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.