Effects of Packaging Method, Display Light and Storage Time On The Microbial Growth and Rancidity of Fresh Pork

Effects of display light, packaging methods and storage time on total aerobic, lipolytic and proteolytic counts and oxidative rancidity of fresh pork stored at 2 ± 1° C were studied at the initial, 7th, 14th and 21st day of storage. Display light significantly increased the total aerobic psychrotroph count. Effects on lipolytic and proteolytic psychiotroph counts were not significant. No anaerobic psychrotrophs were encountered. Total and proteolytic counts of PVC film overwrapped chops and proteolytic and lipolytic psychrotroph counts of chops vacuum packaged accelerated linearly with time. Increases in lipolytic psychrotroph count of PVC packaged and total aerobic psychrotroph count of vacuum packaged chops were quadratic. TBA number and rancid odor scores were not significantly affected by treatments.     

Effect of Packaging Film and Vacuum Level on Regular and Sorbate-Cured Bacon

Bacon was produced with either 40 ppm NaNO₂/0.26% potassium sorbate, or 120 ppm NaNO₂. Slices were packaged in either nylon/Surlyn or nylon/Saran/Surlyn pouches and sealed at either a high or intermediate vacuum level. At 0, 10, 21 and 28 days after packaging, residual nitrite, rancidity, pH, residual salt and pigment conversion were measured. Residual nitrite and pH were lower while nitrosopigment conversion was higher in bacon packaged with the high-barrier film. Vacuum level, however, had no effect on any measured characteristic. The sorbate/reduced nitrite cure resulted in lower pigment conversion, lower residual nitrite, and a higher TBA number.     

Nisin、姜油协同高氧气调包装熟肉保鲜效果的研究

将熟猪肉采用Nisin和姜油处理,结合60%O2+20%CO2+20%N2和80%O2+20%CO2高氧气调包装,于低温和常温条件下贮藏,研究高氧气调包装对熟猪肉制品的保鲜效果,以空气包装的熟肉制品为对照。结果表明:高氧气调包装可显著抑制熟肉制品贮藏期间菌落总数的上升和感官品质的下降,贮藏后期能有效抑制TBA值的上升,防止肉制品的氧化;0.05%乳酸链球菌素、0.08%姜油结合80%O2+20%CO2高氧气调包装,可使肉制品达到最佳的保藏效果,低温下(0～4℃)至少可以保藏28d,常温下可以保藏15d。     

FLAVOR ADJUNCTS FOR RESTRUCTURED PORK

Boneless prerigor pork shoulders were processed to restructured pork chops and formulated with 1% NaCl and .25% sodium tripolyphosphate (STP). Formulations included (1) 100% pork (C), (2) 95% pork - 5% rehydrated dried apples (A), (3) 95% pork - 5 % mushroom slurry (M), and (4) 99.98% pork -.02% liquid smoke extract (S). All samples were stored at -20°C until evaluation at 0, 14 and 42 days after packaging. Although the C chops received higher initial color scores, color of the A samples remained more stable during storage. The Hunter ‘a’ values followed a similar trend. Flavor enhancers and storage times that were evaluated had a minimal effect on product cohesiveness and tenderness. Rehydrated dried apples and the mushroom slurry appeared to be potential flavor enhancers; whereas, liquid smoke appeared to be a flavor protector by retarding oxidative rancidity development after frozen storage for 42 days.     

Effect of Salt, Sugar and Storage Time on Microbiological, Chemical and Sensory Properties of Chinese Style Dried Pork

A Chinese dried pork product was manufactured with combinations of 15, 22.5, and 30% sugar and 0.5, 1.5, and 2.5% salt and evaluated for microbiological, chemical and sensory properties at 0, 7, 14, and 21 days of storage. Aerobic and anaerobic plate counts and TBA values increased during storage with the high sugar and salt combination resulting in the least microbial growth. No major rancidity problems developed. A 30% sugar and 2.5% salted product resulted in the highest panel flavor scores when evaluated by a group of panelists from the Orient.     

