The objective of this study was to evaluate the differences in composition among six brands of conventional soybean and six genetically modified cultivars (GM). We focused on the isoflavones profile and mineral content questioning the substantial equivalence between conventional and GM organisms. The statement of compliance label for conventional grains was verified for the presence of genetic modified genes by real time polymerase chain reaction (PCR). We did not detect the presence of the 35S promoter in commercial samples, indicating the absence of transgene insertion. For mineral analysis, we used the method of inductively coupled plasma-optical emission spectrometry (ICP-OES). Isoflavones quantification was performed by high performance liquid chromatography (HPLC). The results showed no statistical difference between the conventional and transgenic soybean groups concerning isoflavone content and mineral composition. The concentration of potassium, the main mineral component of soy, was the highest in conventional soybeans compared to that in GM soy, while GM samples presented the highest concentrations of iron.
Soybean (Glycine max Merrill), an important oilseed in different human and animal nutrition products, has high economic value in the domestic and international market. In 2012/2013, the world soybean production was 285.89 million tons. The United States, the largest grower, produced 93.08 million tons of soybeans on a cultivated area of 31.13 million hectares, and Brazil was the second largest producer, with an output of 85 million tons and occupancy of 28.25 million hectares [
A genetically modified organism (GMO) or transgenic organism is defined as an “organism whose genetic material has been altered by any genetic engineering technique” [
To regulate the right to information on GM foods and considering that food labels are an important vehicle for communication between producers and society, it is important that the labeling of GMO foods complies with current legislation. In Brazil, the Decree Law No. 4680 of April 4, 2003, Ordinance No. 2658, of December 22, 2003, and Article 40 of Law No. 11.105/2005 address this issue, and regulate the mandatory labeling of foods and food ingredients for human or animal consumption produced from GMOs [
In addition to its economic and nutritional importance, soy has been studied for the presence of bioactive compounds, especially isoflavones, compounds that have a potential effect on health, reducing the risk of neuro degenerative and chronic diseases associated with aging, such as osteoporosis, cognitive dysfunction, hypertension, coronary heart disease, cancer, and menopause-related symptoms [
Isoflavones are a sub-class of flavonoids, which are found naturally as polyphenols and have three benzene rings in their structures. Twelve isoflavones are found in soy, comprising the aglycones daidzein, glycitein, and genistein, the glycosides daidzin, glycitin, and genistin, and their conjugated forms malonyl glucosides and acetyl glucosides [
Some studies have indicated that genetic variation affects the content of isoflavones in soybean cultivars and different concentrations of isoflavones can be found in different crops and different cultivation sites [
Nevertheless, studies on the quantification of isoflavones and mineral contents in different cultivars of genetically modified grains are scarce. Accordingly, we sought to evaluate the profile of isoflavones and minerals in conventional soybeans traded in Belo Horizonte/MG and transgenic cultivars planted in the state of Minas Gerais in the 2010/2011 season, and to correlate this profile with the presence or absence of grain genetic modification. We also assessed the conformity of the labels of the marketed soybeans samples with the legislation on mandatory GMO foods labeling.
We acquired six samples of soybeans from different suppliers in the municipality of Belo Horizonte /MG during November 2011 (SC1, SC2, SC3, SC4, SC5, and SC6). Another six samples of transgenic cultivars were provided by COPAMIL (AGRICULTURAL COOPERATIVE Mista Iraí Ltda). The following varieties were studied: Favorita-S2, Valiosa-S2, 850-S2, 811-S2, 750-C1, and 740-C1 (ST1, ST2, ST3, ST4, ST5, and ST6, respectively).
