Minimal processing of produce using a combination of UV-C irradiation and ultrasound-assisted washing

Microbial contamination is the most significant risk associated with consuming minimally processed fresh food products. The processing time of ultrasound (US)-assisted washing generally exceeds 5 min. To reduce the processing time, yet maintain or improve the efficacy of US-free chlorine (FC, 10 ppm) or -peracetic acid (PAA, 80 ppm) (US-FC/PAA), we simultaneously applied ultraviolet C (UV-C) irradiation. Compared with US-FC/PAA (5 min), US-FC/PAA-UV (3 min; 1.71 kJ/m(2)) treatment of cherry tomato further reduced food-borne pathogens (E. coli O157:H7, non-O157 E. coli, and Salmonella Typhimurium) by 0.45-0.73 log CFU/g and naturally present microbes (aerobic mesophiles, psychrophiles, molds, and yeasts) by 0.28-0.50 log CFU/g. For fresh-cut lettuce, the efficacy achieved using US-FC/PAA-UV did not exceed that using US-FC/PAA, indicating that US-FC/PAA-UV is more effective in reducing contamination on produce with a smoother surface, e.g., cherry tomato. Sensory qualities (color, odor, crispness, and firmness), antioxidant activity, and phenolic, ascorbic acid, lycopene, and chlorophyll content were not affected by any of the treatments. These results suggest that the simultaneous application of US-FC/PAA and UV-C is an effective alternative to US-FC/PAA washing that reduces processing time and thus improves productivity.

Automated summary

Microbial contamination is a significant risk in consuming minimally processed fresh food products. By simultaneously applying ultraviolet C (UV-C) irradiation with ultrasound (US)-assisted washing, the processing time can be reduced while maintaining or improving efficacy in reducing foodborne pathogens and naturally present microbes on produce. The combined treatment was more effective in reducing contamination on produce with a smoother surface, such as cherry tomatoes, compared to US-FC/PAA alone. The treatment did not affect sensory qualities or antioxidant activity and nutrient content.