Fungal Contamination and Invertase Activity in Dates and Date Products in Saudi Arabia

Abstract

Background and Objective: The production of enzymes by fungi is the most likely source of contamination of substrates leading to spoilage in dates and date products. One of these enzymes is invertase, which takes a role in the ripening and maturation of the date fruit and date fruit products and eventually degradation and spoilage. This study was conducted to determine the fungal mycoflora in fresh and dried dates and investigate the production of invertase enzyme in date fruit and date fruit products. Materials and Methods: The mycoflora present in 40 samples of date fruit and date products was investigated using the dilution-plate and the direct plating techniques. Fungal isolates were counted and identified microscopically using the fungal taxonomy. Invertase activity was tested on liquid 20% sucrose-czapek’s medium and was determined in the filtrates using the fehling’s solution. Results: Twenty-seven fungal species and one variety representing 13 fungal genera were isolated and identified. The most common isolates included Aspergillus, Cladosporium, Penicillium, Neurospora and Rhizopus. Aspergillus was the most prevalent isolated fungi, followed by Penicillium and Cladosporium. The total fungal count was less in dates than on date products. Invertase activity was found in 48 isolates. Conclusion: There is a high prevalence of saprophytic fungi in date fruits and date fruit products. There is also a moderate to strong invertase activity in 8 out of 9 fungal isolates. It is highly recommended that extra precautionary measures must be adopted in consumption of ripened dates particularly those near spoilage due to its probable high saphrophytic fungal contents.