Journal of Animal Science and Technology
Korean Society of Animal Sciences and Technology

Exploring effects of organic selenium supplementation on pork loin: Se content, meat quality, antioxidant capacity, and metabolomic profiling during storage

Hyun Young Jung1, Hyun Jung Lee2, Hag Ju Lee1, Yoo Yong Kim1,3, Cheorun Jo1,2,3,*
1Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Science, Seoul National University, Seoul 08826, Korea
2Center for Food and Bioconvergence, Seoul National University, Seoul 08826, Korea
3Institute of Green Bio Science and Technology, Seoul National University, Pyeongchang 25354, Korea
*Corresponding author: Cheorun Jo, Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Science, Seoul National University, Seoul 08826, Korea., Tel: +82-2-880-4804, E-mail:

© Copyright 2024 Korean Society of Animal Science and Technology. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: May 03, 2023; Revised: Jun 25, 2023; Accepted: Jun 26, 2023

Published Online: May 31, 2024


This research was conducted to study the effects of organic selenium (Se) supplements at different levels on pork loin quality during storage. Fifteen pork loins were procured randomly from three groups, Con (fed basal diet), Se15 (fed 0.15 ppm organic Se along with 0.10 ppm inorganic Se), and Se45 (fed 0.45 ppm organic Se along with 0.10 ppm inorganic Se). Each sample was analyzed for Se contents, antioxidant properties (glutathione peroxidase [GPx] activity, 2,2′-azinobis-[3-ethylbenzothiazoline-6-sulfonic acid] [ABTS] and 2,2-diphenyl-1-picrylhydrazyl [DPPH] radical scavenging activities, 2-thiobarbituric acid reactive substances), physicochemical properties (water holding capacity, pH, color), and metabolomic analysis during 14-day storage period. Se45-supplemented group showed significantly higher Se contents and GPx activity than the other groups throughout the storage period. However, other antioxidant properties were not significantly affected by Se supplementation. Selenium supplementation did not have an adverse impact on physicochemical properties. Nuclear Magnetic Resonance-based metabolomic analysis indicated that the selenium supply conditions were insufficient to induce metabolic change. These results suggest that organic Se (0.15 and 0.45 ppm) can accumulate high Se content in pork loins without compromising quality.

Keywords: Pork loin; Selenium supplementation; Meat quality; Antioxidant properties; Metabolites


Pork feed primarily consists of soybean meal and corn, supplemented with various additives such as vitamins and minerals to control the growth rate of pigs [1,2]. The composition of pig feed can also influence pork quality [3]. Many studies have been conducted to improve both pork production and quality by supplementing pig feed with various additives, including antioxidants [4]. Vitamin C, vitamin E, and selenium (Se) have been used as antioxidants in feed, and previous research has shown that their use can modulate the antioxidant capacity, nutritional quality, and fatty acid composition of pork [1,5].

Se is a commonly used in pork farming due to its regulatory and immune system function [6,7]. It can also improve pork quality and nutritional value as it is an essential components of glutathione peroxidase (GPx) [8,9]. GPx is one of the antioxidant enzymes that can reduce lipid hydroperoxides and free hydrogen peroxide in body tissues [10]. Therefore, Se supplementation can increase GPx activity, potentially improving antioxidant capacity of pork [11].

Se exists in two chemical forms in nature, organic and inorganic [12]. Inorganic Se, mainly in the form of selenite and selenium salts, is commonly used in pork feed due to its easy supply and cost-effectiveness [13]. However, the use of inorganic Se has limitations such as low accumulation rate in the body despite high digestion and absorption rate [14], lower absorption rate compared to organic Se [15], and potential toxic effects at high levels [16].

On the other hand, organic Se, in the form of selenomethionine and selenium-yeast, has a higher accumulation efficiency and antioxidant activity when fed to livestock [17,18]. It can also prevent Se deficiency, which frequently occurs in weaning piglets when fed to sows [19]. In addition, organic Se has been reported to delay the post-oxidative reaction of the muscle, improving the nutritional value, flavor, and shelf life of meat, as well as meat color and water holding capacity (WHC) [2022]. Despite being expensive, organic Se has been considered for pig feeding [23].

Recently, there has been emphasis on converting feed supplements from inorganic Se to organic Se due to the limitation of Se and the potential benefits of organic Se [24]. However, economic feasibility is an important factor in livestock industry, and the conversion rate must be considered. Several studies are currently underway to replace and/or combine inorganic Se with organic Se, and some have reported improved antioxidant performance and health levels [25]. While we have confirmed the combined effect of inorganic and organic Se on the growth performance of pigs at different levels (data not shown), their effect on antioxidant capacity and quality has not been studied for our market consumers. Therefore, we evaluated the combined effect of inorganic and organic Se on the quality of pork loin during refrigerated storage.


