnip, salt, bulgur flour	5.25 ± 0.662	0.62 ± 0.523	148.30 ± 0.493	75.38 ± 0.051	82.96 ± 0.335	0.79 ± 0.051	0.75 ± 0.036
H	Water, purple carrot, turnip, salt, bulgur flour, sodium benzoate	5.25 ± 0.426	0.67 ± 0.094	92.20 ± 0.426	53.18 ± 0.295	48.69 ± 1.134	0.08 ± 0.005	0.49 ± 0.046
I	Water, purple carrot, turnip, salt, red chili powder, bulgur flour	4.52 ± 0.591	0.72 ± 0.080	58.40 ± 1.222	48.97 ± 0.472	28.56 ± 1.106	0.20 ± 0.004	0.80 ± 0.012
J	Water, purple carrot, turnip, salt, bulgur flour	4.69 ± 0.533	0.43 ± 0.066	57.47 ± 0.839	44.64 ± 1.094	8.72 ± 1.303	0.08 ± 0.002	0.50 ± 0.013
K	Deionized water, purple carrot, turnip, salt, red chili powder, bulgur flour, sodium benzoate	4.87 ± 0.421	0.54 ± 0.089	67.08 ± 0.056	52.28 ± 1.159	23.74 ± 1.127	0.40 ± 0.005	0.84 ± 0.033
L	Deionized water, purple carrot, turnip, salt, bulgur flour, sodium benzoate	4.91 ± 0.688	0.64 ± 0.034	72.52 ± 0.644	60.48 ± 0.482	62.62 ± 1.147	0.16 ± 0.014	0.37 ± 0.013
M	Water, purple carrot, turnip, salt, red chili powder, bulgur flour,	4.83 ± 0.159	0.59 ± 0.197	94.59 ± 0.670	45.66 ± 0.381	38.29 ± 0.569	0.01 ± 0.002	0.16 ± 0.007
N	Deionized water, purple carrot, turnip, salt, red chili powder, bulgur flour, sodium benzoate	6.15 ± 0.153	0.53 ± 0.023	34.02 ± 3.025	38.04 ± 2.036	47.49 ± 3.025	0.17 ± 0.002	0.17 ± 0.003
Minimum		4.52	0.27	34.02	30.61	8.72	0.01	0.16
Maximum		6.15	0.72	148.30	75.38	82.96	0.79	0.84

Table 3 Minor and ultra trace element composition of shalgam beverage samples (Mean ± Standard Deviation)

