Characteristics of flaxseed hull oil

Oils from two commercial flaxseed hulls extracted by six procedures were evaluated for physicochemical characteristics. Oil yield ranged from 9% to 28% depending on solvent and extraction. Lipid fractionation of crude flaxseed hull oil yielded 92.5% neutral lipids, 3.1% phospholipids, 2.4% acidic lipids and 2.1% free fatty acids. Flaxseed hull oil exhibited three thermal transitions between −35 and −13 °C with solvent dependent polymorphism. Thermal oxidation by differential scanning calorimetry (DSC) revealed three step oxidation of flaxseed hull oil with mean onset and oxidation temperatures at 121 and 150–253 °C, respectively depending on the extraction procedure. Flaxseed hull oil exhibited two-fold difference (0.6–1.2 μm Trolox equivalent/g) in antioxidant activity measured by a photochemiluminescence (PCL) assay. Supercritical CO₂ extracted the most oil with the highest antioxidant capacity of all evaluated procedures resulting in a defatted flaxseed hull containing the highest (53 mg/g) secoisolariciresinol diglucoside (SDG) level.     

Effects of germination on tocopherol,secoisolarlciresinol diglucoside,cyanogenic glycosides and antioxidant activities in flaxseed (Linum usitatissimum L.)

The changes in chemical composition and antioxidant activities of brown and golden flaxseeds (Linum usitatissimum L.) during 5-day germination were investigated. Flaxseeds germinated in a dark and closed incubator at the temperature of 25 °C. With noticeable reduction in fat content, germinated flaxseeds were determined higher percentage of linolenic acid. The total phenolic content and antioxidant activities increased with germination time. The highest amount of secoisolarlciresinol diglucoside (SDG) was found in 2-day germinated brown and golden flaxseeds, which increased 1.04-fold and 1.09-fold, respectively, and germinated flaxseed oil was found rich in SDG. Intriguingly, germination increased the α-tocopherol content from 0 to 4.58 mg per 100 g and 0 to 7.83 mg per 100 g in brown and golden flaxseeds while γ-tocopherol decreased. Germination process also reduced the total content of cyanogenic glucosides, the content of linustatin, neolinustatin and lotaustralin decreased significantly, but caused an increase in the content of linamarin. Therefore, germination can be utilised as an effective method to improve the nutritional value of flaxseed.     

Secoisolariciresinol diglucoside determination in flaxseed (Linum usitatissimum L.) oil and application to a shelf life study

A high-performance liquid chromatographic (HPLC) reliable and sensitive method with diode array detection (DAD) system has been developed for the determination of secoisolariciresinol diglucoside (SDG) in flaxseed oil. An analytical methodology based on the sample extraction with methanol/water (80:20, v/v), subsequent purification of the sample and analysis of the extract by HPLC/DAD is proposed for the determination of SDG in flaxseed oil. The coefficient of determination of the standard calibration curve was 0.999, the limit of detection was 0.08 μg/mL, and the limit of quantification was 0.27 μg/mL. The recovery test was conducted adding four different concentrations of standard solution to the blank sample. The recovery ranged from 90% to 95%. To our knowledge, the presence and quantification of SDG in flaxseed oil has never been reported. The proposed method was tested to study the variation in SDG content in flaxseed oil during a shelf-life test to verify its applicability in quality control for oil industries. The dark and the low temperature of storing together allowed to preserve SDG. A slight pro-oxidant effect was observed for the addition of antioxidant to the flaxseed oil.     

