Flax seeds produced in the brazilian midwest: chemical and physical quality

Chemical and physical flaxseed properties can be altered by Brazilian edaphoclimatic and soil management conditions. The study aimed to evaluate the physical and chemical quality of reddish-brown and golden-yellow flaxseeds produced in a conservation management system (i.e., with low agricultural inputs) in Dourados, MS, Midwest region, Brazil. The experiment design was carried out in random blocks, with three repetitions. Significance in difference between two groups were tested by Student t test at 5%. The reddish-brown and golden-yellow flaxseed from Midwest, cultivated under a conservation management system, exhibited similar physical and chemical patterns. However, the reddish-brown flaxseed had a higher hundred seed mass, width, length, color parameters (luminosity, chromaticity, and color angle), neutral detergent fiber contents, phenolic compounds, and stearic and oleic acids than the golden-yellow flaxseed. The flaxseeds produced in the conservationist management system showed the same grain physical and chemical quality as the international and national grains produced in the conventional management system, described in the literature. Our results corroborate the future incentives for increasingly sustainable production while searching for greater eco-efficiency and food security. Thus, the flaxseed cultivated in a conservationist management system has potential to be an economical alternative for all farmers.


INTRODUCTION
Flaxseed (Linum usitatissimum L.), is cultivated in many countries worldwide, including Canada, the United States, and Argentina (Americas); China, India, and Kazakhstan (Asia); and Belgium, Russia, and Ukraine (Europe) (FAOSTAT, 2020). In Brazil, flaxseed is grown mainly in regions with a subtropical climate, such as the south states (IBGE, 2020), and employing conventional management systems or through notillage systems (STANCK et al., 2017). The flaxseeds are multi-utility, as they can be consumed either fresh or processed into flour for use in baking or mixed with other foods in their raw form. Although flaxseeds were present in the human diet for millennia, most of the flaxseeds cultivated are still destined for oil, dyeing, animal feed, textiles, biodiesel, and biomaterials industries (COSMO et al., 2014;GU et al., 2018;VIEIRA et al., 2015).
Flaxseeds have high potential as a functional food because they possess chemical compounds beneficial to health, such as preventing or reducing the risk of chronic noncommunicable diseases and low-density lipoprotein cholesterol (TAVARINI et al., 2021). Several compounds present in flaxseed, especially the lignans, alpha-linolenic acid (ALA), and fibers, affect physiological functions. In addition, the bioactive compounds possess strong antioxidant properties, which reduce lipid oxidation, while the lignans are biologically active phytochemicals that exhibit potential anticarcinogenic and anti-inflammatory properties (EBRAHIMI et al., 2021).
Two flaxseed varieties, reddish-brown and golden-yellow, and their varieties, are used for human consumption (STANCK et al., 2017). According to the Dietary Reference Intake (2006), a daily intake of approximately 4 g of golden-yellow or reddish-brown flaxseed oil for men, and 3 g for women, would be sufficient to fulfill the nutritional requirements of ALA. Evidence shows that reddish-brown and gold flaxseeds have similar chemical compositions, suggesting the possibility that both have similar bioactivity (THOMPSON & CUNNANE, 2003;BARROSO et al., 2014). It is worth mentioning that the higher concentration of the constituent chemical compounds and the physical properties of the seeds, such as color, moisture, and size, are directly related to the edaphoclimatic and soil management conditions in which they are grown BARROSO et al., 2014;SINGH et al., 2012;TROSHCHYNSKA et al., 2019).
Comparative studies between varieties are scarce in the Brazilian literature, especially regarding the seed physicochemical attributes. Thus, evaluating flaxseed varieties can contribute to a greater appreciation of this food, especially reddishbrown flaxseed, which is the most produced flaxseed in Brazil (IBGE, 2020). Most international and national scientific studies on flaxseeds either do not know the seed origin, or evaluated seeds produced in conventional agricultural management systems. However, it is not known whether soil conservation management systems (i.e., low agricultural input) can increase the physical and chemical quality of flaxseeds (STANCK et al., 2017;CARDUCCI et al., 2018;SINGH et al., 2012).