Sample preparation

A total of 105 growing pigs ([Yorkshire × Landrace] × Duroc) with an average body weight of 39.85 ± 0.01kg were divided into 15 pens with 7 pigs in a randomized complete block design. The pigs were kept in climate-controlled facility that had a fully concrete floor measuring 2.4 by 2.9 m2. A feeder and a nipple drinker were provided in each pen to ensure that the pigs had unrestricted access to food and water. The experimental period was 14 weeks during with three types of experimental treatments were implemented. Each of the 5 pens was assigned to one of 3 treatment groups, resulting 5 pens per group. The experimental treatments were as follows: Con (fed basal diet), Se15 (fed 0.15 ppm organic Se along with 0.10 ppm inorganic Se), and Se45 (fed 0.45 ppm organic Se along with 0.10 ppm inorganic Se). Each treatment group was fed with 0.10 ppm of inorganic Se (Genebiotech, Gongju, Korea), while the addition of organic Se (Sel-PlexTM, Alltechm, Nicholasville, KY, USA) was adjusted to induce Se accumulation in pork. The transformation from inorganic to organic Se was accomplished by partially modifying the feeding quantity of inorganic Se. From each group, 5 pigs were randomly selected and their loins (M. longissimus) were obtained. The samples were cut into 3 pieces (330 ± 20 g) and packaged in air permeable bags. They were then stored at 4°C, and the following experiments were conducted on days 0, 7 and 14. On each storage day, WHC, pH, and meat color were analyzed immediately, and the samples were frozen at −70°C until further analyses.

Se content

The Se concentration in pork loins was determined using the fluorometric method. To perform the analysis, 0.5 g of the sample was added to a screw cap culture tube containing 5 mL of a mixed solution of HClO4 (perchloric acid 70%) and HNO3 (nitric acid 70%) in 1:4 ratio. The culture tube was digested for 4 h in a digestion block at 210°C, then cooled down in room temperature. After cooling, add 0.5 mL HCl was added to the tube and the tube was heated at 150°C for 30 min. Then, the tube was cooled again, and 15 mL of 0.1M EDTA solution and 2 mL of 0.1% 2,3-diaminonaphthalene solution were added. The tube was voltexed for 5 sec and incubate in a water bath at 60°C for 30 min. Following incubation, a 10-second vortexing of the tube was done after adding 5 mL of cyclohexane. The extracted cyclohexane layer was transferred to a cuvette, and the absorbance was measured using 369 nm excitation and 525 nm emission settings.

Glutathione peroxidase (GPx) activity

The activity of GPx activity was measured through the utilization of Glutathione Peroxidase Assay Kit (353919, Sigma-Aldrich, Burlington, USA). Briefly, minced meat sample (5 g) was homogenized with 25 mL of cold homogenization buffer (50 mM Tris-HCl, pH 7.5, 5 mM EDTA, 1 mM DTT) at 12,000 rpm for 1 min (T25 digital ULTRA-TURRAX®, IKA, Staufen, Germany). The homogenized sample was centrifuged (Continent 512 R, Hanil, Incheon, Korea) at 10,000×g for 15 min, and the supernatant was taken. The Assay Buffer, Co-Substrate Mixture, and NADPH included in the kit were mixed with the supernatant. Then, the reaction was initiated by adding hydroperoxide. Thereafter, the absorbance was measured at 340 nm every min for 10 min to confirm the GPx activity.

Antioxidant activity

Ground sample (3 g) was homogenized with 12 mL of deionized distilled water at 9,600 rpm for 30 s (T25 digital ULTRA-TURRAX®, IKA). The homogenized samples were centrifuged (Continent 512 R, Hanil) at 2,265×g for 10 min, and filtered using filter paper (No. 1, Whatman PLC, Maidstone, UK). For the meat extract, after centrifuging at 2,265×g for 10 min, 10 mL of chloroform was added to the filtrate.

For the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay, a solution of 14 mM ABTS and 4.9 mM potassium persulfate was prepared and left in the dark for 16 minutes after vigorous vortexing. The subsequent steps were performed following the protocol described by Choe et al. [26].

For the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, 1 mL of the diluted meat extract was mixed with 1 ml of 0.2 mM DPPH in methanol, vortexed, and placed in the dark for 30 min at room temperature. The subsequent steps were performed following the protocol described by Choe et al. [26].

