Phthalimide Residue in Coffee: Does It Solely Derive from Folpet?

Area of Science:

• Food Chemistry
• Agricultural Science
• Analytical Chemistry

Background:

• Folpet is a fungicide whose residue limit in coffee is based on its sum with phthalimide (PAI).
• PAI can also be formed from phthalate derivatives and ammonia (NH3).
• The origin of PAI in roasted coffee is crucial for accurate food safety assessments.

Purpose of the Study:

• To investigate alternative pathways for phthalimide (PAI) formation in roasted coffee.
• To determine if PAI detection in coffee is exclusively indicative of Folpet fungicide use.
• To explore the role of phthalic anhydride (PAA) and amino acids (AAs) in PAI generation.

Main Methods:

• Thermal treatment of amino acids (AAs) with phthalic anhydride (PAA) at varying temperatures and times.
• Analysis of PAI generation under laboratory and industrial coffee roasting conditions.
• Experiments using diethyl phthalate (DEP) as a phthalate source.

Main Results:

• Phthalimide (PAI) generation from phthalic anhydride (PAA) and amino acids (AAs) is temperature-dependent.
• Optimal PAI formation from diethyl phthalate (DEP) and AAs occurred at 200 °C for 60 minutes.
• PAI was detected in Folpet-free green coffee beans subjected to roasting, confirming non-fungicide origins.

Conclusions:

• Phthalimide (PAI) detection in roasted coffee is not solely indicative of Folpet fungicide contamination.
• Phthalic anhydride (PAA), potentially derived from phthalates, can react with amino acids (AAs) during roasting to form PAI.
• These findings necessitate a re-evaluation of coffee safety regulations concerning Folpet and PAI limits.