Please read the abstract in the section, 00front of this document / Dissertation (MSc (Agric) Food Science and Technology)--University of Pretoria, 2008. / Food Science / MSc / Unrestricted

The objective of this study was to use MAP technology to produce safe, shelf-stable, high quality, hard grated cheeses not requiring preservatives or refrigeration during distribution and sale. Initially, a challenge study with Staphylococcus aureus (S. aureus) was conducted to determine the water activity (Aw) level of high-moisture cheeses necessary to prevent the growth of a food pathogen when packaged under a modified atmosphere (25% CO, and 75% N,). Other microbial analysis included mold and yeast enumerations. Secondly, product quality and shelf stability were determined biweekly by sensory, microbial, and instrumental analysis to evaluate product safety and changes in the natural aromas and flavors of hard grated cheeses. Instrument color analysis CIE L* a* b* values were determined to measure color changes. Parmesan cheese with high Aw levels (Aw= 0.90 and 0.88) supported the growth and survival of S. aureus. The microorganism was incapable of surviving at Aw levels of 0.86 and below. S. aureus was not able to survive on Romano cheese. Mold and yeast proliferated on higher Aw Parmesan cheeses. Visible mold was detected on the Parmesan sample of Aw= 0.90 after 8 weeks of storage. No mold growth was observed on Romano cheese. However, yeast were capable of growing on Romano cheese. The sensory evaluation study of hard grated cheeses was unable to detect a difference between the fresh cheese sample and the cheeses packaged under MAP. / Master of Science