Refined edible oil is sold against colour specifications, most commonly expressed in Lovibond red and yellow units. Hitting these targets reliably is a core job of the bleaching step. This guide explains the Lovibond scale and how activated bleaching earth helps refiners meet colour specs.
What the Lovibond Scale Measures
The Lovibond tintometer compares oil colour against calibrated red and yellow glass standards in a fixed-path cell. Refined oil specs are typically written as maximum red (e.g. 'R ≤ 2.0') with an associated yellow value. Lower numbers mean lighter, more refined-looking oil.
How Bleaching Drives Colour Down
Bleaching earth adsorbs the chlorophyll, carotenoid and oxidation-derived colour bodies that contribute to Lovibond red and yellow readings. Higher surface area and correct acidity mean more colour removed per kilogram of earth, allowing tighter colour targets at controlled dosage.
Dosage vs Colour: Finding the Balance
Increasing dosage lowers colour, but with diminishing returns and rising oil losses. The goal is the minimum dosage that reliably meets spec with a safety margin. A high-bleachability earth shifts this optimum to a lower dosage, saving cost.
The Role of the Deodoriser
Final colour is also affected by heat bleaching in the deodoriser, especially for carotenoid-rich oils. Earth bleaching and thermal bleaching work together; weak earth performance forces the deodoriser to compensate, sometimes at the cost of oil quality.
Consistency Is the Key to Hitting Spec
Colour control is easiest when the bleaching earth performs identically batch after batch. Bleach Master's quality-controlled production gives refiners the repeatability needed to hold tight Lovibond targets.
Frequently Asked Questions
What are Lovibond red and yellow units?
They are colour measurements made by comparing oil against calibrated red and yellow glass standards in a tintometer. Refined oil specs are usually written as a maximum red value with an associated yellow value.
How does bleaching earth lower Lovibond colour?
By adsorbing the chlorophyll, carotenoid and oxidation-derived colour bodies that produce red and yellow readings. Higher surface area and correct acidity remove more colour per kilogram of earth.
Should I just increase dosage to hit colour targets?
Higher dosage lowers colour but increases oil losses with diminishing returns. The best approach is the minimum dosage that reliably meets spec; a high-bleachability earth lowers that minimum.
Does the deodoriser also affect colour?
Yes. Heat bleaching in the deodoriser reduces colour further, especially for carotenoid-rich oils. Earth bleaching and thermal bleaching work together to hit the final spec.
Need Activated Bleaching Earth for Your Refinery?
Contact Umiya Minerals for product samples, technical data sheets, and bulk pricing. We supply pan-India from Bhuj, Gujarat.