Effect of mechanical press oil extraction processing on quality of linseed oil

In the present study an attempt was made to explore the effect of application of single and additional presses during mechanical press oil extraction on quality of linseed oil. A single screw expeller having constant rotating shaft was used to extract single (SPLO), double (DPLO) and triple (TPLO) pressed linseed oil. Physicochemical properties such as refractive index, specific gravity, peroxide value, acid value etc. were used to determine quality of oil. The oil yield was progressively increased from 19.2 +/- 1.5% to 31.9 +/- 0.2% with application of presses in the order SPLO < DPLO < TPLO. DPLO had comparatively high a-linolenic acid (ALA) content than SPLO and TPLO. Saturated (except stearic acid), mono-saturated and polyunsaturated fatty acids were increased with increasing presses in the order SPLO < DPLO < TPLO. Most of the physical properties of SPLO, DPLO and TPLO were remain unaffected during mechanical press processing. Moreover, chemical properties such as peroxide value, iodine value, free fatty acid value and saponification number were found to be changed with application of additional presses. Total phenols and flavonoids content were non-linearly increased with application of additional presses. Results demonstrated that the quality of linseed oil gets changed with application of additional presses. However, application of more than two presses was found to be not an economically viable process. DPLO was of good quality oil, rich in natural phenolic antioxidants and could have added health promoting applications. (C) 2012 Elsevier B.V. All rights reserved.