Effects of germination on chemical composition and antioxidant activity of flaxseed (Linum usitatissimum L) oil

W. Herchia,*, S. Bahashwanb, K. Sebeia, H. Ben Salehc, H. Kallela and S. Boukhchinaa 

aLaboratoire de Biochimie des Lipides, Département de Biologie, Faculté des Sciences de Tunis, 2092 ELmanar-Tunisia

bCollege of Pharmacy, Taibah University, El-Madinah El-Munawarah 116, Saudi Arabia

cLaboratoire des Cultures Industrielles, INRAT- Tunisia

*Corresponding authors: wahid1bio@yahoo.fr

 

SUMMARY

The present study was carried out to determine the changes in proximate composition and physicochemical characteristics of flaxseed during germination. Flaxseed was germinated for 4 days and observations were taken every day throughout the study. Changes in the seed reserve and antioxidant activity were determined during germination. The oil content of the cultivar decreased from 35.10 to 27.22%. During the germination period, the total protein content increased to 23.84%. Germinated flaxseed showed significantly higher unsaturated as compared to saturated fatty acid ratios and higher calculated oxidizability (Cox) values. The Saponification value ranged from 182 to 192 mg KOH·g–1 oil during germination. The highest peroxide value (2.4 mequiv O2·kg−1 oil) was observed at the end of germination. The unsaponifiable contents ranged from 1.62 to 1.18%. The oxidation value of the oil samples were statistically in the same range (4.1–6.4%). After 4 days of germination, oil stability was reduced to 1.0 h. The increase in ascorbic acid content was steady. Total phenolic acid contents differed significantly. The greatest concentration was detected in non germinated flaxseed oil. Germinated Flaxssed oil showed an important free radical scavenging activity towards 1-1-diphenyl-2-picrylhydrazyl (DPPH) free radicals.

 

RESUMEN

Efecto de la germinación sobre la composición química y la actividad antioxidante de aceites de linaza (Linum usitatissimum L). El presente estudio se llevó a cabo para determinar los cambios en la composición y características físico-químicas de aceites de linaza durante la germinación. La linaza se germinó durante 4 días y el estudio se realizó todos los días durante este proceso. Se determinaron los cambios en la reserva de las semilla y la actividad antioxidante. El contenido de aceite de los cultivos disminuyó de 35,10 a 27,22%. Durante este periodo, el contenido de proteína total aumentó a 23,84%. La linaza germinada mostró valores significativamente más altos de la relación de ácidos grasos insaturados frente a saturados y mayor facilidad de oxidación (Cox). El índice de saponificación varió desde 182 hasta 192 mg KOH·g−1 de aceite durante la germinación. El índice de peróxido más alto (2,4 mequiv O2·kg−1 de aceite) se observó al final de la germinación. El contenido de materia insaponificable varió desde 1,62 hasta 1,18%. La oxidación de las muestras de aceite fueron estadísticamente del mismo rango (4.1 a 6.4%). Después de 4 días de germinación, la estabilidad del aceite se redujo a 1,0 h. El aumento en contenido de ácido ascórbico fue estable. Los contenidos totales de ácidos fenólicos diferían significativamente. La mayor concentración se detectó en el aceite de linaza no germinado. El aceite de linaza germinado mostró una importante actividad de eliminación de radicales libres hacia 1-1-difenil-2-picrilhidrazil (DPPH).

 

Submitted: 18 April 2014; Accepted: 11 September 2014

Citation/Cómo citar este artículo: Herchi W, Bahashwan S, Sebei K, Ben Saleh H, Kallel H, Boukhchina S. 2015. Effects of germination on chemical composition and antioxidant activity of flaxseed (Linum usitatissimum L) oil. Grasas Aceites 66 (1): e057. doi: http://dx.doi.org/10.3989/gya.0463141.

KEYWORDS: Antioxidant activity; Germination; Oil; Oil stability; Physicochemical characteristics

PALABRAS CLAVE: Aceite; Actividad antioxidante; Características físico-químicas; Estabilidad de aceite; Germinación

Copyright: © 2015 CSIC. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial (by-nc) Spain 3.0 Licence.


