Presence of Campylobacter jejuni was determined at various locations in turkey carcass processing and further processing of turkey products (wieners, ham and boneless breast). Contamination of turkey carcasses with C. jejuni , in most cases, occurred on the surface of the skin or on the surface of the abdominal cavity lining. No contamination of interior muscle tissue was observed. The percentage of turkeys containing C. jejuni upon entering the processing plant varied (50 to 100%). Large numbers of C. jejuni were killed during scalding of carcasses, but extensive recontamination occurred during mechanical defeathering. After scalding, numbers of C. jejuni peaked during evisceration, but dropped to lower levels after washing. Few or no C. jejuni were recovered from the carcasses after leaving the chill tank. No C. jejuni were detected on frozen turkey carcasses, including the drip, at the wholesale or retail level. However, Campylobacter coli was detected in the drip of a few carcasses that had been in frozen storage at the wholesale level for 2 wk and 3 months. Neither C. jejuni nor C. coli was detected on frozen turkeys at the retail level. Although, in some cases, C. jejuni were recovered from turkey meat during initial stages of further processing, no C. jejuni were recovered from heat-treated, further processed products.

Various cooking procedures (roasting, braising, stewing and microwave cooking) applied to turkey thighs, and washing procedures for contaminated utensils (knives and cutting boards) and food handlers' hands were evaluated for their effectiveness in removing Campylobacter jejuni . Roasting, braising and stewing were effective in destruction of C. jejuni on contaminated turkey thighs even when the meat was undercooked, reaching an internal temperature of 55°C. Destruction of C. jejuni by microwave cooking was assured more fully if a meat thermometer was used to check the internal temperature of the sample rather than by visual evaluation. Washing of utensils with water and detergent, either by hand or in a dishwasher, removed C. jejuni except from wooden cutting boards washed by hand. Minimal hand washing procedures may not assure complete removal of C. jejuni from contaminated hands.

The effect of various initial chilling treatments on the numbers and types of microorganisms of beef, pork and lamb tongues (n = 60) and livers (n = 60) packaged either in polyethylene (PE) film or in vacuum packages in Texas and transported fresh-chilled via transoceanic shipment to Antwerp, Belgium, was evaluated. Initial chilling treatments included: cooler-tempered (4 to 6 h at 2°C), cooler-chilled (24 h at 2°C) freezer-tempered (0.5 to 1 h at −20°C), freezer-chilled (2 h at −20°C), ice-chilled (2 h in ice water slush) and no prechilling (NPC) before packaging and subsequent refrigerated storage at 2°C. After the initial chilling treatments, the microflora was varied with Micrococcus spp. with or without coryneform bacteria being the predominant bacterial types of most samples. After refrigerated storage for 13 to 15 d, lactic acid bacteria became dominant in most vacuum-packaged samples and in pork and lamb samples stored in PE film. Brochothrix thermosphacta and Pseudomonas spp. constituted a greater part of the microflora of beef tongues and livers stored in PE film than that of comparable vacuum-packaged samples. Increases in aerobic plate counts (APC) of refrigerated vacuum-packaged samples nearly always were greatest for samples (NPC) that were not pre-chilled before packaging and usually were smallest for samples that were either freezer-chilled, freezer-tempered or ice-chilled.

A flow-through controlled atmosphere packaging system using a number of different carbon dioxide-enriched gaseous compositions was demonstrated to be effective in retarding the growth of microorganisms on fresh swordfish steaks held at 2°C for 22 d. During the first 14 d of storage, Pseudomonas spp. either dominated or represented a major part of the microflora of steaks in all gaseous atmospheres tested. However, in atmospheres containing 70% CO 2 or in pure CO 2 , heterofermentative Lactobacillus spp. and Brochothrix thermosphacta were a major part of the microflora, particularly after the 14th day of storage. Both total volatile nitrogen and trimethylamine, often used as quality indicators for fresh seafoods, increased more slowly for swordfish steaks stored in CO 2 -enriched atmospheres than steaks stored in air. Advantages of using a controlled atmosphere flow-through system for storage of fresh seafoods include: (a) a stable gas composition, (b) individual portions can be removed from a master package without losing or disrupting the gaseous atmosphere, and (c) volatile off-odors which accumulate during storage in sealed CO 2 -enriched atmospheres are carried off with the flow-through gas.

