Effect of Storage Temperature and Time on the Quality of Vacuum Packaged Dry-Cured Ham Slices

Hams were cured and aged by three methods, two using nitrite and nitrate but with long or short aging times at controlled temperature, and one using no nitrite or nitrate with ambient aging temperature. Hams were sliced, vacuum-packaged and stored at 0°C, 10°C or 21°C for 8 wk and examined weekly for white film, aroma, and aerobic, staphylococci, lactobacilli, yeast and mold counts. White film development was erratic. Aroma was closely related to aerobic counts. At 0°C bacterial counts and aroma remained normal for 8 wk. At 10°C many packages had acceptable counts and aroma at 8 wk but some were unacceptable by 4 or 5 wk. At 21°C many slices were unacceptable microbiologically and sensorily by 3 wk. Storage at or near 0°C is recommended for long shelf life.     

Flavor, Texture, Color, and Hexanal and TBA Values of Frozen Cooked Beef Packaged in Modified Atmosphere

Cooked beef loin slices were packaged with (1) vacuum, (2) 80% N₂ and 20% CO₂ gas mixture, or (3) air and stored at -20°C for 11 wk. Modified packaging of cooked beef improved flavor and odor. After storage and reheating, flavor and aroma of samples in vacuum and N₂/CO₂ packages were more meaty, less warmed-over, less cardboardy, and less oxidized and had lower TBA, less hexanal, and less pentanal than those in air-containing packages. Textural properties of beef were unaffected by packaging treatments. Vacuum-packaged beef slices had higher HunterLab a values than those in N₂/CO₂ and air packages.     

Microbiology of a Ham-Type Product Made from Soy-Extended Cured Beef and Inoculated with Clostridium sporogenes PA3679

The microbiological stability of a new ham-type product made from soy-extended cured beef was examined under wholesale (2–4°C) and retail (5°C) refrigerated storage conditions, and during abuse-temperature holding for 24 and 48 hr at 24-25°C after inoculation with Closrridium sporogenes PA3679. No microbiological effects (P >0.05) could be attributed to the level of soy protein isolate in the injection brine (0, 5, 7.5 or 9%) on the basis of mesophilic, psychrotrophic, anaerobic and lactic bacterial counts. Samples held at 2-4°C did not exceed 10⁴ CFU/g after 4 wk for any bacterial type examined. Product shelf-life was > 3 wk at 5°C and 2 wk at 8–10°C. Inoculated PA3679 did not grow in the product during 24 or 48 hr simulated mishandling (24-2°C).     

EFFECT OF CURING INGREDIENTS, SKINNING, AND BONING ON YIELD, QUALITY, AND MICROFLORA OR COUNTRY HAMS

Green hams were left intact, partially skinned, fully skinned, and fully skinned and boned. They were dry-cured with or without nitrate and aged 3 months. The presence of nitrate had no effect on the variables studies. Percent moisture loss and accompanying weight loss increased with each further removal of protective fat and skin. Percent residual salt was in proportion to weight loss. Residual nitrite was low for all groups Color and aroma scores were similar for all groups. General appearance scores, however, were lowest for the drier boneless group. Shear values were greatest while organoleptic flavor and over-all satisfaction scores were lowest in the boneless group. Tenderness scores were similar for the skinless and boneless group but both were lower than for the intact or partially skinned groups. In general, microbial counts were highest for surface samples from completely skinned fresh hams and lowest for partially skinned fresh hams. Higher counts were obtained for core samples from boneless fresh hams than for intact hams. Aerobic (26° and 37°C), lactobacilli, enterococci. streptococci. yeast and mold surface, and core counts tended to decrease during the manufacture of aged dry-cured hams. No trends in counts due to ham group or cure treatment were observed during the manufacturing process. At the end of the aging period none of the hams contained bacteria of public health significance. Aged dry-cured hams of acceptable microbial quality can be manufactured using intact, partially skinned, skinned or boneless fresh hams without potassium nitrate as part of the cure mixture.     