The evaluation of the labeling was performed taking into account the compliance with current legislation for food and food ingredients for human consumption or feed containing, or produced from, GMOs [
The presence of the transgene was initially verified by the detection of the 35S promoter and, when present, detection of the Roundup Ready (RR) transgene, according to ISO 21570:2005 [
For mineral analysis, the methodology used was that recommended by the Instituto Adolfo Lutz [
The samples were analyzed directly by inductively coupled plasma-optical emission spectrometry (ICP-OES; Perkin Elmer, mod. Optima 2000 DV-sampler, mod. As90plus) in Axial configuration, at 1400 kW radiofrequency power, and 0.60 L∙min−1 gas flow. For analysis of isoflavones, the samples were crushed in a micromill and degreased with n-hexane (HPLC grade). The extraction of isoflavones was performed according to the method proposed by Carrão-Panizzi [
Statistical analysis was performed using analysis if variance (ANOVA) and Tukey’s test for comparison of the means, as well as the Statistica 7.0 program (STATSOFT, 2004), with a significance level of 5%.
Article 40 of Law No. 11.105/2005 defines that “food and food ingredients for human consumption or animal feed containing or produced from GMOs or derivatives should contain information on their labels accordingly” [
Initially, we observed that the label statements in the commercial soybean samples did not comply with the law. However, the results of the genetic analysis did not show the presence of the 35S promoter. Therefore, there was no need to investigate RR gene alterations, as described in the methodology. Thus, since the tested samples effectively contained no detectable amounts of GMOs, the brands sampled in local suppliers were in accordance with the law.
It is interesting to note that although 76% of soybeans grown in Brazil are from transgenic cultivars, the conventional product continues to be prominent in local trades. In a study by Branquinho and colleagues [
Over the last decade, other studies have assessed the presence of GMOs in food available in the consumer market. Cardarelli et al. [
Brod and colleagues [
In 2007, Brod and Arisi [
In 2008, Brod and Arisi [
It is interesting to note that these studies were conducted primarily with soy products, in which the presence of GM soy lecithin and RR was detected but not the 35S promoter. These results suggest that the use of GM soybeans is directed to processed foods.
Regarding the glycoside daidzin (SC 4.61 ± 1.88 and ST 6.76 ± 3.74 mg∙100 g−1 of defatted sample) and its corresponding aglycone form daidzein (SC 55.40 ± 12.64 and ST 67.14 ± 31.95 mg∙100 g−1 of defatted sample), there was no statistically significant difference (p > 0.05) when comparing the ST (GM soy) and SC (commercial soybean) sample groups, which is in accordance with the results of Zhou and colleagues [
The work of Zhou and colleagues [
The absence of statistically significant difference (p > 0.05) between the samples of GM and conventional soy samples found in this study for these two isoflavones (daidzin and daidzein) shows the absence of any effect attributed to the transgene.
In contrast, when we compared the levels of other isoflavones in samples of transgenic cultivars and conventional commercial soy we observed a significant difference (p < 0.05), despite the large intragroup variability observed (
However, for both glycosides glycitin (ST 7.53 ± 1.99 and SC 11.43 ± 4.74 mg∙100 g−1) and genistein (ST 36.97 ± 7.77 and SC 58.08 ± 27.28 mg∙100 g−1), the levels observed were statistically higher for the transgenic cultivars. The mean levels of genistein observed were 2.95 ± 1.24 mg∙100 g−1 in transgenic cultivars, and 4.83 ± 2.41 mg∙100 g−1 for conventional commercial cultivars, which indicated that these, on average, had higher levels of this bioactive isoflavone. However, the wide range of contents of isoflavones in soybeans and transgenic cultivars, especially in conventional commercial cultivars, as verified by the intragroup standard deviation, may have interfered with this significance. The variation in the concentration of isoflavones, especially in the conventional commercial cultivars, can be explained by the potential heterogeneity both with regard to genotype and the place and time of planting, growing conditions, and even storage conditions.
