Assessment of damage caused by Ephestia cautella (Walker) to stored cocoa beans

Abstract

Ephestia cautella is one of the most common storage pests of stored cocoa beans. When left uncontrolled it can cause extensive damage to stored dried cocoa beans. Increased Free Fatty Acid levels (FFA) affect the fat structure and reduce the hardness of cocoa butter. Insects have been found to be a contributory factor to the increased levels of FFA. Inadequate studies have been done exclusively on the influence of E. cautella. The study was to evaluate extent of damage of E. cautella and its impact on the FFA levels, Experiments were conducted under temperature and relative humidity ranges of 27 °C – 36.5 °C and 40 – 85 percent, respectively, in the Insectary building of the Department of Crop and Soil Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana and Quality Control Division of COCOCBOD, Tema, Ghana. Thirty six mini sacks, each containing 400 g of cocoa beans stackes were grouped into four, and placed in a transparent cage measuring 65 cm length × 65 cm width and 75 cm high. Each group had a pile up stack of three, placed side by side, totaling nine mini sacks per group. Twenty newly emerged E. cautella were released into the cage and damaged assessed monthly up to a period of 4 months. The damage caused included significant decrease in weight loss and increase in Free Fatty Acid levels to stored cocoa beans over a period of 4 months. The mean percentage damage to cocoa beans by E. cautella were 10.31 and 29.05 in the first and fourth months, respectively, with corresponding percentage weight losses of 1.21 and 6.53. There were high levels of FFA in damaged beans caused by E. cautella as compared to the controlled beans. The FFA levels in the controlled beans were all below 1 percent, whilst the FFA levels in E. cautella infested beans were above the threshold of 1.75 percent aside month 1. Thus, E. cautella infestation caused increased levels of FFA within stored cocoa beans. There was a strong positive correlation among insect numbers monthly, percentage damage, weight loss and free fatty acid.