PZ Cussons is expanding its food and nutrition business in Nigeria despite difficult trading conditions in the west African country.The company best known in Britain as a soap-maker is establishing a food ingredients business as a joint venture with the large Asian agribusiness Wilmar International.The joint venture will supply branded products such as edible oils and spreads, using a palm oil refinery which is expected to be built within two years. PZ Cussons' share of the investment in the joint venture will be approximately $27m (£17m) over two years. Following completion of the refinery, the joint venture is expected to be earnings enhancing in its first full year of trading, it said.Earlier this month PZ Cussons reported trading in line with expectations, though there is some weakness in Nigeria where liquidity is tight and the timing of presidential elections is causing uncertainty.