For the 2-thiobarbituric acid reactive substances (TBARS) assay, the meat sample (5 g) was homogenized with 15 mL of deionized distilled water and 50 μL of 7.2% butylated hydroxy toluene solution at 9,600 rpm for 30 s (T25 digital ULTRA-TURRAX®, IKA). Then, the subsequent steps were followed by Rupasinghe et al. [27].

Physicochemical analysis

Minced meat sample (5 g) was placed on a filter paper and centrifuged at 252×g for 10 min (Continent 512R, Hanil). The WHC was measured as described by Kwon et al. [28] and pH by Rupasinghe et al. [27], respectively. The meat color of pork loin was measured using a colorimeter (CM-5, Konica Minolta, Osaka, Japan). Prior to measurement, the colorimeter was calibrated with a standard black plate. The meat color was measured at three different locations on the top and the bottom of each sample [22]. The color value was expressed as CIE L*, CIE a*, CIE b* and delta E was calculated as(ΔL*)2+(Δa*)2+(Δb*)2.

Nuclear Magnetic Resonance (NMR)-based metabolic analysis

The NMR analysis was performed according to Kim et al. [29]. In brief, each minced sample (5 g) was homogenized with 20 mL of 0.6 M perchloric acid at 12,000 rpm for 1 min (T25 digital ULTRA-TURRAX®, IKA). The homogenized samples were centrifuged at 2,265×g for 20 min (Continent 512R, Hanil), and the supernatant was transferred in another test tube and adjusted to 7.0 with sodium hydroxide. Then, the subsequent steps were performed following the method [29].

Statistical analysis

The data were analyzed using two-way analysis of variance (SAS 9.4, SAS Institute, Cary, NC, USA). The mean values and standard errors of the means were presented as the results. Differences with a significance level of 0.05 were determined by the Student-Newman-Keuls multiple range test. Partial least squares-discriminant analysis was conducted using MetaboAnalyst 5.0 (


Se content

Throughout all storage days, the pork loin supplemented with Se45 showed the highest Se contents followed by Se15 and Con (Fig. 1; p = 0.0009). This indicates that the higher organic Se supplementation leads to higher residual Se contents in pork loins, as organic Se sources are highly bioavailable [15,29]. When Se-yeast was supplied as organic Se source, the amount of Se in the loin increased with increasing Se concentration in the feed [30]. Zhan et al. [22] also confirmed that pig muscle Se content increased more than double when fed with organic Se compared to inorganic Se. According to the findings of Zhang et al. [31], intramuscular Se content increased significantly when SeMet was used as a feed source, in comparison to inorganic Se sources such as SeNa or basic feeding treatment groups. Furthermore, organic Se has low toxicity, high transfer efficiency, and the ability to build and maintain Se reserve in muscle [30].

Fig. 1. Selenium contents of pork loin raised under different selenium supplementation conditions and storage period. Con, fed basal diet; Se15, pork loin from feeding organic Se 0.15 ppm + inorganic Se 0.10 ppm; Se45, pork loin from feeding organic Se 0.45 ppm + inorganic Se 0.10 ppm. A–CDifferent letters in the same storage days indicate significant differences among selenium feeding conditions (p < 0.05). a,bDifferent letters within the same selenium feeding conditions indicate significant differences during storage (p < 0.05).
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Meanwhile, Se contents were slightly decreased in Se15 and Se45 on day 7 and remained constant thereafter (Fig. 1; p < 0.0001). This reduction in Se content in pork during the refrigerated storage is likely due to microbial activity, temperature, etc. [32]. Despite this decrease, Se15 and Se45 still had higher Se contents than Con, indicating that the effect of Se supplementation can be maintained in pork during storage. We found no further impact from the interaction between the treatment and storage period (p = 0.6826).

The increased Se content in pork can have various impacts, as Se may have prevented oxidative damage from live animals to meat storage [33]. Therefore, high productivity can be promoted for pigs, consumers who lack selenium can be relieved, and several beneficial effects can be provided to consumers. Se supplementation in live animals can improve reproductive physiological characteristics, such as semen volume and semen concentration [34]. Furthermore, Se supplementation in live animals can improve reproductive physiological characteristics, such as semen volume and semen concentration [34]. Furthermore, Se content in milk from sow increases, which has the advantage of solving Se deficiency that can easily occur in piglets [19]. With regards to meat quality, the supplementation of organic Se can enhance meat color stability by protecting myoglobin from oxidation with its antioxidant ability [22]. Calvo et al. [35] confirmed that Se-fed pork has high lipid stability during storage. In addition, consumption of Se-enriched pork may result in a reduction in toxic factors, as Se in pork has the ability to bind with heavy metals (such as cadmium, mercury, zinc, etc.) and facilitate their excretion from the body [36,37]. Moreover, Se content in pork exhibits antioxidant effects by interacting with various antioxidant enzymes in the body, which can prevent DNA damage by averting several harmful effects of free radicals [38]. Therefore, when higher organic Se is fed to pigs, pork with the higher Se content can be served to consumers, providing additional health benefits at the point of their consumption.

