Toxin Development by Clostridium botulinum in Modified Atmosphere-Packaged Fresh Tilapia Fillets During Storage

Potential for toxin development by Clostridium botulinum type E was investigated in retail-type packages of fresh tilapia fillets packaged in high barrier film under selected atmospheres [100% air, a modified atmosphere (MA) containing 75%CO₂:25%N₂, and vacuum] and stored under refrigeration (4°C) and abuse temperatures (8 and 16°C). Toxin development coincided with sensory spoilage at 16°C storage for fillets packaged in either MA, or vacuum. At 8°C, toxin development in fillets packaged in either of the atmospheres occurred 7-23 days after sensory spoilage. At 4°C, none of MA-packaged fillets became toxic until 10 days after onset of sensory spoilage. Toxin development did not precede sensory spoilage in any treatments or temperatures studied.     

Development of Botulinal Toxin and Sensory Deterioration During Storage of Vacuum and Modified Atmosphere Packaged Fish Fillets

Toxin production by C. botulinum type E was studied in cod, whiting, and flounder filets packaged in air-permeable film, vacuum packages and packages flushed with N₂ or CO₂ during storage at 8°, 12° or 26°C. Cod and whiting filets were flushed with CO₂ and stored continuously at 4°C or cycled between 4° or 8° and 26°C. Cod and whiting fillets were flushed with gas mixtures and stored at 8°C or 26°C. Flounder deteriorated rapidly and was rejected by sensory evaluation prior to toxin detection during vacuum or modified atmosphere storage at 12°C and 8°C but after toxin detection at 26°C. Toxin was present either prior to or simultaneously with sensory rejection of cod and whiting fillets for all vacuum or modified atmosphere treatments and temperature regimens.     

Development of Staphylococcal Toxin and Sensory Deterioration During Storage of Nitrogen and Vacuum Packaged Nitrite-Free Bacon-Like Product

Toxin production by S. aureus was studied in nitrite-free bacon-like product packaged in air permeable film, vacuum packages, and packages flushed with N₂ during storage at 8°C, 12°C or 26°C. Product wrapped in air permeable film deteriorated rapidly at 26°C and was rejected by sensory evaluation prior to staphylococcal enterotoxin detection. Enterotoxin was not detected in vacuum or N₂-flushed packages stored at 26°C. Samples stored at 12°C supported S. aureus growth although enterotoxin was not detected at 12°C or 8°C in any packaging environment. The potential for staphylococcal food poisoning resulting from the production of a nitrite-free bacon-like product was limited under the conditions studied.     

Shelf Life and Clostridium botulinum Toxin Development during Storage of Modified Atmosphere-packaged Fresh Catfish Fillets

Shelf life (onset of sensory spoilage) and potential for toxin production by Clostridium botulinum type E in retail type packages of fresh catfish fillets in high barrier film were investigated under selected atmospheres when stored under refrigeration and temperature-abuse conditions. Shelf life of fillets in all atmospheres decreased with increase of storage temperature from 4°C to 16°C. Trimethylamine content associated with onset of spoilage was different for each storage temperature and atmosphere. Surface pH and K-values were not good indicators of onset of sensory spoilage. Toxin development coincided with sensory spoilage at 16°C storage for fillets packaged in either atmosphere. At 4°C, none of the MA-packaged fillets became toxic, even after 37 days of sensory spoilage.     

USE OF FLEXIBLE POLYMER MATERIAL FOR PACKAGING FRESH PEACHES

Fresh peaches (Prunus persica) were overwrapped in trays with 1 of 3 formulations of flexible polyvinyl chloride (PVC) film that differed in gas transmission rate or they were held in nonwrapped trays (controls). The CO₂ transmission rate at 0°C for PVC type III film was 280 mL/m^2. h (1 atmos); that of type II was 4 times greater and that of type I, about 5 times greater. The peaches were stored either 14 days at 0° or 7.5°C, or 7 days each at 0° and 7.5°C plus 2 days at 20°C to simulate retail display. The mean CO₂ levels were 10, 7.2 and 4.7% in packages that were wrapped with PVC III film and held at 7.5°, 0°/7.5° and 0°C, respectively. CO₂ in packages wrapped with PVC I or II was below 3% at each storage temperature. O₂ concentration remained about 4% in all packages. Weight loss was less and fruit was firmer among those packaged in PVC III than among nonwrapped controls at each of the 3 storage temperatures. Storage temperature had no effect on weight loss or of fruit held in PVC III film. External appearance of fruit packaged with the 3 types of film was significantly better than that of the controls. Internal appearance of the peaches was unaffected by any of the treatments. A microatmosphere favorable for fresh peaches can be maintained within packages overwrapped with polymer films that are selectively permeable to respiratory gases.     

