Effects of Nitrite and Erythorbate on Clostridium perfringens Growth during Extended Cooling of Cured Ham.

To control the growth of Clostridium perfringens in cured meat products, the meat and poultry industries commonly follow stabilization parameters outlined in Appendix B, "Compliance Guidelines for Cooling Heat-Treated Meat and Poultry Products (Stabilization)" ( U.S. Department of Agriculture, Food Safety and Inspection Service [USDA-FSIS], 1999 ) to achieve cooling (54.4 to 4.4°C) within 15 h after cooking. In this study, extended cooling times and their impact on C. perfringens growth were examined. Phase 1 experiments consisted of cured ham with 200 mg/kg ingoing sodium nitrite and 547 mg/kg sodium erythorbate following five bilinear cooling profiles: a control (following Appendix B guidelines: stage A cooling [54.4 to 26.7°C] for 5 h, stage B cooling [26.7 to 4.4°C] for 10 h), extended stage A cooling for 7.5 or 10 h, and extended stage B cooling for 12.5 or 15 h. A positive growth control with 0 mg/kg nitrite added (uncured) was also included. No growth was observed in any treatment samples except the uncured control (4.31-log increase within 5 h; stage A). Phase 2 and 3 experiments were designed to investigate the effects of various nitrite and erythorbate concentrations and followed a 10-h stage A and 15-h stage B bilinear cooling profile. Phase 2 examined the effects of nitrite concentrations of 0, 50, 75, 100, 150, and 200 mg/kg at a constant concentration of erythorbate (547 mg/kg). Results revealed changes in C. perfringens populations for each treatment of 6.75, 3.59, 2.43, -0.38, -0.48, and -0.50 log CFU/g, respectively. Phase 3 examined the effects of various nitrite and erythorbate concentrations at 100 mg/kg nitrite with 0 mg/kg erythorbate, 100 with 250, 100 with 375, 100 with 547, 150 with 250, and 200 with 250, respectively. The changes in C. perfringens populations for each treatment were 4.99, 2.87, 2.50, 1.47, 0.89, and -0.60 log CFU/g, respectively. Variability in C. perfringens growth for the 100 mg/kg nitrite with 547 mg/kg erythorbate treatment was observed between phases 2 and 3 and may have been due to variations in treatment pH and NaCl concentrations. This study revealed the importance of nitrite and erythorbate for preventing growth of C. perfringens during a much longer (25 h) cooling period than currently specified in the USDA-FSIS Appendix B.

Dietary nitrate and nitrite: Benefits, risks, and evolving perceptions.

Consumers have an illogical relationship with nitrite (and its precursor, nitrate) in food. Despite a long history of use, nitrite was nearly banned from use in foods in the 1970s due to health concerns related to the potential for carcinogenic nitrosamine formation. Changes in meat processing methods reduced those potential risks, and nitrite continued to be used in foods. Since then, two opposing movements continue to shape how consumers view dietary nitrate and nitrite. The discovery of the profound physiological importance of nitric oxide led to the realization that dietary nitrate contributes significantly to the nitrogen reservoir for nitric oxide formation. Numerous clinical studies have also demonstrated beneficial effects from dietary nitrate consumption, especially in vascular and metabolic health. However, the latest wave of consumer sentiment against food additives, the clean-label movement, has renewed consumer fear and avoidance of preservatives, including nitrite. Education is necessary but may not be sufficient to resolve this disconnect in consumer perception.

Controlling Listeria monocytogenes and Leuconostoc mesenteroides in Uncured Deli-style Turkey Breast Using a Clean Label Antimicrobial.

