Ppm NaNO2 Research Articles

INVESTIGATIONS ON NITROSAMINE REDUCTION IN BONELESS HAMS PROCESSED IN ELASTIC RUBBER NETTINGS

ABSTRACTN‐Nitrosamines have been found in a wide variety of rubber‐containing products. Since many types of boneless hams are processed in elastic nettings made with rubber, the potential exists for forming nitrosamines. In this paper we report that addition of excess nitrite to outer surface ham and netting samples results in a significant increase in N‐nitrosodibenzylamine (NDBzA). Hams were then prepared with 100 ppm ingoing NaNO2 and compared to a standard cure of 200 ppm NaNO2. A highly significant reduction (p <0.01) in NDBzA (31 %) was noted in those made with the lower level of nitrite. In another series of experiments, hams were stored at either −2.2C or 2.2C, for up to six or 12 weeks, with the nettings on or off the ham. The overall results suggest that the level of NDBzA increased with netting contact time. Therefore it is advisable to remove the nettings after processing.

Bacteriology of Hot and Cold Boned Pork Preblends

Ground pork and preblends containing 2% NaCl or 2% NaCl plus 200 ppm NaNO2 were prepared from hot (HB) and cold (CB) boned pork in a commercial slaughtering plant. Total aerobic mesophiles, psychrotrophs, Enterobacteriaceae, salt tolerant, and lactic acid bacteria were enumerated in freshly ground meat and in preblends stored for 1 week at 2°C. Boning method had no effect on mesophillic, psychrotrophic, and salt tolerant counts in freshly ground meat, but Enterobacteriaceae and lactic acid bacteria were found in higher numbers in CB than HB meat (P < 0.05). Addition of salt plus nitrite led to the inhibition of most bacterial groups, although lactic acid bacteria were found in higher numbers in HB preblends after one week of storage (P < 0.05). The data revealed that HB pork preblends of excellent bacteriological quality and stability can be produced in an industrial context.

Comparison of Selective Direct Plating Media for Enumeration and Recovery of L. monocytogenes from Cold-process (smoked) Fish

Three selective media were evaluated for direct plating recovery and enumeration of Listeria monocytogenes in the presence of high levels of a variety of microorganisms occurring on cold-process (smoked) salmon products. Sliced salmon was brined to contain either no added salt, 3, or 5% water-phase NaCl, or 3 or 5% NaCl plus 140 ppm NaNO2. The slices were packaged in oxygen-permeable film or sealed under vacuum in oxygen-impermeable film, and stored at 10°C or 5°C until total microbial loads reached 106 to 109 CFU/g. Oxford formulation of Listeria selective agar and Lee's modification of Listeria selective agar achieved quantitative recovery of 102 cells per ml of L. monocytogenes strain Scott A in the presence of diluted slurries of these fish containing 104 to 108 CFU/ml of background organisms. A modification of lithium chloride-phenylethanol-moxalactam agar containing an iron-esculin indicator system sometimes failed because of interfering growth by the background microflora.

Effect of Sodium Nitrite on Growth of Shigella flexneri

A partial factorial design study of the effect of NaNO2 (0, 100, 200, 1000 ppm) in combination with NaCl (0.5, 2.5, 4.0%), pH (7.5, 6.5, 5.5), and temperature (37, 28, 19°C) on growth of Shigella flexneri is reported. Experiments were done aerobically in brain-heart infusion medium, using an inoculum of 1 × 103 CFU/ml. Growth curves were fitted from plate count data by the Gompertz equation; exponential growth rates, lag times, generation times, and maximum populations were derived for all variable combinations. In the absence of nitrite, the organism grew well under all test conditions at 37 and 28°C but did not grow at 19°C at pH 5.5 nor at pH 7.5 with 4% NaCl. Nitrite did not affect growth in media of pH 7.5 at 37 and 28°C. At pH 6.5 growth was inhibited by 1000 ppm NaNO2. The organism failed to grow at 19°C at all nitrite levels in the presence of 2.5 or 4.0% NaCl. The inhibitory effect of nitrite was much greater in media of pH 5.5 and increased with increasing salt levels. More inhibition was apparent at 28 than at 37°C. While lack of growth was used as a paradigm of the effect of nitrite on S. flexneri, nitrite also increased the lag and generation times and decreased the exponential growth rate. Results indicated that NaNO2 in combinations with low temperature, low pH, and high salt content can effectively inhibit the growth of S. flexneri.

