A digital image-based colorimetric method for measuring free acidity in edible vegetable oils

Area of Science:

• Analytical Chemistry
• Food Science
• Green Chemistry

Background:

• Traditional free acidity (FA) quantification in vegetable oils relies on titration, a method with significant drawbacks.
• This method necessitates toxic chemicals and subjective endpoint detection by analysts, impacting accuracy and safety.

Purpose of the Study:

• To develop and validate a novel digital image colorimetry (DIC) method for measuring FA in vegetable oils.
• To establish a more objective, economical, and environmentally friendly alternative to conventional titration methods.

Main Methods:

• A colorimetric reaction was induced using cupric acetate solution.
• Smartphone-captured images of colored solutions were analyzed using RGB color values (R values).
• Free acidity was quantified via standard addition calibration and compared against titrimetric measurements.

Main Results:

• The DIC method demonstrated excellent correlation with the standard titrimetric method (R² = 0.98).
• A low mean absolute error of 0.06% was achieved, indicating high accuracy.
• Chemical reagent consumption was reduced by approximately 90%.

Conclusions:

• Digital image colorimetry (DIC) presents a viable, less subjective, and more economical approach for FA determination in vegetable oils.
• This method significantly reduces hazardous chemical usage, aligning with green chemistry principles.
• The smartphone-based DIC technique offers a practical and accessible tool for quality control in the vegetable oil industry.