Interest in natural/organic meat products has resulted in the need to validate the effectiveness of clean label antimicrobials to increase safety and shelf life of these products. A Response Surface Methodology (RSM) was used to investigate the effects of varying levels of moisture, pH, and a commercial "clean-label" antimicrobial (cultured sugar-vinegar blend; CSVB) on the growth rate of Listeria monocytogenes and Leuconostoc mesenteroides in uncured turkey stored at 4 °C for 16 wk. Twenty treatment combinations of moisture (60% to 80%), pH (5.8 to 6.4), and CSVB (2.5% to 5.0%) were evaluated during phase I to develop growth curves for both microbe types, whereas the interactive effects of pH (5.8 to 6.4) and CSVB (0.0 to 4.75) were tested in 16 treatment combinations during Phase II at a single moisture level using L. monocytogenes only. CSVB inhibited L. monocytogenes growth in 14 of the 20 treatments tested in Phase I and in 12 of the 16 treatments in Phase II through 16 and 8 wk, respectively. In contrast, CSVB had little effect on L. mesenteroides, with growth inhibited in only 4 of 20 treatments in Phase I and was therefore not tested further in Phase II. Significant interactions of the RSM design coefficients yielded a predictive model for L. mesenteroides growth rate, but due to lack of growth, no growth rate model was developed for L. monocytogenes. CSVB was found to be an effective antilisteral antimicrobial, while having little effect on a spoilage microorganism.

Modeling the Impact of Ingoing Sodium Nitrite, Sodium Ascorbate, and Residual Nitrite Concentrations on Growth Parameters of Listeria monocytogenes in Cooked, Cured Pork Sausage.

Sodium nitrite has been identified as a key antimicrobial ingredient to control pathogens in ready-to-eat (RTE) meat and poultry products, including Listeria monocytogenes. This study was designed to more clearly elucidate the relationship between chemical factors (ingoing nitrite, ascorbate, and residual nitrite) and L. monocytogenes growth in RTE meats. Treatments of cooked, cured pork sausage (65% moisture, 1.8% salt, pH 6.6, and water activity 0.98) were based on response surface methodology with ingoing nitrite and ascorbate concentrations as the two main factors. Concentrations of nitrite and ascorbate, including star points, ranged from 0 to 352 and 0 to 643 ppm, respectively. At one of two time points after manufacturing (days 0 and 28), half of each treatment was surface inoculated to target 3 log CFU/g of a five-strain L. monocytogenes cocktail, vacuum packaged, and stored at 7°C for up to 4 weeks. Growth of L. monocytogenes was measured twice per week, and enumerations were used to estimate lag time and growth rates for each treatment. Residual nitrite concentrations were measured on days 0, 4, 7, 14, 21, and 28, and nitrite depletion rate was estimated by using first-order kinetics. The response surface methodology was used to model L. monocytogenes lag time and growth rate based on ingoing nitrite, ascorbate, and the residual nitrite remaining at the point of inoculation. Modeling results showed that lag time was impacted by residual nitrite concentration remaining at inoculation, as well as the squared term of ingoing nitrite, whereas growth rate was affected by ingoing nitrite concentration but not by the remaining residual nitrite at the point of inoculation. Residual nitrite depletion rate was dependent upon ingoing nitrite concentration and was only slightly affected by ascorbate concentration. This study confirmed that ingoing nitrite concentration influences L. monocytogenes growth in RTE products, yet residual nitrite concentration contributes to the antimicrobial impact of nitrite as well.

Comparison of the Effect of Curing Ingredients Derived from Purified and Natural Sources on Inhibition of Clostridium perfringens Outgrowth during Cooling of Deli-Style Turkey Breast.