EFFECTS OF NITRITE AND SULFANILAMIDE ON THE 2-THIOBARBITURIC ACID (TBA) VALUES IN AQUEOUS MODEL AND CURED MEAT SYSTEMS

The absorbance of the 2-thiobarbituric acid-malonaldehyde (TBA-MA) complex at 532 nm for aqueous model systems and cured meats were measured. Addition of sulfanilamide played a beneficial role in evaluating the oxidative state of cured meats, prepared with the addition of ≧ 100 ppm NaNO2, in that it prevented the underestimation of the TBA values. However, in the absence of nitrite, sulfanilamide may interact with malonaldehyde to produce a 1-amino-3-iminopropene derivative. Fluorescence spectroscopic studies showed an excitation maximum at 395 nm and an emission maximum at 460 nm for the adduct of malonaldehyde and sulfanilamide. Therefore, the TBA test for the evaluation of the oxidative state of cured meats may only be used when the content of nitrite in the cure or final product is known.

Effect of Different Levels of Nitrite and Nitrate on the Survival of Listeria monocytogenes During the Manufacture of Fermented Sausage

The fate of L. monocytogenes during the fermentation of Finnish fermented sausage was examined. L. monocytogenes was able to survive during a 21 d fermentation of sausage with levels of nitrite and salt commonly used in the meat industry today (120 ppm NaNO2 and 3.0% NaCl). Initial numbers of Listeria (103 CFU/g and 105 CFU/g) decreased approximately 1 log 10 CFU/g during the manufacture. Increasing the levels of nitrite/nitrate to those used 30 years ago in meat products had a marked effect on the elimination of Listeria. The numbers of survivors in the sausages was reduced 2.0 log 10 CFU/g during the fermentation of 3 weeks with a combination of 200 ppm NaNO2 and 300 ppm KNO3. With 1000 ppm KNO3, the decrease was 3.3 log 10 CFU/g. L. monocytogenes could not be totally eliminated from highly contaminated sausage by increasing only the levels of nitrite and nitrate. Levels of these additives with best bacteriostatic effect on Listeria are no longer permitted in food.

Value Enhancement of Turkey Dark Meat Through Restructuring Techniques

Turkey dark meat (thigh) was flaked and randomly assigned to formulations: 1) 100% turkey, 2) 90% turkey plus 10% dry-cured ham and 3) 90% turkey plus 10% fresh ham. Products 1 and 3 received .5% NaCl, .5% sucrose, .25% sodium tripolyphosphate (STP), 60 ppm NaNO2,550 ppm sodium erythorbate, and .38% monosodium glutamate (MSG); Product 2 received only 90% of these ingredients because its dry-cured ham already contained salt and nitrite. Three replications of each formulation were mixed, preformed, freeze-tempered, pressed into the shape of boneless porkchops, thermally processed, and sliced into 10 mm-thick chops that were freezer wrapped, stored at −23.3 C, and evaluated at 0, 21, and 84 days. These partially cooked products contained moisture levels similar to previously reported raw products. Product 1 was rated more desirable on content and distribution of fat and on color than Products 2 and 3. Product 2 received higher panel ratings for juiciness and firmness than Products 1 and 3. Instron values indicated that fresh pork tended to improve tenderness. All products had acceptable storage characteristics. These data suggest that, with appropriate handling, manufacturing, and use of selected adjuncts, turkey dark meat can be the primary raw material for low fat, low salt restructured convenience foods.

Sensory and Chemical Characteristics of Pork Chops as Affected by Precooking, Curing and Frozen Storage

ABSTRACTFour processing procedures were compared as methods of reducing warmed‐over flavor (WOF) of pork chops during frozen storage for 84 days, These procedures were (1) oven‐broiled chops, (2) chops from loins precooked with no additives, (3) chops from loins cured with 0.5% salt and 40 ppm NaNO2 and precooked, and (4) chops from loins cured with 2% salt and 120 ppm NaNO2 and precooked. Samples were evaluated by the TBA test, Warner‐Bratzler shear, hydroxyproline assay and by sensory analysis after frozen storage at ‐18°C. Chops from the three precooked treatments were more tender than oven‐broiled chops. Nitrite inhibited WOF development of precooked chops during frozen storage and 40 ppm nitrite was nearly as effective as 120 ppm.