Browning Susceptibility and Changes in Composition During Storage of Carambola Slices

Browning and changes in the composition of sliced and whole carambola (Averrhoa carambola L.) fruit during storage were investigated. Susceptibility to browning after slicing, packaging and storage for 4 wk at 4.4°C varied considerably between four cultivars and five selections. There was no difference in browning susceptibility between fruit harvested at mature green or breaker stages of maturity. Freshly sliced carambola browned only slightly when exposed to air, but packaged slices that had been stored for 2 or more wk at 4.4°C browned rapidly (within 6 hr) when exposed to air. Whole fruit stored at 4.4°C for up to 6 wk, then sliced, showed much less susceptibility to browning. Ascorbic acid decreased and polyphenoloxidase activity increased in carambola slices during storage, but less in whole fruit. Treating slices with 1.0 or 2.5% citric acid + 0.25% ascorbic acid (in water) prior to packaging was very effective in limiting browning.     

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.     

Effects of Frozen Storage on Survival of Staphylococcus aureus and Enterotoxin Production in Precooked Tuna Meat

This study investigated the survival of Staphylococcus aureus in precooked tuna meat for producing canned products during frozen storage (?20 ± 2 °C) as well as its growth and enterotoxin production at 35 to 37 °C after the storage. Samples (50 ± 5 g) of precooked albacore (loin, chunk, and flake) and skipjack (chunk and flake) tuna were inoculated with 5 enterotoxin‐producing strains of S. aureus at a level of approximately 3.5 log CFU/g and individually packed in a vacuum bag after 3 h incubation at 35 to 37 °C. Vacuum‐packed samples were stored in a freezer (?20 ± 2 °C) for 4 wk. The frozen samples were then thawed in 37 °C circulating water for 2 h and incubated at 35 to 37 °C for 22 h. Populations of S. aureus in all precooked tuna samples decreased slightly (<0.7 log CFU/g) after 4 wk of storage at ?20 ± 2 °C, but increased rapidly once the samples were thawed and held at 35 to 37 °C. Total S. aureus counts in albacore and skipjack samples increased by greater than 3 log CFU/g after 6 and 8 h of exposure to 35 to 37 °C, respectively. All samples became spoiled after 10 h of exposure to 35 to 37 °C, while no enterotoxin was detected in any samples. However, enterotoxins were detected in albacore loin and other samples after 12 and 24 h of incubation at 35 to 37 °C, respectively. Frozen precooked tuna meat should be used for producing canned tuna within 6 to 8 h of thawing to avoid product spoilage and potential enterotoxin production by S. aureus in contaminated precooked tuna meat.     

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.     

Shelf Life and Quality of Freshly Squeezed, Unpasteurized, Polyethylene-Bottled Citrus Juice

Florida's chief orange and grapefruit cultivars were used to produce five freshly squeezed, unpasteurized, polyethylene-bottled juices using commercial conditions. Juices were stored at different temperatures. Shelf life depended primarily on storage temperature: ?1.7°C, 20–23 days; 1.1°C, 16–22 days; 4.4°C, 10–16 days; and 7.8°C, 5–8 days. Staleness was the primary off-flavor limiting shelf life at the three lower temperatures while spoilage with diacetyl was primarily responsible at 7.8°C. At the three lower temperatures, microbial counts generally decreased markedly during storage, while at 7.8°C, an increase was generally noted. Ascorbic acid retention after 2 wk of storage at the three lowest storage temperatures was about 91–93% for two orange juices and 86–88% for the grapefruit juice.     

Shelf‐Life Study of an Orange Juice–Milk Based Beverage after PEF and Thermal Processing

ABSTRACT: The effect of thermal and pulsed electric field (PEF) processing on the shelf life of an orange juice–milk beverage (OJMB) was studied. The intensities of the treatments were selected to produce similar inactivation of pectin methyl esterase (PME), an enzyme responsible for the jellification and loss of fresh juice cloudiness. Physical properties (pH, °Brix, and color), microbial population, PME activity, and volatile compounds of the product were analyzed during a 4‐wk storage at 8 to 10 °C. The pH was not affected by any treatment but decreased during the storage in the untreated sample. The °Brix values were decreased by the 2 treatments. The thermal and PEF treatments initially inactivated PME activity by 90%. During storage, the PME activity remained constant in the 2 treated samples and decreased slightly in the untreated sample. The reductions in bacterial as well as yeast and mold counts were similar after the 2 treatments (4.5 and 4.1 log CFU/mL for thermal against 4.5 and 5 log CFU/mL for PEF). Based on the initial bacterial counts of the control, it was estimated that the shelf lives of the OJMB treated with thermal and PEF processing stored at 8 to 10 °C were 2 and 2.5 wk, respectively. Differences were observed in the color parameters of the OJMB between the 2 treatments in comparison with the control, with a higher difference observed in the thermally processed samples. The relative concentration of volatile compounds was higher in OJMB processed by PEF treatment than that in the thermally processed sample. During storage, the loss of volatile compounds was lower in the PEF sample while thermal and control samples had a similar rate of loss. For an OJMB, treatment with PEF achieved the same degree of microbial and enzyme inactivation as the thermal treatment, but better preserved color and volatile compounds.     

