Abstract:

The effects of soaking treatments with citric acid (CTA), sodium chloride (NaCl) and apple polyphenols (APP) on
the populations of bacteria, moulds and yeasts, sensory quality and shelf life of fresh truffles were investigated. Fresh truffles
were soaked with CTA, NaCl and APP alone or in combination for 30 min at 45 ℃, and the total bacterial counts, and mold
and yeast counts were assayed. In addition, the sensory quality was judged and the shelf-life of un-soaked and soaked truffles
of storage in vacuum packaging at 4 ℃ was evaluated. There were noticeable reductions in the populations of bacteria, molds
and yeasts in soaked truffles with the individual agents; the combined treatments had marked synergistic antimicrobial effects
compared with the summation of the effects of each individual treatment. Taking into account 32 as a threshold value for
sensory acceptability, the optimal concentrations f individual treatments were 2.5% CTA, 5.0% NaCl and 2.0% APP. The
optimal concentrations for combined treatments were 2.0% APP + 2.5% CTA, 5.0% NaCl + 2.0% CTA and 2.0% APP + 5.0%
NaCl, respectively. Based on the experimental results from the combinations, the optimal concentration of CTA + NaCl +
APP was 2.0% + 5.0% + 2.0%; the shelf-life of fresh truffles was prolonged to 49 days by this combined treatment.

Key words: fresh truffles, citric acid (CTA), NaCl, apple polyphenols (APP), microbial population, shelf life