In this context, our study aimed to evaluate the physical and chemical attributes of reddish-brown and golden-yellow flaxseeds produced in a conservationist soil management system, in the Dourados, Mato Grosso do Sul (MS), Midwest Region, Brazil. For this, the following hypothesis was tested: The flaxseed produced in the Midwest, in a conservationist soil management system, would have a good pattern of physicochemical profiles, such as, acidity, water activity, moisture, ash, fiber, total phenolic compound and fatty acid profile? Página | 41

DESCRIPTION OF THE STUDY AREA
The evaluations were performed on flaxseeds produced at the experimental farm of the Federal University of Grande Dourados (UFGD), Dourados City, MS (Figure 1-A), in the Midwest Region of Brazil (22°13′16″S, 54°48′20″W; 430 m altitude). The climate of this region is Cwa according to the Köppen classification. The soil was classified as Rodic Haplustox -Soil Taxonomy, with a very clayey texture (656 g kg -1 clay, 205 g kg -1 silt, and 138 g kg -1 sand).
Flax has been cultivated in the Dourados, MS since 2017 in a conservationist soil management system; that is, soil protection practices are employed, such as the substitution of chemical inputs for organic ones, no-tillage, and the maintenance of residues from the previous crop, which in turn make the production system environmentally sustainable .
We used two flaxseed landrace varieties, that is, the reddish-brown color flaxseeds, were acquired from the Federal University of Santa Catarina (UFSC)campi Curitibanos, Santa Catarina (SC) (Figure 1-B), Brazil, where they have been cultivated in a soil conservation management system since 2014 (STANCK et al., 2017). The golden-yellow color flaxseeds were obtained from the Agricultural Research and Rural Extension Company of Santa Catarina (Epagri), Campos Novos, SC, and cultivated in an agroecological system since 2010 (PARIZOTO et al., 2013) ( Figure 2). Following harvest, the seeds were cleaned by removing dirt, dust, residues, and damaged seeds, and then sorted using sieves by 50 mesh.

CHEMICAL AND PHYSICAL ANALYSES OF FLAXSEEDS
The acidity index in oleic acid (AOA) were estimated according to the titrimetric method 325/IV (IAL, 2008). The content expressed as (g) acidity in oleic acid (AOA)/100g of flaxseed flour was calculated.
The seeds were milled in an industrial processor and hermetically stored in a refrigerator at 10°C, following which they were used to analyze the water activity, cold-extracted lipids, proteins (5.75 conversion factor), and contents of ash and the neutral detergent fiber (NDF), according to the American Oil Chemists' Society-American Open Currency Standard (AOAC, 1993). The total caloric value was calculated as the sum of calories (kcal) provided by carbohydrates, lipids, and protein, by multiplying their values in grams with the respective conversion of 4, 9, and 4 kcal g -1 using Atwater general factor (FAO, 2003). The total carbohydrate content was calculated by subtracting the protein, lipid, ash, and moisture contents from 100%. To determine the content of phenolic compounds, a hydrophilic extract obtained after the flour extraction with methanol (3:1 mass:volume) was used, following homogenization and filtration in non-woven fabric, according to BARROSO et al. (2014). The total phenolic compounds content was determined using the Folin-Ciocalteu colorimetric method. For this, 1.0 ml of the extract was transferred to a test tube. Then, 0.5 ml of the Folin-Ciocalteu reagent and 1.0 ml of 20% sodium carbonate solution were added, and the volume was brought up to 10 ml by adding distilled water. This solution was then maintained in temperature about 25°C for one hour, and the absorbance was measured at 760 nm using a 7305 UV/Visible Spectrophotometer (Jenway®, Jena, Germany). Gallic acid was used for the calibration curve (Y = 0.0909X + 0.0195, R 2 = 0.9966), and all values were expressed as mg gallic acid equivalents (GAE)/100 g dry base. All analyses were performed in triplicate.
