EFFICACY OF SELECTED SPICES IN MITIGATION OF FUNGAL GROWTH AND MYCOTOXINS PRODUCTION IN TEA AND COFFEE

Abstract

Tea and coffee, consumed for their neutraceutical, health and stimulating benefits, can be easily contaminated by mycotoxin-producing fungi, due to agro-ecological factors, poor handling and storage. Spices such as Curcuma longa, Xylopia aethiopica and Piper guineense possess antimicrobial properties with potential to reduce fungal growth in tea and coffee. However, there is limited information on their use and effectiveness in mitigating mycotoxins production in processed tea and coffee. This study was designed to investigate the extent of fungal contamination and possibility of inhibiting growth of fungi and their metabolites in tea and coffee using the selected spices. Tea and coffee, randomly obtained from fourteen warehouses each in Ibadan and Mambilla, were subjected to microbial screening and mycotoxins quantitation following ISO methods. Fungal isolates were characterised using RAPD analysis, and metabolites recovered were quantified using HPLC. Freshly harvested tea and coffee from Ibadan and Mambilla were processed to green and black products using standard procedures, and treated with milled Curcuma longa roots, as well as Xylopia aethiopica and Piper guineense seeds at 1000, 2000, 3000 and 4000 µg/g. The treated and untreated (control) samples were packaged in tea bags and stored at ambient condition (28±3oC; 70±5% Relative Humidity) for 24 weeks. During the storage period, microbial activities were monitored and polyphenol levels determined bi-weekly using AOAC methods. Data were analysed using ANOVA at α0.05. Aspergillus flavus, Aspergillus niger, Penicillium georgiense, Fusarium solani and Gliocladium cibotti were prominent fungal species identified in the tea and coffee. The tea and coffee contained metabolites of Aspergillus (15, 2), Penicillium (8, 6), Fusarium (4, 5) and other fungal species (18, 12). Mambilla tea and coffee had significant higher level of contamination than Ibadan samples. Seventy toxins were quantified, with Aflatoxin B1 (85.3-427.2 µg/kg), deoxynivalenol (1.3-5.2 µg/kg), beauvericin (2.5-5.0 µg/kg), brevianimide (33.6-106.2 µg/kg), and sporidesmolide II (7.3-10.8 µg/kg), being major in the tea and coffee. Aflatoxin B1 and deoxynivalenol, which are of major public health concern, were dominant in black tea and coffee. Green tea and coffee were also contaminated with abscisic acid, unspecific rugulusovin, sporidesmolide II, unspecific emodin and unspecific tryptophol. Curcuma longa (4000 µg/g), Piper guineense (4000 µg/g) and Xylopia aethiopica (1000 µg/g) had 92.0±1.1%, 92.0±1.8% and 91.3±2.4% microbial activity reduction on Aspergillus flavus and 53.2±0.8%, 36.4±1.5% and 37.8±2.7% on Fusarium solani, respectively. Microbial inhibition of the spices varied significantly with concentration. The source of samples did not significantly influence the efficacy of the treatment. Total phenolic content increased with spice addition, in black tea and coffee (3.0-7.1 mg/g), and in green tea and coffee (15.5-22.0 mg/g), respectively. High number of Fungi species and their metabolites were present in the tea and coffee. Xylopia aethiopica was most effective in reducing fungal growth and mycotoxin production in the tea and coffee.