Ultraviolet-C light and peracetic acid extend the shelf life of fresh and frozen strawberries

The postharvest life of strawberries is short, and disinfection processes for fresh-cut and frozen strawberries are needed to address the risk posed by foodborne pathogens in this kind of product. For this, a process involving immersion in a 40 mg L−1 peracetic acid (PA) solution accompanied by the use of an emerging technology, ultraviolet-C for 2 min, was studied for its impact on strawberry quality and microbial load as a novel alternative method to chlorine sanitation. The shelf life of the washed strawberries was evaluated in fresh (whole or fresh-cut) product for 11 days at 4 °C and in product that had been frozen for 12 months at –20 °C (air or modified atmosphere, 20% CO2, 5% O2, and 75% N2). After washing, total aerobic mesophylls, yeast, and mold decreased by 0.5–1.0 log units and these counts remained low during storage. The fresh and fresh-cut fruits’ firmness (2.3 ± 0.5 N at day 11) and lightness (expressed by L*, averaging 31.0 ± 0.1) were maintained. Although antioxidant activity, expressed by the amount of radical 2,2-diphenyl-1-picrylhydrazyl (DPPH), decreased during storage in fresh-cut samples, total ferric reducing antioxidant power (FRAP), total phenolic content, and total anthocyanin content were maintained in all the formats during storage (averaging 1.33 ± 0.04 g kg−1 ascorbic acid equivalents, 0.212 ± 0.01 g kg−1 gallic acid equivalents, and 0.03 ± 0.01 g kg−1 pelargonidine-3-glucoside). An increase in red color (from 32.1 to 39.3 a* values) and a loss of firmness of up to 46.8% was observed after the first month of frozen storage with no changes in the nutritional quality. Considering the sanitizing effect of water UV-C with peracetic acid (WUVPA) and the results obtained in the present study, the addition of this process in the production chain of strawberries could be an effective method to maintain the shelf life of the fruits, especially for fresh-cut strawberries.

This research was funded by \u2018Ministerio de Educaci\u00F3n, Econom\u00EDa y Cultura\u2019 for the financial support of the project AGL2016-78086-R. This work was also supported by the CERCA Programme of Generalitat de Catalunya. I. Nicolau-Lape\u00F1a is in receipt of a predoctoral grant awarded by the \u2018Ministerio Espa\u00F1ol de Econom\u00EDa, Industria y Competitivdad\u2019 (grant number BES-2017-079779). J. Ortiz-Sol\u00E0 is in receipt of a predoctoral grant awarded by Universitat de Lleida (grant number (BOU186-243/2017 UdL). Dr. I. Aguil\u00F3-Aguayo thanks the National Programme for the Promotion of Talent and Its Employability of the \u2018Ministerio de Econom\u00EDa, Industria y Competitividad\u2019 of the Spanish Government and the European Social Fund for her Postdoctoral Senior Grant \u2018Ramon y Cajal\u2019 (RYC-2016-2019 949). The authors also would like to thank S. Villar\u00F3, J. Costa, and M. Anguera for their technical support. The authors would like to thank Carburos Metalicos S.A. for kindly providing the freezing tank.