The oxidative stability of lard at −20°C: Evidence for a synergistic prooxidant effect of copper and curing salts

In connection with an interest in the problem of rancidity development in cold-stored cured meat products (particularly bacon), the effect of certain trace components and permitted food additives on the oxidative stability of model systems containing lard was examined. Lard, to which additions of various single additives or combination of additives had been made, was stored for periods of up to 16 weeks at ?20°C. Samples were removed during this time to assess the extent of their oxidation by chemical analysis (peroxide value determination) and sensory evaluation (odour). The additives studied included water, sodium chloride, sodium nitrate, sodium nitrite and copper (as palmitate, acetate and sulphate). It was observed that there was progressive oxidative deterioration of the lard with noticeable rancidity developing after 8 to 16 weeks' storage at ?20°C when water, sodium chloride, sodium nitrate, sodium nitrite and copper were present in combination.     

Effect of frozen and dried leek on processing and quality characteristics of Greek traditional sausages

Blanching of leek at boiling temperature for 1min reduced (p<0.05) the nitrate content. Freezing of leek at -18°C and storage for 5 months, with or without vacuum, also reduced (p<0.05) the nitrate content, while drying at 85°C for 2h and storage for 5 months, with or without vacuum, had no effect (p>0.05) on nitrate content. Frozen leek as a whole plant was unsuitable for the production of traditional sausages. The most appropriate level of dried leek for sausage production was 20g/kg of meat mixture. The nitrate content of sausages with frozen and dried leek ranged on the 7th day from 24.5±14 to 36.3±13ppm and the nitrite content from 1.4±0.4 to 2.6±1ppm. Sausages with dried leek had better (p<0.05) colour, higher (p<0.05) pH and lower (p<0.05) TBA values. Sausages with frozen and dried leek had the same (p>0.05) sensory attributes as those produced with fresh leek. Vacuum packaging affected (p<0.05) the odour of fresh sausages with frozen and dried leek and the overall acceptability of fresh sausages with frozen leek. Sausages with frozen and dried leek stored under vacuum had higher scores for sensory attributes, which were not always significant.     

Monitoring of nitrite and N-nitrosamine levels in irradiated pork sausage

Residual nitrite and N-nitrosamine levels were monitored on irradiated emulsion-type cooked pork sausage in aerobic or vacuum packaging states during storage. The sausage was irradiated at 0, 5, 10, and 20 kGy and stored at 4 degrees C for 4 weeks. The residual nitrite levels were significantly reduced by gamma irradiation (P < 0.05), whereas the vacuum packaging was more effective for nitrite reduction than aerobic packaging during storage. N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine (NPYR) levels were significantly reduced in the vacuum packaged sausage irradiated with 20 kGy after 4 weeks. Reduction of NPYR in aerobically packaged sausage was also found after 4 weeks by irradiating with a 5-kGy or higher dose. NDMA reduction was shown in vacuum packaging and irradiation at 20 kGy. Gamma irradiation was effective in reducing the residual nitrite all throughout storage and N-nitrosamines in sausage after storage.     

Effect of light on colour and reaction of nitrite in sliced pork bologna under different chilled storage temperatures

The effect of different lighting conditions (darkness and exposure to 1900 ± 100 lux) on colour stability, conversion of added nitrite (residual nitrite, nitrite converted to nitrate, nitroso heme pigments, and protein-bound nitrite) and oxidative rancidity (2-thiobarbituric acid index) in sliced, vacuum-packaged pork bologna as a function of storage temperature (0 ± 1°C and 7 ± 1°C) was studied. Colour (redness) losses over the storage period were more dependent upon photochemical processes than on thermal processes, and the action of temperature on colour was attributable to its effect on microbial growth, which in turn also affects oxygen availability. Conversion of nitrite into the different fractions studied was chiefly temperature-dependent, but exposure to light lowered the residual nitrite content. Nevertheless, the effect of illumination on the constant rate of residual nitrite depletion was dependent on the storage temperature. Recovery of the added nitrite, i.e. the total of the nitrite in all the fractions combined, was highly dependent upon fluctuations in the residual nitrite levels and varied over the storage period. Under the conditions of the experiment, photo-oxidation did not appear to be a determining factor in lipid oxidation.     

