Optimization of Kreis test for edible oils

Quality evaluation of edible oils is tested by different methods. Among the chemical methods, Kreis test is a promising one for early detection of ran cidity, particularly aldehydes with a characteristic odor impact. Positive relationship of these breakdown products with perceived deterioration in qu ality evoked interest in re-examining the Kreis test. The color development in the test is critical and requires optimization. In continuation of stud ies in edible oils, the present investigation deals with sunflower and must ard oils. Through central composite rotatable design, response surface was fit as a function of oil quantity (0.3-3.3 mL) 1% phloroglucinol (0.08 mol) in acetic acid (0.3-3.3 mL) and incubation period (10-90 min). The polynom ial fits were excellent with multiple correlation of >0.90. Optimized condi tions were obtained for the two oils. Thus, use of 1 mt oil, 1 mL of 1% phl oroglucinol, incubation time of 20 min and absorbance readings at 545 nm is derived and found applicable to all edible oils for routine tests.