Code	Sample information	Cu (mg L^−1)	Zn (mg L^−1)	Ni (mg L^−1)	Sn (mg L^−1)	Pb (mg L^−1)	Cd (mg L^−1)
A	Deionized water, purple carrot, turnip, salt, red chili powder, bulgur flour, sodium benzoate	0.27 ± 0.005	nd	0.05 ± 0.001	0.37 ± 0.012	0.11 ± 0.001	0.04 ± 0.012
B	Deionized water, purple carrot, turnip, salt, bulgur flour, sodium benzoate	0.10 ± 0.002	0.06 ± 0.002	0.07 ± 0.005	0.30 ± 0.021	0.06 ± 0.003	0.01 ± 0.002
C	Water, purple carrot, turnip, salt, bulgur flour	0.09 ± 0.007	nd	0.04 ± 0.002	0.26 ± 0.034	0.02 ± 0.000	nd
D	Water, purple carrot, turnip, salt, red chili powder, bulgur flour, sodium benzoate	0.02 ± 0.001	nd	0.04 ± 0.001	0.22 ± 0.014	0.03 ± 0.001	nd
E	Water, purple carrot, turnip, salt, bulgur flour, sodium benzoate	0.02 ± 0.003	nd	0.03 ± 0.001	0.23 ± 0.021	nd	nd
F	Water, black carrot, turnip, salt, red chili powder, bulgur flour	0.01 ± 0.003	nd	0.06 ± 0.012	0.23 ± 0.002	nd	nd
G	Water, black carrot, turnip, salt, bulgur flour	0.03 ± 0.006	nd	0.05 ± 0.003	0.31 ± 0.003	0.01 ± 0.000	0.01 ± 0.000
H	Water, purple carrot, turnip, salt, bulgur flour, sodium benzoate	0.05 ± 0.001	nd	0.05 ± 0.003	0.21 ± 0.012	nd	nd
I	Water, purple carrot, turnip, salt, red chili powder, bulgur flour	0.01 ± 0.003	0.23 ± 0.021	0.05 ± 0.002	0.26 ± 0.015	0.03 ± 0.003	nd
J	Water, purple carrot, turnip, salt, bulgur flour	0.01 ± 0.002	nd	0.04 ± 0.000	0.16 ± 0.002	nd	nd
K	Deionized water, purple carrot, turnip, salt, red chili powder, bulgur flour, sodium benzoate	nd	nd	0.05 ± 0.001	0.20 ± 0.002	0.03 ± 0.002	nd
L	Deionized water, purple carrot, turnip, salt, bulgur flour, sodium benzoate	nd	nd	0.06 ± 0.002	0.20 ± 0.035	nd	nd
M	Water, purple carrot, turnip, salt, red chili powder, bulgur flour,	0.03 ± 0.001	nd	0.01 ± 0.006	0.20 ± 0.004	0.01 ± 0.003	nd
N	Deionized water, purple carrot, turnip, salt, red chili powder, bulgur flour, sodium benzoate	nd	nd	0.04 ± 0.008	0.18 ± 0.015	nd	nd
Minimum		0.00	0.00	0.01	0.18	0.00	0.00
Maximum		0.27	0.23	0.07	0.37	0.11	0.04
nd: Not detected.

The metabolism of the minerals, calcium and phosphorus, plays a fundamental role in the rapid skeletal development of the young. The lowest Ca level was found to be 34.02 mg L⁻¹ for N, whereas the highest Ca level was 148.30 mg L⁻¹ in G. The concentration of P in shalgam beverage samples was found in the range of 8.72 mg L⁻¹ (for J)–82.96 mg L⁻¹ for (G). İyicinar[13] reported that the calcium and phosphorus contents in shalgam beverage varied between 34.32–92.57 mg L⁻¹ and 4.38–51.36 mg L⁻¹, respectively. In another study, the ranges of 89–173 mg L⁻¹ calcium and 10.6–22.2 mg L⁻¹ phosphorus were found for shalgam beverage.[11] These values are similar to our findings.

Magnesium is widely distributed in foods and plays diverse roles in protein and carbohydrate metabolism. The magnesium level in the shalgam beverage samples varied from 30.61 mg L⁻¹ (in B) to 75.38 mg L⁻¹ (in G). The level of magnesium reported in this study was relatively high studying comparison to the Mg levels reported by İyicinar[13] as 20.85–46.576 mg L⁻¹.

The lowest and highest levels of iron were found to be 0.16 mg L⁻¹ for M and 0.84 mg L⁻¹ for K, respectively. Previously reported iron values in shalgam beverage samples ranged from 0–0.78 mg L^−1[13] and 0.2–2.9 mg L⁻¹.[11] The iron values in the present study are in agreement with the values in the literature. Iron has several vital functions, such as carrying oxygen from the lungs to the tissues as a component of hemoglobin in red blood cells and electron transport within cells, and it participates in important enzyme systems in various tissues in the body.[18,19] It is known that adequate iron in the diet is very important in order to decrease the incidence of anemia.

Manganese is recognized as an essential trace element in several metabolic pathways, including Mn-containing enzyme systems.[20] The lowest and highest contents of manganese were found at 0.01 mg L⁻¹ for M and 0.79 mg L⁻¹ for G, respectively. The Mn contents in shalgam beverage were stated as 0–0.40 mg L⁻¹.^[13] The Institute of Medicine recommends that the intake of manganese from food should not exceed the tolerable daily upper limit of 11 mg per day.[21] The intake of Mn, with the assumed average consumption of the analyzed shalgam beverage samples is well below this limit.