Development of Chinese steamed bread enriched in bioactive compounds from barley hull and flaxseed hull extracts

Hull from cereal and oilseed grains represent low-cost agricultural materials that have not be fully explored as functional food ingredients. The objectives of the present study were to investigate the phytochemical profile and antioxidant activity of Chinese steamed bread (CSB) containing extracts of barley hull and flaxseed hull. HPLC and LC–MS/MS analyses showed that the phytochemical profile of CSB containing barley hull extract was enriched in ferulic and p-coumaric acids. The flaxseed hull extract introduced secoisolariciresinol diglucoside (SDG), ferulic acid glucoside (FeAG) and coumaric acid glucoside (CouAG) into CSB. All the major phenolic compounds originating from the two types of hulls were found in CSB when barley–flaxseed hull co-extracts were added to the formulation. The total phenolic content was improved by 83.1, 138.3 and 70.3%, respectively when barley, flaxseed, and barley–flaxseed hull extracts were added. The antioxidant activity of CSB containing hull extracts was increased by 34.5–90.7% compared to the control. CSB containing hull extracts had significantly higher (p < 0.05) DPPH radical scavenging activity compared to the control. However, barley–flaxseed hull co-extracts resulted in the highest enhancement of ORAC values of the CSB, although no significant differences were found (p < 0.05). The findings indicate that extracts from barley hull, flaxseed hull and barley–flaxseed can be targeted for development as functional food ingredients that can enhance the phytochemical content of refined flour products, such as steamed bread.     

Dehulling Characteristics of Selected Flaxseed Varieties

Dehulling characteristics of six different flaxseed varieties namely Shikha, Rashmi, Shekhar, Sweta, Padmini and Neelam at different residence times (40, 50 and 60 s) were investigated using dry dehulling. The dried flaxseed samples were dehulled in a laboratory model abrasive dehuller (rice polisher) and various dehulling parameters were determined. It was found that dehulling parameters namely embryo recovery, extraction rate, yield, hull and hullability were affected by residence time and varietal characteristics. The embryo recovery, extraction rate, yield, hull and hullability for studied varieties of flaxseed and residence time were 23.71?±?0.77–61.35?±?0.94 %, 58.26?±?2.20–79.11?±?0.43 %, 22.96?±?0.44–43.85?±?1.38 %, 16.83?±?1.75–61.54?±?5.11 % and 45.92?±?0.51–90.62?±?2.85 % (dry basis), respectively. Among the studied flaxseed varieties, Padmini and Neelam varieties were found suitable for dehulling purposes at 60 s residence time. The dehulled flaxseed (embryo), thus obtained, can be utilized for obtaining the good quality edible oil and meal for human consumption and hull as lignin-rich product.     

Cellulase-assisted release of secoisolariciresinol from extracts of flax (Linum usitatissimum) hulls and whole seeds

Extraction of secoisolariciresinol from seed hulls and whole seeds of flax was improved using an enzymatic step with cellulase R10 from Trichoderma reesei that allowed better yield as compared to β-glucosidase. The cellulase assisted extraction process was further optimised for different parameters such as duration and concentration of hydromethanolic extraction, duration of alkaline hydrolysis, pH, duration and incubation temperature as well as enzyme concentration. Best results were obtained using a method including the following successive steps: 16 h of 70% hydromethanolic extraction, 6 h of 0.1 M sodium hydroxide hydrolysis followed by a 6 h incubation with 1 unit ml⁻¹ of cellulase R10 in 0.1 M citrate–phosphate buffer pH 2.8 at 40 °C. Under these conditions, all forms of the main flax lignan were recovered as the aglycone form, i.e. secoisolariciresinol. Highest yields in secoisolariciresinol diglucoside (SDG) equivalent reached 7.72% of flaxseed hull (cv. Baladin) dry weight and 2.88% of whole seed (cv. Barbara) weight, thus allowing a significant improvement in comparison with published methods.     

Microwave‐assisted extraction of secoisolariciresinol diglucoside from flaxseed hull

Microwave‐assisted extraction (MAE) of secoisolariciresinol diglucoside (SDG) from defatted flaxseed hull (DFH) was studied. The effects of pre‐soaking methods and extraction parameters (ethanol concentration (0–100%, v/v), microwave energy input (50–390 W), liquid to solid ratio (5:1 to 40:1, mL g^?1) and irradiation time (10–330 s)) on the SDG yield were investigated. Response surface methodology (RSM) was applied to optimise the MAE conditions as irradiation time 90.5 s, ethanol concentration 40.9% (v/v), liquid to solid ratio 21.9:1 (mL g^?1) and microwave power 130 W. The SDG recovery from DFH with MAE was 11.7 g SECO kg^?1 DFH (on dry‐weight basis), which was significantly higher than that of stirring extraction (10.0 g SECO kg^?1 DFH) and Soxhlet extraction (7.60 g SECO kg^?1 DFH). Compared with stirring extraction and Soxhlet extraction, MAE showed its superiority in improving SDG yield and saving time and energy. Copyright © 2007 Society of Chemical Industry     

