E: Food Engineering & Physical Properties High-Pressure Effects on the Microstructure, Texture, and Color of White-Brined Cheese N. Koca, V.M. Balasubramaniam, and W.J. Harper Abstract: White-brined cheeses were subjected to high-pressure processing (HPP) at 50, 100, 200, and 400 MPa at 22 ◦ C for 5 and 15 min and ripened in brine for 60 d. The effects of pressure treatment on the chemical, textural, microstructural, and color were determined. HPP did not affect moisture, protein, and fat contents of cheeses. Similar microstructures were obtained for unpressurized cheese and pressurized cheeses at 50 and 100 MPa, whereas a denser and continuous structure was obtained for pressurized cheeses at 200 and 400 MPa. These microstructural changes exhibited a good correlation with textural changes. The 200 and 400 MPa treatments resulted in significantly softer, less springy, less gummy, and less chewy cheese. Finally, marked differences were obtained in a ∗ and b ∗ values at higher pressure levels for longer pressure-holding time and were also supported by E ∗ values. The cheese became more greenish and yellowish with the increase in pressure level. Keywords: cheese, color, high pressure, microstructure, texture Practical Application: The quality of cheese is the very important to the consumers. This study documented the pressure- induced changes in selected quality attributes of semisoft and brine-salted cheese. The results can help the food processors to have knowledge of the process parameters resulting in quality changes and to identify optimal process parameters for preserving pressure-treated cheeses. Introduction High-pressure processing (HPP) of food is of great interest to the food industry, especially for inactivating microorganisms and extending the shelf life of foods, while causing minimal changes in food quality. In cheese technology, the prominent research top- ics were the use of HPP to inactivate microorganisms and to accelerate cheese ripening. HPP has also found other applica- tions in cheese technology such as accelerating brine absorption (Messens and others 1998; Pavia and others 2000), increasing cheese yield (Drake and others 1997; Trujillo and others 1999; Huppertz and others 2004), increasing the shelf life of fresh cheese (Daryaei and others 2006), increasing enzymatic activ- ity of lactic acid bacteria (Upadhyay and others 2007; Katsaros and others 2009), improving low-fat cheese texture (Sheehan and others 2005), and improving shredability of cheese (Serrano and others 2005). Turkish white cheese is a semisoft cheese with closed texture that is brine salted and ripened in brine for 2 to 3 months. Research was undertaken to determine the microbial inactiva- tion by HPP in white cheese by Akdemir-Evrendilek and oth- ers (2008) who reported that pressures from 300 to 600 MPa at 25 ◦ C resulted in 2 to 5 log CFU/g reduction in total Enter- obacteriacea and Listeria monocytogenes. Not only is the success of HPP on microbial inactivation important, but also the de- MS 20101475 Submitted 12/31/2010, Accepted 3/21/2011. Author Koca is with Dept. of Food Engineering, Ege Univ., 35100 Bornova,Izmir, Turkey. Authors Balasubramaniam and Harper are with Dept. of Food Science and Technology, The Ohio State Univ., 43210-1007 Columbus, OH, U.S.A. Direct inquiries to author Koca (E-mail: nurcan.koca@ege.edu.tr). gree of changes in cheese qualities such as cheese texture, ap- pearance, and flavor is important to the consumer. It has been reported that HPP of cheese after manufacture caused the textural and structural changes in Mozzarella (O’Reilly and others 2002), Gouda (Messens and others 2000), cheddar (Wick and others 2004; Rynne and others 2008), Garrotxa (Saldo and others 2000, 2001), ewes’ milk cheese (Juan and others 2007), and fresh goat’s milk cheese (Capellas and others 2001). In addition, Koca and others (2007) reported that high-pressure application could reduce the oversetting in Swiss cheese by eliminating nucleation sites and changing textural properties. Depending on the changes in pro- tein matrix, color changes induced by HPP were reported (Saldo and others 2000, 2002a; Capellas and others 2001; Sheehan and others 2005). The extent of structural, textural, and color changes by HPP notably depends on the cheese variety having different moisture content and initial structure. In general, the same pressure level, processing time, and temperature may improve the quality of some cheese varieties, while they may have negative effects on that of others. Although a moderate amount of research has been pub- lished on HPP effects on texture and microstructure on hard or semihard cheeses, there has been a lack of information on the soft and semisoft cheeses such as white and feta cheese. It is impor- tant to be aware of the quality changes induced by high pressure for brine-salted cheese in order to suggest using high pressure for reasons such as microbial inactivation, ripening acceleration, and so on. Accordingly, our aim was to determine the effects of pressure treatment on the compositional, textural, microstructural, and color changes of white-brined cheese. The ripening effects related to pressure applications in terms of texture and color were also determined. C  2011 Institute of Food Technologists R  doi: 10.1111/j.1750-3841.2011.02201.x Vol. 76, Nr. 5, 2011  Journal of Food Science E399 Further reproduction without permission is prohibited