The antimicrobial impact of purified and natural sources of both nitrite and ascorbate were evaluated against Clostridium perfringens during the postthermal processing cooling period of deli-style turkey breast. The objective of phase I was to assess comparable concentrations of nitrite (0 or 100 ppm) and ascorbate (0 or 547 ppm) from both purified and natural sources. Phase II was conducted to investigate concentrations of nitrite (50, 75, or 100 ppm) from cultured celery juice powder and ascorbate (0, 250, or 500 ppm) from cherry powder to simulate alternative curing formulations. Ground turkey breast (75% moisture, 1.2% salt, pH 6.2) treatments were inoculated with C. perfringens spores (three-strain mixture) to yield 2.5 log CFU/g. Individual 50-g portions were vacuum packaged, cooked to 71.1°C, and chilled from 54.4 to 26.7°C in 5 h and from 26.7 to 7.2°C in 10 additional hours. Triplicate samples were assayed for growth of C. perfringens at predetermined intervals by plating on tryptose-sulfite-cycloserine agar; experiments were replicated three times. In phase I, uncured, purified nitrite, and natural nitrite treatments without ascorbate had 5.3-, 4.2-, and 4.4-log increases in C. perfringens, respectively, at 15 h, but <1-log increase was observed at the end of chilling in treatments containing 100 ppm of nitrite and 547 ppm of ascorbate from either source. In phase II, 0, 50, 75, and 100 ppm of nitrite and 50 ppm of nitrite plus 250 ppm of ascorbate supported 4.5-, 3.9-, 3.5-, 2.2-, and 1.5-log increases in C. perfringens, respectively. In contrast, <1-log increase was observed after 15 h in the remaining phase II treatments supplemented with 50 ppm of nitrite and 500 ppm of ascorbate or ≥75 ppm of nitrite and ≥250 ppm of ascorbate. These results confirm that equivalent concentrations of nitrite, regardless of the source, provide similar inhibition of C. perfringens during chilling and that ascorbate enhances the antimicrobial effect of nitrite on C. perfringens at concentrations commonly used in alternative cured meats.

Impact of Clean-Label Antimicrobials and Nitrite Derived from Natural Sources on the Outgrowth of Clostridium perfringens during Cooling of Deli-Style Turkey Breast.

Organic acids and sodium nitrite have long been shown to provide antimicrobial activity during chilling of cured meat products. However, neither purified organic acids nor NaNO2 is permitted in products labeled natural and both are generally avoided in clean-label formulations; efficacy of their replacement is not well understood. Natural and clean-label antimicrobial alternatives were evaluated in both uncured and in alternative cured (a process that uses natural sources of nitrite) deli-style turkey breast to determine inhibition of Clostridium perfringens outgrowth during 15 h of chilling. Ten treatments of ground turkey breast (76% moisture, 1.2% salt) included a control and four antimicrobials: 1.0% tropical fruit extract, 0.7% dried vinegar, 1.0% cultured sugar-vinegar blend, and 2.0% lemon-vinegar blend. Each treatment was formulated without (uncured) and with nitrite (PCN; 50 ppm of NaNO2 from cultured celery juice powder). Treatments were inoculated with C. perfringens spores (three-strain mixture) to yield 2.5 log CFU/g. Individual 50-g portions were vacuum packaged, cooked to 71.1°C, and chilled from 54.4 to 26.7°C in 5 h and from 26.7 to 7.2°C in an additional 10 h. Triplicate samples were assayed for growth of C. perfringens at predetermined intervals by plating on tryptose-sulfite-cycloserine agar. Uncured control and PCN-only treatments allowed for 4.6- and 4.2-log increases at 15 h, respectively, and although all antimicrobial treatments allowed less outgrowth than uncured and PCN, the degree of inhibition varied. The 1.0% fruit extract and 1.0% cultured sugar-vinegar blend were effective at controlling populations at or below initial levels, whether or not PCN was included. Without PCN, 0.7% dried vinegar and 2.0% lemon-vinegar blend allowed for 2.0- and 2.5-log increases, respectively, and ∼1.5-log increases with PCN. Results suggest using clean-label antimicrobials can provide for safe cooling following the study parameters, and greater inhibition of C. perfringens may exist when antimicrobials are used with nitrite.

The role of red and processed meat in colorectal cancer development: a perspective.

This paper is based on a workshop held in Oslo, Norway in November 2013, in which experts discussed how to reach consensus on the healthiness of red and processed meat. Recent nutritional recommendations include reducing intake of red and processed meat to reduce cancer risk, in particular colorectal cancer (CRC). Epidemiological and mechanistic data on associations between red and processed meat intake and CRC are inconsistent and underlying mechanisms are unclear. There is a need for further studies on differences between white and red meat, between processed and whole red meat and between different types of processed meats, as potential health risks may not be the same for all products. Better biomarkers of meat intake and of cancer occurrence and updated food composition databases are required for future studies. Modifying meat composition via animal feeding and breeding, improving meat processing by alternative methods such as adding phytochemicals and improving our diets in general are strategies that need to be followed up.