Large increases in counts cf Leuconostoc spp., Lactobacillus coryneformis , Lactobacillus plantarum , Lactobacillus viridescens and Lactobacillus curvatus occurred over a 28-d display period when aseptically fabricated steaks were inoculated with 10 3 to 10 4 cells/cm 2 of these species and then were vacuum-packaged. With Lactobacillus cellobiosus 2, Serratia liquefaciens or Hafnia alvei as inoculum, increases in count were much smaller. Counts of L. cellobiosus 1, Brochothrix thermosphacta , a Moraxella sp. and Alteromonas putrefaciens of inoculated steaks decreased during display. With a higher inoculum (10 6 cells/cm 2 ), increases in counts of lactic acid bacteria usually were smaller. Some lactic acid bacteria caused marked decreases (0.2 to 0.5) in the pH of the meat surface. Changes in surface discoloration of uninoculated and inoculated steaks over a 28-d display period were not significant (P>0.05). Off-odor scores of both uninoculated and inoculated steaks were lower (more off-odor) after display but few of the differences were significant. Off-odors of steaks inoculated with lactic acid bacteria were described as “sour”, “buttermilk”, “sulfur-like” and “H 2 S”.

Swordfish ( Xiphias gladius ) steaks were held in retail packages containing 100% CO 2 and in mixtures of 40% and 70% CO 2 in combination with either oxygen or nitrogen. Controls were stored in air. Samples were removed for chemical and microbiological analyses after 2–22 d of storage at 3.5°C. The inhibitory effect of CO 2 on psychrotrophic, aerobic gram-negative spoilage bacteria was proportional to the CO 2 tension in the packages. Maximum inhibition of growth was achieved with 100% CO 2 . Except for steaks stored in 40% CO 2 :60% O 2 heterofermentative Lactobacillus spp. became a dominant part of the microflora of steaks stored in CO 2 -enriched atmospheres. Pseudomonas spp. continued to be a major part of the microflora of steaks stored in 40% CO 2 :60% O 2 . During the first 2 d of storage, there was a decrease in the surface pH of the swordfish steaks proportional to the CO 2 tension in the packages. Swordfish steaks stored in CO 2 -enriched atmospheres had lower total volatile nitrogen (TVN), trimethylamine (TMA) and total volatile acid (TVA) values than steaks stored in air. Oxidative rancidity was not a flavor problem of fish in any of the atmospheres after 20 d of refrigerated storage.

Survival and/or growth of Pseudomonas fluorescens , Micrococcus luteus , Micrococcus sp. 102 and Staphylococcus aureus was studied in raw, frozen, pasteurized or heat-sterilized pooled human skim milks. Growth response of P. fluorescens at 25°C was essentially the same in the untreated and treated milks with an increase in count/ml of 4 log cycles during a 24-h incubation period. Counts (per ml) of S. aureus in raw, pasteurized and frozen milks increased approximately 3 log cycles. Growth of S. aureus in heat-sterilized milk was somewhat less. Micrococcus sp. 102 could not be recovered from raw and frozen milk after incubation at 37°C for 14 and 24 h, respectively. The count (per ml) of this organism in pasteurized milk decreased approximately 2 log cycles during the 24-h incubation period, whereas counts in sterilized milk increased approximately 2 log cycles. In no instance did M. luteus survive in raw, pasteurized or frozen milks at 37°C even for short periods after inoculation. The organism survived in heat-sterilized milk for 14 h at 37°C, but then decreased in numbers until the organism could be recovered from only 1 of 5 pools after 48 h of incubation.

