Effect of alternative sanitizers on functional parameters of watercress leaves (Nasturtium officinale) stored under modified atmosphere

Abstract

Currently in the industry of fresh salads, watercress is shown as an alternative supply of gourmet products, being recognized for its high content of health promoting compounds such as antioxidants and phenolic compounds. The aim of this study was to evaluate different sanitizing agents such as chlorine dioxide (CD, 10 mg L-1), acidified sodium chlorite (ASC, 500 mg L-1) and peroxyacetic acid (PAA 90 mg L-1) as an alternative to sodium hypochlorite (SH, 100 mg L-1). The treated samples were stored under modified atmosphere packaging (MAP) for 13 days at 5°C and 95% RH. Watercress treated with SH in a perforated bag (air atmosphere conditions) was used as a control. The evolution of the psychrophilic bacteria counts, during 13 days of refrigerated storage, was determined in Plate Count Agar, and incubated at 5°C for 7 days. Determinations were performed in triplicate. Sensory analyses were carried out to determine the effect of all treatments on the watercress quality. All treatments in MAP showed a gradual decrease in O2 levels by 37% and an increase in CO2 levels by 316% on day 13, relative values on day 0. During the storage period, MAP maintained the antioxidant levels of around 2 mg g-1 of Trolox activity, while watercress stored in perforated bags showed a decrease to 1 mg g-1 Trolox activity on day 13. The total phenolic contents showed a similar trend as the antioxidant levels, where MAP and perforated bags reached 3 and 3.9 mg g-1 gallic acid equivalents (GAE). Initial counts of psychrophiles in raw material reached 6.4 log CFU g-1. However, after one day of storage all treatments reduced to counts between 1 and 2 log units. The modified atmosphere combined with all sanitizers turned out to be a useful tool to maintain bioactive compounds levels as well as extend the shelf-life of watercress stored at 5°C.