Vol.35, No.9 (1986) 725 ORIGINAL Determination of Content of Linseed Oil in Edible Soybean Oil Poorna P. MANANDHAR*, Akihiko NAGAO** and Megumi YAMAZAKI** *Central Food Research Laboratory , Ministry of Agriculture, Nepal (Babar Mahal, Kathmandu, NEPAL) **National Food Research Institute , Ministry of Agriculture, Forestry, and Fisheries, (Yatabe, Tsukuba, Ibaraki) A method for detecting and computing the quantity of adulterant linseed oil in soybean oil was developed by determining the fatty acid, sterol and tocopherol compositions of component oils and adulterated mixtures. In adulterated oil samples, a decrease in linoleic acid and increase in linolenic acid content were observed with increase in the amount of linseed oil. Analysis of sterol constituents of linseed oil showed a characteristic component having a retention time of 78 minutes which was also clearly observed for the oil mixtures. A remarkable decrease in stigmasterol content was observed with increase in linseed oil. Analysis of tocopherols showed the linseed oil to be richer than soybean oil in ƒÀ-toco- pherol content and there to be a significant increase in ƒÀ-tocopherol content with increase in linseed oil. These findings provide sufficient evidence of the presence of adulterant linseed oil in soybean oil. The limit of detection was as low as 5•`10% linseed oil in soybean oil. 1 Introduction In Nepal, soybean oil is becoming increa- singly popular and acceptable as the cooking oil. Linseed oil1),23) on the other hand, is not accepted as cooking oil, and is less expensive than soybean oil. Hence, as the demand and high price can lead to the adulteration, there is a high chances of soybean oil to be adul- terated with less expensive linseed oil. There are a number of specific tests for de- tecting defferent individual vegetable oils in the oil mixtures2),3). Apart from the usual and conventional determination of analytical con- stants of vegetable oils, the analysis of fatty acid compositions, sterols, glycerides, and to- copherols had been carried out in different ways and by different means using paper, thin layer, column, gas, and liquid chromatographic techniques of analysis; a lot of efforts had been and is being exerted in the development of methodology concerning detection of one vegetable oil in another oil or oil mixture4)•`20), But, for the detection of many kinds of spe- cific adulterant oil, the details are still lacking. The Codex Alimentarius Committee on Fats and Oils of the Food and Agriculture Orga- nisation/World Health Organisation21) also had taken great deal of interest in this field and has compiled a list of fatty acid ranges for several commercial oils and fats. These ranges are to be used for the authentication of the different oils and fats. But, the ranges con- tained in this list are very wide and hence several oils could be classified under more than one type of oil20). In addition, in adulterated oil with low pro- portions of one or more kinds of oils, the mere determination of the overall fatty acid com- positions is not sufficient to reveal the admix- ture or to identify the adulteration. Hence, a deeper and wider analysis of other important constituents of oils are essentially important for the proper identification and estimation of the nature and extent of adulteration. In our previous paper1), a characteristic sterol component, and linolenic as well as stearic acid contents of linseed oil were discussed as the criteria for detection and estimation of 5 •`10% linseed oil when mixed with rapeseed 37