1. ARC Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch 7599, South Africa; Department of Food Science, Stellenbosch University, Private Bag X1, Matieland (Stellenbosch) 7602, South Africa; and PROMEC Unit, Medical Research Council, P.O. Box 19070, Tygerberg 7505, South Africa