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.