Quality characteristics of Chinese sausages made from PSE pork

Chinese sausages made from normal and different levels of PSE pork (100% Normal, 50%Normal+50% PSE and 100% PSE) were vacuum-packaged and stored at 4 °C for 45 days. The composition, processing yield, pH value, thiobarbituric acid (TBA) value, water activity, lactic acid bacteria counts and sensory properties of the meat products were evaluated. PSE pork loins had lower pH value, water holding capacity, moisture, fat and myofibrillar proteins content, but higher L^* value, drip loss and protein content than normal pork. Sausages made from 100% PSE pork had lower pH value, processing yield, moisture and fat content, but higher protein content than those of the 100% Normal and the 50% Normal+50% PSE treatments. Water activity was higher in the 100% PSE treatment than in other treatments. No differences in lactic acid bacterial counts among these treatments were observed. The pH values and water activity of the meat samples decreased, while lactic acid bacterial counts increased with storage time. TBA values among these treatments were not significantly different; however, the increase% of TBA values was higher for the 100% PSE treatment. TBA values of all treatments remained relatively low during storage. Chinese sausages made with 50–100% PSE pork had lower sensory texture, flavor and overall acceptability scores than the control samples, but were of acceptable quality.     

Antioxidative activity of α-tocopherol in cooked and uncooked ground pork

The effect of α-tocopherol (0, 100, 200 ppm) on lipid oxidation either in cooked or uncooked ground pork was studied during aerobic storage at 4°C and -20°C. Lipid oxidation was measured using the 2-thiobarbituric acid (TBA) method and rancidity development was scored by a trained sensory panel. Alpha-tocopherol slowed the rate of oxidation in cooked ground pork stored at either 4°C or -20°C and uncooked samples refrigerated for extended periods of time (12 days). In cooked product stored at 4°C where oxidation development was intense and off-flavors were strong, panelists did not detect flavor differences due to treatments. But in cooked product stored at -20°C sensory results were consistent with TBA analysis. Pre-rigor grinding, known to induce a high pH and inhibit lipid oxidation in uncooked fresh pork, had no protective effect on lipid oxidation as measured by TBA values in cooked ground pork, regardless of storage condition. TBA numbers increased during storage of cooked product at 4°C with an increase in internal cooking temperature between 50°C and 80°C. Internal cooking temperatures of 70°C or higher induced a rapid rate of oxidation when stored at 4°C.     

Color and Oxidative Rancidity of Gamma and Electron Beam-Irradiated Boneless Pork Chops

Color and oxidative rancidity were determined for chilled (3 ± 2°C) and frozen (?17 ± 3°C) boneless pork chops packaged in vacuum or air and irradiated to an absorbed dose of 0, 1.5 or 2.5 kGy (chilled) or 0, 2.5 or 3.85 kGy (frozen) of electron beam or cobalt⁶⁰ irradiation. Irradiation of vacuum-packaged chops produced redder, more stable (color and rancidity) product. More pronounced oxidative rancidity and less stable display color were noted for samples irradiated in aerobic packaging. Irradiation source had varying but limited effects on color and rancidity. Optimum packaging conditions can control color and rancidity changes in boneless chops, thereby enabling irradiation to be a useful intervention technology.     

