Shamsideen Olusegun Aroyeun, Cocoa Research Institute of Nigeria, Nigeria
Gabriel Olanrewaju Adegoke, University of Ibadan, Nigeria
Janos Varga, University of Szeged, Hungary
Purpose: Several factors including pH, water activity and temperature affect the growth of A. flavus and production of aflatoxin B1 in cocoa beans. Use of the spice Aframomum danielli in aflatoxin B1 reduction need to be studied to establish which combination of the variable factors together with A. danielli will optimize reduction of Aspergillus flavus growth and production of aflatoxin B1 in cocoa beans using Response surface methodology (RSM).
Design/methodology/approach: The factors and levels used in this experiment include water activity aw (0.94–0.98), pH (5–9), Temperature TOC, (15–35OC), and the essential oil of A. danielli (500ppm–2500ppm). The effects of each environmental factor on reduction of A. flavus growth and aflatoxin B1 production were determined by using a 4 factor, 5 level Central Composite Rotatable Design (CCRD).
Findings: The measure of fit of the data (R2) was quite high for all the dependent variables, 0.90 for A. flavus growth and 0.85 for aflatoxin B1 production. pH, aw, Temperature and essential oil of A. danielli affected the growth of A. flavus and aflatoxin B1 production. The Response Surface methodology (RSM) plots had saddle points as stationary points, which indicated the absence of a unique maximum. The quadratic effects of temperature and A. danielli were highly significant (p<0.01) with minimum A. flavus growth between TOC of 20–25OC and A. danielli of 1500ppm, pH 5–7, aw of 0.94–0.98.
Practical implications: The use of A. danielli in this study can form a synergy of barriers with two or more environmental factors against the production of afB1 and A. flavus growth. At every combination of abiotic factors and the A. danielli, where growth occurred, the levels of afB1 detected in contaminated cocoa beans was less than the current regulatory standard of 20µg/kg for afB1 in foods meant for human consumption.
Originality/value: Many of the existing interventions on reduction of aflatoxin B1 in cocoa beans have not grasped the need to combine environmental details, which this study has established.
Keywords: Cocoa bean, Response Surface Methodology, A. danielli, A. flavus, pH, Water activity