Development of probiotic yoghurts with high protein content by ultrafiltration

The ultrafiltration technique (UF) was used to achieve skim milk protein concentration and develop probiotic Greek-style yoghurt. Two yoghurts were prepared from ultrafiltered milk (with concentration factors 3 and 1.5, CF1 and CF2 samples, respectively) added with probiotic (Bifidobacterium animalis subsp. lactis) and compared to a control yoghurt. Proximal composition and physicochemical analyses were carried out after one day of pro-cessing. The microbiological viability of the starter and probiotic cultures, physicochemical composition, and technological properties of yoghurts during 28 days of storage were also evaluated. CF1 yoghurts showed the highest increase in protein content compared to the yoghurt CF2 and control. Consequently, this feature favoured lower post-acidification, better texture, higher water holding capacity, and absence of syneresis. Ultrafiltration was also satisfactory for enhancing the mineral content, especially calcium, phosphorus, and zinc. The probiotic bacteria remained viable throughout the refrigerated storage period, hence the use of ultrafiltered milk proved to be appropriate for producing high protein content probiotic yoghurts.