Effectiveness of sodium metabisulphite in mitigating fungal spoilage of dates fruit under climate change scenarios

Dates ( Phoenix dactylifera L.) are an economically and nutritionally important fruit that are vulnerable to fungal spoilage and mycotoxin contamination, posing serious challenges to food safety and food waste and loss. These risks are expected to intensify under climate change conditions, including elevated temperature and atmospheric carbon dioxide (CO₂) levels, necessitating effective preservation strategies. This study aimed to (i) characterize the fungal diversity associated with date fruits, (ii) evaluate the efficacy of sodium metabisulphite in controlling dominant spoilage fungi and (iii) assess the effects of simulated climate change scenarios. Fifty-six samples belonging to four date cultivars were analyzed using culture-based and molecular methods. Overall, 80% of the samples were contaminated, and 25 fungal species belonging to 11 genera were identified. Aspergillus was the predominant genus, occurring in 48% of the samples and accounting for 50% of the recovered isolates. Aspergillus tubingensis A4, Aspergillus niger A45 and Talaromyces verruculosus A51 were selected for subsequent in vitro experiments. The combined effects of water activity (a w ; 0.92 and 0.98), temperature (30 and 35°C) and atmospheric CO 2 concentration (400 and 1000 ppm) were assessed on a date-based medium. Fungal responses were isolate dependent with T. verruculosus A51 showing the lowest growth rates and the greatest resilience to increased temperature, whereas the two black aspergilli maintained comparatively high growth across the tested conditions. Elevated CO 2 partially alleviated the effects of reduced water availability in some treatments, although its influence varied among isolates. The antifungal efficacy of sodium metabisulphite (NaMBS) was evaluated at 0.90, 0.95 and 0.99 a w . NaMBS efficacy increased as water activity decreased and differed significantly among isolates. T. verruculosus A51 was the most sensitive isolate, while A. niger A45 showed the greatest tolerance. Complete inhibition of the black aspergilli occurred at 1250 mg/L at 0.95 and 0.99 a w , but at 500 mg/L under 0.90 a w . These findings demonstrate that the growth of date-associated fungi and their susceptibility to NaMBS are strongly influenced by interacting environmental conditions. NaMBS therefore shows potential as an in vitro control strategy for fungal spoilage in dates, particularly under conditions of reduced water availability. Overall, these findings demonstrate that both climate-related environmental conditions and water availability shape the growth and NaMBS susceptibility of date-associated fungi. GRAPHICAL ABSTRACT Improved presevation of dates under future climate change.