Bacteriology and Retail Case Life of Pork After Storage in Carbon Dioxide

Abstract

The effects of prolonged, anoxic storage, under C0 2 at -1.5°C, upon the bacteriology and case life of pork on its subsequent transfer to the aerobic conditions of simulated retail display at 8°C was examined. Brochothrix thermosphacta, lactic acid bacteria, enterics, and pseudomonads were enumerated. Panel scores for odor and appearance acceptability were used to quantify retail case life. Lactic acid bacteria were the only bacteria found during loin storage in C0 2 for up to 24 weeks. Those organisms reached maximum number of 10 7 CFU/cm 2 within 9 weeks. The number of lactic acid bacteria initially found on the freshly cut surfaces of loin chops increased linearly during the first 9 weeks of loin storage in C0 2 . Thereafter, they continued to grow on the chops and domi-nated the spoilage flora during retail display. The pseudomonads grew rapidly and emerged as the next most numerous organism, while B. thermosphacta and enterics showed only limited aerobic growth. The acceptability of pork chop appearance and odor was adversely affected by loin storage time. Each 6-week interval of loin storage produced a 1 d reduction in case life. Should controlled atmospheres be a practicable means of meat distribution to the retail marketplace, efforts will be necessary to assure a maximum case life after their removal from preservative packagings. Preservative packagings are the most effective and ac-ceptable means of prolonging the storage life of chilled meat, without the need for chemical preservatives and with the potential to maintain product quality and assure safety. The technology, spoilage, and safety of modified and controlled atmosphere packaging (MAP, CAP) have been reviewed in detail (8,12). From a bacteriological perspective, the success of MAP and CAP is attributable to the restricted growth of the putrefactive spoilage floras and the emergence of lactic acid bacteria as the numerically dominant species (5). Although those latter bacteria are known to antagonize undesirable organisms, they can mediate a sour spoilage after maximum population densities are achieved (4,6). Of the packaging systems available, the Captech process has proven most promising for chilled meats (9). This system relies upon the integration of hygienic processing, optimum