TBA Values, Sensory Characteristics, and Volatiles in Ground Pork During Long-term Frozen Storage: Effects of Packaging

Ground pork (30% fat) was packaged in vacuum bags (V), polyvinyl chloride film (P), Saran Wrap?(S), aluminum foil (A), or Saran?-aluminum foil combination (SA) and frozen at - 17°C for 13, 26, and 39 wk. Samples were analyzed for TBA value and pH. Volatiles were steam distilled, volatilized at 60°C, and 1 mL samples of headspace gas was analyzed using gas chromatography and mass spectrometry. Spectra for individual peaks on the total ion chromatograms were identified with spectra from known standards. Ground pork (cooked to 75°C) was evaluated by a trained sensory panel for flavor and texture. Rancid and acid odor and flavor scores and TBA values increased over time regardless of packaging treatment; however, V-packaged pork had lower scores and P-packaged had higher scores at all time periods than did that in other materials. Eighteen volatiles were identified and quantified using GC/MS; 3-hydroxy-2-butanone had the highest correlation coefficients with TBA value, odor, and flavor scores.     

Stability of Precured Beef Blends

Preblends of lean beef were prepared using 20% water, 75 ppm nitrite, 3 or 6% salt (based on raw meat wt.) and stored at – 10, 0 and 15°C for 3 days. The nitrite levels in preblends were drastically reduced at 15°C storage temperature; but, after the initial loss following nitrite addition, the residual nitrite remained almost unchanged for products stored at 0 and – 10°C. Samples stored at 15°C increased in microbial numbers during storage and neither 3% nor 6% salt prevented this increase. Samples at both salt levels stored at 0°C or – 10°C did not show a significant change in bacterial numbers during storage. Salt and storage temperature had a significant effect on TBA values, with 6% salt resulting in higher TBA values than 3% salt and storage at 15°C resulting in higher TBA values than storage at 0 or ?10°C.     

Lipid Oxidation in Ground Beef Patties as Affected by Time-Temperature and Product Packaging Parameters

Oxidative rancidity in fresh and stored ground beef samples was measured using a thiobarbituric acid (TBA) assay with antioxidant protection. The independent variables were fat concentration (15 or 30%), package type (polyethylene or vacuum-packaged), freezer storage temperature (-12.2°, -23.3° or -34.4°C) and storage time (4, 8, 12, 16, or 20 weeks). At the end of each storage time samples were thawed and TBA values were determined on the samples before and after cooking. TBA values increased during the first 12 to 16 weeks after which time it decreased for both the cooked and uncooked samples. The higher fat samples, packaged in polyethylene, had higher TBA values for both cooked and uncooked patties. Uncooked patties stored at - 12.2°C had higher TBA values than those stored at -23.3°C or -34.4°C but cooked sample TBA values showed no dependence on storage temperature.     

Effect of Packaging on Physical and Sensory Characteristics of Ground Pork in Long-term Frozen Storage

Effects of packaging materials on water-holding capacity (WHC), thaw and cook losses, TBA value, moisture and fat content, and sensory characteristics of ground pork held in frozen storage for 13, 26, or 39 wk were examined. Moisture and juiciness decreased and total losses (thaw + cook) increased over time regardless of packaging. WHC decreased most in PVC-packaged pork (fresh = 0.53, 39 wk = 0.17) and least for vacuum-packaged pork (39 wk = 0.25). After 39 wk TBA values were highest for PVC-packaged (2.98) and lowest for vacuum-packaged pork (1.16). Rancid and sour odors and flavors followed similar trends.     

Reduction of Carcinogenic N-Nitrosamines and Residual Nitrite in Model System Sausage by Irradiation

Gamma irradiation was used to reduce the N‐nitrosamines and residual nitrite in model system sausage during storage. Aerobic or vacuum packaged sausage was irradiated at 0, 5,10, 20, and 30 kGy. The residual nitrite levels were significantly reduced by gamma irradiation, and, in vacuum packaging, the reduction was dose dependent. The N‐nitrosodimethylamine of the sausage irradiated at 10 kGy or above reduced in aerobic packaging, while a dose of 20 kGy was needed in vacuum packaging. The N‐nitrosopyrrolidine reduction was found at 20 and 30 kGy‐irradiation. Results indicated that high dose irradiation (> 10 kGy) was needed to reduce the carcinogenic N‐nitrosamine and nitrite levels in pork sausage during storage.     

