OMEGA-3 Fatty Acids Retention, Oxidative Quality, and Sensoric Acceptability of Spray-Dried Flaxseed Oil

Institute of Home and Food Sciences, Faculty of Life Sciences, Government College University, Faisalabad, Pakistan University Institute of Diet and Nutritional Sciences, Faculty of Allied Health Sciences, %e University of Lahore, Lahore, Pakistan Department of Dairy Technology, University of Veterinary and Animal Sciences, Lahore, Pakistan National Agriculture Education College, Kabul, Afghanistan


Introduction
Globally, consumers are more conscious about what they eat and what are beneficial aspects gained from specific ingredients for maintaining good health. Diet-based therapy is a unique prospect to use innovative functional foods. ese foods play an outstanding role in promoting health, longevity, and prevention of chronic diseases [1]. In this connection, polyunsaturated fatty acids (PUFAs) are the most important families of omega-3 and omega-6 fatty acids, gaining importance as part of functional food ingredients. As human body cannot synthesize them so they must be present in the diet in ample amounts. ese PUFAs such as linolenic acids (ALA), eicosapentaenoic acids (EPA), and docosahexaenoic acids (DHA) have potential health benefits including antiinflammatory, antimicrobial, antithrombotic, antihypertensive, antiaging, anticancer, and antidiabetic properties [2].
Flaxseed (Linum usitatissimum L.) belongs to family Linaceae. It has recently grown a great popularity and scientific attention owing to its huge amount of lipid content, increased acceptance by the consumers, and its functional and nutritional values. It is an industrial major crop used for oil and fiber contents. e main benefits of using flaxseed in human nutrition are its very high dietary fiber (28-30%) and abundance of ALA (C 18:3 ). Nearly, 80% of flaxseed oil (FSO) is used for the purposes of different industries and remaining 20% is used for edible purposes [3]. Practically, every part of the flaxseed plant is commercially useable, either directly or after processing [4,5]. Nowadays, FSO is frequently used in food processing industries predominantly in the formulation of products such as cookies and bread recipes, and such products have acquired enormous competence in the market [6]. However, food industries are facing problem of oxidation of these unstable PUFAs during processing and storage [7]. Moreover, the resultant oxidation products such as ketone, aldehydes, and free acids have capability to crosslink to proteins and bind covalently to nucleic acids and ultimately results to enhance aging, carcinogenesis mechanisms, and mutagenesis in the biological system [8].
us, besides achieving maximum extraction efficiency of PUFAs enriched oils, it is also crucial to find out an effective way to preserve bioactive contents of the oil [9].
Microencapsulation is now being largely employed for the production of dry edible oil stuffs. It has been documented that microencapsulation prolong the shelf stability of polyunsaturated oils by shielding them from oxidative damage. Microencapsulation of edible oils by powder particles, comprising carbohydrate or proteins is a scientific process followed to protect polyunsaturated oils from oxidation resultantly preserving flavors, aroma, and transport bioactive oils into easily managed dried solids for food supplementation [10][11][12]. Spray-drying is one of the most commonly used microencapsulation techniques [13,14]. e associated beneficial health effects of spray-dried PUFAs enriched oils depend on their metabolic digestion and bioavailability [15]. Hence, it is much important to discuss and evaluate the in vitro digestion models of spray-dried encapsulated oils under various gastrointestinal conditions [16]. erefore, the mandate of the study was to enlighten the effects of spraydrying conditions on retention of omega-3 fatty acids in FSO samples and evaluation of spray-dried flaxseed oil (SDFSO) samples for oxidative quality and sensoric acceptability.

Preliminary Processing of Oilseed Material.
Flaxseeds (Linum usitatissimum L.) cultivar Chandani obtained from the Institute for Oilseed Research, Faisalabad, Punjab, Pakistan, were cleaned to take out dirt and other foreign substances.

Oil Extraction.
Raw flaxseeds were weighed by using electronic scales (model Kern 440-35N) and were processed with the mini oil presser (model 6YL-550, with 2-3 kg/hour capacity) for oil extraction.

Polysaccharides Gums (PSG) Extraction.
e flaxseed meal samples were operated using ultrasound-assisted technology (model VCX 750, Sonics & Materials, Inc., USA) to derived polysaccharide gum (PSG) [17]. e extracted solutions of PSG were filtered over a 40-mesh screen and precipitated with two volumes of 95% ethanol. e separation of PSG was done by centrifugation, and further dried in a benchtop laboratory freeze dryer.

