New horizons in microbiological food safety: Photodynamic Decontamination based on a curcumin derivative

Abstract

Outbreaks of foodborne diseases are regularly reported worldwide. In particular, uncooked plant food is considered risky in terms of microbiological safety. Food is also the most important transmission route for resistant microorganisms from animals to humans. Photodynamic Decontamination (PDc) of foodstuff was recently introduced as a novel approach for increasing microbiological food safety. We investigated the efficiency of PDc on plant food with different geometries (flat, spherical and complex) using a two-dimensional LED array as a light source (435 nm, 33.8 J cm⁻²) and the cationic curcumin derivative SACUR-3 as a photosensitiser. A photoantibacterial effect (>3 log₁₀ CFU reduction) was achieved on all flat substrates (slices of cucumber, tomato and lettuce) with 10 μM, 50 μM or 100 μM SACUR-3. The maximal photokilling with a relative inactivation of 5.6 log₁₀ was measured on lettuce using 50 μM of the photoactive compound. Phototreatment of non-germinated fenugreek seeds and mung beans was successful if the spherical objects were rotated while under illumination (antibacterial effect at 100 μM SACUR-3). The decontamination of mung bean germlings with a more complex geometry using the PDc approach was ineffective with the two-dimensional light source. In conclusion, PDc based on the cationic curcumin derivative SACUR-3 is very effective at improving the microbiological safety of plant food with a flat or spherical geometry. More complex objects will require the development of novel illumination devices.