 

CONTENT

1. INTRODUCTIONTOP

Flaxseed (Linum usitatissimum L.) is a globally important agricultural crop grown both for its seed oil as well as its stem fiber. Flaxseed is used as a food source and has many valuable nutritional qualities. The seed oil also has multiple industrial applications such as in the manufacture of linoleum and paints and in preserving wood and concrete (Vaisey-Genser and Morris, 2001). Nutritionally, flaxseed has multiple desirable attributes. It is rich in dietary fiber and has a high content of essential fatty acids, vitamins and minerals. The seeds are composed of ~45% oil, 30% dietary fiber and 25% protein. Around 73% of the fatty acids in flaxseed are polyunsaturated. Approximately 50% of the total fatty acids consist of α-linolenic acid (ALA), a precursor for many essential fatty acids in the human diet (Sebei et al., 2007). Flaxseed is also a rich source of the lignan component secoisolariciresinol diglucoside (SDG). In addition to having anti-cancer properties, SDG also has antioxidant and phytoestrogen properties (Touré and Xueming, 2010). Flaxseed contains about 400 g·kg−1 total dietary fiber. This seed fiber is rich in pentosans and the hull fraction contains 2–7% mucilage (Vaisey-Genser and Morris, 1997). The other major constituents of flaxseeds are storage proteins that can range from 10–30% (Sebei et al., 2007).

Seeds generally consist of the embryo, endosperm tissue, and seed coat. One of the main purposes of the endosperm is to serve as a nutrient source for the germinating embryo (Linkies et al., 2010). Germination is the result of different physiological processes and the germination process is initiated by water uptake. The imbibition of seeds induces other physiological processes, resulting in the breakdown of reserves, the mobilization and utilization of the broken-down products, and the growth and expansion of the embryo. Germination is assumed to be completed when the radicle emerges from the endosperm and seed coat (Bewley and Black, 1994). The germination of seeds mobilizes reserves from the seed to the growing seedling; increased metabolic activities in turn result in chemical changes in the macromolecules (Wanasundara et al., 1999a). Although the germination effect on flaxseed composition has been studied (Wanasundara et al., 1999a; Wanasundara et al., 1999b; Sebei et al., 2007), no information is available, in the literature, on the effect of germination on the physicochemical properties and antioxidant activity of flaxseed oil.

The purpose of the present investigation is to study the changes in proximate constituents during germination. Changes in oil characteristics including physicochemical properties, Fuel properties, and antioxidant activity are also reported.

2. MATERIALS AND METHODSTOP

2.1. Chemicals and reagentsTOP

All solvents and standards used in the experiments were purchased from Fisher Scientific Company (Ottawa, Ontario, Canada).

2.2. Germination of flaxseedTOP

The seeds of flaxseed (L. usitatissimum L.) variety, ‘‘I61’’ were supplied by the “Institut National de la Recherche Agronomique de Tunis” (INRAT, Tunisia). Whole flaxseeds (400 g) were germinated on sterile filter paper in Petri dishes. The dishes were incubated for 4 days in the dark at room temperature (20 ± 2°C). The germinated flaxseeds were dried in a dryer at 40 °C and were ground and packed in air tight bags for further analysis.

2.3. Proximate compositionTOP

The dry matter contents of flaxseed were determined by drying in an oven at 105 °C for 24 h to constant weight (AOAC, 1990). The crude protein contents were calculated from the nitrogen contents (N × 6.25) obtained using the Kjeldahl method by AOAC (1990). The crude fat contents were determined by continuous extraction in a Soxhlet apparatus for 5 h using petroleum ether as solvent (AOAC, 1990). The total ash contents were determined by incinerating flaxseed (2 g) in a furnace at 550 °C for 6 h, then weighing the residue after cooling to room temperature in a desiccator (AOAC, 1990). The carbohydrate contents were determined by difference which is by deducing the mean values of other parameters that were determined from 100.

