The determination of cochineal (E-120) in strawberry jam was carried out in the presence of carmoisine (E-122) using the four-way PARAFAC decomposition and excitation-emission fluorescence matrices. In the measured conditions, there was no fluorescence signal for carmoisine due to a strong quenching effect and this colorant also led to a decrease of the fluorescence signal of cochineal. The European Union has fixed a maximum residue level, MRL, for cochineal in jam (100 mg kg−1). Therefore, the addition of other food colorant (carmoisine) in the jam could lead to false compliant decisions. The four-way PARAFAC decomposition avoided false compliant decisions caused by the quenching effect.
Cochineal was unequivocally identified. Detection capability (CCβ) was 0.72 mg L−1 for probabilities of false positive and false negative fixed at 0.05. Cochineal was detected in the jam (104.63 mg kg−1) above the MRL. This amount was compared with the one obtained using a HPLC/DAD method.