The Effect of Low-dose X-ray Irradiation on the Quality of Fresh-cut Asparagus in Microwaveable Vacuum Skin Packs

Abstract

Low-dose x-ray irradiation was used on vacuum skin-packaged fresh-cut asparagus to extend its shelf life and improve its microbial safety. Freshly imported Peruvian asparagus (Asparagus officinalis L.) spears were obtained from a local source, cleaned, trimmed, and sanitized and then vacuum skin-packaged (VSP) in a tray pack system. A breathable lid film was vacuum-sealed to protect the product from contamination and allow for gas exchange. Asparagus were packaged in VSP, which modified the package atmosphere, and exposed to a target dose of 1.0 kGy or left untreated. Asparagus were also placed in low-density polyethylene (LDPE) bags as a control. All samples were then stored at 4 °C for 24 days. To determine the effectiveness of the irradiation treatment, sample packages were periodically removed from storage and several measurements were used to evaluate the product, including headspace gas content, microbial growth, water soluble sugar content, and enzyme activity. A dose of 1.0 kGy reduced initial microbial population up to 3.8 log colony-forming units (cfu)/g and maintained 20% more of the initial sugar content relative to the non-irradiated VSP asparagus. Phenylalanine ammonia-lyase (PAL) activity in VSP asparagus was lower than in the control package (LDPE bag) regardless of irradiation treatment (P < 0.05). However, x-ray treatment increased the PAL activity of asparagus in VSP up to Day 8 (P < 0.05).