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

Abstract

Summary 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.

The Effect of Roasting on the Protein Profile and Antiradical Capacity of Flaxseed Meal

“…The SDS-PAGE R profiles ( Figure 1 b) showed six main protein bands with MW of ≈32–11 kDa, which were described as 1b–6b ( Table 2 ). These results were similar to the findings of our previous studies [ 29 , 30 ]. The protein profile of the untreated flaxseeds also corresponds with the results of SDS-PAGE profiles described previously for flaxseed meal [ 17 ] and flaxseed cake [ 43 ].…”

“…The thermal treatment of the flaxseeds was conducted according to the procedure described in detail by Waszkowiak et al [ 28 ]. The parameters were selected on the basis of the previous results [ 25 , 29 , 30 , 33 ] in order to maintain the acceptable sensory quality of roasted flax seeds. The seeds were roasted in a thin layer (3 mm) to achieve homogenous thermal stress.…”

“…Moreover, heating before cold-pressing of oilseeds generally increases oils yield [ 26 ]. On the other hand, roasting damages the cell structure [ 27 ] and increases the sensitivity of valuable flaxseed compounds to changes induced by thermal treatment [ 28 , 29 , 30 , 31 ]. An earlier study by Waszkowiak, Siger et al [ 28 ] showed that the roasting of flaxseeds at a temperature of 160–220 °C considerably influenced the nutritional quality of flaxseed oil (e.g., the content of total tocopherol decreased, but the content of plastochromanol-8 increased) and deteriorated its oxidative stability.…”

“…An earlier study by Waszkowiak, Siger et al [ 28 ] showed that the roasting of flaxseeds at a temperature of 160–220 °C considerably influenced the nutritional quality of flaxseed oil (e.g., the content of total tocopherol decreased, but the content of plastochromanol-8 increased) and deteriorated its oxidative stability. Other studies [ 29 , 30 ] revealed changes in the percentage share of individual protein fractions in the protein profiles of roasted (in the ranges of 160–200 °C and 8–24 min) and steamed (100 °C, 16 min) flaxseeds. However, the differences between the cultivars were not assessed in these studies.…”

Cold‐pressed flaxseed oil by‐product as a new source of fat replacers in low‐fat salad dressing formulation: Steady, dynamic and 3‐ITT rheological properties

“…Therefore, the cold‐pressed by‐products could also be utilized as fat mimetics (Akcicek & Karasu, 2018). Flaxseed has a potential functional food due to having a high amount of dietary fiber (two‐third is insoluble, and one third is soluble fiber) and high‐quality protein and a good source of unsaturated fatty acid (Li et al., 2019; Waszkowiak, Mikołajczak, Gliszczyńska‐Świgło, & Niedźwiedzińska, 2019). The high amount of polysaccharide and proteins in flaxseed provide some important properties such as the good emulsifying property, the stabilization of emulsions, water‐holding capacity, surface or interfacial properties, the suspension of particles, control of crystallization, encapsulation, the formation of a film, and thickening and gelling agent for o/w emulsions (Drozłowska, Łopusiewicz, Mężyńska, & Bartkowiak, 2020; Feng, Yang, Sun, Xu, & Zhou, 2018).…”