The Research Of Production Technique On Detoxified Flaxseed Cakes And The Application Of Detoxified Flaxseed Cakes In Staple Food Steamed Bread

Flax is one of the important oilcrops rich in ω-3 fatty acid. Flaxseed production in China is about 500,000 tons every year, the total planting area and production of flaxseed in China ranks second in the world after Canada. Flaxseed is abundant in functional bioactive components such as linolenic acid, dietary fiber, lignans, etc. And they have good functions in antioxidation, enhancing immunity, etc. At present, flaxseed in China is mainly used for extracting or pressing flaxseed oil, a large number of flaxseed cakes left contain higher protein, lignans, dietary fiber and other nutrients, which have great potential in developting new products. In addition, flaxseed cakes contain cyanogenic glycosides limiting the utilization of flaxseed cakes, which are harmful to human and animal health. Therefore, the technique of microwave pretreatment on producing detoxified flaxseed cakes and the effect of microwave pretreatment on quality of pressed flaxseed oil were studied, and parameters of roasting and mirowave treatment method on detoxification of flaxseed cakes were optimized. Finally the application of detoxified flaxseed cakes on steamed breads was also studied. Main results are as follows:(1) The technique parameters of microwave pretreatment on producing detoxified flaxseed cakes were optimized by orthogonal experiments, and the optimal parameters were: microwave density 4.375w/g, time 6 min, flaxseed moisture 17%. Under the condition, the content of cyanogenic glycosides in pressed Gansu flaxseed cakes decreased from(241.84 ± 1.92) mg/kg to(4.18 ± 0.23) mg/kg; The content of cyanogenic glycosides in pressed Harbin fiber flaxseed cakes was reduced to(15.40 ± 0.47) mg/kg, the content of cyanogenic glycosides in four other kinds of pressed flaxseed cakes was lower than 5 mg/kg,which suggested the optimal microwave technique could make flaxseed cakes satisfy cyanide limit stipulated by food hygiene standard.The quality of six kinds of pressed flaxseed oil before and after being treated by the optimum microwave detoxification condition was compared. Compared with directly pressed flaxseed oil, acid value of pressed Harbin flaxseed oil treated by microwave significantly increased by 0.69 mg KOH/g, acid value of pressed Ningya 17 flaxseed oil treated by microwave significantly increased by 0.14 mg KOH/g, acid value of other varieties of pressed flaxseed oil treated by microwave had no significant changes; Peroxide value of pressed Harbin flaxseed oil treated by microwave significantly increased by 0.51 mmol/kg, peroxide value of pressed Baya 9 flaxseed oil significantly decreased by 0.24 mmol/kg, peroxide value of other varieties pressed oil had no significant changes; Fatty acid composition of six kinds of pressed flaxseed oil had no significant differences; The total phenolic content of six kinds of pressed flaxseed oil significantly increased. Phytosterol content of pressed Harbin flaxseed oil significantly increased, but the increment was small(3.23mg/100g), phytosterol content of other varieties of pressed oil didn’t change significantly; The VE content of pressed Longya 10 flaxseed oil significantly decreased, but the decreasing value was merely 0.66mg/100 g, the VE content of other five kinds of pressed flaxseed oil did not change significantly. Therefore, under the optimal microwave conditions microwave density 4.375w/g, time 6min, flaxseed water 17%, the content of cyanogenic glycosides in flaxseed cakes could be effectively removed, and the quality of pressed oil treated by microwave was not severly impaired.(2) The optimal parameters of microwave detoxifying cyanogenic glycosides in flaxseed cakes optimized by the single factor experiment of microwave time, microwave density, flaxseed cake moisture were microwave density 8.89w/g, time 5min, moisture 30%, the content of cyanogenic glycosides in flaxseed cakes was reduced from(205.10±4.12) mg/kg to(18.85 ± 0.41) mg/kg; When loading unit was 0.315g/cm2, the optimal parameters of roasting detoxification optimized by the single factor experiment of time, temperature, flaxseed cake moisture were time 60 min, temperature 115℃, moisture 35%, the content of cyanogenic glycosides was reduced from(205.10±4.12) mg/kg to(26.23±0.96) mg/kg. Roasting and microwave directly detoxifying flaxseed cakes could significantly reduce the content of cyanogenic glycosides, but they could not make the content of cyanogenic glycoside satisfy the cyanide limit under 5mg/kg of food hygiene standard.After roasting and microwave detoxification, fatty acid composition of residual oil in flaxseed cakes did not significantly change, peroxide value increased significantly, VE content significantly decreased; The acid value of oil extracted from flaxseed cakes treated by microwave decreased significantly, while the acid value of oil extracted from flaxseed cakes treated by roasting and cold-pressed cakes almostly had no discrepancy; Phytosterol content of oil extracted from flaxseed cakes treated by microwave significantly increased, but phytosterol content of oil extracted from flaxseed cakes treated by roasting decreased significantly. Therefore, microwave and roasting detoxification process could affect the quality of residual oil in flaxseed cakes.(3) Farinographic studies showed that the suitable level of adding detoxified flaxseed cakes was 6%. With the increased level of detoxified flaxseed cakes, steamed bread’ s specific volume and expansion ratio decreased, with the color darkening; The hardness, plastic sticky, chewiness of steamed breads increased with the increased level of detoxified flaxseed cakes, while elasticity, cohesiveness and resilience decreased; Fat, protein, lignans, ash also increased and lignans in steamed bread containing 15% detoxified flaxseed cakes could be up to 3.34 mg.g-1; The amino acids expect proline showed an increasing trend; Total phenolic content and antioxidant capacity of steamed bread significantly increased with the addition of detoxified flaxseed cakes. There were significantly positive correlations between total phenolic content and different antioxidant assays including DPPH radical scavenging capacity, ABTS radical scavenging capacity, FRAP, inhibiting β- carotene bleaching capacity(r>0.9), and total phenolic content determined the antioxidant capacity of steamed bread;The sensory evaluation of steamed bread gradually decreased with the increased level of detoxified flaxseed cakes, but there were no significant differences between 3% and 6% level, and the two groups got higher sensory scores than other groups adding detoxified flaxseed cakes. Moreover, 3% and 6% level get scores more than 90. As the 6% level had more fat, protein, lignans and other nutrients, steamed bread was optimised at 6% level.