Antioxidant properties
Glutathione peroxidase (GPx) activity

GPx is an antioxidant enzyme that contains Se [8,9] and can be increased by Se supplementation in pigs [39,40]. As a result of confirming GPx activity in this study, organic Se supplementation had a significant effect on GPx activity (Fig. 2; p = 0.0179), but the effect of interaction between organic Se supplementation and storage period was not confirmed (p = 0.7874). Previous research has indicated that selenium can be absorbed through the digestive system and subsequently accumulated in various organs [6]. The accumulated Se undergoes various metabolic processes and plays a key role in the synthesis of GPx. As GPx contains Se in its active center, increased uptake and accumulation of Se in the body can promote its activity [41].

Fig. 2. Glutathione peroxidase (GPx) activity of pork loin raised under different selenium supplementation conditions and storage period. Se15, pork loin from feeding organic Se 0.15 ppm + inorganic Se 0.10 ppm; Se45, pork loin from feeding organic Se 0.45 ppm + inorganic Se 0.10 ppm.
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The increased activity of antioxidant enzymes may improve the storage stability of meat. Although the Se content in muscle decreased as the storage days increased in the experimental groups fed Se, Se45 had the highest Se content on all storage days. The increased activity of antioxidant enzymes can increase the antioxidant capacity of meat, which can have a positive effect on improving meat quality such as storage stability.

2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities

To investigate antioxidant capacity of Se-supplemented pork, ABTS/DPPH scavenging activities were conducted (Table 1). Organic Se supplementation did not significantly change the ABTS scavenging activity, the DPPH scavenging activity showed a similar trend in each treatment, possibly due to their strong correlation (r = 0.906). These unexpected results could be attributed to the fact that the change in GPx activity was not sufficient to affect the antioxidant activity of meat (Figs. 1 and 2). Although GPx plays a role in reducing lipid peroxide to alcohol and free hydrogen peroxide to water [10], ABTS/DPPH scavenging activities confirm the antioxidant effect through scavenging of free radicals, not hydrogen peroxide, and may not directly related to the high activity of GPx.

Table 1. Antioxidant properties of pork loin as raised under different selenium supplementation conditions and storage period
Item Treatment Storage period (days) SEM1)
0 7 14
TBARS (mg MDA/kg) Con2) 0.18 0.15 0.18 0.016
Se15 0.18a 0.13b 0.18a 0.011
Se45 0.16ab 0.12b 0.18a 0.015
SEM 0.021 0.009 0.010
ABTS scavenging rate (%) Con 32.59b 39.79a 39.63a 1.815
Se15 31.28c 36.70b 42.31a 1.233
Se45 33.11b 42.46a 44.79a 1.495
SEM 0.948 1.987 1.484
DPPH scavenging rate (%) Con 82.42a 60.56c 68.26b 2.267
Se15 81.06a 59.89c 68.46b 1.473
Se45 83.72a 61.87c 71.36b 1.180
SEM 1.530 1.901 1.657

n = 15.

Con, fed basal diet; Se15, pork loin from feeding organic Se 0.15 ppm + inorganic Se 0.10 ppm; Se45, pork loin from feeding organic Se 0.45 ppm + inorganic Se 0.10 ppm.

Different letters within the same row differ significantly (p < 0.05).

TBARS, 2-thiobarbituric acid reactive substances; ABTS, 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid); DPPH, 2,2-diphenyl-1-picrylhydrazyl.

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During 14 days of storage period, the tendencies in DPPH and ABTS scavenging activities were different (Table 1). ABTS scavenging activity was gradually increased, possibly due to the increased functional peptides from protein degradation during post-mortem (p < 0.05) [42]. However, in the case of DPPH assay, its activity was significantly decreased on day 7 and increased thereafter. The different results in ABTS and DPPH scavenging activities may be attributed to different mechanisms and subjects of both analytical methods. The ABTS assay is for both hydrophilic and lipophilic antioxidants, whereas DPPH assay is more applicable to hydrophobic system. It seems that post-mortem changes in pork induced stronger impact on ABTS and DPPH scavenging activities than that from organic Se supplementation.