Effect of Tumbling and Tumbling Temperature on Total Aerobic Plate Counts (Incubated at 25°C) and Quality of Boneless, Cured Hams

The effects of intermittent tumbling (up to 18 hr) and processing temperature (25°C or 3°C) on internal temperature and exudate total aerobic plate counts incubated at 25°C (ATPC) in boneless, cured hams were determined. The design used 80 hams in five replicates involving four treatment groups (tumbled at 25°C tumbled at 0°C, control held at 25°C and control held at 0°C). The significant (P < 0.01) tumbling effect on the rise in internal ham temperature occurred after 3 hr, but only accounted for a difference of 1.26°C-1.32°C, independent of processing temperature. While tumbling significantly improved the cooked yield by 3.45%, processing at 25°C rather than at 0°C resulted in a significant (P<0.05) yield reduction of 2.15% after 9 hr of processing. The exudate ATPC was significantly (P<0.01) reduced after 18 hr of tumbling.     

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.     

Storage Study of a Gas-Packaged Bakery Product

English style crumpets were packaged in the atmosphere of CO₂ and N₂ (3:2) and stored at 20°, 22°, 24° and 30°C. In all cases, package volume and headspace CO₂ concentration decreased during the first week of storage. At 30°C, the volume started to increase after 12 days due to production of CO₂ and other metabolites by microorganisms. At 24°C, the volume did not start to increase until after 25 days, while at 22° and 20°C it remained stable or gradually decreasing. Aerobic plate counts and metabolites were higher in the product stored at 30°C for 19 days than those stored at 20°C for 1 month. Product pH after 1 month at 20°C was lower (5.9) than that at 30°C for 19 days (6.5) due, essentially, to the absorption of CO₂.     

Effects of packaging type, gas atmosphere and storage temperature on survival and growth of Listeria spp. in shredded dry coleslaw and its components

The survival and growth of Listeria populations inoculated on to dry coleslaw mix and its components were investigated, focusing on effects of storage temperatures and gas atmospheres within packaging films or storage chambers. There were few significant effects of packaging film at 3 °C, but at 8 °C the elevated CO₂/low O₂ atmospheres generated within orientated polypropylene (OPP) packages and used in controlled atmosphere chambers were inhibitory. Although two strains of Listeria monocytogenes had survival characteristics comparable with Listeria innocua, L. monocytogenes ATCC 19114 survived better at 3 °C and also in the elevated CO₂/low O₂ atmospheres within OPP at 8 °C. The effects of product components on the survival of L. innocua were linked to storage temperature. Shredded carrot reduced initial counts and at 8 °C inhibited survival of L. innocua in comparison with shredded cabbage.     

Mackerel Cathepsins B and L Effects on Thermal Degradation of Surimi

During surimi processing, cathepsins B and L activities in minced, leached and NaCl-ground meats were 6.02, 5.23, and 4.07 units/g, respectively. About 80% activity remained in surimi after 8 wk storage at ?40°C suggesting that these proteinases were stable and difficult to remove. At 40°～ 55°C, pH 6.5 ～ 7.5, cathepsins B and L and purified cathepsin B had high hydrolytic activity on myosin heavy chain (MHC). The strength of surimi gel with cathepsins B and L or with purified B decreased (p < 0.05) after 2 hr incubation at 55°C. This suggested that the residual cathepsins B and L had MHC-degrading activity and consequently caused gel softening.     