Effects of starter cultures and additives on the quality of Turkish style sausage (sucuk)

The effects of starter cultures and additives on the quality of Turkish style sausage (sucuk) were investigated during ripening and storage. Total aerobic plate counts (aerobic bacteria), mould and yeast counts, pH, thiobarbituric acid (TBA) value and biogenic amine formation were followed. Aerobic bacteria increased (P<0.05) during the first 10 days of ripening to 9.26 log CFU/g and they decreased (P<0.05) to 5.70 at the end of the storage. Larger reductions (P<0.05) were observed in sausages made with high levels of potassium sorbate, nitrite and nitrate than in those containing low levels of additives and those without additives at the end of storage. During the first 3 days of ripening, the pH values of all sausages decreased (P<0.05) from 5.98 to about 4.53. Later, the pH values increased slowly, due to decomposition of acids to an approximately constant value of about 5.20. TBA values were higher (P<0.05) in the sausages made without additives than in the others. Sausages prepared using high concentration of additives had lower (P<0.05) concentrations of biogenic amines than the others. Addition of starter culture with high concentration of additives (nitrite, nitrate, α-tocopherol, ascorbic acid, potassium sorbate, potassium pyrophosphate and di-potassium hydrogenphosphate) decreased the formation of biogenic amine.     

Effect of Packaging on Color and Physical Characteristics of Ground Pork in Long-term Frozen Storage

Ground pork, 30% fat, was packaged in 454g units in Cryovac bags heat scaled under vacuum (V), Saran Wrap? (S), aluminum foil (A), Saran? overwrapped with aluminum foil (SA), and polyvinyl chloride (PVC) and frozen 13, 26, or 39 wk at ? 17°C. TBA values increased over time regardless of packaging. Those materials that excluded oxygen delayed lipid oxidation longest. Red color (CIE a* value and % reflectance difference at 630 and 580 nm) decreased over time; this was greater on exterior than interior of the meat block. Materials that excluded oxygen prevented loss of red color during the first 26 wk storage. Changes in redness and TBA appeared unrelated to pH. Changes in L* and b* values did not appear related to packaging treatment or storage time.     

Time-dependent depletion of nitrite in pork/beef and chicken meat products and its effect on nitrite intake estimation

The food additive nitrite (E249, E250) is commonly used in meat curing as a food preservation method. Because of potential negative health effects of nitrite, its use is strictly regulated. In an earlier study we have shown that the calculated intake of nitrite in children can exceed the acceptable daily intake (ADI) when conversion from dietary nitrate to nitrite is included. This study examined time-dependent changes in nitrite levels in four Swedish meat products frequently eaten by children: pork/beef sausage, liver paté and two types of chicken sausage, and how the production process, storage and also boiling (e.g., simmering in salted water) and frying affect the initial added nitrite level. The results showed a steep decrease in nitrite level between the point of addition to the product and the first sampling of the product 24 h later. After this time, residual nitrite levels continued to decrease, but much more slowly, until the recommended use-by date. Interestingly, this continuing decrease in nitrite was much smaller in the chicken products than in the pork/beef products. In a pilot study on pork/beef sausage, we found no effects of boiling on residual nitrite levels, but frying decreased nitrite levels by 50%. In scenarios of time-dependent depletion of nitrite using the data obtained for sausages to represent all cured meat products and including conversion from dietary nitrate, calculated nitrite intake in 4-year-old children generally exceeded the ADI. Moreover, the actual intake of nitrite from cured meat is dependent on the type of meat source, with a higher residual nitrite levels in chicken products compared with pork/beef products. This may result in increased nitrite exposure among consumers shifting their consumption pattern of processed meats from red to white meat products.