Flaxseed is among unique oil seed crops because of its exceptionally high content of α-linolenic acid (ALA), contains 35 to 45% oil, of which 45 to 52% is α-linolenic aci . Flaxseed (Linum Usitatissimum L.) is also one of the oldest domesticated crop that is under cultivation in Europe and Asia since dating back thousands of years (3000–5000 BC). Approximately more than two hundred species of flaxseed have been recognized . Flaxseed is grown as oil crop, as fiber crop and oil is extracted from oilseed varieties. A large proportion of flaxseed comprises nutritional components such as oil, soluble fiber, protein, lignans, vitamins and minerals .
Nutritionists during last two decades are actually clear about selected foods that play an important role in maintaining physical and mental health status of consumers. Beyond meeting nutrition needs, it is generally recognized that dietary factors are considered to modulate detrimental development of some chronic diseases. With increased consumption of highly saturated fat foods, it seems feasible that modern diets do not meet healthy eating guidelines and deficient in certain long chain omega-3 fatty acids. It is widely accepted that inadequate intakes of omega-3 polyunsaturated fatty acids (PUFA), principally alpha-linolenic acid (ALA) and docosahexaenoic acid (DHA), adversely affect cardiovascular function . Flaxseed is rich source of omega-3 polyunsaturated fatty acids and it is helpful in prevention of cardiovascular diseases and cancer. The flaxseed contains all essential amino acid of the protein. It is an excellent source of fiber, lecithin, vitamins and minerals. Moreover, flaxseed is of fastidious significance for its role in lowering the risk of breast and colon cancers . A large proportion of flaxseed comprises nutritional valuable components such as protein (200-240 g/kg), dietary fiber (250–280 g/kg) and flax oil (350-450 g/kg).
The health benefits are related with the ingestion of polyunsaturated fatty acids (PUFA) and dietary fiber. The flaxseed oil contains almost 50% essential fatty acid like alpha-linolenic acid of the total fatty acids that play a significant role in reducing the risk of coronary heart diseases . However, the drawbacks with the dietary inclusion of flaxseed are the presence of anti-nutritinal factors, which may limits its utilization in poultry diets. Mucilage coming from hull, linatin dipeptide (vitmine B6 antagonistic), cyanogenic glycosides, trypsin inhibitor and phytic acid are the most important antinutritional factors found in flaxseed .
Alpha-linolenic acid (ALA) and linoleic acid (LA) are the essential fatty acids among the polyunsaturated fatty acids. Human body cannot synthesize alpha-linolenic acid linoleic acid so they should be present in the diet. LA and LNA are metabolized to long chain PUFA in mammalian cells. The omega-6 fatty acid LA is converted to γ-LNA and diomo-γ-LNA by desaturase and elongase enzymes to produce arachidonic acid (AA). AA is further metabolized to eicosanoids or docosapentaenoic acid (DPA). LNA which is omega-3 fatty acid is converted to stearidonic acid and eicosatetraenoic acid to synthesize eicosapentaenoic acid (EPA) by the same enzymes used in synthesis of AA. Eicosapentaenoic acid is then metabolized to docosahexaenoic acid (DHA) or eicosanoid .
The limiting consumption of flaxseed is due to presence of anti-nutritional factors such as cyanogenic compounds and tannin which negatively influence the health and well-beings of the masses. The cyanogenic glycosides (CG) are amino acids derived from flaxseed constituents which release a potent cell respiration inhibitor; toxic hydrogen cyanide (HCN) via hydrolysis. The presence of these compounds restricts flaxseed applications in feed and foodstuff by producing bitterness in final products . Presence of phytic acid in the diet reduces micronutrient bioavailability and metabolizeable energy which ultimate lead towards poor growth of poultry birds. Anti-vitamin B6 compound named as ''linatine'' reduces dry matter and produces vitamin B6 deficiency. Omega-3 enriched meat has several health benefits. It plays an important role in prevention or treatment of cardiovascular disease, hypertension, arthrosclerosis, cancer neurological disorders and inflammatory disease. The increased intake of omega-3 fatty acids decreases serum cholesterol which beneficially affects blood pressure, skin diseases, thrombosis atherosclerosis and diabetes, arterial compliance and hyperlipidemia response .
Extrusion cooking is highly adaptable and focused form of processing in which food or feedstuff is enforced to flow under controlled conditions of heating and shearing through a terminal die. Extrusion processing of feed ingredients has become very popular during the last two decades. The principal features of extrusion cooking include flexible product characteristics, high energy efficiency, less space required for operation, new feed products formulations, automated control system with high productivity and product quality with no effluent showing environmental-friendly technology to be used. Optimized results for temperature (146.0°C), feeding rate (32.7 kgh−1), screw speed (152.5rpm), moisture content (12.5%) and the hydrocyanic acid removal rate (93.23%) were founded during the extrusion detoxification technique on flaxseed via stepwise non-linear regression analysis and response surface method. It has been demonstrated that maximum removal rate of mucilage (60.3%) from flaxseed meal can be achieved at different co-rotating twin-screw extruder die temperatures (80-160°C), screw speeds (300-900rpm) and initial moisture contents ranged as 18.8-35.1% . There exist a relationship between the stability of the flaxseed derived protein and antifungal activity with temperature variable (50-90°C) using response surface methodology . Regression analyses recommended the significant negative consequences on the residual antifungal activity against all test fungi using treatment variable. The protein content exits in flaxseed by means of response methodology with 5 central points and 4 axial points for independent variables . Extrusion cooking improved the degradation of flaxseed mucilage and negatively influences the compact fiber structure flow behavior index with the addition of initial moisture content, high temperature and decreased screw speed .
Incorporation of n-3 fatty acids from flaxseed into eggs and meat is an efficient process tool to increase the polyunsaturated fatty acids content of meat and eggs. The chicken is able to digest flaxseed in the digestive tract, absorb nutrients from flaxseed in the small intestine, and then further metabolize some of the alpha-linolenic acid (ALA; C18:3n-3), elongating and desaturating the ALA to eicosapentaenoic acid (EPA; C20:5n-3) and docosahexaenoic acid (DHA; C22:6n-3) for deposition in lipid stores such as egg yolk, and phospholipids in meat products. Flaxseed is a valuable and natural source of n-3 fatty acids for the poultry producer wanting to market an n-3 polyunsaturated fatty acid (PUFA) enriched poultry product. 300 mg of omega-3fatty acids per 100 g of breast meat can be achieved in 26.2 days at 10% ground flaxseed meal . Keeping in view the breakthrough results in flaxseed or flaxseed meal studies, the present study was carried out to compare the effects of extruded flaxseed meal supplementation on broiler growth performance, oxidative stability, ALA, polyunsaturated fatty acids content, quality attributes of broiler meat and sensory acceptability of meat products.