Sugar and sweetener firm Tate & Lyle posted a sharp fall in profits after facing impairment charges and tough trading conditions.Profit before tax in the year to 31 March fell to £113m from £182m the previous year even as revenues climbed to £3.55bn from £2.87bn.The fall in profits was largely due to an impairment charge of £97m decision to mothball a sucralose facility in Alabama and produce all sucralose from a newer facility in Singapore. Excluding exceptional charges, pre-tax profits totalled £247m, compared with £253m the previous year.The company maintained a final dividend of 16.1p, making a total dividend of 22.9p a share, compared with 22.6p previously.Chairman Sir David Lees said the decision to maintain the final dividend was made in light of the need to keep the firm's investment grade ratings.Chief executive Iain Ferguson noted that market conditions had become more challenging in recent months, but said: "Our focus on the food and beverage sector, which comprises over 70% of our total sales, gives us a measure of resilience, although not immunity, to the economic downturn."The firm said that, while the new financial year has started in line with expectations, uncertain economic conditions made it difficult to predict the outlook for the current year.