JOHANNESBURG (Reuters) - South Africa's Pioneer Foods Group said on Thursday it expects half-year operating profit and headline earnings to increase by up to 44 percent and 32 percent respectively. Pioneer, which sells food, beverages and related products, said it expects operating profit for the six months ended March 31 of between 922 million rand ($77.37 million) and 991 million rand versus 688 million a year earlier. Adjusted headline earnings per share is expected to increase to between 309.1 cents and 334.5 cents from 253.4 cents. The group, with brands that include Bokomo Weet-Bix cereal and Liqui Fruit long-life juice, said sales volumes in the period were 4.3 percent higher while group turnover fell by 2.8 percent to 9.9 billion rand, largely due to sales price deflation in soft commodities. ($1 = 11.9166 rand) (Reporting by Nqobile Dludla; editing by Jason Neely)