Appearance and Microbial Quality of Thawed Retail Cuts of Beef, Pork and Lamb

Abstract

Retail cuts of beef. pork and lamb were fabricated. packaged, evaluated for appearance traits. swabbed, and subsequently frozen. After storage for 7 days, one-half of the cuts were thawed at 4 C. The other cuts were thawed at 25 C. At 0, 4, 8, 24 and 48 h. the thawed retail cuts of meat were rated for appearance and swabbed. Taxonomy was conducted before freezing and after each thaw period. Evaluation revealed that differences (P < .05) in appearance for beef and pork existed between those samples thawed for 24 h and a h. Beef and pork cuts thawed at 25 C were less (P < .05) desirable in appearance after 24 h than for 8 h. Cuts thawed at 4 C for 48 h were less desirable than for 24 h. A higher thaw temperature increased (P < .05) microbial growth at 24 h on beef; but this trend was not observed among cuts of lamb and pork. Thaw time beyond 24 h increased (P < .05) the microbial load of only lamb and pork. Microorganisms most prevalent among samples were Pseudomonas, micrococci and staphylococci. These data suggest that retail cuts of meat should be thawed at refrigerated temperature, especially if thaw time exceeds 8 h. Appearance and bacteriological condition of meat is of special interest to the food industry and the consumer. It has been known for some time that microorganisms cause meat color and flavor degradation (2,15). Past studies have enumerated microbial flora of fresh ground beef and other products (5,7,8.15,19.26,27,28.31). Other research (13,23) has determined the effect of freezing on the microbial load of meat. A trend has existed among consumers (32) to purchase fresh retail cuts of meat from a grocery store, place the meat in a refrigerator or freezer for freezing and later thaw the meat before cookery. Previous research (22) on microbial quality of retail cuts of meat has determined that freezing extends the lag phase of microbial proliferation. Additional work (23) suggested that freezing can be responsible for some decrease in microbial load due to metabolic injury of bacterial cells. According to results of previous investigations (24,34), bacterial genera are more critical to spoilage than is total microbial load. These observations are supported by results which indicate that certain genera cause discoloration, undesirable flavor and food poisoning at ' lower (P < .OS) levels of contamination than do other microorganisms. Other research (9) has revealed that various food poisoning microorganisms are unable to compete effectively with the natural flora of raw ground beef over a wide range of refrigerated temperatures. These workers' results and the fact that a cooking step is involved (12) explain why this product is rarely involved as a vehicle in food poisoning by microorganisms. Investigations have shown that fresh meats at the retail level have high bacterial counts (4,14,16,17.25). A survey conducted Ql) of raw beef patties produced at federally inspected plants revealed that bacteriological quality of the product was a measure of the cumulative increase of bacterial growth on meat from the time of slaughter through manufacture. Although it is difficult to demonstrate a real or potential health hazard from contamination or time-temperature abuse, microbial load may be related indirectly to a health hazard (6). Thus additional study of thaw time and temperature seems appropriate to determine what constitutes time-temperature abuse and to provide additional information of interest to the industry and the consumer. Although results of storage of fresh and frozen retail cuts of meat for various periods have been documented, very little is known about resultant effects of various thaw periods at different temperatures on the appearance and microbial load of such meat. Therefore, this investigation was designed to evaluate the role of two thaw temperatures and five thaw periods on the stability of beef, pork and lamb cuts. MATERIALS AND METHODS Beef loin steaks, pork loin chops and lamb chops were fabricated from wholesale loins, aerobically packaged with polyvinyl chloride film as retail cuts of meat and displayed in a fresh meat case. The beef steaks were cut from loins that were previously cut and vacuum-packaged by a beef fabricator. The pork loins were fabricated by a pork slaughtering firm, wrapped in parchment, shipped to a retail store and then cut into chops, whereas the lamb loins were cut irom lamb carcasses by a lamb slaUghtering ftml and shipped unwrapped to the retail store for retail cutting and packaging. Retail cuts from beef and pork were fabricated, packaged and displayed in the same store in east Texas, but the lamb chops were produced in another store in the same geographic area. Beef and pork cuts were packaged the day of purchase, but the lamb chops had been packaged and displayed for two days before being acquired. These retail cuts of meat were randomly selected from the display case and purchased. Enough samples were secured to provide five replications per treatment. The samples were