The profile of total isoflavones for ST cultivars and SC cultivars (ST 502.60 ± 65.63 and SC 358.90 ± 135.21 mg∙100 g−1) was similar to that observed by Bhom et al. (2008) (ST 211.2 and SC 182.2 mg∙100 g−1), who found that, even though lower levels of these compounds were observed in GM varieties, the total isoflavone content was higher. It is important to note that, in our study, this difference was statistically significant. In another study by Barbosa et al. [
Samples | Daidzein | Genistein | Total Isoflavones |
---|---|---|---|
mg/100g | |||
ST1 | 6.53 ± 0.27c | 4.34 ± 0.14d | 591.29 ± 14.44a |
ST2 | 2.32 ± 0.00g | 1.13 ± 0.02h | 533.73 ± 13.56b,c |
ST3 | 5.58 ± 0.19d | 3.22 ± 0.01e | 549.08 ± 3.55b |
ST4 | 2.17 ± 0.02g | 1.64 ± 0.01g | 413.86 ± 7.55f,g |
ST5 | 6.51 ± 0.01c | 4.08 ± 0.08d | 491.94 ± 0.58d |
ST6 | 4.58 ± 0.01e | 3.28 ± 0.05e | 435.72 ± 1.59e,f |
SC1 | 5.30 ± 0.07d | 4.28 ± 0.04d | 227.22 ± 0.39h |
SC2 | 3.36 ± 0.06f | 2.07 ± 0.04f | 508.09 ± 4.43c,d |
SC3 | 11.16 ± 0.18a | 7.93 ± 0.02a | 447.63 ± 1.19e |
SC4 | 9.47 ± 0.01b | 6.05 ± 0.13c | 434.05 ± 1.90e,f |
SC5 | 9.74 ± 0.01b | 6.80 ± 0.08b | 392.64 ± 3.40g |
SC6 | 1.52 ± 0.07h | 1.83 ± 0.09f,g | 143.78 ± 0.77i |
ALL | 5.69 ± 3.09 | 3.89 ± 2.10 | 430.75 ± 127.24 |
Means followed by the same lower case letter in columns do not differ according to the Tukey’s test at 5% significance. The results are expressed in mg∙100 g−1 of dry, defatted sample. The GM soybeans ST1-ST6 correspond to the following cultivars, respectively: BRS Favorita, BRS Valiosa, BRSMG 850G, BRSMG 811C , BRSMG 750S, and BRSMG 740S. ST = Transgenic; SC = Conventional.
When grouping isoflavones by their radical groups, the average percentages observed for the different cultivars (19.82 and 38.61 mg∙100 g−1 of β-glycosides, 78.68 and 58.11 mg∙100 g−1 of malonylglycosides, 1.49 and 3.28 mg∙100 g−1 of aglycones and no acetylglycosides, for transgenic soybean cultivars and conventional commercial cultivars, respectively) were in agreement with the findings of Carrão-Panizzi [
Regarding the aglycones, the values found in this study were similar to those obtained by Benedetti [
The results of the analysis of micro- and macrominerals are summarized in
Mineral | Calcium | Magnesium | Phosphorus | Sodium | Potassium | |
---|---|---|---|---|---|---|
Samples | mg/Kg | |||||
Favorita-S2 (T) | 1606.12 ± 87.38b,c | 1789.75 ± 127.48b | 4728.30 ± 153.29c,d | 100.12 ± 7.74a,b | 14281.81 ± 1917.94a | |
Valiosa-S2 (T) | 1419.50 ± 43.96b,c | 2049.40 ± 20.84a,b | 5698.98 ± 31.23a,b | 131.53 ± 13.65a,b | 12119.69 ± 756.75a | |
850-S2 (T) | 1655.84 ± 591.21b,c | 1689.52 ± 571.29b | 3736.44 ± 60.59e | 113.54 ± 15.95a,b | 12280.15 ± 65.39a | |
