Screw pressing performance of whole and dehulled flaxseed and some physico-chemical characteristics of flaxseed oil

Abstract

Screw pressing performance of whole and dehulled flaxseed at different seed moisture (6.4 to 11.1 % d.b.) and press head temperature (80-120°C) was investigated. Oil recovery, residual oil, press rate and sediment content and some important physico-chemical characteristics were determined at six different levels (50, 60, 70, 80, 90 and 100 %) of dehulled flaxseed. Oil recovery decreased with increasing moisture content as well as press head temperature. Press rate was found maximum for 100 % dehulled flaxseed while minimum for 50 % dehulled flaxseed at 6.4 % moisture content. Colour of oil samples was found affected both with the level of dehulled flaxseed and press head temperature. Free fatty acids content of oil ranged from 1.07 % to 2.70 % and lower at 80°C press head temperature. Oil and cake temperatures ranged from 53.10°C to 65.95°C and 69.15 to 103.75°C, respectively. The α-linolenic acid content of different oil samples obtained at 80°C was in the range of 53.34±0.95 to 54.21±1.04 %. In view of maximum oil recovery (82.9 % d.b.), lower FFA content, and oil and cake temperature, 7:3 ratio of dehulled and whole flaxseed having 6.4 % d.b. moisture content and 80°C press head temperature may be considered for screw pressing of flaxseed.

Oil expelling of dehulled sunflower: Optimization of screw pressing parameters

“…of pre‐treated whole flaxseed. Increased press rate at higher moisture content was also reported by Mridula et al () for dehulled and whole flaxseed sample. Similarly, Singh et al () reported decrease in press rate from 5.8 to 5.2 kg/h and 6.1 to 5.2 kg/h for cooked and uncooked crambe seeds with decrease in moisture content from 9.2 to 3.6% d.b.…”

“…Though variable amount of sediments was observed in crude oil samples expelled following different press head temperatures but the variation was statistically insignificant (Table ). Contrary to this, Mridula et al () reported significant impact of press head temperature with minimum sediment content at 120°C with three studied temperature as 80–120°C. This variation in the findings in different studies may be due to the variation in the level of studied parameters and the crop properties.…”

“…Studies also indicated decrease in residual oil content in cake with decreasing moisture content for pressing of sunflower seed in 6–14% moisture range (Singh, Farsai, Stewart, & Douglass, ); for cooked and uncooked crambe seed in 3.6–9.2% moisture range (Singh et al, ). Mridula et al () also observed a proportional increase in residual oil in flaxseed cake with increasing moisture content. This might be attributed to higher frictional resistance at lower moisture content of seed in the screw barrel during the pressing of dehulled sunflower.…”

“…Similarly Singh et al () also not observed significant impact of oilseed moisture in case of pretreated whole flaxseed on sediment content in crude oil. Contrary to this, Mridula et al () indicated the low sediment content at higher moisture content during expelling of a mixture of whole and dehulled flaxseed. Sediment content in crude oil of dehulled sunflower sample with wheat bran, expelled at different level of press head temperature was ranged from 8.36% to 9.99%, 8.06% to 9.98%, 9.52% to 10.19% and 6.03% to 18.07% at 50, 70, and 90°C, respectively.…”

Supercritical CO2 extraction in chia oils production: impact of process duration and co-solvent addition

“…Solvent extraction is the most efficient method and allows the recovery of over 98% of available oil. The disadvantages of this process are high costs and the necessity of using highly inflammable chemicals and possible solvent residues in the obtained oil [5]. Screw pressing is less expensive than solvent extraction because it requires only a mechanical power input instead of heat or organic solvents [6].…”