Gluconic acid is a mild organic acid, neither caustic nor corrosive and with an excellent sequestering power. Non-toxic and readily biodegradable (98 % after 2 days), it occurs naturally in plants, fruits and other foodstuffs such as wine (up to 0.25 %) and honey (up to 1 %). Gluconic acid is prepared by fermentation of glucose, whereby the physiological d-form is produced.
Gluconic acid has versatile properties through being a polyhydroxycarboxylic acid, with both hydroxyl and carboxyl groups which can react.
Concentrated solutions of gluconic acid contain some lactone (GdL), the neutral cyclic ester, which is less soluble in the cold and possesses no actual acid properties. About 5 % of GdL are present in the 50 % gluconic acid solution at room temperature.
The outstanding property of gluconic acid is its excellent chelating power, especially in alkaline and concentrated alkaline solutions. In this respect, it surpasses all other chelating agents, such as EDTA, NTA and related compounds. Calcium, iron, copper, aluminium and other heavy metals are firmly chelated in alkaline solution and masked in such a way that their interferences are eliminated.
Gluconic acid is stable at the boiling point even of concentrated alkaline solutions. However, it is easily and totally degraded in waste water treatment plants (98 % after 2 days).