Increasing protein content in yoghurt implies the milk fortification either concentration processes(evaporation or ultrafiltration) or by addition of SMP. More recently, whey protein concentrate (WPC) are also used due to their availability and low cost. Despite WPC are largely applied as attractive food ingredient in a wide range of food applications, the direct reincorporation of liquid whey protein
concentrates (LWPC) in dairy products, being a less expensive alternative, is seldom referred. The effect of the replacement of SMP by WPC on textural and physicochemical properties of yoghurts has been reported by several authors [1-4], but in some cases their conclusions were contradictory. The reasons pointed for that are the significant variations in the functionality of WPC resultant from the whey processing conditions, specially heating [5-10] and the whey source [6, 11, 12]. In Portugal, bovine and
ovine cheese production represents approximately 60×103 and 15×103 ton/year respectively [13], and the last product is normally associated with Protected Geographical Indication Labels. Based on the cheese production the overall volume of whey produced annually is estimated in approximately 560 000 tonnes.
In Mediterranean countries as well as in Portugal, small and medium scale dairy industries represent the majority of producers and face simultaneously environmental problems related to their whey disposal, low production yields and difficulties to succeed in the market due to their specialization in just one product.
The use of membrane technologies, namely ultrafiltration (UF) and diafiltration (DF) enables the extraction and concentration of whey proteins from whey to its reincorporation in production, solving their environmental problems and add value to existing products.