Emulsion Preparation.
e PSG as wall materials was added to distilled water at a temperature of 25°C. e combination was agitated until it completely dissolved. Addition of FSO to the wall material solution was fixed. Emulsions were formed using a homogenizer operating at 18000 rpm for 5 min [18].

Spray-Drying Process.
e oil microcapsules enriched with omega-3 fatty acids were prepared with a mini spray-dryer (Toption Lab Spray Dryer, Xi'an, China). e graphic diagram for the lab-scale spray-dryer is demonstrated in Figure 1.
In the present study, spray-drying operating factors such as the inlet air temperature (120, 140, and 160°C), feed flow rate (200, 250, and 300 mL/hr), atomization speed (12000, 16000, and 20000 rpm), and the outlet air temperature (60, 70, and 80°C) were optimized as given in Table 1. e FSO microcapsules were collected in a single cyclone separator and stored at 25°C and 4°C, respectively, after packaging for successive 2 months.

Encapsulation Efficiency.
e encapsulation efficiency of SDFSO samples was investigated by adopting the procedure of Bae and Lee [19]. Hexane (15 mm) was introduced into a glass container, containing 1.5 g of dried oil powder. e container was shaken to extract free oil. Subsequently, Whatman No. 1 filter paper was used for filtration. en with 20 mL of hexane, the remaining powder on the filter was washed off. e leftover solvent was put to evaporate. e amount of surface oil was calculated by measuring the difference in mass between the early clean flask and the other one containing the residual oil extract. e total amount of FSO in microcapsules was computed using numerical expression [19]. EE(%) � (total amount of oil − surface oil) total amount of oil * 100. (1)

ALA Fatty Acid Profile of SDFSO Samples.
e ALA fatty acid profile of FSO and SDFSO samples was recorded by gas chromatograph equipped with a column and flame ionization detector (FID). Briefly, the fatty acids were transformed to methyl esters using acid catalyzed methanolysis method [20]. e transport gas was nitrogen with a flowing speed of 1 mL/min. e temperature of the injection port and detector was set at 170°C and 240°C, respectively. e estimation of ALA percentage was calculated by measuring the respective peak area.  [23]. Informed consent form was explained for risks and benefits of participation, and each participating judge gave the written consent prior to the study. e brief definitions of sensoric attributes such as color, off-flavor, and overall acceptability regarding FSO and SDFSO samples were described each time to participating judges. Samples were presented to participating judges in sensory booths under controlled conditions and white lighting. e order of presentation was balanced to avoid carry over effects. Each participating judge received the FSO and SDFSO samples assigned with random three-digit code numbers. Each participating judge was asked to list preference on a 9 cm comparison line (1 � extremely dislike to 9 � extremely like) for color and overall acceptability parameter while (1 � extremely like to 9 � extremely dislike) for off-flavor sensoric attribute. e sensoric analysis was performed at different storage intervals for experimental FSO and SDFSO samples.

Statistical Design and Data Analysis.
e Box-Behnken design of response surface methodology was applied to determine the optimized values of the inlet air temperature, feed flow rate, atomization speed, and the outlet air temperature for spray-drying process parameters. e response data of FSO and SDFSO obtained for each treatment were subjected to a statistical analysis using software package (MATLAB), according to the described method [24] for determination of mutual effects. e average of the three runs was reported as the measured value with the standard deviation. e analysis of samples for storage stability and sensoric acceptability was accomplished in triplicate and significant differences among the means were calculated at a 5% probability level.

Encapsulation Efficiency of SDFSO Samples.
Encapsulation efficiency is the degree of oil protection, and it depends on numerous factors. e most crucial factors defining encapsulation efficiency are the wall material and inlet air temperature of a spray-dryer [25]. e temperature employed for drying of FSO in this study were, 120, 140, and 160°C. e maximum oil protection efficiency was recorded as 90.78% at 160°C and the lowest was observed as 85.27% at 120°C as shown in Figure 2. e high inlet air temperature   may have contributed towards high encapsulation efficiencies that were observed during this research. In a trial conducted by Aghbashlo et al. [26], increased inlet temperatures may contribute to swift formation of the microcapsules and a stable membrane that minimized the migration of oil to the surface of encapsulated microcapsules. Moreover, the wall material used for encapsulation, flaxseed PSG, may also be responsible for its higher viscosity and contributes for the high efficiency [18]. is outstanding efficiency noticed in this study may also be related to the better stability revealed by the emulsion prepared with the flaxseed PSG as wall material [27]. is coating material provided shield to the emulsion droplets and prevented from disruption and disintegration during the atomization process. It is also documented that starch or carbohydrate-based materials are great in film forming as compared to proteins, which can certainly influence the microencapsulation process and avoid oil migration to the powder surface [28].