Antioxidant properties and shelf‐life extension of fresh‐cut tomatoes stored at different temperatures

BACKGROUND: The feasibility of using modified atmosphere packaging (5 kPa O₂ + 5 kPa CO₂) to maintain the antioxidant properties of fresh‐cut tomatoes during shelf‐life was assessed through storage at different temperatures (5, 10, 15 and 20 °C). Health‐related compounds, antioxidant capacity, microbiological counts, physicochemical parameters and in‐package atmosphere of tomato slices were determined. RESULTS: Initial lycopene, vitamin C and phenolic contents and physicochemical parameters of tomato slices were well maintained for 14 days at 5 °C. Lycopene and total phenolic contents were enhanced over time in tomato slices stored at 15 and 20 °C. However, this increase in antioxidant compounds of fresh‐cut tomatoes during storage may be associated with excessive amounts of CO₂ (R² = 0.5679–0.7328) in the packages due to microbial growth. Although keeping tomato slices at temperatures above 10 °C increased their antioxidant content, the shelf‐life of the product was reduced by up 4 days. CONCLUSIONS: A storage temperature of 5 °C is appropriate for maintaining the microbiological shelf‐life of fresh‐cut tomatoes for up to 14 days and also allows the antioxidant properties of tomato slices to be retained over this period, thus reducing wounding stress and deteriorative changes. Copyright © 2008 Society of Chemical Industry     

Stability of Shredded Mozzarella Cheese Under Modified Atmospheres

Stability of Mozzarella cheese was studied under 8 modified atmospheres (air, vacuum and mixtures carbon dioxide/nitrogen) during 8 wk. Samples, packaged in barrier bags and stored at 10°C, were periodically evaluated to investigate microbiological quality and composition of headspace gases. Both consumption of oxygen and production of carbon dioxide occurred in many packages. Modified atmospheres containing carbon dioxide efficiently stabilized lactic and mesophilic flora, while inhibiting staphylococci, molds and yeast. Psychrotrophs grew in all samples but were less numerous in high CO₂ atmospheres. Levels of 75%CO₂ were optimal to repress undesirable organisms and reduce gas formation.     

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.     

Fate of Listeria innocua during production and ripening of smeared hard cheese made from raw milk

The fate of 2 different Listeria innocua strains was analyzed during the production and ripening of smeared raw milk Greyerzer cheese (Gruyère). These strains were used as surrogates for the pathogenic Listeria monocytogenes, as they are physiologically very similar. Bacterial cells were added to the cheese milk at levels of 10⁵ cfu/mL. During the first 24 h of cheese making, the number of the test strains decreased to a level of below 10² cfu/g. Obviously, the cooking temperature of 56°C and the subsequent slight temperature decrease to 50°C within 70 min contributed to a distinct reduction of Listeria counts. The counts in the cheese cores did not exceed 10³ cfu/g within 12 wk of cheese ripening and Listeria was not detectable after 24 wk. In contrast to the cores of the cheeses of the 4 batches in this study, their rinds always contained a high listerial load of approximately 10⁶ to 10⁸ cfu/g throughout the entire ripening period. The smeared surface showed an increase of pH to alkaline values, corresponding to smear microbiota development. Coryneforms and Staphylococcus counts were stable at >10⁷ cfu/cm² over 175 d, whereas yeast counts decreased to about 10⁵ cfu/cm² at the end of ripening. The study shows that the smear culture had no noticeable anti-listerial potential. When removing the rind or portioning such smeared cheese loaves with a cutting device, a postprocess contamination of the core might occur, thus presenting a major hygienic risk.     

Pectolytic Enzyme Activity During Intermittent Warming Storage of Peaches

Pectin enzyme evolution in peaches intermittently warmed at 15°C (15°C-IW) and at 20°C (20°C-IW) for 24 hr every 8 days of storage at 0°C, was followed. Cold storage increased PME activity until a constant level was reached, whereas PG decreased after 2 wk. 15°C-IW had a similar effect to conventional cold storage. 20°C-IW induced a different behavior, PG activity increasing and PME activity decreasing after 2 wk of storage. This different behavior seemed to be related to the development of chilling injury, since 15°C-IW did not alleviate chilling injury but 20°C-IW did. Chilling injury development during storage was associated with continuous PME activity and inhibition of endo-PG activity after the second week of storage, regardless of exo-PG activity.