2.4. Gas chromatography–flame ionization detectionTOP

The quantification of fatty acid methyl esters was performed using a gas chromatography-flame ionization detection (GC–FID) apparatus. Fatty acid methyl esters were prepared by simultaneous extraction and methylation following the procedure described by Metcalfe et al. (1966) modified by Lechvallier (1966). Methyl esters were analyzed by GC, using an HP 4890 gas chromatograph equipped with an FID detector on a capillary column coated with SupelcowaxTM 10 (30 m long × 0.25 mm i.d., and 0.2 μm film thickness). Helium was used as the carrier gas at a flow rate of 1mL·min−1. The temperatures of the column, detector, and injector were 200, 250, and 230 °C, respectively. The identification of the peaks was achieved by retention times by means of comparing them with standards analyzed under the same conditions. The area under each peak was measured and the percentage expressed in regards to the total area. To evaluate the efficiency of the desaturation pathway during the maturation process (Mondal et al., 2010) the desaturation ratios from oleic to linoleic (ODR, oleic desaturation ratio) and from linoleic to linolenic acid (LDR, linoleic desaturation ratio) were calculated as follows:

ODR = [% C18: 2 + % C18: 3 / % C18: 1 + % C18: 2 + % C18: 3] × 100

LDR = [% C18: 3 / % C18: 2 + % C18: 3] × 100

The magnitude of desaturation ratios represents the amount of substrate which is successfully desaturated from C18:1 to C18:2 and C18:3, thus providing a proportional measure of the desaturating enzyme activities during seed germination. The Cox value of the oils was calculated based on the percentage of unsaturated C18 fatty acids, applying the formula proposed by Fatemi and Hammond (1980):

Cox value = [1 (18: 1%) + 10.3 (18: 2%) + 21.6 (18: 3%)] / 100

2.5. Physicochemical characteristicsTOP

Determinations of Saponification value (SV), Acid value (AV), Free fatty acids (FFA), Iodine value (IV), p-anisidine value (p-AV), Peroxide value (PV), UV absorption characteristics (K232 and K270), and unsaponifiable matter (UM) of the extracted oil were carried out by standard IUPAC methods for the analysis of fats and oils (Dieffenbacher and Pocklington 1987). Oxidation value (OV) was calculated from Holm’s equation, OV = p-AV + 2 (PV), while theoretical flavor scores (F) were obtained from the equation F = 7.7–0.35 (OV) (List et al., 1974). Oxidative stability was evaluated by the Rancimat method (Gutiérrez, 1989). Stability was expressed as the oxidation induction time (hours), measured with the Rancimat 743 apparatus (Metrohm Co., Basel, Switzerland), using an oil sample of 3 g warmed to 100 °C with an air flow of 10 L·h−1.

2.6. Total chlorophyll and carotenoidsTOP

A 1.5 g sample of germinated flaxseed oil was fully dissolved in 5 mL cyclohexane. Chlorophyll and carotenoid were determined colorimetrically following the method of Minguez-Mosquera et al. (1991). The maximum absorption at 670 nm is related to the chlorophyll fraction and at 470 nm is related to the carotenoid fraction. The values of the coefficients of the specific extinction applied were E0 = 613 for the pheophytin as a major component in the chlorophyll fraction and E0 = 2,000 for lutein as a major component in the carotenoid fraction. Thus the pigment contents were calculated as follows:

Chlorophyll (mg·kg−1) = (A670 × 106) / (613 × 100 × d)

Carotenoid (mg·kg−1) = (A470 × 106) / (2, 000 × 100 × d)

Where A is the absorbance and d is the spectrophotometer cell thickness (1 cm). The data reported is based on oil weight (mg·kg−1 flaxseed oil).

2.7. Polyphenols contentsTOP

The extraction and determination of total phenolic acid and flavonoid contents were carried out according to the method of Gutfinger (1981).

2.8. Fuel propertiesTOP

The Higher Heating Value (HHV), known as the gross calorific value or gross energy, represents the heat released by the oxidation of a fuel in air. The HHV is the amount of heat produced by the complete combustion of a unit quantity of fuel. The HHV of germinated flaxseed oil was calculated from the iodine value (IV) and saponification value (SV) derived using the following formula adopted by Demirbas (1998):

HHV = 49.43−(0.041× SV)−(0.015 × IV)

The cetane number of the oil was determined according to Bose (2009):

CN = 46.3 + 5458/SV–0.225 × IV

2.9. Determination of antioxidant activityTOP

The oil obtained was subjected to screening for its possible antioxidant activity. The oil was assessed using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay. All the data were the averages of triplicate determinations of three tests. The DPPH free radical-scavenging activity of the oil was measured using the method described by Gorinstein et al. (2004). A 0.1 mM solution of DPPH in methanol was prepared. An aliquot of 0.2 mL of sample was added to 2.8 mL of this solution and kept in the dark for 30 min. The absorbance was immediately measured at 517 nm. The ability to scavenge the DPPH radical was calculated with the following equation:

Inhibition percentage = (I %) = [(A0−A1) / A0] × 100

Where A0 is the absorbance of the control, A1 is the absorbance in the presence of sample.