Retention Yield of ALA in FSO and SDFSO Samples.
In current research, effect of spray-drying conditions, i.e., inlet and outlet air temperatures, atomization pressure, and feed flow rate, was examined on ALA retention in SDFSO. e oil extracted from flaxseeds is naturally a rich source of PUFAs, especially ALA, which exhibits nearly 57% of its entire fatty acid profile. Additionally, ALA is also precursor for long chain (omega-3) fatty acids like EPA and DHA. is high level of ALA fatty acid contents of FSO lets its attribution to functional food, which means besides its nutritional significance, its consumption may also have positive health effects [29]. Moreover, numerous studies have also proven their protective role against inflammation and cardiovascular disease [30]. However, the relatively short shelf stability of PUFAs rich oils limits their application in various food formulations.
Hence, in this respect, the retention of ALA in SDFSO was investigated in 30 samples at three stages, i.e., in freshly prepared samples at 0, 30, and 60th day of storage at two different temperatures of 4°C and 25°C, accordingly as shown in Table 2. e initial ALA content in FSO (control) samples was 57.05 ± 0.34%. ere was no significant difference among the ALA contents of FSO and SDFSO samples at 0 days. It is evident from the results that the ALA contents of SDFSO samples were not stable instead they fluctuate under varied interval and conditions of storage. e highest percentage for ALA retention was recorded as 54.72 ± 0.86% and 53.95 ± 0.76% at 4°C (spray-drying run 9), while the lowest retention percentage for SDFSO samples was observed as 48.63 ± 0.64% and 46.25 ± 0.56% at 25°C after 30 and 60 days of storage, respectively. Moreover, the control FSO samples showed the minimum retention of ALA contents (44.12 ± 0.50%) at 25°C after 60 days of storage. e inlet and outlet air temperatures were considered as key factors contributing decline in retention of ALA of SDFSO ( Figure 3). Moreover, ALA content was decreased significantly when stored at higher temperature as compared to lower temperature under different storage intervals.
Hence, it may be concluded that the SDFSO samples stored at lower temperature are more stable as compared to     Journal of Food Quality 5 others stored at higher temperature. However, the values for ALA contents did not changed significantly and remained in the acceptable limits, showing the effectiveness of the spraydrying encapsulation technique. Similar findings are also reported by Javed et al. [31] as they produced spray-dried PUFAs enriched egg powder, and stated that the PUFAs stayed stable up to two months when stored at 4°C as contrarily some decline was observed in samples stored at high temperature.

Free Fatty Acids (FFAs) Contents of FSO and SDFSO
Samples. e influence of spray-dryer and storage conditions on free fatty acids (FFAs) contents of SDFSO have been shown in Table 3. e FFAs contents of FSO and SDFSO samples reached to their peaks, i.e., 1.22 ± 0.13% and 0.75 ± 0.07%, respectively, after 60 days of storage at 25°C. e increasing pattern shows that lipid oxidation has enhanced with storage. It is evident from the results that the SDFSO samples stored for 30 days at lower temperature are quite stable than stored at higher temperature for 60 days. e values for FFAs contents of all the SDFSO samples were well below the limit of 2%, which is considered a trigger of rancidity. e oxidation of PUFAs in foods generates FFAs, aldehydes, hydroperoxides, and polymeric substances that end up in adverse health consequences and possibly leading to some chronic illnesses such as cardiovascular, cancer, and neurological disorders [32].

Oxidative Stability of SDFSO Samples.
In the current study, the progression of lipid oxidation in SDFSO was monitored by measuring the formation of various oxidation products like, peroxide value (PV), malondialdehyde (MDA), and conjugated dienes (CDs). Encapsulated FSO in the powder form is more stable to oxidative damage when compared to free oil. e initial PV of FSO (control) was 0.16 ± 0.03, which increased to 0.34 ± 0.05 (4°C) and 1.10 ± 0.07 (25°C) meq/kg O 2 at the end of 60 days storage. According to Table 4, the PV of SDFSO samples ranged from 0.16 ± 0.03 to 0.20 ± 0.05 meq/kg O 2 along with change in the inlet air temperature of 120 to 160°C. e results showed that there were no significant differences between PV of SDFSO samples and control on initial days of the experimental trial; however, as the storage period proceeded from 30 to 60 days, the PV of SDFSO samples was also increased from 0.25 ± 0.06 to 0.30 ± 0.07 at temperature of 4°C, while the PV was noted as 0.37 ± 0.07 and 0.62 ± 0.07 meq/kg O 2 when stored at 25°C for similar storage period. In the present investigation, the data further revealed a two-fold increase in PV for the FSO samples as compared to the SDFSO samples. In general, higher oil loads led to higher peroxide values. According to the previous observations by different researchers, the reason for increasing PV during storage may be due to the high oil load on the surface of SDFSO, leading to low encapsulation efficiency [27].
is can lead to poor protection of dried oil from lipid oxidation. is nonencapsulated oil on the surface, when comes in contact with oxygen becomes more susceptible to lipid oxidation than the encapsulated oil. According to the findings of Andersen et al. [33], when the oil is subjected to encapsulation into a wall matrix, some oil particles may oxidize slowly whilst, others may oxidize more rapidly owing to the variability in the degree of encapsulation.       Journal of Food Quality