Packaging Film Permeability in Conjunction with Sodium Nitrite, Potassium Sorbate or Lactic Acid Starter Culture for Control of Clostridium sporogenes (PA3679) Growth in Sliced Bologna

A sliced bologna was prepared and inoculated with Clostridium sporogenes (PA3679), packaged in films ranging in oxygen permeability from 0.1 cc/m²/24 hr to 120 cc/m²/24 hr and stored at 5°C, 15°C or 25°C. Subsequent bologna preparations included either 156 ppm sodium nitrite, 0.26% potassium sorbate or a lactic acid starter culture. Water activity, pH, TBA number and PA3679 counts were monitored during 28 days of storage. TBA numbers increased in packages with over 60 cc/m²/24 hr permeability but PA3679 counts did not change as a function of packaging film. Nitrite and sorbate were equally effective as inhibitors. At 15°C and 25°C, the lactic acid culture allowed the least PA3679 growth. Oxygen permeability did not alter any inhibitory effects even when increased TBA numbers resulted from using an oxygen-permeable film.     

Clostridium botulinum Growth and Toxigenesis in Shelf-Stable Noodles

Unacidified and acidified noodles were inoculated with a composite of C. botulinum types A and B spores. Noodles were cooked, packaged in oxygen-permeable polypropylene bags, steamed, cooled, then stored aerobically at 7 or 23°C, or anaerobically at 30°C. Toxin did not develop in any aerobically stored samples at pH ±4.5. Toxin developed in samples with pH >5.0, stored aerobically and anaerobically. In addition, toxin was detected in one anaerobically incubated acidified unit where pH had been increased by microbial growth. Proper acidification of product prevented toxic growth of C. botulinum.     

Control of Microbial Spoilage on Fresh Poultry using a Combination Potassium Sorbate/Carbon Dioxide Packaging System

The effects of potassium sorbate combined with vacuum or carbon dioxide modified atmosphere packaging on natural poultry spoilage flora were examined. Fresh chicken thighs were dipped into either 2.5% potassium sorbate solution or distilled water, adjusted to pH 6.0 and packaged on trays in Nylon/Plexar/Surlyn bags. Atmospheres of either air, vacuum or 100% C0₂ were created in the packages which were then stored at 10 ± 1°C for 10 days. Changes in aerobic plate counts, lactic acid bacteria and pseudomonads were monitored. The combination of CO₂ packaging and sorbate treatment provided the most effective inhibitory system against the poultry spoilage organisms, especially Pseudomonas species, without creating a selective environment for the growth of lactic acid bacteria and premature souring of the product. The shelf life of the sorbate/CO₂ samples was extended 3 days over the control/air samples at 10°C.     

Centralized Packaging of Beef Loin Steaks with Different Oxygen-Barrier Films: Physical and Sensory Characteristics

Vacuum packaged beef strip loins (n = 72) were stored (2 ° 1°C) for either 0, 12 or 24 days before fabrication; steaks were packaged and displayed (2°C or 7°C) up to 6 days in oxygen-permeable film or up to 30 days in vacuum packages (medium or high oxygen-barrier film). Steaks displayed at 2°C, rather than 7°C, tended to have higher overall appearance scores especially when steaks were from 12 or 24 day subprimals. Overall palatability of vacuum packaged steaks was unacceptable after 10–15 days of display. Vacuum packaged steaks can be displayed for 10 days if: (1) steaks are from relatively fresh subprimals, (2) steaks are vacuum packaged with high oxygen-barrier film, and (3) steaks are displayed at 2°C. Although visual scores for vacuum packaged steaks were acceptable for 20–30 days, off-odors and off-flavors were limiting factors in determining shelf-life.     

Using A New Measure To Define Shelf Life Of Fresh Whitefish

An acceptor set size measure was successfully employed to examine shelf life trade-offs when fresh lake whitefish fillets (Coregonus clupeaformis) were dipped in 0.0, 2.5 or 5.0% (w/v) potassium sorbate, packaged in low, intermediate, or higher barrier bags, placed in 100% CO₂ modified atmosphere packaging system and held under refrigeration at less than 3°C. When sorbate was varied, shifts in acceptor size indicated that fillets dipped in 5.0% sorbate had the longest shelf life, exceeding 14 days. No significant difference was found when film permeability was varied. For all barrier films, shelf life exceeded 15 days although the low barrier bag had smaller acceptor sizes.     