Inhibition of Clostridium perfringens growth by potassium lactate during an extended cooling of cooked uncured ground turkey breasts.

The U.S. Department of Agriculture's Food Safety and Inspection Service compliance guideline known as Appendix B specifies chilling time and temperature limits for cured and uncured meat products to inhibit growth of spore-forming bacteria, particularly Clostridium perfringens. Sodium lactate and potassium lactate inhibit toxigenic growth of Clostridium botulinum, and inhibition of C. perfringens has been reported. In this study, a cocktail of spores of three C. perfringens strains (ATCC 13124, ATCC 12915, and ATCC 12916) were inoculated into 100-g samples of ground skinless, boneless turkey breast formulated to represent deli-style turkey breast. Three treatment groups were supplemented with 0 (control), 1, or 2% potassium lactate (pure basis), cooked to 71 °C, and assayed for C. perfringens growth during 10 or 12 h of linear cooling to 4 °C. In control samples, populations of C. perfringens increased 3.8 to 4.7 log CFU/g during the two chilling protocols. The 1% potassium lactate treatment supported only a 2.5- to 2.7-log increase, and the 2% potassium lactate treatment limited growth to a 0.56- to 0.70-log increase. When compared with the control, 2% potassium lactate retarded growth by 2.65 and 4.21 log CFU/g for the 10- and 12-h cooling protocols, respectively. These results confirm that the addition of 2% potassium lactate inhibits growth of C. perfringens and that potassium lactate can be used as an alternative to sodium nitrite for safe extended cooling of uncured meats.

Ingested nitrate and nitrite and stomach cancer risk: an updated review.

Nitrite and nitrate are naturally occurring molecules in vegetables and also added to cured and processed meats to delay spoilage and pathogenic bacteria growth. Research over the past 15 years has led to a paradigm change in our ideas about health effects of both nitrite and nitrate. Whereas, historically nitrite and nitrate were considered harmful food additives and listed as probable human carcinogens under conditions where endogenous nitrosation could take place, they are now considered by some as indispensible nutrients essential for cardiovascular health by promoting nitric oxide (NO) production. We provide an update to the literature and knowledge base concerning their safety. Most nitrite and nitrate exposure comes from naturally occurring and endogenous sources and part of the cell signaling effects of NO involve nitrosation. Nitrosation must now be considered broadly in terms of both S- and N-nitrosated species, since S-nitrosation is kinetically favored. Protein S-nitrosation is a significant part of the role of NO in cellular signal transduction and is involved in critical aspects of cardiovascular health. A critical review of the animal toxicology literature of nitrite indicates that in the absence of co-administration of a carcinogenic nitrosamine precursor, there is no evidence for carcinogenesis. Newly published prospective epidemiological cohort studies indicate that there is no association between estimated intake of nitrite and nitrate in the diet and stomach cancer. This new and growing body of evidence calls for a reconsideration of nitrite and nitrate safety.

Validation of pepperoni process for control of Shiga toxin-producing Escherichia coli.

The objective of this study was to compare the survival of non-O157 Shiga toxin-producing Escherichia coli (STEC) with E. coli O157:H7 during pepperoni production. Pepperoni batter was inoculated with 7 log CFU/g of a seven-strain STEC mixture, including strains of serotypes O26, O45, O103, O111, O121, O145, and O157. Sausages were fermented to pH ≤4.8, heated at 53.3°C for 1 h, and dried for up to 20 days. STEC strains were enumerated at designated intervals on sorbitol MacConkey (SMAC) and Rainbow (RA) agars; enrichments were completed in modified EC (mEC) broth and nonselective tryptic soy broth (TSB). When plated on SMAC, total E. coli populations decreased 2.6 to 3.5 log after the 1-h heating step at 53.3°C, and a 4.9- to 5-log reduction was observed after 7 days of drying. RA was more sensitive in recovering survivors; log reductions on it were 1.9 to 2.6, 3.8 to 4.2, and 4.6 to 5.3 at the end of cook, and at day 7 and day 14 of drying, respectively. When numbers were less than the limit of detection by direct plating on days 14 and 20 of drying (representing a 5-log kill), no more than one of three samples in each experiment was positive by enrichment with mEC broth; however, STEC strains were recovered in TSB enrichment. Freezing the 7-day dried sausage for 2 to 3 weeks generated an additional 1- to 1.5-log kill. Confirmation by PCR revealed that O103 and O157 had the greatest survival during pepperoni productions, but all serotypes except O111 and O121 were occasionally recovered during drying. This study suggests that non-O157 STEC s trains have comparable or less ability than E. coli O157 to survive the processing steps involved in the manufacture of pepperoni. Processes suitable for control of E. coli O157 will similarly inactivate the other STEC strains tested in this study.