Optimisation of aqueous extraction of gum from durian (Durio zibethinus) seed: A potential, low cost source of hydrocolloid

The main goal of the present study was to investigate the effect of aqueous extraction conditions on the extraction yield and physicochemical properties of the durian seed gum. The studied aqueous extraction variables were water/seed (W/S) ratio (20:1-60:1, w/w), temperature (25.0-85.0 °C), and pH (4.0-10.0). The results indicated that the aqueous extraction variables exhibited the least significant (p < 0.05) effect on oil-holding capacity (OHC). Conversely, they had the most significant (p < 0.05) effect on the span and extraction yield. The current study revealed that the interaction effect of aqueous extraction variables showed the least significant (p < 0.05) effect on the solubility and OHC of durian seed gum. The optimum extraction condition led to the production of durian seed gum with a relatively high extraction yield (56.4%), solubility (27.9%), volume-weighted mean (98.7 μm), span (3.8), water-holding capacity (WHC) (270.6 g water/100 g gum), and OHC (146.5 g oil/100 g gum).     

Calibration of artificial neural network and partial least squares regression models for the prediction of secoisolariciresinol diglucoside contents in microwave-assisted extracts of various flaxseed (Linum usitatissimum L.) samples

Partial least squares (PLS) and artificial neural network (ANN) regression models were calibrated for predicting the content of secoisolariciresinol diglucoside (SDG) in six flaxseed cultivars, defatted flaxseed meal and flax hulls extracts. The SDG was quantified by HPLC after microwave-assisted extraction (MAE) from flaxseed; the data were used in conjunction with the light absorption of the extracts measured after Folin–Ciocalteu’s assay at 289, 298, 343 and 765 nm, in order to calibrate the predictive PLS and ANN models. The accuracy and the predictive ability of the models ranged from good to excellent as indicated by RPD values (the ratio of the standard deviation of the reference values to the standard error of prediction) of 5.03–13.7. The PLS and ANN predictive models are useful to the flaxseed processing industry for rapidly and accurately predicting the SDG contents of various flaxseed samples based on their UV–Vis light absorption.     

The effective parameters for subcritical water extraction of SDG lignan from flaxseed (Linum usitatissimum L.) using accelerated solvent extractor

The aim of this study was to investigate the effective parameters for subcritical water extraction of secoisolariciresinol diglucoside (SDG) lignan from flaxseed using accelerated solvent extractor. For this aim, the influence of extraction parameters such as material shape (flaxseed, ground flaxseed meal and flaxseed meal sticks), temperature (120, 140, 160 and 180 °C), extraction time (15, 30, 60 and 90 min), pressure (1.500 and 2.000 psi), fresh water (5, 40 and 100 %) and sample amount (5 and 10 g) was studied. SDG lignan analysis has been carried out by LC–MS/MS. It was shown that material shape, temperature, extraction time and sample amount had significant effect on SDG lignan content in water extracts (p < 0.05). The highest amount (12.94 mg/g) and extraction yield (72.57 %) were obtained at 180 °C for 15 min, 1.500 psi and 40 % fresh water using 5 g of flaxseed meal sticks.     