2-thiobarbituric acid reactive substances (TBARS)

Lipid oxidation is a major concern in pork quality, as it can negatively affect acceptability of the meat. The oxidation of lipids can occur due to the inadequate scavenging capacity of antioxidants against the release of free radicals [43]. The extent of lipid oxidation during storage was assessed by conducting TBARS analysis as shown in Table 1. In the present study, organic Se supplementation did not exhibit a significant impact on lipid oxidation compared to the control group. This was unexpected as meat GPx activity can counteract free radicals, thereby influencing lipid oxidation [44]. Several factors may have contributed to this finding. Firstly, slow lipid oxidation rate by low-fat content in pork loin may have made it difficult to observe the differences from the enhanced GPx activity in the Se-supplemented groups (Fig. 2), as fat content is one of the main factors affecting lipid oxidation [43]. Additionally, the progress of lipid oxidation may have been delayed as the samples were stored at low temperatures. Consequently, we found that the lipid oxidation barely occurred in all groups after 14 days of storage, regardless of different Se feedings (Table 1). On day 7, a slight but significant decrease in TBARS value was found only in the Se-supplemented groups. Secondly, the increase in GPx may not have been enough to inhibit further lipid oxidation in pork loin. Hoac et al. [45] reported a certain decrease in lipid oxidation by GPx activity when 4 U/g GPx was added to chickens and ducks.

Taken the results from antioxidant properties together, although Se supplementation improved the activity of GPx, these changes did not affect the antioxidant activity and the lipid stability of pork loin during storage.

Physicochemical properties
Water holding capacity (WHC) and pH

During the storage period, no significant difference was observed in WHC and pH between the control and groups supplemented with organic Se (Table 2; p = 0.5897 and p = 0.2557, respectively). However, the changes in these properties varied depending on the levels of organic Se supplementation. During 14 days of storage, the WHC changed by 13.59%, 18.79%, and 18.89% in the control, Se15, and Se45 groups, respectively. It can be attributed to the decrease in water content over time (data not shown), as its decrease may limit free water release [46]. Similarly, the pH decreased at different rates in each group, with the control group having a decrease of 0.39, while Se15 and Se45 had reduction of 0.26 and 0.24, respectively. Even though several studies have reported that organic Se supplementation can increase WHC and reduce the decrease in pH in pork after slaughter [33,47], in this study, organic Se supplementation (15 or 45 ppm) with 10 ppm inorganic Se did not affect WHC and pH in pork during 14 days of storage.

Table 2. Water holding capacity (WHC) and pH of pork loin raised under different selenium supplementation conditions and storage period
Item Treatment Storage period (days) SEM1)
0 7 14
WHC (%) Con2) 59.35b 61.50b 72.94a 2.414
Se15 57.80b 65.27b 76.59a 2.681
Se45 55.37c 61.06b 74.26a 1.289
SEM 2.319 2.336 1.960
pH Con 5.90a 5.53b 5.51b 0.058
Se15 5.79a 5.50b 5.53b 0.050
Se45 5.81a 5.54b 5.57b 0.048
SEM 0.067 0.047 0.038

n = 15.

Con, fed basal diet; Se15, pork loin from feeding organic Se 0.15 ppm + inorganic Se 0.10 ppm; Se45, pork loin from feeding organic Se 0.45 ppm + inorganic Se 0.10 ppm.

Different letters within the same row differ significantly (p < 0.05).

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Meat color

In regards to meat color, there was no significant difference in the CIE L*-, CIE a*-, and CIE b*-values among different organic Se supplementation, except for CIE a*-value on day 7 (Table 3). While previous studies have reported that organic Se supplementation at 0.3 ppm can increase CIE a* and CIE b*-values [35], this study did not observe any changes in meat color due to the lack of pH change in pork. The pH plays an important role in the mechanism by which oxymyoglobin is oxidized to metmyoglobin. In the case of Se-yeast, a type of organic Se fed in this experiment, it was absorbed through the methionine transporter and incorporated into the protein constituting the body, suggesting that it may not have affected meat quality, including its color. Nevertheless, previous research has indicated that consumption of organic Se may enhance muscle antioxidant capacity, protecting myoglobin from oxidation and thereby improving color stability [22]. Conversely, inorganic Se has been reported to induce lighter color than pigs fed with organic Se, mainly due to water droplet loss that occurred when fed with inorganic Se [21].