For the fatty acid profile, the reddish-brown and golden-yellowgolden-yellowyellow flaxseeds were milled separately in a home food processor, and the flour was stored at −20 °C until analyzed. The oils were extracted from the seeds using a cold mechanical press. The content of fatty acids, in the form of methyl esters, was determined as g 100 g -1 of the lipid extract. Fatty acid methyl esters were analyzed by gas chromatography using a Focus GC (Thermo Fischer Scientific, Waltham, MA, USA) chromatograph with a fused-silica capillary column (Restek RT 2560; 100.0 mm length, 0.25 mm internal diameter, and 0.20 μm) and a flame ionization detector. Flow rates were as follows: nitrogen carrier, 30 ml min -1 ; hydrogen, 30 ml min -1 ; and synthetic air, 300 ml min -1 . The temperature was set at 130ºC at the start and was maintained as such for one minute, and then raised to 170ºC at a rate of 5ºC/min, and then to 215ºC at 2ºC/min, where it was maintained for 15 min, and then finally to 230ºC at 30ºC/min (Gondim-Tomaz et a., 2016). The injector and detector temperatures were 280ºC. The injection volume was 1 μl with a 1:10 split. Fatty acids were identified by comparing the retention time of the methyl ester patterns (Sigma-Aldrich, St. Louis, Missouri, USA) with the samples, and were quantified by the external standard method using the peak area, following MATTHÄUS & ÖZCAN (2011). These analyses were conducted in the Laboratory of Instrumental Analysis of the State University of Mato Grosso do Sul (UEMS), Dourados, MS.
The moisture of seeds was determined following the Rules for Seed Analysis (BRASIL, 2009) and presented as a decimal dry basis.
The hundred seed mass was measured in five subsamples of each replicate. Seeds were counted manually and then weighed using a precision balance (0.01 g).
The dimensions of the flaxseeds were measured using a digital pachymeter with 0.01 mm accuracy. The measurements in the three mutually perpendicular axes, that is, length, width, and thickness. Ten seeds from each experimental unit were used. Subsequently, the geometric diameter (Gd) of the flaxseed seed was calculated according to COSKUNER & KARABABA (2007).
The specific mass per unit (ρu), or real specific mass, was evaluated using the volume supplementation method with a solvent (IAL, 2008). Toluene (C7H8) was added to a calibrated volumetric flask (50 ml) containing 20 g of seeds at 25°C, and the solvent mass used to fill the flask was determined (calculated from the density, i.e., 0.87 g ml -1 , and the exact volume of solvent used). The volume of flaxseeds was determined, and the relationship between mass and volume was expressed in kg m -3 .
The apparent specific mass (ρap) was determined using a 25 ml graduated cylinder to which a seed sample was added. The mass was then measured for the subsequent calculation of the mass:volume ratio, expressed in kg.m -3 (COSKUNER & KARABABA, 2007).
The color of whole flaxseeds was determined from seeds placed in a Petri dish using a CR-400 Chroma Meter (Konica Minolta Sensing, Inc. Osaka, Japan) colorimeter using D65 illuminant. The measurements were expressed using the color coordinates L*, C*, and H* according to the color model of the International Commission on Illumination (CIE) (BECHLIN et al., 2019;TROSHCHYNSKA et al., 2019).

EXPERIMENTAL DESIGN AND STATISTICAL ANALYSES
The experimental design was in randomized blocks with two treatments: reddish-brown and golden-yellow-yellow flaxseed and with three repetitions. This experimental design was used in the field (for sowing and cultivation of flaxseeds) and maintained for laboratory analysis. We obtained a data set equivalent to 10 physical and 10 chemistry variables, totaling 120 observations. The results were expressed as mean ± standard deviation. Means were compared using a Student t test (p ≤ 0.05). Statistical analyses were performed using Statistica 7.0 (Statsoft, 2007).

RESULTS AND DISCUSSION
The Table 1 present the Grains chemical attributes and fatty acid composition of grain oils of both flaxseeds: reddish-brown and golden-yellow cultivated in a conservation management system in Midwest Region, Brazil.
The AOA did not differ significantly between the two varieties (Table 1), which showed similar values. There was a significant difference (p ≤ 0.05) in the fiber content (NDF), phenolic compounds, and fatty acids between the varieties, with higher values observed for the reddish-brown flaxseed. However, there were no significant differences between the flaxseeds for the other parameters. The acidity indices were low for both flour and oil, meeting the quality criteria of percent of acid oleic values < 3% for crude flaxseed oil recommended by AOCS (AOAC 1993;DENG et al., 2017). Similarly, low values were reported by Barroso et al. (2014) for crude oil. However, in the present study, the raw material used was processed flour, such as that used domestically or industrially to produce processed foods. In our study, processed flour had a lower concentration of organic acids compared to crude oil, which was also observed by CARDUCCI et al. (2018) when analyzing the flour of three reddish-brown flaxseed varieties (UFSC-Brazil, Caburé and Aguará-Argentina) produced under a conservation management system.