Seven pooled human milks, each from at least 6 different breast-feeding mothers (4 weeks post-partum) were studied for microbial population and flora changes during storage at 37°C. Coagulase-negative Staphylococcus spp. constituted a considerable part (39–100%) of the microflora in 6 of 7 pools of fresh milk, with coryneform bacteria, Lactobacillus , Micrococcus and Streptococcus spp. isolated less frequently. Storage of raw milk for 8 h caused a shift in flora favoring the Lactobacillus spp. After 24 h, coagulase-negative Staphylococcus were dominant in 4 of 7 pools, coryneform bacteria in 2 of 7, and Lactobacillus and Micrococcus spp. each in 1 of 7 pools. Low levels of bacteria were detected in 2 of 7 pasteurized pools, consisting of Staphylococcus spp. or yeasts. Freezing of the milk before storage at 37°C had little effect on the aerobic plate counts.

Sheepshead ( Archosargus probatocephalus ) fillets were stored in air and in modified gas atmospheres consisting of: 100% CO 2 , 80% CO 2 :20% O 2 , 60% CO 2 :40% O 2 , 30% C0 2 :60% O 2 , 20% CO 2 :80% O 2 , 40% CO 2 :60% N 2 and 44% CO 2 :36% O 2 :20% N 2 At regular intervals during refrigerated storage, numbers and types of microorganisms and total volatile nitrogen (TVN) were determined. Increases in aerobic plate counts of fish fillets held in air and in 20% C0 2 :80% O 2 were greater than those for fillets stored in the other gas atmospheres. The most effective combinations of gas for limiting bacterial growth were 100% CO 2 and 40% CO 2 :60% N 2 . Total volatile nitrogen values of samples stored in air and in 20% CO 2 :80% O 2 increased similarly to those of fish held on ice. At higher CO 2 concentrations, however, increases in TVN were slow and the rate of TVN production appeared inversely proportional to CO 2 tension.

Aerobic plate counts (APC) of vacuum-packaged beef livers, beef kidneys and pork livers during refrigerated storage were nearly always, particularly after 14 days at 2 C, much lower than those of comparable samples packaged in polyvinyl chloride (PVC) film. The pH of vacuum-packaged livers and kidneys decreased during refrigerated storage; the same was true for products stored in PVC film except that the pH of kidneys increased. In refrigerated vacuum-packaged livers and kidneys, lactic acid bacteria (homo- and heterofermentative lactobacilli, streptococci, Leuconostoc sp.) became more predominant, whereas in products packaged in PVC film, gram-negative bacteria frequently became more dominant.

Aerobic plate counts (APC) of livers, kidneys and hearts obtained from beef, pork and lamb soon after slaughter were nearly always <10 4 and often <10 3 per cm 2 . Differences in APC of different sites of the same liver, kidney or heart, within each species, were not significant (P>0.05). APC of livers, kidneys and hearts from pork and lamb after storage for 1, 3 or 5 days at 2 C were not significantly different (P>0.05) from those at day 0. APC of beef livers, kidneys and hearts after 5 days at 2 C differed significantly (P<0.05) from those at day 0, 1 and 3. Temperature abuse of fresh organs for 6–12 h at 30 C before freezing caused major increases in count. Frozen storage of livers, kidneys and hearts (4 days at −20 C) did not cause significant changes in APC. The initial microbial flora of fresh livers, kidneys and hearts was varied with coryneform bacteria and Micrococcus sp. often constituting a major part (>25%) of the microbial flora. After storage for 5 days at 2 C, Pseudomonas sp. more often became a major part of the microbial flora of liver samples. Frozen storage for 4 days at −20 C did not change the microbial flora of beef samples greatly; in pork and lamb, coryneform bacteria more frequently became a major part of the microbial flora after freezing. Changes in pH of livers, kidneys and hearts during storage for 5 days at 2 C were small.