Growth and toxin production by Clostridium botulinum in fish (Mugil cephalus) and shrimp (Penaeus indicus) tissue homogenates stored under vacuum

Toxin production by Clostridium botulinum types A–E in mullet and shrimp tissue homogenates stored between 4 and 30°C under vacuum for 6 weeks was evaluated. Mullet and shrimp tissue homogenates were inoculated with C. botulinum spores, then packaged under vacuum and held at 4, 10, 15 and 30°C. At 30 and 15°C storage, growth and toxin production by types A–E resulted in both mullet and shrimp tissue homogenates. Only type E toxin was observed in the homogenates held at 4 and 10°C. The storage temperature and the growth substrate markedly influenced the toxin titres.     

Antimicrobial Activity and Functionality of Reduced Sodium Chloride and Potassium Sorbate in Uncured Poultry Products

Uncured turkey and chicken breast meat products, formulated with NaCl (0.65 and 1.30%) and potassium sorbate (0 and 0.26%), were tested for antimicrobial activity and functional properties. The chopped products were inoculated (Clostridium sporogenes, 10/g) in cans and in packages and abused at 20°C. Microbial growth and gas production were rapid at both NaCl levels tested. Inclusion of potassium sorbate in the formulation delayed initiation and rate of microbial growth and gas production. Potassium sorbate also reduced (P<0.05) weight losses during cooking of the low NaCl turkey product. Rates of gas production were similar in canned and vacuum packaged products. Differences in microbial growth and gas production between chicken and turkey products were minor.     

Centralized Packaging of Beef Loin Steaks with Different Oxygen-Barrier Films: Microbiological Characteristics

Vacuum packaged beef strip loins (n = 72) were stored (2° 1°C) for either 0,12 or 24 days before fabrication; steaks were packaged and displayed (2°C or 7°C) up to 6 days in oxygen-permeable film or up to 30 days in vacuum packages (medium or high oxygen-barrier film). For steaks displayed in oxygen-permeable film, Pseudomonas spp. were a considerable (25–49%) or dominant (>50%) part of the microflora. The microflora of vacuum-packaged steaks from 0 day loins was dominated by a combination of hetero- and homofermentative Lactobacillus spp.; when vacuum-packaged steaks were from 12 and 24 day loins, the microflora was in most cases dominated by the heterofermentative Lactobacillus cellobiosus.     

Effects of Vacuum Packaging and Potassium Sorbate on Yield, Yeast and Mold Growth, and Quality of Dry-Cured Hams

Two trials were conducted. In the first trial hams were cured by a standard process and aged 1 month at 24°C. Group I hams were not packaged or treated. Group II hams were vacuum packaged and Group III hams were dipped in a 2.5% potassium sorbate solution and also vacuum packaged. All hams were examined after 1 month and the treated group was dipped in a 5% sorbate solution, vacuum packaged and aged an additional 2 months. Vacuum packaging practically eliminated further weight loss while potassium sorbate reduced but did not eliminate mold growth. In the second trial hams were again cured by a standard process and aged at 24°C until they were officially country hams (18% weight loss). Group I hams were not treated whereas group II hams were dipped in a 10% potassium sorbate solution. All were vacuum packaged. After aging one month they were unpacked, weighed, and examined for molds. No significant weight loss had occurred but mold counts were lower in the dipped group. The dipping procedure was reversed so that group I hams were treated and group II hams were not treated. All hams were again vacuum packaged and held a second month. No additional weight loss was noted. Mold growth, though not eliminated, was minimal, and visual and aroma scores for the cut hams were similar and highly acceptable. Tenderness, flavor, saltiness, and overall satisfaction scores for cooked slices were similar and highly acceptable. In general, mold growth can be greatly reduced by the use of potassium sorbate and weight loss can be controlled by vacuum packaging.     

Evaluation of Changes in Listeria monocytogenes Populations on Frankfurters at Different Stages from Manufacturing to Consumption

ABSTRACT: This study evaluated the fate of inoculated Listeria monocytogenes on frankfurters stored under conditions simulating those that may be encountered between manufacturing and consumption. Frankfurters with or without 1.5% potassium lactate and 0.1% sodium diacetate (PL/SD) were inoculated (1.8 ± 0.1 log CFU/cm²) with a 10‐strain composite of L. monocytogenes, vacuum‐packaged, and stored under conditions simulating predistribution storage (24 h, 4 °C), temperature abuse during transportation (7 h, 7 °C followed by 7 h, 12 °C), and storage before purchase (60 d, 4 °C; SBP). At 0, 20, 40, and 60 d of SBP, samples were exposed to conditions simulating delivery from stores to homes or food establishments (3 h, 23 °C), and then opened or held vacuum‐packaged at 4 or 7 °C for 14 d (SHF). Pathogen counts remained relatively constant on frankfurters with PL/SD regardless of product age and storage conditions; however, they increased on product without antimicrobials. In vacuum‐packaged samples, during SHF at 4 °C, the pathogen grew faster (P < 0.05) on older product (20 d of SBP) compared to product that was fresh (0 d of SBP); a similar trend was observed in opened packages. At 7 °C, the fastest growth (0.35 ± 0.02 log CFU/cm²/d) was observed on fresh product in opened packages; in vacuum‐packages, growth rates on fresh and aged products were similar. By day 40 of SBP the pathogen reached high numbers and increased slowly or remained unchanged during SHF. This information may be valuable in L. monocytogenes risk assessments and in development of guidelines for storage of frankfurters between package opening and product consumption.     

