The effect of particle size and drying temperature on drying rate and oil extracted yields of Buccholzia coriacea (MVAN) and Butyrospermum parkii (ENGL) was investigated. Air drying studies carried out on B. coriacea and B. parkii, tropical food sources subject to high post-harvest losses, have resulted in the establishment of a significant difference between oil yields extracted from samples of various particle size pretreatments (paste, 4 mm, 8 mm and whole kernels) dried at 45 and 60°C with the highest oil yield given by the 4 mm thick slices dried at 45°C. The influence of temperature and particle thickness on the drying rate has been evaluated. The drying constants were found to depend on both temperature and particle thickness. Analysis of the oil extracted from the 4 mm thick slices dried at 45°C showed that apart from the acid value (52.4%), the saponification (181.2 mg g )1 KOH), peroxide (8.6 meq kg )1 ) and the unsaponifiable (7.43%) matter values of the extracted shea butter remain within the limits cited in the literature while a close analysis of the cake suggests that it could be a good mineral source.

The response surface method employing Doehlert's experimental design was used to optimise the cooking of sheanuts to strike a balance between the advantages and disadvantages usually offered by the process. The independent factors investigated were cooking time, cooking temperature and nut size while the responses were moisture content of the kernels, amount of oil extracted, acid and peroxide values of the butter. Second order polynomial models were generated to describe the process for the responses studied. The validity of the models was tested and it was found that they could be used to explain respectively 83%, 99% and 95% of the variation of moisture content, acid value and peroxide value. The cooking process greatly reduced the free fatty acid values of the butter (<6%) but increased its peroxide value (up to 20 meq/kg). The cooking process was significantly influenced by all three independent factors investigated. The optimum conditions defined for the cooking process were: cooking time (95-120 min), cooking temperature (75-90°C) and nut size (40-45 mm). These optimal conditions gave the following responses: moisture content 51.97% w.b., amount of oil extracted 47.47%, acid value (as FFA) 2.76% and peroxide value 3.87 meq/kg. The parameters of the cooking conditions could be set to appropriate values to give butter of either category 1, 2 or 3 in terms of acid and peroxide values.number of experiments r 2 regression coefficient RSEE relative standard error of the estimate Δu increment V titre volume (ml) V 0 volume of blank (ml) x i coded value of variable i x 1 coded value of cooking time (dimensionless) x 2 coded value of cooking temperature (dimensionless) x 3 coded value of nut size (dimensionless) X i real value of variable i X 0 i central value of the real variable i X 1 real value of cooking time (min) X 2 real value of cooking temperature (°C) X 3 real value of nut size (mm) Y 1 moisture content (% w.b.)

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