Sales of cottage cheese have been on the decline since 1972. Several factors have contributed towards this decline, including limited shelf-life. Cottage cheese shelf-life is estimated to be 10-21 days, in standard, non-barrier containers held at refrigeration temperatures. Shelf-life is shortened when aerobic, psychrotrophic microorganisms grow at refrigeration temperatures, producing changes which are undesirable. Previous studies have demonstrated that modified atmosphere packaging (MAP) is able to maintain cottage cheese quality and extend shelf-life over air packaging. The objectives of our study were to evaluate the ability of MAP to maintain cottage cheese quality, while establishing the proper atmosphere to be used. Further, we wanted to determine the potential for discoloration and development of undesirable acid flavors in cottage cheese by elevated CO₂ levels. Direct-set cottage cheese was packaged in barrier containers and flushed with 100% CO₂, 75% CO₂:25% N₂, 100% N₂, and air, and stored at 4°C for 28 days. Product quality was assessed by sensory evaluation. Microbiological and chemical tests were conducted to obtain a better understanding of the effects of MAP on cottage cheese. Results obtained demonstrated that there was no change during storage for headspace gas composition. Psychrotrophic and lactic acid bacteria increased for air treated samples. Counts for MAP cottage cheese remained unchanged. In contradiction to previous studies, elevated CO₂ levels did not cause product discoloration. Acidity increased over storage life; however, the increase in acidity was not perceived organoleptically. These results contradicted previous studies which demonstrated that elevated CO₂ levels imparted a sharp acid flavor to the food product. Lactic acid did not contribute towards increased acidity. Sensory evaluation demonstrated that air treatment was inadequate in maintaining product quality past day 19. Cottage cheese packaged under 100% CO₂ was judged most acceptable, followed by 75% CO₂ - 25% N₂, and 100% N₂ treatments. / Master of Science