Human safety controversies surrounding nitrate and nitrite in the diet.

Nitrate and nitrite are part of the human diet as nutrients in many vegetables and part of food preservation systems. In the 1950s and 1960s the potential for formation of nitrosamines in food was discovered and it ignited a debate about the safety of ingested nitrite which ultimately focused on cured meats. Nitrate impurities in salt used in the drying of meat in ancient times resulted in improved protection from spoilage during storage. This evolved into their deliberate modern use as curing ingredient responsible for 'fixing' the characteristic color associated with cured meats, creating a unique flavor profile, controlling the oxidation of lipids, and serving as an effective antimicrobial. Several critical reports and comprehensive reviews reporting weak associations and equivocal evidence of nitrite human health safety have fostered concerns and debate among scientists, regulators, press, consumer groups, and consumers. Despite periodic controversy regarding human health concerns from nitrite consumption, a building base of scientific evidence about nitrate, nitrite, heme chemistry, and the overall metabolism of nitrogen oxides in humans has and continues to affirm the general safety of nitrate/nitrite in human health. As nitrite based therapeutics emerge, it is important to consider the past controversies and also understand the beneficial role in the human diet.

Determining the impact of varying levels of cherry powder and starter culture on quality and sensory attributes of indirectly cured, emulsified cooked sausages.

Indirect curing is a process that utilizes ingredients high in naturally occurring nitrate and a nitrate reducing bacterial starter culture (SC) to provide quality and sensory attributes similar to nitrite-added cured meats. The objective of this study was to determine the effects varying concentrations of starter culture and the addition of cherry powder (CP) had on improving quality and sensory attributes of indirectly cured sausages. Four treatments (TRTs) (TRT 1: low SC+no CP; TRT 2: low SC+CP; TRT 3: high SC+no CP; and TRT 4: high SC+CP) and a sodium nitrite-added (156 ppm) control were investigated. Residual nitrite levels throughout storage declined most rapidly in TRTs 2 and 4 (P<0.05). Few differences existed between TRTs and C for pH, objective color, or cured pigment concentrations. Consumer sensory panel scores revealed all treatment combinations were comparable (P>0.05) to the C for all sensory attributes.

Investigating the effect of incubation time and starter culture addition level on quality attributes of indirectly cured, emulsified cooked sausages.

A process of "natural curing" utilizes vegetable juice/powder and a nitrate reducing starter culture to generate cured meat characteristics. The objective was to determine the effect varying levels of a mixed-strain bacterial starter culture (SC) and incubation time (INC) had on the quality characteristics of indirectly cured sausages. Four treatments (TRT) (TRT 1: 0.01% SC, 0 min INC; TRT 2: 0.01% SC, 90 min INC; TRT 3: 0.02% SC, 0 min INC; TRT 4: 0.02% SC, 90 min INC) and a control (C) were investigated. TRTs 2 and 4, and C revealed higher (P<0.05) CIE a* redness values and greater (P<0.05) cured pigment concentrations than TRTs 1 and 3 at days 0 and 14 while TRTs 2, 3, 4, and C were also redder (P<0.05) than TRT 1 at days 28, 56, and 84. The results indicated the use of an incubation step was more critical than increasing the level of SC.