Factors such as environmental conditions, locality, and the management of the soil system can influence the lipid content of flaxseeds (OOMAH et al., 1996;VAISEY-GENSER & MORRIS, 2003). The lipid content attributes observed in the flaxseeds grown in the county of Dourados under a conservationist soil management system (with the exclusion of chemical inputs and the use of organic inputs) were higher than those found in other studies, including those reported by NOVELLO & POLONIO (2012) and BARROSO et al. (2014), who analyzed grains from the Brazilian retail trade (unknown origin). The protein content of the evaluated seeds (Table 1) was similar to that reported by OOMAH (2001) and VAISEY-GENSER & MORRIS (2003), who evaluated seeds of Canadian origin and found 20% of protein.
The differences in the fatty acid composition and grain physical quality of the two varieties from our study may be attributed to the cultivation practice, soil type, developmental stage of seeds, seed physical attributes (diameter, color, moisture, mass), and factors related to their origin, which has been shown in other studies on flaxseed (BARROSO et al., 2014;SINGH et al., 2012;DENG et al., 2017).
Flaxseeds are natural foods with a low content of saturated fatty acids (EBRAHIMI et al., 2021). A study conducted in India found that the ALA content of 11 flaxseed varieties ranged from 37.5% to 54.59% (SINGH et al., 2013). Furthermore, less than 5% of the ALA content was found in the Solin variety from Canada (BARTHET et al., 2014). Although a higher stearic acid content was found in the reddish-brown flaxseed than the golden-yellow flaxseed, 2.83 and 1.02 g.100g -1 respectively (Table 1) and similar to a previous study from Barroso et al., (2014). This fatty acid is considered non-atherogenic because it is rapidly converted endogenously into oleic acid, which seems to have neutral effects on cholesterol (that is, it is non-hypercholesterolemic, which contrasts with other saturated fatty acids) (SANTOS et al., 2013). The flaxseeds analyzed here can be considered a source of ALA due to the high content of this fatty acid (Table1). Omega 3 is obtained from ALA, which undergoes an endogenous enzymatic reaction to form eicosapentaenoic and docosahexaenoic acids (CIABOTTI et al., 2019).
Regarding the phenolic compounds, there was a significant difference between the two flaxseeds (p ≤ 0.05), with higher values for the reddish-brown flaxseed of 679.3 mgGAE g -1 compared to 589.8 mgGAE g -1 for the golden-yellow flaxseed. The stearic acid content (C18:0) was higher in the reddish-brown flaxseed, whereas the oleic acid content (C18:1) was significantly higher in the golden-yellow flaxseed (p ≤ 0.05).
The main bioactive compounds reported in flaxseeds are hydroxylated derivatives of benzoic and cinnamic acids, coumarins, and flavonoids (OOMAH et al., 1996). The phenolic acids present in flaxseed support its antioxidant properties and are beneficial to health, even in small quantities (BARROSO et al., 2014;SINGH et al., 2012).
Although flaxseeds are known to exert antioxidative effects, some studies have detected differences in the quality of flaxseed varieties worldwide, suggesting geographical and varietal specificity (DENG et al., 2017). The phenolic compounds contents reported in the present study (Table 1) were similar to those observed by OOMAH et al. (1995), who obtained values ranging from 790-1030 mg/100 g for Canadian flaxseeds and these values were higher than soybean, for example (CIABOTTI et al., 2019).
The grains physical attributes of two flaxseeds: reddish-brown and goldenyellow cultivated in a conservation management system in Midwest Region of Brazil were presents in Table 2. The flaxseed moisture ranged from 8.9 to 11.5 % (dry basis). There was a significant difference between the hundred seed mass. For the seed color attributes these significant differences was already expected. The highest values of the hundred seed mass (> 0.50 g; Table 2) were observed for the reddish-brown flaxseed, while the chromaticity (C*>4), color angle (H*>60°), and luminosity (L*>9) were higher for the golden-yellow flaxseed.