Table 3. Meat color of pork loin raised under different selenium supplementation conditions and storage period
Item Treatment Storage period (days) SEM1)
0 7 14
CIE L* Con2) 55.56 54.47 50.93 1.353
Se15 54.77a 55.14a 48.85b 0.833
Se45 54.63ab 57.94a 51.17b 1.120
SEM 0.816 1.320 1.247
CIE a* Con 6.70b 11.26ABa 10.41a 0.636
Se15 6.78c 12.04Aa 10.28b 0.565
Se45 6.76b 10.03Ba 9.05a 0.585
SEM 0.431 0.529 0.775
CIE b* Con 13.10c 17.11a 15.49b 0.509
Se15 13.05c 17.87a 14.89b 0.317
Se45 12.09c 16.31a 14.15b 0.593
SEM 0.285 0.676 0.415
Chroma Con 14.74b 20.52a 18.73a 0.631
Se15 14.75c 21.60a 18.14b 0.525
Se45 13.86c 19.19a 16.85b 0.747
SEM 0.371 0.792 0.683
Hue angle Con 62.97a 56.73b 56.48b 1.649
Se15 62.56a 56.32b 55.66b 1.269
Se45 60.87 58.57 57.67 1.290
SEM 1.386 0.965 1.773
ΔE Con - 7.50 6.69 1.437
Se15 - 7.21 7.30 0.985
Se45 - 6.57 5.47 1.221
SEM - 1.075 1.362

n = 15.

Con, fed basal diet; Se15, pork loin from feeding organic Se 0.15 ppm + inorganic Se 0.10 ppm; Se45, pork loin from feeding organic Se 0.45 ppm + inorganic Se 0.10 ppm.

Different letters within the same column indicate significant differences (p < 0.05).

Different letters within the same row differ significantly (p < 0.05).

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During storage, different atmospheres can cause variation in the meat color of pork can [46]. The total color difference (ΔE) was calculated to confirm the changes in color (Table 3). Overall, no distinct color changes were observed in this study, indicating that the organic Se supplementation did not affect meat color in pork loin. The CIE L*-value tended to decrease, possibly due to an increase in WHC (Table 2), regardless of the type of organic Se supplementation. The CIE a*-value in each group was also affected by post-mortem changes. Its increases on day 7 is possibly due to the oxygenation of myoglobin and the value decreased due to oxidation to metmyoglobin [48]. No previous study has investigated the effect of mixed feeding of organic and inorganic Se on the meat color of pork. Based on the results of this study, the organic Se supplementation treatment did not affect meat color.

Nuclear Magnetic Resonance (NMR)-based metabolic analysis

We performed NMR-based metabolic analysis to investigate the effects of different Se supplementation on the metabolic profiles of pork loin during 14 days of storage. Table 4 presents a total of 31 metabolites that were identified across all groups, including 15 free amino acids, 4 nucleotide-related products, and 3 organic acids. To assess the metabolomic differences among treatment groups and storage periods, multivariate analysis was performed, as shown in Figs. 3 and 4, respectively. The metabolic profiles of Con, Se15, and Se45 were not distinctly different from each other on each storage day, as indicated in Fig. 3. This suggests that the accumulated Se content in Se15 and Se45 did not have an impact on the metabolic differences during the storage period. No significant changes in metabolites, except for a few such as tyrosine, inosine, and betaine on day 0 and glutamate on day 14, were observed with different Se supplementation. Furthermore, lactate content was not significantly different between Con and both Se-supplemented groups (Table 4), but its content increased during storage, leading to a pH decrease (Table 2). Although slight changes in the metabolites in each group were observed during storage period, in overall, these changes were not distinct (Fig. 4). Each group exhibited different changes in the levels of amino acids (alanine, asparagine, creatine, glutamate, glutamine, glycine, isoleucine, leucine, methionine, phenylalanine, threonine, tyrosine, and valine) and nucleotide-related compounds (hypoxanthine and inosine), as shown in Table 4. These changes can be attributed to the degradation of proteins and nucleic acids during storage, leading to an increase in the content of degradation products [49]. Additionally, lactate, which was previously mentioned, the other metabolites (acetate, carnosine, ethanol, glucose, N,N-dimethylglycine, niacinamide, and O-acetylcarnitine) also showed significant changes during 14 days of storage, but not due to Se supplementation. These results suggest that the Se feeding conditions used in this experiment were not sufficient to induce metabolomic changes in pork loin.

