Using direct contact membrane distillation for whey protein concentration

Abstract

Whey protein has passed from being a cheese manufacturing waste product to a valuable food additive in a variety of foods from baby food to health drinks. Traditionally whey protein concentrates are produced by concentrating the whey content in the cheese runoff from 6.5% (w/w) dissolved solids (DS) to 20% DS by ultrafiltration followed by diafiltration to remove dissolved salts and sugars. This is followed by evaporation to 40% DS and spray drying, producing an 80% DS whey protein product [1]. As evaporation takes place at 70°C some valuable whey protein denature giving a lower nutrition value of the product. The evaporation at the same time is a relatively costly process. Both problems could be avoided if the evaporation step could be removed. This is not possible using ultrafiltration, as the osmotic pressure limits this operation to between 25% and 28% DS and this at an uneconomical price [2]. This paper describes the use of direct contact membrane distillation (DCMD) as a method for concentrating whey protein up to a concentration of at least 34% (DS) based on preliminary laboratory scale experiments using a commercially available microfiltration membrane and compares the measured flux with the flux predicted from simple a priori model based on the dusty gas model (DGM).