Effects of gamma irradiation on the shelf-life and bioactive compounds of Tuber aestivum truffles packaged in passive modified atmosphere

Abstract

The effects of gamma irradiation (0.5, 1.0, 1.5 and 2.5 kGy doses) on Tuber aestivum packaged under modified atmosphere was evaluated. The respiration rate, microbial populations, sensory characteristics and content of bioactive compounds (total carbohydrates, chitins, β-glucans, proteins, total phenols and sterols) were monitored from immediately after treatment up to day 42 of storage at 4 °C. All the irradiation treatments tested reduced the microbial groups studied by more than 3 log cfu/g. Increasing irradiation doses slowed down the subsequent microbial development throughout the conservation period for all the groups studied. The irradiation treatments did not negatively affect truffle sensory characteristics. Only a slight visible superficial yeast growth was detected at the end of the shelf-life in all doses applied. Total carbohydrate content, chitins, β-glucans and proteins levels were not affected after irradiation. However, sterols, particularly stigmasterol, slightly decreased after irradiation, while levels of phenolic compounds doubled during storage. Gamma irradiation (2.5 kGy) could be used to extend the shelf-life of summer truffles packaged under modified atmosphere, since no remarkable reduction of bioactive compounds were noticed after 42 days of storage, and their sensory and microbial parameters were of higher quality than those of non-irradiated controls.

Keywords: Bioactive compounds; Microbial degradation; Sensory analysis; Sterols; Summer truffle.