2.10. Statistical analysisTOP

The analyses were performed with three replicates. All data are reported as means ± standard deviation of three samples. Differences were tested for significance using the ANOVA procedure, using a significance level of p<0.05.

3. RESULTS AND DISCUSSIONTOP

3.1. Changes in proximate composition and fatty acid contents of flaxseed during germinationTOP

The moisture content of flaxseed was significantly (p<0.05) affected by germination (Table 1). It ranged from 5.22% to 11.27% during the germination period. During the study period, the oil content of flaxseed progressively decreased, suggesting that oils are the major source of energy during germination and the early periods of seedling growth (Graham, 2008). The protein content increased during germination and showed no significant difference (p<0.05). The increase in protein content may be attributed to the synthesis of cell constituents and enzymes, which lead to the degradation of other constituents (Lee and Karunanithy, 1990). The ash content remained at the same level before and after germination. During germination, the ash content showed no significant difference (p<0.05). The carbohydrate content increased after 4 days of germination, reaching 37 mg per 100 g, which is significantly (p<0.05) higher than that of sesame (30 mg·100 g−1 ) (Hahm et al., 2009). Hahm et al., (2009) reported that the degradation of reserve nutrients (lipids and carbohydrates) during germination is a process whose essential purpose is to provide the energy required for protein synthesis in plant growth. As shown in Table 1, the ratio between unsaturated and saturated fatty acids (USFA/SFA ratio) and the Cox value of flaxseed were statistically (p<0.05) the same during the germination period. Germinated Flaxseed oil was characterized by its higher polyunsaturated fatty acids (PUFA) (linoleic acid, C18:2) and lower SFA percentages (Palmitic acid, C16:0, and stearic acid, C18:0), which make it particularly prone to oxidation. Indeed, the higher value of LDR indicates higher linolenic acid production during the germination period. This suggests that the biosynthetic pathway of fatty acids is efficient in the formation of linolenic acid, justifying therefore the higher amount of the latter fatty acid. The higher ratio of n-3/n-6 (2.63 vs. 2.87) indicated that flaxseed oil had greater nutritional value.

Table 1. Proximate composition and fatty acids contents of flaxseed during germination
Component Duration of germination (days)
0 1 2 3 4
Proximate composition (%)
Moisture (%) 5.22±0.36a 10.50±0.42b 11.27±0.40b 10.29±0.24b 9.42±0.28b
Oil (%) 35.10±1.18a 33.61±2.04a 30.14±1.83a 28.74±1.33b 27.22±1.15b
Protein (%) 22.65±1.24a 23.12±1.39a 23.44±1.00a 23.60±1.12a 23.84±0.90a
Ash (%) 2.90±0.10a 3.17±0.22a 3.10±0.16a 2.86±0.20a 2.91±0.18a
Total carbohydrate (%) 34.12±0.78a 29.60±1.08b 32.05±0.62a 34.51±0.86a 36.61±1.14a
Fatty acid contents (%)
C16:0 6.62±0.05a 6.71±0.06a 6.27±0.04a 6.40±0.08a 6.69±0.07a
C18:0 5.81±0.08a 5.72±0.04a 5.40±0.06a 5.67±0.05a 5.66±0.05a
C18:1 28.36±0.20a 30.29±0.27b 30.74±0.15b 28.74±0.11a 28.91±0.19a
C18:2 15.77±0.12a 14.93±0.10a 15.59±0.14a 15.06±0.12a 15.30±0.20a
C18:3 42.53±0.25a 41.70±0.18a 41.07±0.33a 43.24±0.30b 41.46±0.21a
ΣSFAa 12.43±0.13a 12.43±0.10a 11.67±0.10b 12.07±0.13a 12.35±0.12a
ΣMUFAb 28.36±0.20a 30.29±0.27a 30.74±0.15a 28.74±0.11a 28.91±0.19a
ΣPUFAc 58.30±0.27a 56.63±0.28a 56.66±0.47a 58.30±0.42a 56.76±0.41a
TU 86.66±0.47a 86.92±0.56a 87.40±0.62a 87.04±0.53a 85.67±0.60a
TU/TSd 6.97±0.04a 7.00±0.08a 7.48±0.06b 7.21±0.06b 6.93±0.06a
n-3/n- 6 2.69±0.02a 2.79±0.06a 2.63±0.08a 2.87±0.04b 2.71±0.02b
Cox value 11.09±0.24a 10.84±0.14a 10.78±0.18a 11.17±0.20a 10.82±0.32a
ODR 67.27±0.27a 65.15±0.19b 64.82±0.33b 66.98±0.35a 66.25±0.17a
LDR 72.95±0.30a 73.63±0.21a 72.48±0.18a 74.16±0.24b 73.04±0.33a
Fatty acids detected: C16:0 (Palmitic), C18:0 (Stearic), C18:1 (Oleic), C18:2 (Linoleic), C18:3 (Linolenic).
% GC area, mean of three measurements.
aSum of major saturated fatty acids;
bSum of major monounsaturated fatty acids;
cSum of major polyunsaturated fatty acids;
dtotal unsaturated fatty acids to total saturated fatty acids ratio. Values given are the means of three replicates ± standard deviation. Means with different letters (a–c) within a row are significantly different at p≤0.05.