Inhibition of Salmonella by Sodium Nitrite and Potassium Sorbate in Frankfurters

All beef frankfurters and beef-pork frankfurters containing various levels of sodium nitrite (0, 50, or 156 ppm) or potassium sorbate (0, 0.26, or 0.39%) alone or in combination (50 ppm nitrite + 0.26% sorbate) were prepared. Frankfurters were inoculated with nalidixic acid resistant Salmonella and incubated at 15°C and 27°C for up to 21 days. Frankfurters formulated with 50 or 156 ppm nitrite and incubated at 27°C, or 50 ppm nitrite and incubated at 15°C failed to inhibit the growth of Salmonella. Sorbate alone and sorbate in combination with 50 ppm nitrite were equally effective in inhibiting Salmonella at either temperature and were equivalent to 156 ppm nitrite in inhibiting Salmonella at 15°C.     

Control of Two Major Pathogens on Fresh Poultry Using a Combination Potassum Sorbate/Karbon Dioxide Packaging Treatment

Salmonella enteriditis and Staphylococcus aureus were separately inoculated onto fresh chicken thighs prior to dipping in 0, 1.0, 2.5, or 5.0% potassium sorbate solutions adjusted to pH 6.0. Treated samples were packaged in Nylon/Plexar/Surlyn bags under air, vacuum, 20%, 60%, or 100% CO₂ atmospheres and stored at 10°C ± 1.0°C for 10 days. Changes in gaseous headspace composition, sorbate concentrations, surface pH, and microbial numbers were monitored during the storage period. S. enteriditis was more sensitive to potassium sorbate than S. aureus; growth on poultry of the latter organism was more effectively inhibited by exposure to high levels of CO₂. Increased concentrations of sorbate dip solutions in combination with higher concentrations of CO₂ in the package environment provided a more effective inhibitory system against growth of both pathogens on fresh poultry.     

Effects of Sodium Chloride Reduction and Polyphosphate Addition on Clostridium Botulinum Toxin Production in Turkey Frankfurters

Mechanically deboned turkey meat emulsions were made with 1.0, 1.5, 2.0, 2.5, or 3.0% salt (NaCl), or with combinations of 1.5% or 2.0% salt with 0.4% sodium tripolyphosphate (TPP), sodium hexametaphosphate (HMP), or sodium acid pyrophosphate (SAPP). Sodium nitrite levels were constant at 150 ppm. Emulsions were inoculated with a mixture of 10 strains of C. botulinum (10³/g) and incubated at 27°C. Increasing NaCl content from 1.0% to 3.0% delayed toxin production by 3 days on the average. Toxin production was detected earlier when TPP was added, HMP had no effect, and SAPP delayed toxin production.     

Blood Fraction Effects on the Antibotulinal Efficacy of Nitrite in Model Beef Sausages

Toxin production by Clostridium botulinum was studied in a model cured beef sausage containing 0–5% added dried bovine blood fractions. Controls which contained nitrite but without blood fractions, were toxic by bioassay in 3 wk at 27°C. Controls without nitrite or blood fractions were toxic at 1 wk, while model sausages supplemented with hemoglobin, red cells, or whole blood were toxic in 1–3 wk. Plasma yielded no detectable toxin for 4 to > 10 wk depending upon addition level. Sausages showing delayed toxigenesis had pH values lower than those which developed toxin earlier. These results demonstrated that use of blood fractions that increased iron levels in beef above 30 μ.g/g interfered with the antibotulinal efficacy of sodium nitrite.     

Survival of Clostridium botulinum in modified atmosphere packaged fresh whole North American ginseng roots

Fresh North American ginseng roots (Panax quinquefolius) were packaged in medium transmission film in air. Six roots were used per pouch. Anaerobic conditions developed during 2, 10 and 21°C storage, most rapidly at the elevated temperatures. Clostridium botulinum challenge tests were performed for 10 and 21°C samples. At 21°C storage, neither uninoculated control nor inoculated roots showed C. botulinum toxin production after 6 weeks of storage. At 10°C, C. botulinum toxin production occurred after 14 weeks in inoculated roots, while roots maintained an acceptable appearance. This highlights the potential risk of food poisoning by ginseng packaged under modified atmosphere when anaerobic conditions develop.