Atomic force microscopy studies on whey proteins

beta-Lactoglobulin, standard whey protein concentrate (WPC 80) and cold-gelling whey protein concentrate (mWPC 80) were dried onto mica sheets at 0.03-3 mu g cm(-2) surface load and imaged with atomic force microscopy (AFM) in tapping mode. beta-Lactoglobulin and WPC 80 spread to a fairly even 2.5 nm thick layer at about monolayer surface load, while mWPC showed particle sizes of 20-30 nm laterally. There is little difference in the observed structures between 0.3 and 3 mu g cm(-2) apart from the higher surface load. At 0.03 mu g cm(-2), beta-lactoglobulin spread somewhat more thinly than WPC 80. With the addition of DTT, mWPC spread evenly with only few particles in evidence. AFM appears to be a convenient method for the characterization of aggregation states of sub-micrometer protein particles. (C) 1998 Elsevier Science Ltd. All rights reserved.