Understanding the Postharvest Phytochemical Composition Fates of Packaged Watercress (Nasturtium officinale R. Br.) Grown in a Floating System and Treated with Bacillus subtilis as PGPR.

Giuseppe Pignata,Silvana Nicola,Andrea Ertani,Catalina Egea-Gilabert,Juan A Fernández,Diana Niñirola,Manuela Casale

doi:10.3390/plants11050589

Abstract

The physiological changes and phytochemical pathways of processed watercress (Nasturtium officinale R. Br.) undergone during storage are not well known. The objective of this work was to evaluate the respiration rate and the inherent and external quality of watercress inoculated with B. subtilis and packaged as a fresh-cut product and stored at 4 °C for 11 days. Watercress was grown using continuous flotation (FL) in a greenhouse using substrate disinfection and inoculated or not with Bacillus subtilis as a plant-growth-promoting rhizobacteria (PGPR). The fresh-cut watercress respiration rate and phytochemical profile changed during the shelf life. The inherent phytochemical compounds were retained during the storage of the fresh-cut salad bags. The best results were found in watercress grown in a disinfected substrate but were less satisfactory when seeds and substrates were inoculated with PGPR. In general, the external quality and the pigment contents progressively decreased during the shelf life and the browning enzyme activities responsible for phenolic oxidation increased at different intensities throughout storage. At the end of the shelf-life period, the fresh weight loss of the fresh-cut product was less than 1% of the original weight. The results demonstrated that watercress grown in FL is a standardised baby leaf vegetable that is suitable for processing in the fresh-cut industry and for storing for more than 10 days. Unclear results were obtained for Bacillus subtilis in the postharvest period due to the inconsistent responses of the different analysed parameters.

Highlights

IntroductionWatercress is rich in carotenoids, antioxidants, phenols, vitamin C, phosphorus and calcium [4], and it has been used as a medicinal and food crop for over 2000 years [5]
The results showed that the O2 content in the headspace of all the fresh-cut salad bags was consumed, CO2 was produced [23,51,52,53], and the respiration rate was intense in the first five days of the shelf life (Table 1)
During shelf life in this study, the watercress respiration rate followed the expected O2 consumption and CO2 production trends in the fresh-cut salad bag headspace, with the former only being below 2% at d11

Summary

Introduction

Watercress is rich in carotenoids, antioxidants, phenols, vitamin C, phosphorus and calcium [4], and it has been used as a medicinal and food crop for over 2000 years [5]. Chlorophyll a and b contribute to the green intensity and the external appearance of plant leaves, but they can degrade during the postharvest shelf life of fresh-cut products [7,8]. The yellowing that results from chlorophyll degradation is considered a common disorder for most leafy green vegetables during storage [9]. Another postharvest decay index is leaf tissue browning due to physiological dynamics, which involves phenolic oxidation and browning enzyme activity [10,11]. The antioxidant capacity and vitamin C content of BLVs could reduce the incidence of browning phenomena [12]

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Conclusion