Table 4. Metabolites profiles (mg/100 g) of pork loin raised under different selenium supplementation conditions and storage period
Item Treatment Storage period (days) SEM1)
0 7 14
Free amino acids
 Alanine Con2) 29.67 22.10 28.83 2.752
Se15 24.89ab 22.15b 31.60a 2.291
Se45 28.67 26.81 33.32 2.033
SEM 3.125 1.922 1.870
 Asparagine Con 3.54b 3.77b 6.67a 0.770
Se15 2.93b 4.11ab 4.95a 0.451
Se45 3.21b 4.64ab 6.08a 0.606
SEM 0.506 0.497 0.813
 Creatine Con 391.88b 431.87b 509.16a 16.008
Se15 406.25c 453.50b 488.20a 9.882
Se45 410.58 476.93 504.61 30.326
SEM 10.728 30.223 15.654
 Glutamate Con 7.08b 8.34b 12.49Ba 1.179
Se15 8.87b 10.99ab 14.211ABa 1.284
Se45 9.05b 11.28b 16.74Aa 0.996
SEM 1.161 1.194 1.121
 Glutamine Con 27.97a 16.53b 18.89b 2.882
Se15 25.37 17.02 18.51 3.409
Se45 26.81 22.90 19.65 2.703
SEM 4.629 2.143 1.105
 Glycine Con 26.71 34.43 41.64 7.313
Se15 28.90b 36.20ab 43.24a 3.604
Se45 27.88 36.75 36.57 4.295
SEM 4.004 5.113 6.537
 Isoleucine Con 2.47b 4.25b 7.40a 0.868
Se15 2.96c 5.80b 8.93a 0.430
Se45 3.48b 5.24b 8.43a 0.786
SEM 0.269 0.728 0.977
 Leucine Con 2.80b 5.28b 9.22a 1.197
Se15 4.18c 7.12b 11.27a 0.667
Se45 4.12b 6.65b 10.95a 0.975
SEM 0.568 0.983 1.241
 Methionine Con 5.59b 6.82b 11.39a 1.250
Se15 5.12c 8.79b 11.96a 0.636
Se45 5.97b 8.97b 12.71a 1.107
SEM 0.345 1.186 1.290
 Phenylalanine Con 2.68c 5.13b 7.96a 0.743
Se15 3.35c 6.34b 9.54a 0.304
Se45 3.83b 5.92b 9.25a 0.722
SEM 0.192 0.653 0.838
 Taurine Con 38.23 35.77 40.20 4.510
Se15 36.53 40.09 43.24 3.619
Se45 46.18 42.41 38.74 2.928
SEM 3.399 4.239 3.534
 Threonine Con 6.30c 9.82b 12.72a 0.920
Se15 7.28 13.99 13.14 1.950
Se45 7.71b 11.35a 13.83a 1.073
SEM 0.429 2.217 0.839
 Tyrosine Con 3.69Bb 8.54b 14.82a 1.632
Se15 4.45Bc 10.18b 16.50a 0.708
Se45 5.60A 10.19 16.78 1.408
SEM 0.307 1.288 1.842
 Valine Con 4.16b 6.10b 9.68a 1.124
Se15 4.78c 7.94b 11.87a 0.627
Se45 5.70b 7.58b 11.60a 0.992
SEM 0.439 0.941 1.250
 β-alanine Con 7.49 7.33 8.40AB 0.591
Se15 7.72 7.96 7.99B 0.381
Se45 7.84 9.05 9.55A 0.498
SEM 0.393 0.641 0.420
Nucleotide-related products
 Hypoxanthine Con 11.43 9.47 12.92 1.168
Se15 11.74ab 10.15b 13.40a 0.709
Se45 12.24 11.69 13.47 1.051
SEM 1.373 0.745 0.731
 IMP Con 79.80 92.02 76.74 5.137
Se15 89.49 90.69 73.91 5.777
Se45 90.51 100.20 82.46 7.372
SEM 7.590 7.072 2.549
 Inosine Con 37.95Bb 54.53b 75.34a 6.024
Se15 37.73Bc 57.22b 77.24a 2.165
Se45 42.24Ac 60.48b 74.93a 4.201
SEM 0.820 4.769 5.934
 UMP Con 2.94 3.68 2.95 0.212
Se15 3.52 3.65 3.54 0.173
Se45 3.20 3.48 3.16 0.232
SEM 0.215 0.217 0.188
Organic acids
 Acetate Con 3.41b 4.73b 6.55a 0.434
Se15 3.37c 5.33b 7.16a 0.269
Se45 3.99 5.33 5.95 0.529
SEM 0.223 0.467 0.522
 Lactate Con 266.39b 345.02a 389.90a 18.649
Se15 284.39b 360.10a 384.63a 13.010
Se45 277.13b 362.30a 371.84a 24.988
SEM 16.370 24.980 15.794
 Methylmalonate Con 5.59b 7.15b 8.96a 0.529
Se15 6.15b 8.04a 8.79a 0.297
Se45 5.68b 7.82a 8.60a 0.590
SEM 0.302 0.560 0.557
 Betaine Con 34.96B 30.79 30.13 2.225
Se15 34.86B 35.28 28.78 4.596
Se45 46.01A 44.94 38.50 3.970
SEM 2.740 3.920 4.355
 Carnosine Con 224.98b 313.86a 357.50a 15.515
Se15 284.85 323.75 347.96 27.245
Se45 221.90b 315.65a 337.96a 28.333
SEM 28.347 27.062 15.810
 Ethanol Con 0.88 1.78 2.28 0.391
Se15 1.04b 2.47a 2.40a 0.141
Se45 1.04b 2.19a 2.25a 0.285
SEM 0.107 0.253 0.423
 Glucose Con 42.92 72.18 81.68 19.945
Se15 46.56b 74.86ab 87.63a 9.465
Se45 67.56 89.19 77.10 25.165
SEM 17.404 18.664 21.666
 Glycerol Con 9.06 9.29 10.76 1.339
Se15 9.65 9.24 12.96 1.112
Se45 11.32 10.64 11.31 0.627
SEM 0.829 0.892 1.393
 Methanol Con 0.74a 0.30b 0.33b 0.105
Se15 0.61 0.38 0.35 0.082
Se45 0.75 0.49 0.41 0.100
SEM 0.136 0.091 0.033
 N,N-Dimethylglycine Con 1.93b 2.27b 2.81a 0.158
Se15 1.90c 2.45b 2.71a 0.055
Se45 2.01b 2.58ab 2.83a 0.190
SEM 0.058 0.189 0.158
 Niacinamide Con 4.55b 6.70a 7.69a 0.471
Se15 5.05c 6.99b 7.86a 0.244
Se45 5.16b 6.91a 7.60a 0.537
SEM 0.351 0.564 0.358
 O-Acetylcarnitine Con 7.56a 2.60b 3.46b 0.783
Se15 7.51 3.64 3.96 1.300
Se45 7.66a 4.56b 4.14b 0.764
SEM 1.541 0.658 0.280