811-S2 (T) | 1101.81 ± 446.06c | 1730.69 ± 610.22b | 5718.49 ± 273.91a.b | 121.72 ± 27.63a,b | 13544.75 ± 1144.75a | |
750-C1 (T) | 2167.74 ± 259.42a,b | 2854.71 ± 326.47a | 5252.64 ± 105.52b,c | 121.06 ± 7.02a,b | 12307.43 ± 1127.58a | |
740-C1 (T) | 2908.53 ± 52.14a | 2464.76 ± 67.56a,b | 4980.12 ± 15.43b,c,d | 145.51 ± 5.91a | 12851.25 ± 286.19a | |
Commercial 1 (C) | 1240.22 ± 37.37c | 2349.18 ± 39.77a,b | 5372.40 ± 489.95b | 123.65 ± 3.23a,b | 15158.29 ± 3040.44a | |
Commercial 2 (C) | 2971.15 ± 124.07a | 2625.78 ± 99.17a,b | 4620.21 ± 87.41d | 148.18 ± 13.36a | 13605.48 ± 706.93a | |
Commercial 3 (C) | 1560.34 ± 459.13b,c | 1900.22 ± 510.69b | 5978.96 ± 125.24a | 107.94 ± 12.42a,b | 12797.47 ± 352.74a | |
Commercial 4 (C) | 1796.07 ± 249.56b,c | 2201.59 ± 296.17a,b | 5694.39 ± 267.23a,b | 85.39 ± 35.62b | 15302.11 ± 610.67a | |
Commercial 5 (C) | 1928.78 ± 192.67b,c | 2288.56 ± 166.66a,b | 6151.77 ± 139.01 a | 133.06 ± 4.99a,b | 15536.83 ± 140.98a | |
Commercial 6 (C) | 1618.48 ± 49.27b,c | 2279.14 ± 36.10a,b | 4935.65 ± 174.28b,c,d | 117.89 ± 15.93a,b | 13825.31 ± 160.56a | |
Mean ST | 1809.92 ± 660.59A | 2096.47 ± 540.80A | 5019.16 ± 704.64A | 123.29 ± 16.43A | 12897.52 ± 1209.12B | |
Mean SC | 1852.50 ± 593.35A | 2274.08 ± 306.96A | 5458.90 ± 601.02A | 118.31 ± 26.89A | 14370.91 ± 1518.34A | |
Total Mean | 1831.21 ± 619.21 | 2185.28 ± 442.64 | 5239.03 ± 682.89 | 120.80 ± 22.11 | 13634.22 ± 1545.34 | |
T = Transgenic; C = Conventional; ST = Grouped Transgenic Soybeans; SC = Grouped Conventional Soybeans. Mean values (±standard deviation) with the same letter do not differ significantly according to the Tukey’s test at 5% significance. Lower case letters, comparison of samples by mineral. Uppercase letters, comparison between GM and commercial soybeans by mineral.
Mineral | Barium | Copper | Chromium | Iron | Manganese | Zinc | ||
---|---|---|---|---|---|---|---|---|
Samples | mg/Kg | |||||||
Favorita-S2 (T) | 5.93 ± 0.36c | 91.19 ± 4.56a | 0.42 ± 0.10b | 101.73 ± 6.48b | 21.15 ± 1.32a,b,c,d | 98.49 ± 0.24a | ||
Valiosa-S2 (T) | 4.93 ± 0.17c | 13.77 ± 0.31b,c | 0.43 ± 0.15b | 74.33 ± 0.75f,g | 21.10 ± 0.03a,b,c,d | 56.54 ± 0.49b,c | ||
850-S2 (T) | 24.57 ± 7.86a | 11.89 ± 1.91b,c | 0.61 ± 0.27b | 127.38 ± 8.79a | 22.53 ± 7.09a,b,c | 44.96 ± 6.09d,e | ||
811-S2 (T) | 5.44 ± 0.38c | 12.75 ± 0.53b,c | 0.53 ± 0.14b | 94.16 ± 3.34b,c,d | 12.93 ± 4.06d | 50.74 ± 3.37b,c,d | ||
750-C1 (T) | 12.04 ± 2.51b,c | 11.59 ± 1.48b,c | 0.61 ± 0.16b | 78.6 ± 1.75e,f,g | 15.64 ± 2.01c,d | 47.13 ± 7.64c,d,e | ||
740-C1 (T) | 5.51 ± 0.27c | 12.18 ± 0.3b,c | 0.19 ± 0.07b | 93.52 ± 1.06b,c,d,e | 16.72 ± 0.07b,c,d | 41.93 ± 3.23d,e | ||
Commercial 1 (C) | 5.98 ± 0.23c | 15.92 ± 0.54b | 0.50 ± 0.17b | 82.53 ± 11.35d,e,f,g | 23.16 ± 0.63a,b,c | 45.76 ± 5.33c,d,e | ||