U.S. Choice boneless beef strip loins from four suppliers were used to determine the effect of using previously vacuum-packaged beef subprimals and the effect of using subprimals at different storage intervals--0, 14 or 28 days--after arrival at our laboratory on the retail appearance of steaks packaged in 75% O 2 + 25% CO 2 . After packaging, steaks were stored for 9 days in the dark in a 1 ± 1-C refrigerated cooler and displayed under 1030 lux of incandescent light in a retail case for 4 days at 2 ± 2 C. Selected subprimals were repackaged and held at 1 ± 1 C for 9 days in the dark and steaks were removed and packaged in polyvinyl chloride (PVC) film and displayed for 4 days to serve as display controls. With regard to surface discoloration, overall appearance and off-odor scores, modified gas atmosphere (MGA)-packaged steaks from strip loins fabricated at Day 0 were not different (P>.05) from PVC-packaged steaks, however, MGA-packaged steaks from strip loins fabricated at Day 14 or Day 28 were less desirable (P<.05) than PVC-packaged steaks or steaks that were MGA-packaged on Day 0. When comparisons of retail appearance characteristics were made among loins from different suppliers, the results were mixed; data from steaks that were MGA-packaged at Day 14 revealed (P<.05) differences among loins from different suppliers in surface discoloration and off-odor while data from steaks that were MGA-packaged at Day 28 revealed no (P>.05) differences among loins from different suppliers in surface discoloration or overall appearance. Data indicate that modified gas atmosphere packaging of beef loin steaks can be successful if very fresh subprimals are used; however, extended vacuum-storage of beef subprimals (14 or 28 days) did not provide raw material that was amenable to subsequent storage-display in modified gas atmosphere packages.

Numbers and types of bacteria were determined on steaks after refrigerated storage (1 ± 1 C) in 75% O 2 plus 25% CO 2 for 9 days in the dark plus display at 2 ± 2 C for 4 days under simulated retail conditions. Steaks were prepared from strip loins (IMPS #180) as received from the supplier (trial 1) and also from the same or similar loins that were vacuum-packaged at day 0 (trial 1) and then stored under refrigeration for 14 (trial 2) or 28 days (trial 3). Initially (day 0, trial 1), the microflora of steaks consisted primarily of Micrococcus and Moraxella-Acinetobacter sp. Following refrigerated storage in vacuum packages for either 14 or 28 days, Lactobacillus and Leuconostoc sp. became dominant. Refrigerated storage and display of steaks in 75%O 2 plus 25% CO 2 shifted the microbial population in favor of Leuconostoc sp. Initial log counts of steaks (day 0, trial 1) ranged from 0.88 to 2.02. Counts of steaks stored for 9 or 13 days in 75% O 2 plus 25% CO 2 nearly always exceeded 10 6 per cm 2 when steaks were prepared from loins which had been stored in vacuum packages for either 14 or 28 days. The pH values of steaks prepared from loins which had been stored under refrigeration for 14 days were lower (0.27–0.56) than those of steaks prepared from comparable loins as they were received from the supplier (day 0, trial 1). Refrigerated storage of vacuum-packaged loins for an additional 14 days did not cause marked changes in pH of the steaks. No consistent differences in microbial flora were detected between green- and normal-pigmented areas of steaks prepared from vacuum-packaged loins which had been stored refrigerated for 14–28 days.

The microflora of steaks prepared from 14-day old vacuum-packaged beef strip loins obtained from a commercial packing plant consisted primarily of Leuconostoc sp. with smaller percentages of Pseudomonas sp. and homofermentative lactobacilli. Steaks stored for 10 days at 1 ± 1 C in O 2 (65–80%) + CO 2 (20–25%) + N 2 (0–10%) atmospheres in the dark were rated inferior (surface discoloration, overall acceptability) to steaks prepared from loins which had been stored for an additional 10 days in vacuum packages. Additional storage for 4 days under retail conditions (2 ± 2 C) caused further deterioration of quality. Aerobic plate counts of steaks prepared from loins which had been stored in vacuum packages for an additional 10 days were about 2 logs lower than those of comparable steaks held in O 2 -CO 2 -N 2 atmospheres.

Biceps femoris steaks were inoculated with each of four Lactobacillus sp. (atypical streptobacteria and beta bacteria) at a high or low level of cell concentration, vacuum-packaged and stored for up to 35 days at 1–3 C. Total lactobacillus counts of inoculated steaks were numerically higher than those of corresponding control (non-inoculated) steaks at nearly all of the storage intervals tested. Differences in lactobacillus counts between steaks inoculated with a high concentration of Lactobacillus cultures 5, 8 and 642, and those of control steaks usually were significant (P < 0.05) after storage for 0 to 28 days. Differences in lactobacillus counts between steaks inoculated with a low concentration of Lactobacillus cultures and those of control steaks were seldom significant (P < 0.05). After storage for 35 days at 1–3 C, differences in lactobacillus counts of inoculated (high or low levels of inoculum) and control steaks usually were not significant (P > 0.05). The lactobacilli encountered on the inoculated steaks consisted primarily of the type added by inoculation.

