|Van Hekken, Diane|
|FARKYE, N. - California Polytechnic State University|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2013
Publication Date: 9/23/2013
Citation: Van Hekken, D.L., Tunick, M.H., Farkye, N.Y., Tomasula, P.M. 2013. Effect of hydrostatic high-pressure processing on the chemical, functional, and rheological properties of starter-free Queso Fresco. Journal of Dairy Science. 96:6147-6160. DOI: 10.3168/jds.2012-6212.
Interpretive Summary: High pressure processing (HPP), known to kill bacteria, was evaluated as a post-packaging treatment for the popular high-moisture, high-pH Hispanic-style cheese, Queso Fresco (QF). QF made from pasteurized homogenized milk and without starter cultures was processed at different conditions to understand the effects of HPP on the functional and textural properties of QF. The highest pressure was then used to determine the long term effects of HPP on the quality traits and shelf life. Results showed that the color and non-melt properties of QF were not affected by HPP, but HPP had a detrimental effect on the texture and moisture contents. Once processed, the firmness of QF increased as the length of HPP exposure and aging temperature increased while all other properties were stable over 12 weeks of storage. HPP negatively affected the quality traits of QF and should not be used on high-moisture, fragile-curd cheeses such as Queso Fresco.
Technical Abstract: Queso Fresco (QF), a popular high-moisture, high-pH Hispanic-style cheese sold in the U.S., underwent high-pressure processing (HPP), which has the potential to improve the safety of cheese, to determine the effects of this process on quality traits of the cheese. Starter-free rennet-set QF (manufactured from pasteurized, homogenized milk, milled prior to hooping, and chilled for 12 h at 4 C) was cut into 4.5 x 4.5 x 15 cubic cm blocks and double vacuum packaged. Phase 1 of the research examined the effects of HPP on the quality traits of fresh QF that had been warmed to a core temperature of 22 or 40 C; processed at 200, 400, or 600 MPa for 5, 10 or 20 min; and stored at 4 C for 6-8 d. Phase 2 examined the long term effects of HPP on quality traits when QF was treated at 600 MPa (the highest pressure examined for inactivation of Listeria monocytogenes in Phase 1) for 3 or 10 min, and stored at 4 or 10 C for up to 12 wk. The amount of whey that accumulated in the package increased when QF was warmed to 40 C prior to HPP, as the pressure and length of processing increased, and as the storage time and storage temperature increased. HPP resulted in harder and less chewy cheese. The control QF, regardless of the aging temperature, was significantly softer than HPP cheeses over the 12 wk of storage. The hardness, shear stress, and shear rigidity at fracture increased with length of exposure time and storage temperatures, with minor changes in the other properties. QF remained a bright white, weak body cheese that crumbled and did not melt upon heating. Although high pressures or long processing times may be required for elimination of pathogens, HPP altered the rheological properties of QF and resulted in the accumulation of whey in the package which would not recommend this process for use on non-pressed, high-moisture cheese such as QF.