Effect of Sodium Chloride Levels in Frankfurters on the Growth of Clostridium sporogenes and Staphylococcus aureus

ABSTRACTFrankfurters were made with 100%, 80%, and 60% of the normal 2.5% added NaCl, plus 150 ppm NaNO2 and 430 ppm ascorbate. They were either untreated or inoculated with Staphylococcus aureus or Clostridium sporogenes and incubated at a moderate abuse temperature of 11°C for up to 11 days. A slightly more rapid growth of the natural flora was noted in the frankfurters containing 60% of the normal salt compared to those containing higher levels of salt. No outgrowth of clostridial spores occurred in any inoculated sample. Staphylococcal growth was slow and inconsistent, with no effect related to salt levels. Incubating frankfurters at higher tern. peratures showed that abuse temperature had a greater effect on total aerobic and staphylococcal growth than did the salt levels tested.

Inhibition of Clostridium botulinum Types A and E Toxin Formation by Sodium Nitrite and Sodium Chloride in Hot-Process (Smoked) Salmon

Sodium nitrite and NaCl were evaluated as inhibitors of outgrowth and toxin production by Clostridium botulinum types A and E in abuse-stored (25°C) hot-process salmon. Salmon steaks were brined in NaCl or NaCl plus NaNO2 and inoculated intramuscularly with spores. Steaks were then heated in a simulated hot-smoke process to internal temperatures of 62.8 to 76.7°C (145 to 170°F) for the final 30 min of a 3- to 4-h process, packaged in oxygen-impermeable film and stored at 25°C. During 7 days of storage, toxin production in steaks inoculated with 102 spores per g was inhibited by more than 3.8% water-phase NaCl for type E and 6.1% for type A. Presence of nitrite substantially reduced the salt level required to prevent toxin production. When steaks had more than 100 ppm NaNO2, only 2.5% NaCl inhibited type E toxin production; 150 ppm NaNO2 and 3.5% NaCl inhibited production of type A toxin. When storage time was lengthened to 14 days or the spore inoculum increased to 104 spores per g, more salt and nitrite were required for inhibition. Residual nitrite in samples stored under refrigeration (3.3°C) did not change during 22 days of storage. Under abuse temperature (25°C), residual nitrite decreased to less than 6 ppm by the 14th day in all samples tested regardless of the original nitrite concentration.

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

ABSTRACTBacon 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.

EFFECT OF METAL IONS ON RESIDUAL NITRITE

The effect of various metal ions on residual nitrite was studied in both a meat system and a model system. Reducing ability, nitrosylhemochrome, nitrate and pH were determined in an attempt to explain the mechanism of loss of nitrite in the system. The control meat system contained 2% NaCl and 156 ppm of NaNO2 while treatment groups had 0.05% of metal ions (Fe++, Fe+++, Cu++, Zn++, Ca++, and Mg++ as chloride salts) substituted for the same amount of NaCl. The results showed that ferrous (Fe++), ferric (Fe+++), cupric (Cu++) and Zinc (Zn++) ions caused a depletion of nitrite while calcium (Ca++) and magnesium (Mg++) ions did not have any effect on residual nitrite. The model system consisted of 25 mM PIPES buffer at pH 5.8 to which was added 156 ppm NaNO2 with or without 0.05% metal ions. Only ferrous (Fe++) ion decomposed more nitrite than the control after heating. Considering the results from both systems, the mode of action for each ion appeared to be different; ferrous ion appeared to act directly as an electron donor, ferric ion acted like ferrous after being reduced, cupic ion appeared to act as an electron donor after being reduced and then as an electron acceptor, and zinc ion seemed to be effective only by decreasing the pH of the system.

The accumulation of unacceptably high levels of nitrite in vacuum packed back bacon

SummaryBacks from two bacon weight pigs, one of high ultimate pH and the other of normal ultimate pH, were slice cured with either nitrate free or nitrate containing brines and then stored in vacuum packs. Microbiological conditions likely to occur in chemically similar bacons produced by the traditional Wiltshire method were produced in half the packs using an inoculum from mature Wiltshire bacon sides. Changes in nitrite concentration were followed in the M. longissimus dorsi and in the total slice during storage at 5°C. Although the initial levels of nitrite and nitrate (where added) in the total slice were within currently permitted limits, rapid conversion of nitrate, and with little or no nitrite depletion produced 380 ppm NaNO2 within the first week of storage in the inoculated bacon from the high pHu pig. The implications of these findings with regard to commercial practice are discussed.