Microwave-Assisted Extraction of Secoisolariciresinol Diglucoside��Method Development

An optimized microwave-assisted extraction (MAE) method was developed for extracting secoisolariciresinol diglucoside (SDG) from flaxseed. This paper presents the optimization of factors for maximizing the extraction yield of SDG. This work was conducted using the experimental domain identified in a previous study by means of screening designs, that is, samples of 1 g defatted flaxseed meal (DFM) were extracted with 50 ml NaOH of concentration of 0.5–1 M, at microwave power levels of 60–360 W, for 3–9 min, with the microwave power applied intermittently (power on 30 s/min) and continuously (power on 60 s/min). The MAE of SDG was maximized when 1 g DFM was extracted with 50 ml 0.5 M NaOH, at 135 W, for 3 min in intermittent power mode (power on 30 s/min). The optimized MAE achieved a 6% increase in the extraction yield (21.45 mg SDG per gram DFM) as opposed to a direct hydrolysis method (20.22 mg SDG per gram DFM). The MAE of SDG was governed by the microwave–NaOH interaction, which had a curvilinear dependence on the microwave power level, and linear dependence on the NaOH concentration. The microwave-induced effects accounted for a 10% increase in the SDG extraction yield (21.45 mg SDG per gram DFM) as opposed to a microwaveless control method (19.45 mg SDG per gram DFM). The optimized MAE method has good repeatability, a 97% recovery of the target compound; it is fast and efficient and can be used for precise quantification of SDG in flaxseed.     

Phenolics and antioxidant activity of lentil and pea hulls

Hulls obtained by pilot-scale dehulling process from green and red lentils and yellow peas were fractionated into hulls (> 500 ??m) and residues (< 500 ??m). These fractions together with the corresponding whole seeds were extracted with four solvents, aqueous (70%) acetone, (80%) ethanol, hot water (70-80 °C) and water (22 ± 1 °C) and evaluated for antioxidant activity in relation to phenolic contents. Aqueous acetone (70%, v/v) extracted the highest level of total phenolics at about 87 mg of catechin equivalent per gram of sample from lentil hulls followed by hot water, water and aqueous ethanol (80%, v/v). Red lentil hull with maximum concentration of phenolic compounds exhibited the strongest antioxidant activity of 260 mg (1040 ??M) trolox equivalent/g hull. Hot water and water extracted significantly higher total phenolics from whole pulse and their residue than other solvents, but with weaker antioxidant activity. Aqueous ethanol was always the best extractant of phenolic antioxidant from yellow pea irrespective of its millstream. The most potent phenolic antioxidant was obtained from water extract of green and red lentil hulls, followed by those extracted with ethanol, acetone, and hot water. Total phenolic content was highly correlated with antioxidant activity of pulses and its millstreams.     

Laws of flaxseed mucilage extraction

This study examined the application of few-stages aqueous extraction of mucilage from whole flaxseed. Key processing conditions included temperature (40-100 °C), duration (0-60 min), seed to water ratio (1 to 5-30) and mixer rotational speed (0-240 revolutions per minute). It was found, that mucilage extraction from flaxseed is appropriate to carry out without swelling. The maximum yield of flaxseed mucilage was obtained at 80 ± 2 °C with seed to water ratio of 1 to 25. The equation, which described equilibrium solid yield during the extraction depending on the phases’ ratio and the temperature, was found. The equation of solid yield depending on duration and mixer rotational speed under the temperature of 80 ± 2 °C and the seed to water ratio of 1 to 25 was determined. It was showed, that the use of stirring is not expedient for the intensifying the process. The rational duration of extraction under the selected parameters was 30 ± 1 min. To increase the solid content in the extract the few-stages extraction was applied. The three-stage countercurrent extraction of flaxseed mucilage from whole seeds under the temperature of 80 ± 2 °C, the seed to water ratio of 1 to 25, the duration of each stage of 30 ± 1 min was established to receive flaxseed mucilage extract with content of solids from 0.70 to 0.72%, i.e. to extract from 98.3 to 99.1% of mucilage from flaxseed.     