3.2. Changes in physicochemical characteristics of Flaxseed during germinationTOP

The physicochemical characteristics of flaxseed oils and their values in the literature are shown in Tables 2A and 2B, respectively. The saponification value is an index of average molecular weight (or chain length) of all the fatty acids present. The observed saponification value increased with germination (182–192 mg KOH·g–1 oil) and there were statistically significant differences among them (p<0.05). These values indicate the absence of lauric acid in the investigated flaxseed oils, and this range is indicative of oils characterized by medium chain-length FAs. Acid value varied significantly (p<0.05) during the germination period. The lower acidity value of germinated flaxseed oil indicates that the oil has a better quality and longer shelf life. The acid values of all the extracted samples in this study were not different from those reported by Teh and Birch (2013) and Choo et al. (2007), and higher than those determined for hemp oil and canola oil. Peroxide value was found between 1.4 and 2.6 (mequiv O2·kg−1 oil) and showed significant differences (p<0.05). These results are in accordance with those reported by Teh and Birch (2013) and Choo et al. (2007) and were not different from the results reported for hemp oil and canola oil. According to the Codex Alimentarius Commission (2006) standard for virgin oils and cold pressed fats and oils, a good quality oil should have a peroxide value of less than 10 mequiv O2·kg−1 oil. Lower acid and peroxide values have indicated that germinated flaxseed oil was more suitable as an edible oil. The iodine value, which indicates the degree of unsaturation of an oil, decreased during the germination period. The IV (172–160) obtained in this study indicates that the oils contain appreciable level of unsaturated FAs, which is confirmed by the FA profile of the germinated flaxseed investigated. The p-anisidine values of germinated flaxseed oils showed slight increases. These may be attributed to the light increase in carbonyl compounds. A good quality oil should have a p-anisidine value of less than two (Subramanian et al., 2000). All the oil samples from the literature had low p-anisidine values (Table 2B), reflecting the p-anisidine value of a good quality oil. The oxidation value of flaxseed oils ranged from 4.1 to 6.4% and showed no significant difference among all the samples (p>0.05). These relatively higher oxidation values prompted a separate study for the lipoxygenase activity of chickpea oil. These values were similar to those reported in the literature (Table 2B). The values of K232 and K270 extinction coefficient showed a slight increase during germination. Oil stability decreased during flaxseed germination. This decrease (1.4 h−1.0 h) in stability is explained by the loss of natural antioxidants. The relative decrease in the unsaponifiable content observed during the germination period may possibly be due to the initial loss lipids and other major reserves of the seed. A parallel decrease in the content of triglycerides was also observed. The ascorbic acid of flaxseed increased in the early stages of germination and then remained constant until the fourth day of germination. A significant decrease in total phenolic acid content was observed during germination (108.58−73.11 mg·g−1). The total phenolic acid content showed no significant difference (p<0.05). The decrease in TPC has also been attributed to enzymatic activity during germination (Gujral et al., 2011). Randhir et al. reported that germination causes a decrease in the total phenolic content in Green mung. All the respective values were similar to those reported from the literature (Table 2B). In addition, these results are lower than those reported for hemp oil and higher than those reported for canola oil. The Total flavanoid content increased to 14.10 mg·g−1 on the second day then dropped down at the end of day 3. The highest level of chlorophyll and carotenoids was detected by the end of the germination period (6.27−7.37 mg·kg−1 oil, respectively). The fuel properties shown in Fig. 1 indicate that there was no significant difference for HHV and the cetane number during germination. The HHV, which is one of the most important properties of a fuel, is the amount of heat released during the combustion of 1 g of fuel to produce CO2 and H2O at its initial temperature and pressure. The highest heating value (39.39 MJ·kg−1) was obtained from ungerminated flaxseed oil. The heating values are the same for most of the oils (39–40 MJ·kg−1) except for castor oil (37.3 MJ·kg−1). The cetane number (CN) is one of the most commonly cited indicators of diesel fuel quality, especially the ignition quality (Bamgboye and Hansen, 2008). The highest CN (37.87) was obtained for germinated flaxseed oil (1 day of germination). The values of CN of soybean oil-derived biodiesel ranged from 45 to 60, whereas those of rapeseed oil-derived biofuel ranged from 48 to 61.2 (Bamgboye and Hansen, 2008). Higher CNs are associated with greater combustibility, good ignition, and assist in easy engine starting, low temperature starting, low ignition pressures, and smooth operation with lower knocking characteristics (Aminul Islam et al., 2012). Germinated Flaxseed oils with good physicochemical properties will have potential to be biodiesel feedstocks.