Electrical stimulation of rabbit muscles caused a reduction in count of Pseudomonas putrefaciens and of a Lactobacillus sp. when inoculated muscles were held for 45 min after electrical stimulation. Little if any change in count was detected on rabbit muscles immediately after electrical stimulation and after 20 min of storage. Electrical stimulation (ES) of pork carcasses did not affect the aerobic plate count (APC) of the skin surface. APC of cutaneous trunci from electrically stimulated sides of beef and lamb carcasses were similar to those of muscles from unstimulated sides or carcasses. APC of ground beef and blade steaks fabricated pre-rigor from electrically stimulated sides were often numerically lower after 3 days of storage than those of corresponding samples from unstimulated sides. Differences in APC between conventional and ES samples of ground beef prepared from vacuum packaged top round were significant (P < 0.05) after 6 days of storage. However, none of the other differences in count were statistically significant (P < 0.05). Electrical stimulation did not cause any consistent substantial changes in microbial types of ground beef, blade steaks, T-bone steaks or rib steaks. When minced, aseptically excised supraspinatus muscle was inoculated with either P. putrefaciens or a Lactobacillus sp., counts of these species in tissues from electrically stimulated beef often were significantly lower than those of corresponding unstimulated samples.

Yersinia enterocolitica was recovered from 6 of 45 (13%) oyster, 2 of 50 (4%) shrimp and 12 of 58 (21%) blue crab samples. No single method of enrichment (cold mannitol broth or modified Rappaport broth for 7, 21 or 60 days) was most effective for the three types of shellfish examined. The effect of refrigerated storage on Y. enterocolitica depended upon the type of shellfish, condition (raw or boiled), strain of Y. enterocolitica and temperature and time of storage. In general, Y. enterocolitica counts increased in ( a ) raw oysters stored at 0–2 C for 14–21 days and at 5–7 C for 2–10 days, ( b ) in boiled shrimp stored at 3–5 C for 7–21 days and ( c ) in cooked crab meat stored at 5 C for 14 days. Freezing and heating of shrimp and crab meat caused extensive destruction of Y. enterocolitica . Biotypes capable of causing human illness (when inoculated into seafoods) survived and under certain conditions multiplied at refrigeration temperatures. Biochemical characteristics of the isolates from raw shellfish differed from those of clinically significant types.

A microbiological examination of vacuum-packaged strip loin steaks that were defective (gassy packages, hydrogen sulfide odor) revealed high total counts (10 7 –10 8 /cm 2 ) with Hafnia alvei , Lactobacillus and Pseudomonas spp. as major isolates. Re-inoculation experiments indicated that H. alvei was the likely cause of the hydrogen sulfide odor. Gas formation resulted from the activity of heterofermentative lactobacilli and H. alvei . Improvements in plant practices and temperature control eliminated the problem.

Yersinia enterocolirica -like isolates from meats produced, black colonies on eight of nine lots of bismuth sulfite agar. Differences were observed in size and black metallic sheen of colonies on different lots of this medium. In addition, inhibition of Pseudomonas spp, differed among lots.

No survivors of Yersinia enterocolitica were detected in beef roasts inoculated at levels as high as 3.1–3.8 × 10 6 viable cells per g when the final internal temperature in the center was 60 to 62 C. At 51 C some Y. enterocolitica survived. Extensive destruction of Y. enterocolitica occurred on beef during frozen storage. Counts of surviving organisms were greater on tryptic soy agar than on bismuth sulfite agar plates. Growth of Y. enterocolitica in brain heart infusion was better at pH 7 and 8 than at 6 or 9. Little or no growth occurred at pH 5.