ISSN: 0041-3216 (Online), 0041-3216 (Print)
Volume 90 Number 3
Determination of development of acids in blanched and raw sesame seeds in extracting of edible grade sesame oil. (149)
Controlling the development of acid value below 6.0 in sesame seeds (Sesamum indicum) in Sri Lanka is an important prerequisite in order to extracting edible grade sesame oil, because free fatty acid level of extracted oil must be maintained below 3.0. However, maintaining of acid value of sesame seeds below 6 is an extremely difficult task because, incremental increase of acid value steadily takes place during storage, due to the influence of storage temperature, seed moisture and enzymes present in the seed itself. Therefore, a study was conducted using 30kg of seed with known initial acid value known (3.3) as described in the methodology. Results revealed that acid values of raw sesame seeds increased steadily from 3.3 to 4.05, while blanched sesame seeds showed a declining acid value from 3.20 to 3.13 during the 60 days testing period. In the case of decorticated raw and blanched sesame seeds, acid values continuously declined from 2.1 to 1.2 and from 1.7 to 1.1 respectively throughout the storage period. However, as the decortication process involved with water, it is an unproductive method because of the extra energy and time needed for drying. Therefore, storing of blanched undecorticated sesame seeds is recommended as a productive treatment for extracting edible grade sesame oil. The data obtained from the study on “acid value against period of storage for un decorticated sesame seeds were subjected to regression analysis in order to develop quantified relationships, between Y = Acid value, x = Age of the seeds - Month). These were Y = 3.3086+ 0.0081X and Y = 3.205 – 0.0014X for raw and blanched sesame seeds respectively.
Keywords: Acid value, Sesamum indicum, free fatty acid, Regression analysis and blanching process