Safety of Ready‐to‐Eat Watercress Using Environmentally Friendly Sanitization Methods

Chlorine-based washing systems have been widely used by the fresh-cut industry. However, there is much interest in developing safer and more environmentally friendly sanitization methods. Watercress was immersed in sodium hypochlorite (100 mg/L), hydrogen peroxide (167 mg/L) or citric acid (10 g/L) or exposed to ultraviolet C (UV-C) light (6 or 18 kJ/m2 by exposure for 3 or 7 min, respectively), and stored in modified atmosphere packaging at 5C and 95% relative humidity. The respiration rate, packaging gas composition, color, microbiological growth (psychrotrophic and mesophilic microorganisms, Enterobacteriaceae, mold and yeasts), antioxidant capability, polyphenol content and sensory quality were measured. The different treatments did not affect the respiration rate (average 22 mg CO2/kg·h) after 14 days. Psychrotrophic bacteria reached approximately 7 log10 cfu/g, regardless of the treatment, after 14 days. UV-C decreased mesophilic counts, while H2O2 reduced Enterobacteriaceae. UV-C exposure increased the antioxidant capability, which was maintained throughout the storage. None of the treatments affected the color parameters and sensory quality. All of the treatments analyzed, especially UV-C, may be useful for maintaining watercress quality. Practical Applications Increasing popularity of nontraditional vegetables has created a new opportunity for innovation in the development of horticultural minimally processed fresh products. This industry is interested in developing safer and more environmentally friendly sanitization methods to replace chlorine-based washing systems. This study focused on the assessment of immersion in three chemical-sanitizer solutions (sodium hypochlorite, hydrogen peroxide and citric acid) or the exposure to ultraviolet C (UV-C) light in combination with modified atmosphere packaging and refrigerated storage (5C and 95% relative humidity). The evaluated disinfection methods resulted as or more effective at reducing microbial growth than chlorine washing. The UV-C treatments improved the functional quality of watercress by increasing the total antioxidant capability and total polyphenol content. The implementation of low cost sanitization methods such as the tested alternative sanitizers or UV-C light may be useful for maintaining the overall quality and extending the shelf life of ready-to-eat watercress and other vegetables.