An application of optical activity and Faraday Effect to
promote food security: A case study of vegetable oils

Eric R. R. Mucunguzi-Rugwebe; J. P. Wefafa; N. W. Nzala

doi:10.14303/ajfst.2012.042

African Journal of Food Science and Technology

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An application of optical activity and Faraday Effect to promote food security: A case study of vegetable oils

Abstract

*Eric R. R. Mucunguzi-Rugwebe, J. P. Wefafa and N. W. Nzala

The purpose of the study was to examine the relationship between the angle of rotation of the Vibration Plane and Calorific Value of Transparent Oils. Fourteen different types of vegetable oils were studied and three transparent mineral and one animal oil samples were investigated for the sake of comparison. For vegetable oils contaminated with impurities or expired, the cut-off angle �?¯�?�?¦ was found to satisfy the relationship A VHL v Vegi imp �?¯�?�?¦ �?¯�?�?��?½ �?¯�?�?��?« (1) where Av is the impurity concentration in the sample, V is the Verdet constant, H is the magnetization and L is the length traversed by the light in the sample. For vegetable oils without impurities and unexpired therefore suitable for human consumption, the cut-off angle obeyed the equation. �?¯�?�?¦ �?¯�?�?��?½ VHL (2) For transparent mineral oils the cut-off angle gave the relationship A VHL eral �?¯�?�?��?½ �?¯�?�?��?« min min �?¯�?�?¦ (3) where min A is the constant that causes intrinsic circular birefringences responsible for optical activity in mineral oils. The calorific values of both mineral and vegetable oils were determined by using the equation K �?¯�?�?�?��?¯�?�?��?¨W W �?¯�?�?��?© �?¯�?�?»t n VI �?¯�?�?��?¨VI V �?¯�?�?��?© �?¯�?�?½�?¯�?�?/W 1 2 / 2 �?¯�?�?��?½ �?¯�?�?��?« �?¯�?�?��?« �?¯�?�?��?« �?¯�?�?��? (4) where W1 is the weight of water in grams, W2 is water value of the apparatus in grams and W is weight of oil sample, it is temperature rise during test, VI is the rate of temperature fall in degrees per minute at the end of the test and V is the rate of temperature rise in degrees per minute at the beginning of the test, n is the number of minutes between the ignition and attainment of the maximum temperature. The graph of angle of rotation �?¯�?�?¢ per unit current against calorific value of oils was plotted. A straight line graph of the relationship y �?¯�?�?��?½ 8.781x �?¯�?�?��? 25.25 was obtained. This technique is a potential method for designing a an instrument that can be used to determine calorific values of transparent oils by using Faraday Effect.

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