Investigation of the effects of membran filtration techniques on composition and quality of white brined cheese

Turkish white cheese is a kind of brined cheese and it is the most popular traditional cheese in Turkey. It has soft or semi-hard texture and a salty, acid taste. There are similar types of Turkish white cheese around the world such as Bulgaria's Sirene, Romania's Telamme, Greece's Feta,Yugoslavia's Primonski Sir and Grobniciki Sir, Israel's Brinsa, America's Queso Blanco and Pickle Cheese and Egypt's Domiati cheese. Membrane filtration techniques are used in the milk industry for several purposes such as fractionation of milk fat from whole milk, removal of bacteria and spores from milk, standardization or enrichment of protein content of the milk etc. Membrane filtration techniques are readily used in cheese production, since cheese production is actually a kind of concentration (enrichment) process. Ultrafiltration and microfiltration are the major membrane processes employed in the cheese industry. These filtration processes are used to produce cheese from milk retentates. Ultrafiltration has been applied to cheese production over the past 45 years, whereas microfiltration is a more recent technology. Although ultrafiltration offers some benefits in cheese manufacturing such as improvement in hygienic capacity, minimal heating, increased cheese yield, homogeneity of the quality of the final cheese product, it is observed to have negative impacts on cheese quality due to the enrichment of whey proteins in the ultrafiltrated milk. However, in microfiltration larger membrane pore sizes are used. For this reason, the enrichment of whey proteins in cheese milk is less. Milk is a complex mixture of different components such as fat, protein, lactose, minerals, etc. These components have unique nutritional and functional characteristics. Whey proteins represent approximately 20 % of the milk proteins. In traditional cheese production whey proteins remain in the whey with fat, caseinomacropeptides, rennet, etc. For this reason, purification or concentration of whey proteins is difficult and expensive. Also, whey has low solid content and high biological oxygen demand (BOD), which creates a major disposal problem. On the other hand, the permeate stream obtained after microfiltration of milk is referred to as "ideal whey" since it contains whey proteins that do not contribute to the cheesemaking process. Thus, unlike classical whey, ideal whey has sterile native components with higly functional properties and also no fat in its composition. The presence of fat in whey leads to decreased functional properties and shorter storage life. Moreover, microfiltered whey proteins maintain their biological activity and have a better flavor profile than classical whey. Therefore, ideal whey is a much better raw material for manufacturing high quality whey protein ingredients. The aim of the present study is to investigate the chemical composition and the quality parameters of white brined cheese obtained from pasteurized milk enriched upon microfiltration. For this purpose, two types of microfiltration membranes were used: a polyethersulfone membrane (MP005) with a pore size of 0.05 μm, and a polyvilidene fluoride membrane (MV020) with a pore size of 0.20 μm. Microfiltration equipment used is a laboratory scale SEPA CF-II membrane test unit equipped with a flat plate. Enrichment factors of 1.59, 1.71, 1.85, and 1.93 were achieved with the polyethersulfone membrane, whereas the enrichment factor was 1.24 with the polyvilidene fluoride membrane. Chemical compositions of the permeate and the retentate streams were analyzed with respect to dry matter, protein, fat and ash contents. White cheese was obtained from the retentate streams enriched upon microfiltration. White cheese obtained directly from pasteurized milk was used as the control sample. Chemical compositions of the white brined cheese samples were analyzed with regard to dry matter, protein, fat, ash, salt contents and acidity. Whey obtained upon cheese making was analyzed with respect to dry matter, protein and ash contents. Color (L*, a*, b*) and texture parameters (hardness, adhesiveness, springiness, cohesiveness, gumminess, chewiness, resilience) of cheese samples including the control were measured and evaluated. Sensory tests with regard to color, odor, texture and flavor performed by 14 untrained panelists by ranking the cheese samples. Sensory test results were evaluated using Duncan Multiple Comparison Test (p<0.05). Process effectiveness, which defined as hundred times of amount of cheese obtained per unit mass of retentate (milk for the control), was evaluated as 11.16 % for the control sample. Upon enrichment using the MP005 membrane, process effectiveness increased to 31.89 %, 33.24 %, 31.66 % and 36.35 % corresponding to enrichment factors of 1.59, 1.71, 1.85 and 1.93, respectively. Thus, the amount of whey produced as the waste material of the cheese making process, which includes caseinomacropeptides, rennet, whey proteins and milk fat, decreased substantially. Enrichment using the MP005 membrane did not cause substantial differences in the composition of white brined cheese obtained from microfiltration retentates in comparison with the control. In addition, chemical compositions of all white brined cheese samples including the control were in accordance with values reported in the literature for white brined cheese. Cheese making in the laboratory setting may have suffered from minimal procedural variations, and these variations may have caused differences in the appearance, color, texture and the sensory properties of the cheese samples. However, measured properties of cheese samples made from microfiltration retentates obtained using the MP005 membrane, were comparable with those of the control sample. At the very beginning of microfiltration, milk fat formed a layer on the membrane offering extra resistance to mass transfer. Thus, only water, lactose, non-protein nitrogen and minimal amount of whey proteins were allowed to pass through the membrane. Thus, protein composition was practically unaffected by the enrichment process. However, the physical and sensory properties of the cheese sample obtained from the retentate enriched by using the MV020 membrane (with a larger pore size) were practically quite different from the control. One of the most important observations in the present study was visually observed differences in porosity of the cheese blocks interfered with measurements of especially color and texture parameters. Thus, not only porosity, but also the pore structure may have hindered independent measurement of color and texture parameters. It seems that the porous characteristics of cheese samples may have contributed to the variability in color results, and also in the results of textural and sensory properties. It can be concluded that enrichment by using the MP005 membrane has a potential in decreasing the amount of cheese waste that needs to be processed and/or treated on site. Also, decrease in the volume of the material to be processed to cheese is expected to decrease operating costs. Thus, microfiltration technology is promising as an environmentally friendly technology to be used by the cheese making industry.