Copper and zinc are essential minerals for all life forms and required cofactors for enzymatic reactions.[22] Copper was detected in sample A with the highest concentration (0.27 mg L⁻¹). İyicinar[13] did not detect copper in shalgam beverage; however, Sahin^[8] reported the presence of this element to be in the range of 218–234 μg L⁻¹. The highest level of zinc was found to be 0.23 mg L⁻¹ for sample I. Zinc concentrations of shalgam beverage samples have been previously reported in the ranges of 530–580 μg L^−1[8] and 0.03–0.73 mg L⁻¹.^[13] Our values for Zn for all the samples were below the maximum tolerable daily intake (0.3–1 mg kg⁻¹) of Zn recommended by the World Health Organization.[23]

The interest in minor elements has recently increased, as their presence can represent a qualitative parameter used, for example, as an index of a production process, environmental pollution, sanitary conditions. and the quality of raw material, which can all affect the properties of shalgam beverage and its health aspects. In this respect, some elements, such as Ni, Cd, Pb, and Sn, are of particular importance because of their correlation with environmental pollution, and others, such as Cd, Cu, and Fe, for their release from metal alloys of the equipment utilized for shalgam beverage production. The overall concentrations of Ni, Pb, and Sn were below 1 mg L⁻¹ in almost all of the samples. The Pb and Ni contents of shalgam beverage samples have been reported to be in the range of 57–65 μg L⁻¹ and 49–242 μg L⁻¹, respectively.^[8] The content of Pb in the samples exceeds the maximum permissible concentration for food according to the Turkish Food Codex, which is 0.05 mg L⁻¹.[24] There is no limit or data on the contents of Ni, Cd, and Sn in shalgam beverage. The correlation test was performed to investigate the interrelations between the element contents in shalgam beverage samples. Table 4 reports the correlation coefficients between major, minor, and ultra trace elements for variables studied. Some variables show significant correlations with each other. Pb is correlated weakly and negatively between calcium and magnesium, −0.482 and −0.481, respectively (p < 0.05).

Table 4 Correlation coefficient between major, minor, and ultra trace element concentrations in shalgam beverage samples

	P	Na	K	Ca	Mg	Fe	Cu	Zn	Mn	Ni	Pb	Sn	Cd
P	1
Na		1
K			1
Ca	0.583 ^**			1
Mg	0.628 ^**			0.823 ^***	1
Fe						1
Cu							1
Zn						0.456*		1
Mn	0.479*				0.477*	0.638 ^**			1
Ni						0.519*				1
Pb				−0.482*	−0.481*		0.873 ^***				1
Sn							0.794 ^***		0.541 ^**		0.780 ^***	1
Cd							0.919 ^***				0.869 ^***	0.819 ^***	1
*p < 0.05; ^** p < 0.01; ^*** p < 0.001.

CONCLUSIONS

The results of the ICP–OES analysis showed that shalgam beverage can contribute a considerable portion of the supply of major and minor elements in the diet. The values obtained revealed that Na, K, Ca, Ma, and P were the most abundant essential elements in shalgam beverage samples. The diversity results are marked for Na, Ca, Mg, P, and Cu. In this case, factors such as raw material origin, genetic variety of carrot and turnip, fermentation process, and industrial procedure should be considered, as well as the amount of the added NaCl and preservatives, such as sodium benzoate. This is a pioneer study that provided important information on safety and quality standards of shalgam beverage in Turkey and the information obtained is very important in order to know the content of these elements in a kind of food that is consumed by a large proportion of the population.

ACKNOWLEDGMENT

The authors would like to acknowledge valuable technical ICP-OES assistance from Nilgun Taban.