EFFECT OF SORBIC ACID AND SODIUM NITRITE ON Clostridium botulinum OUTGROWTH AND TOXIN PRODUCTION IN CANNED COMMINUTED PORK

ABSTRACTExperiments to determine the effect of sorbic acid alone and in combination with low nitrite and phosphate on botulinal toxin production in inoculated perishable, canned, comminuted, cured pork were conducted. Forty‐eight test lots of product were inoculated with approximately 100 spores per gram of five strains each of type A and B Clostridium botulinum. Twenty‐five cans of each test lot were incubated at 27° C for up to 110 days. The time of swelling was recorded for each can and the first 10 swells per test lot were tested for toxin. Multiple regression analysis of the time to first swell showed nitrite concentration had a significant linear effect on delaying outgrowth and toxin production of C. botulinum. Sorbic acid concentration was also significantly related to inhibition but through the fourth power of sorbic acid concentration. The use of either sodium acid pyrophosphate or sodium hexametaphosphate was synergistic with sorbic acid as indicated by their statistically significant positive interactions. Several test lots containing 0.2% sorbic acid and either phosphate had no toxic swells after 110 days of incubation with or without 50 ppm NaNO2. These data indicate that sorbic acid may be a potential alternative preservative to high levels of nitrite in canned, comminuted pork products.

FACTORS AFFECTING INHIBITION OF Clostridium botulinum IN CURED MEATS

ABSTRACTGround pork trim was formulated with various levels of nitrite and one of two NaCl concentrations, canned and heated at 90, 100 or 110°C. Cured meats were similarly prepared with meat whose sulfhydryls had been reacted with silver ions. Antibotulinum activity in these cured products was tested by inoculating Clostridium botulinum spores directly into canned meats (96 spores/150g) or into homogenates (1:1, w/v) adjusted to 30 ppm NaNO2 (48 spores/16.5 ml). Antibotulinum activity was detected by both challenges. It was greater in meats cured with higher nitrite concentrations, was lower if processing was at high temperature (110 vs 90° C) and decreased during storage of the cured meats. Inhibitory activity was found in cured products made of silver‐treated meats.

Effect of Potassium Sorbate on Toxinogenesis by Clostridium botulinum in Bacon

In an effort to reduce the initial levels of nitrite used to cure bacon and still supply the botulinal inhibition expected in cured meats, bacon was produced at nitrite levels of 0 and 40 ppm NaNO2 with and without 0.13 and 0.26% potassium sorbate. This bacon was inoculated with 1100 spores per g of a mixture of five Type A and five Type B strains of Clostridium botulinum. The time for occurrence of the first swollen package and number of toxic swells were recorded over 110 days of incubation at 27 C. The above variables were compared to bacon containing 80 and 120 ppm NaNO2 as well as a commercial sample. Presence of potassium sorbate in the cure significantly reduced the number of toxic swollen packages occurring during incubation and lengthened the time before a toxic swollen package was observed. The presence or absence of 40 ppm NaNO2 appeared to have no significant effect on the sorbate inhibition of C. botulinum in bacon in this study. Microbial growth of uninoculated samples was also retarded by addition of potassium sorbate to the brine. Flavor panel evaluations indicated that potassium sorbate decreased preference slightly using experienced judges. Also, reduced occurrence of nitrosopyrrolidine with reduced nitrite was observed.

EFFECT OF NITRITE AND ERYTHORBATE ON RECOVERY OF Clostridium perfringens SPORES IN CURED PORK

ABSTRACTFresh pork shoulders were boned and ground through a 12.7 mm plate, packed in 1‐kg packages, frozen at −28.9°C and stored at −17.8°C for 2 wk. The frozen pork samples were thawed for 24 hr at 3°C, then blended with a curing mixture consisting of 6 parts of NaCl and 1 part sugar at a rate of 47.5g/kg of meat with erythorbate and NaNO2 added to give levels of 0,183, 366 or 550 ppm of erythorbate and 0, 50,100, 150 or 200 ppm nitrite in the meat. The pork was then inoculated at the rate of 11 spores of Clostridium perfringens (UK92)/g, packed in quart jars (500/g jar) and cured for 2 wk at 1‐4°C followed by 2 wk salt equalization at 12.8°C. Enumeration for C. perfringens began at this time and continued on alternate weeks during the 6‐wk aging period. Recovery of C. perfringens spores was significantly reduced by NaNO2. After 4 wk, 80% of the inoculated spores were recovered from samples with no added nitrite while only about one‐third of the spores were recovered from samples with the lowest level of NaNO2. Higher levels of nitrite and increased aging time reduced the number of spores recovered. At 10 wk, recovery was 38.0, 12.0, 5.4, 3.6 and 0.9% of inoculated spores, respectively, for 0, 50, 100, 150 and 200 ppm NaNO2. Sodium erythorbate had no significant effect on recovery of spores. Nitrite levels in the meat decreased rapidly with less than 60% of initial levels remaining after 24 hr. Only about 10% of initial concentrations were present after 4 wk. Results generally were similar for survival of C. perfringens spores and for nitrite losses when ground pork samples were dry‐cured in stockinettes and aged for the same time and at the same temperature as those cured in jars.