Evaluation of a Microwave-Assisted Extraction Method for Lignan Quantification in Flaxseed Cultivars and Selected Oil Seeds

An optimized microwave-assisted extraction (MAE) method was evaluated through repeatability, recovery and efficiency testing. The repeatability tests, performed by three users over time, were not significantly different. The recovery of lignan throughout the extraction, preparation and analysis steps is 97.5% with a coefficient of variation <1%. The MAE method is efficient for extracting lignans from the plant matrix, and it achieves significantly higher extraction yields than the two established reference methods. The applicability of the MAE method was demonstrated by extracting lignans from a variety of plant samples. The secoisolariciresinol diglucoside (SDG) content of seven flaxseed cultivars grown in Saint-Mathieu-de-Beloeil, QC, in 2009 ranged from 14.6 to 18.9 mg SDG per gram of seed. Flax hulls produced in Winchester, ON, in 2010 were very rich in lignan; their SDG content was 40.0 mg/g of flax hull. Sesame seeds contained 0.18–1.89 mg SECO (aglycone of SDG) per gram of seed, with significant differences among black, white and brown sesame seed. Chia seeds contained 0.99–1.29 mg SECO per gram of seed, with significant differences among batches of seeds. Sunflower seeds had 0.046 mg SECO per gram of sample and almonds had 0.029 mg SDG per gram of sample. The optimized and evaluated MAE method is recommended for the general analytical quantification of lignans in plant samples.     

Moisture-dependent engineering properties of sunflower seeds with different structural characteristics

The present study was carried out to investigate the effect of the moisture content of the seeds on engineering properties of sunflower hybrids with different structural characteristics. The properties were evaluated at seven levels of moisture from 2.0% to 20.1% (dry basis) for three selected sunflower hybrids. For both black-hull oilseed hybrid and confectionary hybrid, the variation in moisture content showed a statistically significant effect on dehulling ability, percentage of fines (broken grains with a diameter smaller than 2 mm) and all the physical properties studied (size, true density, bulk density, porosity, volume and weight, volumetric expansion coefficient, equivalent diameter and sphericity), except seed length in the confectionary hybrid and seed length and thickness in the black-hull oilseed hybrid. For the striped-hull oilseed hybrid, moisture content showed a significant effect only on dehulling ability, percentage of fines, seed width and thickness, bulk density and porosity. Of the oilseed hybrids, the striped hull genotype (higher hull content and both lower oil content and seed size) presented a higher dehulling ability. Nevertheless, the black hull hybrid resulted more sensitive to seed moisture changes. Although the confectionary hybrid showed a higher seed size, hull thickness and hull content, and lower oil content than the oilseed hybrids, the dehulling ability resulted fairly similar in the striped hull sunflower hybrids. The results suggest that sunflower seeds with different structural characteristics need to be conditioned with different moisture content before being subjected to the dehulling process.     

Rheological properties of corn oil emulsions stabilized by commercial micellar casein and high pressure homogenization

The rheological behavior of corn oil emulsions prepared by high pressure homogenization (HPH) was investigated. Coarse emulsions of corn oil (10-30 g oil/100 g emulsion) in casein dispersions containing 0.5-3.5 g micellar casein/100 g casein dispersion in an oil-free basis were homogenized at 0-300 MPa. Flow behavior under continuous increasing (0-150 s⁻¹) or decreasing (150-0 s⁻¹) shear rate was tested. Emulsions that showed macroscopic change in consistency were tested for viscoelasticity (G′). Homogenization of emulsions with low oil concentration (10 g/100 g) resulted in Newtonian behavior for all treatment pressures. The rheological behavior of emulsions with higher oil concentration (30 g/100 g) was dependent on casein concentration in the aqueous phase and varied from Newtonian to shear thinning. Homogenization pressures between 20 and 100 MPa induced the formation of a gel-like structure possibly through pressure-induced interactions between caseins surrounding adjacent droplets.     