Commercial 2 (C) | 11.98 ± 0.38b,c | 12.63 ± 0.16b,c | 0.98 ± 0.63b | 86.19 ± 1.43c,d,e,f | 29.25 ± 1.1a | 46.92 ± 1.82c,d,e | ||
Commercial 3 (C) | 11.78 ± 3.66b,c | 9.48 ± 2.57c | 0.73 ± 0.39b | 75.19 ± 2.76f,g | 15.07 ± 3.91c,d | 56.22 ± 1.14b,c | ||
Commercial 4 (C) | 12.57 ± 2. 22b,c | 10.87 ± 1.74b,c | 0.55 ± 0.11b | 70.82 ± 3.95g | 17.71 ± 2.56b,c,d | 51.37 ± 3.07b,c,d | ||
Commercial 5 (C) | 15.72 ± 2.08b | 11.97 ± 1.20b,c | 0.64 ± 0.23b | 77.66 ± 1.27f,g | 17.91 ± 1.92b,c,d | 60.20 ± 1.02b | ||
Commercial 6 (C) | 6.3 ± 0.95c | 14.96 ± 0.29b | 1.18 ± 0.43a | 99.22 ± 4.73b,c | 24.53 ± 0.15a,b | 38.72 ± 2.38e | ||
Mean ST | 9.74 ± 7.80A | 25.56 ± 30.26A | 0.46 ± 0.20B | 94.95 ± 18.23A | 18.34 ± 4.61A | 56.63 ± 20.18A | ||
Mean SC | 10.72 ± 3.96A | 12.64 ± 2.57A | 0.76 ± 0.40A | 81.94 ± 10.49B | 21.27 ± 5.29A | 49.87 ± 7.65A | ||
Total Mean | 10.23 ± 6.12 | 19.10 ± 22.16 | 0.61 ± 0.35 | 88.44 ± 16.08 | 19.81 ± 5.11 | 53.25 ± 15.43 | ||
T = Transgenic; C = Conventional; ST = Grouped Transgenic Soybeans; SC = Grouped Conventional Soybeans. Mean values (± standard deviation) with the same letter do not differ significantly according to the Tukey’s test at 5% significance. Lower case letters, comparison of samples by mineral. Uppercase letters, comparison between GM and commercial soybeans by mineral.
In study by Zobiole et al. [
The six brands of conventional soybean marketed in the municipality of Belo Horizonte were labeled for the presence of genetically modified organisms, in accordance with current legislation.
Although differences among groups were observed for some minerals, the same trend was observed within the group, which could be explained by genetic differences among cultivars as well as by environmental conditions during cultivation. The highest levels of potassium and the main mineral present in soy were found in conventional cultivars when compared with transgenic cultivars, which in turn had higher content of iron.
The variation in total isoflavone contents of soybeans from local suppliers confirms the need for labels to bear information regarding these levels. In addition, information is needed regarding unknown parameters such as variety, cultivation region, and maturation of the commercially available grains.
The authors thank COPAMIL for providing the soybean seeds; Dr. Nilson César Castanheira Guimarães, from LANAGRO (National Agricultural Laboratory), for the analysis of GMOs; Dr. José Marcos Gontijo Mandarino Embrapa Soja for the analysis of isoflavones; FAPEMIG for the financial support; to CAPES for the scholarship granted to our graduate student and the Pro-Rectory of Research of the UFMG (Pro-Reitoria de Pesquisa da UFMG) for their support.