THE FATE OF SODIUM NITRITE IN BACON

ABSTRACTUsing 1 5 N‐labelled sodium nitrite cured pork bellies, with and without the addition of sodium ascorbate, we have attempted to trace the reaction pathways of nitrite in bacon. The depletion of nitrite, originahy at 156 ppm, was followed during the processing operation. Subsequent experiments during the storage of the 1 5 N labelled, sliced, vacuum packaged bacon showed the further depletion of nitrite in both the lean and adipose tissue portions, the lower nitrite levels being found in the bacon to which ascorbate had been added. The formation and depletion of nitrate was also noted. Analysis of the protein and lipid portions showed incorporation of 1 5 N into both. Mass spectral measurements showed that between 73 and 87% of the added 1 5 N remained in the bacon lean portion. The adipose portion contained much less 1 5 N, equivalent to between 20–25% of that added. A hot water extract of both lean and adipose fractions showed the presence of 1 5 N greater than the 1 5 N due to nitrite and nitrate. One effect of the addition of ascorbate was to force 1 5 N into water soluble compounds. Examination of connective tissue protein isolated from the adipose tissue portion showed incorporation of 1 5 N equivalent to 6 ppm NaNO2 in bacon without ascorbate compared to 2.5 ppm for bacon with added ascorbate. 1 5 N data also showed incorporation of approximately 25% of the added nitrite into the muscle proteins of both bacons, and incorporation of 10% of the added nitrite into the lipid fraction of the adipose tissue.

Nitrite in Meat Products Determined by Fluorescence Quenching of p-Aminobenzoate Ion

A direct fluorometric method is presented for determining nitrites in meat products by means of quenching. The extracted sodium nitrite is consumed in a diazotization reaction with a measured excess of the fluorescent reagent p-aminobenzoic acid (PABA) in boiling water and at pH less than or equal to 1.4. The amount of decrease in fluorescence (quenching) of PABA, in alkaline medium (pH 11.0) with excitation at 265 nm and fluorescence at 339 nm, is directly related to the amount of nitrite present. The slope for that standard curve is 1% decrease in relative fluorescence intensity per 2.76 ppm NaNO2. Results obtained for a series of 20 meat samples analyzed by this fluorometric method are in good agreement with results obtained by a colorimetric method with an average difference of +/- 6.1 ppm NaNO2.

STATUS OF THE RADAPPERTIZATION OF MEATS

Considerable progress has been made toward development of highly acceptable radappertized meats through application of a heat treatment to an internal temperature of 65–80 C to inactivate proteolytic enzymes before irradiation, low temperature (−30 ± 10 C) of the food during irradiation, and addition of low levels of tripolyphosphate and sodium chloride. To assure that radappertized meats are free of potential pathogens and spoilage microorganisms they are given a minimum radiation dose (MRD) computed to effect a 12 log cycle reduction in the most radiation resistant strains of Clostridium botulinum spores. Inoculated pack studies are carried out to obtain the specific microbiological data required for computing the MRD. Cured meats normally have a lower MRD than uncured meats. In model systems concentrations of sodium chloride (NaCl) up to 4.0% (w/v) present during irradiation had no effect on radiation resistance, but NaCl did inhibit recovery of irradiated spores. A mixture of salts (4.0% NaCl, 30 ppm NaNO2 500 ppm NaNO3) had essentially the same effect as NaCl alone. Of 11 genera of vegetative cells examined, Micrococcs radiodurans and Streptococcus faecium were shown to be the most resistant to low-temperature gamma irradiation. Before the radappertization process can be established commercially it is necessary to provide proof that products so treated are safe for human consumption. An intensive animal feeding study of radappertized (4.7–7.1 Mrads) beef was initiated in 1971 and is expected to be completed in 1976.