Purpose: Molecular identification and determination of in vitro growth potential of fungi isolated from filled brioche products and their raw materials.
Methods: Freshly produced praline-, biscuit- or strawberry- filled brioche or raw materials (flour, fillings) were supplied daily by the manufacturer and analyzed immediately or during their shelf life (20-37oC, 50-60 days) for fungal presence. A total of 91 fungal isolates were molecularly identified by sequencing the internal transcribed spacer (ITS) region. In vitro fungal growth of selected isolates (40 out of 91), representing the major fungal genera identified, was assessed with spot inoculation on Malt Extract Agar of pH 6.1 (adjusted with 5N NaOH) and aw 0.99 (without glycerol) and 0.83 (adjusted with 38% v/v glycerol). The low aw was studied to imitate the respective values of brioche and brioche fillings. Fungal growth was monitored at 25oC (recommended temperature by the industry) and 37oC (as temperature abuse) by measuring radial diameter for max. 60 days.
Results: More than 65% of fungal isolates were identified as Penicilium sp., followed by 20% of Cladosporium sp. and 7% of Aspergillus sp. In vitro growth assessment revealed that high aw permitted the growth of all isolates (n=40) at 25oC, whereas only 33% had a growth potential at 37oC, most of which belonged to genus of Penicillium. On brioche-like media (aw 0.83), no growth was observed at all isolates except for an Aspergillus flavus isolate at 37oC. Contrary to temperature abuse conditions, more than 80% of the isolates, which included all the identified genera, were able to grow at 25oC and aw0.83, highlighting the potential visual deterioration of brioche products during their shelf life.
Significance: Results of the present study could contribute to the identification and minimization of the risk of fungal spoilage in brioche-like products.