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Journal of Food Quality e data pertaining to MDA concentration of SDFSO powder stored at temperatures 4°C and 25°C for a period of 0, 30, and 60 days are presented in Table 5. e value for MDA of FSO samples was increased from 0.16 ± 0.02 nmol/g of lipids (0 day) to 0.39 ± 0.06 nmol/g of lipids at 60 days (4°C) while the value for MDA of SDFSO samples was increased from 0.17 ± 0.01 nmol/g of lipids (0 day) to 0.34 ± 0.07 nmol/g of lipids at 60 days (4°C), and the same increasing trend was observed at 25°C. It has been observed in different previous research studies that the reaction of free oxygen with unsaturated oils (lipid peroxidation) generates a wide variety of oxidation products. From many years, MDA has been extensively used as an expedient biomarker for lipid peroxidation of PUFAs due to its reaction with thiobarbituric acid (TBA). It is actually a product generated by decomposition of arachidonic and large chain PUFAs. MDA reacts with cellular and tissue proteins or DNA to form products resultantly, causing biomolecular damages leading to disease [34].
e results for effects of various storage time intervals for CDs are shown in Table 6. e maximum value for control samples was observed 0.32 ± 0.08 while the maximum value was recorded as 0.29 ± 0.09 under four factors of a spraydryer, i.e., inlet air temperature (160°C), outlet air temperature (80°C), feed flow rate (300 mL/hr), and atomization speed (20000 rpm) for the SDFSO samples stored at 25°C after 60 days of storage.
e results of the current study can be explained by the fact that the CDs decompose into secondary volatile oxidation products by high temperature at the commencement of the microencapsulation process. e data indicate that the level of CDs in the SDFSO samples showed a nonsignificantly increasing trend until the second month of storage. However, none of the value went beyond its safe limit. ese observations are in harmony with previous results recorded by Kolanowski et al. [35] as they narrated that the encapsulated fish oil oxidized quickly in the presence of air. Nevertheless, stability was enhanced when the powder was stored under vacuum. Similar results were also reported by Drusch et al. [36], who noticed incline in level of CDs in microencapsulated fish oil kept in closed bottles and stored for 17 days at 20°C. Reduction in stability of microencapsulated oil samples stored in contact with oxygen might be due to increased ratio of surface-to-oil volume and subsequently higher accessibility of oxygen to these oils [37].

Sensoric Evaluation of the SDFSO Samples.
e FSO (control) and SDFSO samples were also evaluated for different sensory parameters like color, off-flavors, and overall acceptability as depicted in Figure 4. e data regarding scores of different attributes highlight the differences due to spray-drying and storage condition as well as storage duration. e average hedonic scores assigned to color, offflavor, and overall acceptability differ in a quite narrow range for all SDFSO samples at the start of the storage period, irrespective of the encapsulation processing conditions. In the case of color and overall acceptability, the lowest evaluation scores were awarded to the FSO samples. Furthermore, the highest score for off-flavor was attributed to FSO samples stored at high temperature for 60 days of storage.

Conclusions
e results of the present study conclude that the optimized SDFSO powder showed maximum encapsulation efficiency and retention of omega-3 fatty acids as compared to FSO control samples. e validated optimized inlet air temperature (120°C), feed flow rate (250 mL/hr), atomization speed (16000 rpm), and outlet air temperature (60°C) conditions were found for maximum retention of ALA, oxidative stability, and sensoric acceptability. e results further revealed that SDFSO samples were oxidatively stable and the process of spray-drying did not significantly alter the sensoric attributes during different storage intervals. Furthermore, the present study suggests that the incorporation of SDFSO powder into different food products and their effect in the biological system should be evaluated in future studies.
Data Availability e datasets supporting the conclusions of this article are included within the article.

Conflicts of Interest
e authors declare that they have no conflicts of interest.