Figure 1. Effect of germination on Fuel properties.

 
Table 2A. Physicochemical Characteristics of Flaxseed oil during germination
Properties Duration of germination (days)
0 1 2 3 4
Saponification Value (mg KOH·g–1 oil) 182±1.42a 183±1.17a 188±0.96b 190±0.82b 192±0.47b
Acid value (mg KOH·g–1 oil) 0.94±0.05a 1.36±0.08ab 1.72±0.06b 2.10±0.04c 2.48±0.08c
FFA content (% as oleic acid) 0.50±0.02a 0.74±0.02a 0.94±0.03b 1.17±0.04b 1.33±0.03b
Iodine value (g of I2·100 g−1 oil) 172±1.10a 170±0.90a 167±1.15b 163±1.10b 160±1.38c
Peroxide value (mequiv O2·kg−1 oil) 1.6±0.18a 1.8±0.22a 2.0±0.16b 2.3±0.24b 2.4±0.16b
p-Anisidine value 0.9±0.16a 1.1±0.20a 1.2±0.14a 1.5±0.31b 1.6±0.25b
Oxidation value 4.1±0.16a 4.7±0.18a 5.2±0.20b 6.1±0.16c 6.4±0.18c
Theoretical flavor scores (F) 6.3±0.10a 6.0±0.09a 5.9±0.12a 5.6±0.10b 5.5±0.12b
K232 1.46±0.18a 1.55±0.12a 1.63±0.14a 1.79±0.10b 2.12±0.10b
K270 0.24±0.10a 0.28±0.14a 0.32±0.11b 0.36±0.10b 0.44±0.12c
Oil Stability (h) 1.4±0.24a 1.4±0.20a 1.3±0.14a 1.2±0.18a 1.0±0.10b
Unsaponifiable matter (% w/w) 1.62±0.15a 1.44±0.17a 1.35±0.10b 1.30±0.22b 1.18±0.28b
Triglyceride (%)a 97.88±1.14a 97.82±0.83a 97.71±0.90a 97.53±1.15a 97.49±1.22a
Ascorbic acid (mg·100 g−1) 1.35±0.12a 2.18±0.32b 2.38±0.19b 3.45±0.35b 2.74±0.26a
Total phenolic acids, as ferulic acid equivalents (mg·100 g−1 oil) 108.58±7.45a 97.35±6.28a 88.14±5.93b 82.69±6.85b 73.11±4.29b
Total Flavanoids, 10.64±1.84a 12.36±2.27a 14.10±2.68b 11.61±2.52a 11. 82±1.20a
as luteolin equivalents (mg·100 g−1 oil)
Carotenoids (mg·kg−1 oil) 2.23±0.05a 4.11±0.04b 5.30±0.06b 6.19±0.08c 6.27±0.07c
Chlorophyll (mg·kg−1 oil) 4.45±0.12a 5.13±0.17a 5.72±0.24a 6.20±0.32b 7.37±0.28b
aTriglyceride (%) = 100 - {(free fatty acid, %) + (unsaponifiable matter, %)}.
Values given are the means of three replicates ± standard deviation.
Means with different letters (a–c) within a row are significantly different at p≤0.05.
Table 2B. Physicochemical characteristics of flaxseed oil, hemp and canola seed oils from the literature (Teh and Birch (2013), (Choo et al., 2007)
Properties Valued in the literature***
Flaxseed oil Flaxseed oil Hemp oil Canola oil
Saponification Value (mg·KOH g–1 oil)
Acid value (mg KOH·g–1 oil) 0.50–2.50 1.49 1.76 1.43
FFA content (% as oleic acid) 0.25–0.98 0.75 0.89 0.72
Iodine value (g of I2·100 g–1 oil)
Peroxide value (mequiv O2·kg–1 oil) 0.70–3.00 2.04 1.94 2.39
p-Anisidine value 0.36–0.74 0.52 0.62 0.27
Oxidation value 1.30–6.00 4.6 4.5 5.05
Theoretical flavor scores (F) 7.24–5.60 6.09 6.12 5.93
K232 1.8–2.8 2.08 1.53 2.21
K270 0.20–0.40 0.02 0.02 0.02
Oil Stability (h)
Unsaponifiable matter (% w/w) 0.39–0.71 0.40 0.26 0.54
Triglyceride (%) a 99.36–98.31 98.85 98.85 98.74
Ascorbic acid (mg·100 g–1)
Total phenolic acids, 76.8–307.3 136.93 188.23 57.17
as ferulic acid equivalents (mg·100 g–1 oil)
Total Flavanoids, 12.7–25.6 18.75 19.50 16.41
as luteolin equivalents (mg·100 g–1 oil)
Carotenoids (mg·kg–1 oil) 0.6 2.2
Chlorophyll (mg·kg–1 oil) 0.80–5.76 6.78 75.21 0.86
aTriglyceride (%) = 100 - {(free fatty acid, %) + (unsaponifiable matter, %)}.
***Teh and Birch (2013), (Choo et al., 2007).