n = 15.

Con, fed basal diet; Se15, pork loin from feeding organic Se 0.15 ppm + inorganic Se 0.10 ppm; Se45, pork loin from feeding organic Se 0.45 ppm + inorganic Se 0.10 ppm.

Different letters within the same column indicate significant differences (p < 0.05).

Different letters within the same row differ significantly (p < 0.05).

Download Excel Table
Fig. 3. Partial least squares-discriminant analysis of metabolites by storage period from pork loin raised under different selenium supplementation conditions and storage period. Con, fed basal diet; Se15, pork loin from feeding organic Se 0.15 ppm + inorganic Se 0.10 ppm; Se45, pork loin from feeding organic Se 0.45 ppm + inorganic Se 0.10 ppm.
Download Original Figure
Fig. 4. Partial least squares-discriminant analysis of metabolites by treatment group from pork loin raised under different selenium supplementation conditions and storage period. Con, fed basal diet; Se15, pork loin from feeding organic Se 0.15 ppm + inorganic Se 0.10 ppm; Se45, pork loin from feeding organic Se 0.45 ppm + inorganic Se 0.10 ppm.
Download Original Figure


This study found that different levels of organic Se (0.15 and 0.45 ppm) combined with inorganic Se did not significantly affect pork quality during 14 days of storage, despite an increase in tissue Se content and GPx activity. Therefore, high Se content in the organic Se-fed group may have a positive effect on Se accumulation in pig muscle, but organic Se supplementation up to 45 ppm does not affect pork quality during storage periods of up to 14 days. In the results of supplementation with Se, the same phenomenon as the control group was confirmed on all days of storage. Therefore, through this study, it was confirmed that Se, a trace mineral used for pig breeding management, does not adversely affect pork quality.

Competing interests

No potential conflict of interest relevant to this article was reported.

Funding sources

This research was supported by the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (IPET) through the Useful Agricultural Life Resources Industry Technology Development Project, funded by the Ministry of Agriculture, Food and Rural Affairs (MAFRA) (120051022SB010).


Not applicable.

Availability of data and material

Upon reasonable request, the datasets of this study can be available from the corresponding author.

Authors’ contributions

Conceptualization: Lee Hyun Jung, Kim YY, Jo C.

Data curation: Lee Hyun Jung.

Formal analysis: Jung HY, Lee Hag Ju.

Methodology: Jung HY, Lee Hyun Jung.

Investigation: Jung HY, Lee Hag Ju.

Writing - original draft: Jung HY, Lee Hyun Jung.

Writing - review & editing: Jung HY, Lee Hyun Jung, Lee Hag Ju, Kim YY, Jo C.

Ethics approval and consent to participate

This article does not require IRB/IACUC approval because there are no human and animal participants.



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