Effect of thermal pre-treatment on the phenolic and protein profiles and oil oxidation dynamics of golden flaxseeds

The food industry is interested in the application of thermally pre-treated flaxseeds because the treatment improves their sensory acceptability and reduces anti-nutrient contents. However, it may influence the health benefits of flaxseed compounds. The changes in the phenolic and protein profiles, and in situ oil oxidation dynamics after steaming or roasting of flaxseeds were analysed to study this effect. The results showed that the pre-treatment of flaxseeds did not affect the content of major flaxseed phenolics. Steaming and roasting considerably changed the flaxseed protein profile. The thermally induced protein aggregation and/or cross-linking occurred. The most significant changes were found for the 13 and 53 kDa proteins. Flaxseed roasting deteriorated the oil oxidative stability significantly more than steaming. These changes may decrease the nutritional quality and shelf life of roasted or steamed flaxseeds. They should be monitored when pre-treated flaxseeds are intended to be used as a food ingredient.     

Composition and characteristics of oil extracted from flaxseed-added corn tortilla

Flaxseed has recently gained attention as a functional food, and the effect of adding flaxseed (10%, 15%, and 20%) to tortillas was evaluated. The physicochemical characteristics and the free fatty-acid (FFA) content of the oil extracted from flaxseed-added corn tortilla were determined. The results showed that the lipid (4.27%) and protein content (9.10%) of the control sample was statistically lower (p ? 0.01) than the tortillas added with flaxseed. In general, the total amylose content did not change with the flaxseed-added content; however, the amylose apparently decreased with the amount of flaxseed, indicating the presence of starch–lipid complexes. The saponification value was 95.37 (mg KOH/g oil) in the tortilla added with 10% flaxseed and increased to 100 (mg KOH/g oil) for the 20% flaxseed treatment. The peroxide value was observed to increase (p < 0.05) when the flaxseed flour was added at 10%, 15%, and 20%. In this study, the tortillas exhibited a high amount of total unsaturated fatty acids, 26.32–30.08% (oleic acid). Thus, the flaxseed-added corn tortilla could represent a valuable staple in improving the nutritional value of the original food product.     

Optimization of SC-CO2 extraction of oil from almond pretreated with autoclaving

Supercritical carbon dioxide (SC-CO₂) extraction parameters affecting oil recovery from almond were optimized through response surface methodology (RSM). The optimum extraction conditions were as follows: extraction pressure, 44.1 MPa; extraction temperature, 43.8 °C; dynamic extraction time, 93.6 min; and CO₂ flow rate, 10.1 mL/min. Under these conditions, a mean value of 86.54 ± 0.66 g/100 g (n = 3) was observed, which is well matched with the predicted value of 87.32 g/100 g. Furthermore, the effects of autoclaving pretreatment for the almond particles on the oil recovery, fatty acids' composition, and almond particles' microstructure were also investigated by calculating the percentages of the oil yield, gas chromatograph fitted with a mass spectrometer (GC-MS), and scanning electron microscopy (SEM) analysis, respectively. The results showed that autoclaving pretreatment had minor modifications of the fatty acids' profile of the extracted oil, but greatly promoted the disturbing of almond cell walls, and increased the oil recovery by 6.44%.     

Mechanical stress on canola seed during dehulling

The mature canola seed comprises an embryo, a group of structures that have a high content of protein and oil, and a fibrous seed coat held together by endosperm tissues. High-quality canola meal production requires removal of fiber-rich seed hull that typically contributes little nutrient value. Canola hull accounts for more than 70.0% of the insoluble fiber within the seed, which limits its uses as feed. Dehulling canola seed, before oil extraction, increases the protein content and decreases fiber content in the meal, to up to 50.0% and to down to 10.0%, respectively. Due to the complexity in dehulling canola seeds, several methods have been explored by the canola processing industry. However, little research has been conducted in analyzing the effects that mechanical dehulling methods have on seeds. In this study, we conducted mechanical tests to characterize seed behavior and hull fracture under uncoupled stresses such as compression and shear;stresses generated by the common dehulling equipment used in the industry, such as mills. All tests were carried out on single seeds at different moisture contents, from 5.00% to 25.0% wet mass basis (w.b.). Over a range of moisture contents studied, shear loading mode limited deformation of embryos in comparison to compression loading. Additionally, hardness tests were performed with a nano-indenter machine to determine seed hull properties. The overall results from these experiments provided information used to construct a computational model that represents canola seed deformation under compression stress.