Cheese whey treated by membrane separation as a valuable ingredient for barley sourdough preparation

• Cheese whey was tested as an ingredient for production of sourdough with health benefits.
• Novel processes were used for preparation of dried barley sourdough.
• Whey was treated by filtration, fermentation, low temperature drying and/or extrusion.
• Filtration efficiency and recovery of components during NF and UF was studied.
• Sourdough had a high activity of bacteria and elevated amount of propionic acid.

Utilisation of cheese whey for production of healthier food has been the main task of this study. Cheese whey, which is often considered as a waste material, was treated by a series of processes including fermentation, membrane filtrations, mixing with barley flour, drying, and/or extrusion to produce barley sourdough.In the first series of experiments, the effect of membrane ultrafiltration (UF) and nanofiltration (NF) on separation of whey components has been studied. Non-fermented sweet cheese whey was treated by pilot-plant membrane ultrafiltration (50 kDa tubular ceramic membrane, TAMI Industries, France), followed by three step diafiltration to minimise losses of lactose, glucose, galactose, and organic acids (namely lactic acid) in retentate. The UF permeates were used for the subsequent nanofiltration and diafiltrations (spiral wound membrane NF 270-2540, Filmtec, Dow Chemicals, USA). The results showed high recovery of proteins (81%) during UF and reduction of lactose and propionate losses by using diafiltration. Rejections of components on the NF membrane were: 93% lactose, 77% galactose, and 76% lactic acid. However, the diafiltration on the NF membrane reduced the relative recovery both for carbohydrates and organic acids.In the second series of experiments, cheese whey was concentrated by reverse osmosis (RO) and the obtained retentate was fermented with Lactobacillus plantarum, Lactobacillus sanfranciscensis and Propionibacterium freudenreichii subsp. freudenreichii. Part of the fermented whey was mixed with barley flour and dried by cold air fluid drying to produce sourdough pellets. The other part of fermented whey was filtered by nanofiltration and both permeate and retentate were sprayed on the surface of sourdough pellets in several layers and dried again. The extrusion of a mixture containing barley flour and fermented whey was tested for pellet production as well. The main aims were to obtain sourdough rich in natural preservatives, and maintain the present microorganisms active. That is why all the technological processes, including drying, were carried out under low temperatures. The content of organic acids (lactic, acetic and propionic) was analysed in final sourdough samples.