3.3. Changes in the antioxidant activity of Flaxseed oil during germinationTOP

Antioxidant activity is expressed as percent DPPH radical scavenging activity with higher values indicating greater antioxidant activity. The antioxidant activity ranged from 40.14 to 52.48% (Fig. 2) with the highest activity exhibited by ungerminated flaxseed and the lowest exhibited by germinated flaxseed oil at the end of day 3. During germination, the antioxidant activity significantly decreased (p<0.05) up to 3 days of germination and then further increased upon 4 days of germination. The decreasing trend of antioxidant activity during germination is similar to the trend observed in lentils (Lens culinaris) while the increasing trend of antioxidant activity is similar to beans (Phaseolus vulgaris) and peas (Pisum sativum) (López-Amorós et al., 2006). Wong et al. (2006) stated that one of the possible reasons for the decreased value obtained from the DPPH assay for plant samples could be due to the presence of compounds which are not reactive towards DPPH free radicals. Polyphenols may be more efficient as reducing agents in reducing ferric iron but some may not scavenge DPPH free radicals as efficiently due to stearic hindrance. All the samples showed significant difference (p<0.05). The scavenging action of plant constituents has been found to relate to polyphenolic compounds (Siger et al., 2008). Although the constituents of germinated flaxseed oil, which show free radical scavenging action are still unclear, it is possible that the antioxidative activity of germinated flaxseed oil is caused, at least in part, by the presence of polyphenols (Azhari et al., 2014; Anwar et al., 2013; Gujral et al., 2011) and other yet to be discovered antioxidant compounds.

Figure 2. Effect of germination on antioxidant activity.

 

4. CONCLUSIONSTOP

Phytochemical contents changed during flaxseed germination. The crude fat content was reduced significantly from 35% in ungerminated seeds to less than 28% after germination. The ash and crude protein content remained at the same level before and after germination. Cox value and LDR showed no significant difference (p>0.05). The total phenolic acids content was highly accumulated on non-germinated flaxseed. On the basis of our physicochemical evaluation of flaxseed oil we conclude that oil originating from each day of germination has its own special characteristics. According to the test carried out on the crude oil in order to assess the efficiency of the DPPH method of antioxidant evaluation, this oil can be a source for use in the food, cosmetics and pharmaceutical industries.

 

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