The moisture can directly influence the size of seeds and determine their deterioration time; that is, the lower the moisture of seeds, the better the physical conditions for their storage and subsequent viability (RÊGO et al., 2015). In this study, reddish-brown flaxseeds exhibited a mean moisture of 0.115 g -1 (10.27%), which was within the commercial standard limit (up to 13%) (BRASIL, 1999). This finding was consistent with the results of BECHLIN et al. (2019) ( Table  2). The higher moisture may have influenced the higher values of hundred seed mass as well as the length and width of reddish-brown flaxseeds, as observed by SINGH et al. (2012) when assessing the dimensions of flaxseed cv. Neelam with different moisture. These authors attributed such an increase in seed size to the expansion of intracellular spaces due to water absorption. However, in our study, the greater size of reddish-brown flaxseeds resulted in a reduced ε of the samples, and consequently, lower aeration between the seeds (Figure 3). Furthermore, it increased the ρap values more than 680 kg m -3 , which was also reported in previous studies (SINGH et al., 2012;COSKUNER & KARABABA, 2007;RÊGO et al., 2015;PRADHAN et al., 2010).  Figure 3. Width, length, thickness, geometric diameter, unitary density (ρu), and apparent specific mass (ρap) of the grains from two flaxseed varieties (reddish -brown and golden-yellow) cultivated in a conservationist management system in Midwest Brazil. NOTE: *(p≤0.05), Ns: not significant. Equal lowercase letters do not significantly differ by a Student test (p≤0.05). Bars indicate standard deviations from the mean.
There were no significant differences in the physical variables of the specific mass per unit (ρu) and the apparent specific mass (ρap) between the two varieties. However, the width and length (2.20 and 4.50 mm for reddish-brown and goldenyellow flaxseed, respectively) were different between the two varieties, with higher values observed for reddish-brown flaxseed (Figure 3), while the porosity (ε) remained above 20% for both grains color ( Table 2).
The values of length, width, and thickness of the reddish-brown flaxseeds observed in this study were similar to those reported by PRADHAN et al. (2010) in Canada. However, the results for these parameters were lower than those documented by SINGH et al. (2012) in India for the cv. Neelam despite the climatic conditions in Mato Grosso do Sul State be more similar to this. It must be noted that in addition to the variety, the cultivation system, soil and climate conditions can effectively influence the physical properties of seeds SINGH et al., 2012;SINGH et al., 2013).
In the present study, ρu and ρap (Figure 3) varied inversely with the moisture content. Corrêa et al. (2006) stated that the higher the moisture of seeds, the lower their density. Thus, the reduction in ρap was due to the increase in water volume, and not the mass (SINGH et al., 2013). Assessing the physical properties of flaxseeds is important for developing and operating systems and equipment for seed storage, processing, and transportation (SHARMA, SHARMA, & PRASAD, 2015).
The color parameter L* indicates the luminosity of the evaluated material (Table 2), and ranges from 0 (absolute black) to 100 (white). In this study, the L* values were observed to be low, indicating that the analyzed seeds had darker colors. Chromaticity (C*) is a color variable expressed as the hypotenuse of the point formed in the color space by the coordinates a* (green-red) and b* (blueyellow). The C* values observed in the present study were low, which can be attributed to the low composition of green-red and blue-yellow in the reddishbrown-colored flaxseed. Conversely, the golden-yellow flaxseeds exhibited higher values for the yellow coordinate (+b) in the color composition, resulting in higher C* values. The colorimetric differences between the seeds are also related to their nutritional quality, since lighter or darker skin results from different concentrations of plant secondary metabolites, such as carotenoids and bioactive compounds (TROSHCHYNSKA et al., 2019;BECHLIN et al., 2019). In this study, the highest concentration of phenolic compounds was observed in the reddish-brown flaxseed, which had lower values for the color parameters evaluated (Tables 1 and 2).

CONCLUSION
The reddish-brown and golden-yellow flaxseed from Midwest Brazil, cultivated under a conservation management system (i.e., with low agricultural inputs), exhibited similar physical and chemical patterns as founded to other author with grains grown in a conventional system. However, the reddish-brown flaxseed showed high hundred seed mass, width, length, color parameters (L*, C*, and H*), NDF contents, phenolic compounds contents, and stearic and oleic acid contents compared to the golden-yellow flaxseed. The flaxseeds produced in the conservationist management system showed the same grain physical and chemical quality as the international and Brazilian grains produced in the conventional management system, described in the literature, especially reddish-brown flax. As grain quality were not negative impacted by the conservationist management system, these results corroborate with incentives for increasingly sustainable flaxseed production with greater eco-efficiency and food security. Thus, this soil management system is an economical alternative that should be made available to all farmers.