Nitrite-embedded packaging film was investigated for potential effects on the color stability of alternatively cured meats. The impact of nitrite-embedded film on color stability of large-diameter sandwich bologna was assessed over a 125-d lighted display period. Five treatments of large-diameter bologna were manufactured: (1) a conventionally cured control packaged with conventional film (“CON-CF”), (2) an alternatively cured formulation (cultured celery juice powder plus cherry powder) packaged with conventional film (“CJP-CF”), and (3) an alternatively cured formulation (cultured celery juice powder plus cherry powder) packaged with nitrite-embedded film (“CJP-NEF”). An additional alternatively cured formulation (4) Natpre T-10 EML Plus S was packaged with conventional film (“NT10-CF”) and (5) with nitrite-embedded film (“NT10-NEF”). In-package surface a* values were significantly higher (
The widespread consumer demand for alternatively cured meat products continues to rise, due to negative consumer perceptions of conventional, chemical sources of nitrate (NO3) and nitrite (NO2) as chemical preservatives. Alternatively cured meat products typically rely on natural sources of nitrate and/or nitrite, which are generally vegetable-based substitutes and which provide an alternative source of nitrate and nitrite that is perceived more positively by consumers. However, replacement of nitrate/nitrite with natural sources can lead to vegetable-like flavors and aromas in the final product (
An area of current research in meat packaging is active packaging, in which the package environment promotes a favorable interaction with the meat product (
This research did not include animal or human subjects and therefore did not require review and approval by institutional animal care or human subjects committees.
Three product formulations of all-beef, large-diameter sandwich bologna were manufactured in the Iowa State University Meat Laboratory, Ames, Iowa, to provide 3 different concentrations of ingoing nitrite. The 3 formulations were packaged in conventional and nitrite-embedded film films as follows. (1) The first formulation (“CON-CF”) was a conventionally cured control (nitrite from Modern Cure, with sodium erythorbate, both provided by A.C. Legg Inc., Calera, AL), which was vacuum packaged with conventional, high-barrier film that is commercially available (Sealed Air Corporation, Duncan, SC). The second (“CJP-CF”) and third (“CJP-NEF”) formulations were an alternatively cured bologna formulation utilizing nitrite from cultured celery juice powder (VegStable 506) and cherry powder (VegStable 515) supplied by Florida Food Products, Inc. (Eustis, FL), with (2) one-half of the batch (CJP-CF) vacuum packaged in conventional film and (3) the second half of the batch (CJP-NEF) vacuum packaged in nitrite-embedded film (Bemis Company Inc., a division of Amcor Flexibles North America, Oshkosh, WI) pouches. An additional alternatively cured formulation was produced using Natpre T-10 EML Plus S (Productos Sur, S.A. [Prosur], San Ginés, Murcia, Spain), with (4) one-half of the batch (“NT10-CF”) vacuum packaged in conventional film and (5) the second half of the batch (“NT10-NEF”) vacuum packaged in nitrite-embedded film pouches. The Natpre T-10 EML Plus S was chosen for this study because it was a commercially available alternative cure that provided a very low ingoing nitrite concentration for the bologna. The nitrite concentration for the Modern Cure (CON-CF) ingredient was 62,500 parts per million (ppm) sodium nitrite, which resulted in 156 ppm ingoing sodium nitrite for the bologna as formulated; the cultured celery juice powder (VegStable 506) ingredient (CJP-CF and CJP-NEF groups) contained 22,500 ppm sodium nitrite, which resulted in 99 ppm ingoing sodium nitrite; and the Natpre T-10 EML Plus S ingredient (NT10-CF and NT10-NEF groups) contained 1,700 ppm sodium nitrite, which resulted in 21 ppm ingoing sodium nitrite. Nitrite concentrations of Modern Cure and celery juice powder were provided by respective commercial ingredient suppliers, and the nitrite concentration of Natpre T-10 EML Plus S was determined by analysis using AOAC Method 993.30 (
Formulations for bologna treatments (as percent of meat block)
Ingredient | CON-CF | CJP | NT10 |
---|---|---|---|
Beef 80 trim | 67.00 | 67.00 | 67.00 |
Beef 50 trim | 33.00 | 33.00 | 33.00 |
Water/ice | 20.00 | 20.00 | 20.00 |
Salt | 2.000 | 2.00 | 2.00 |
Spices | 3.31 | 3.31 | 3.31 |
Modern Cure (6.25% NO2) | 0.25 | ||
Natpre T-10 EML Plus S | 1.25 | ||
VegStable 506 | 0.44 | ||
Sodium erythorbate | 0.05 | ||
VegStable 515 | 0.50 |
CON-CF = control (1) conventionally cured and vacuum packaged in conventional film.
CJP = formulation for treatments (2) CJP-CF and (3) CJP-NEF = alternatively cured with cultured CJP and packaged in conventional or nitrite-embedded film.
NT10 = formulation for treatments (4) NT10-CF and (5) NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and packaged in conventional or nitrite-embedded film.
CJF = celery juice powder.
The beef used for this study was harvested from market weight animals obtained from university farms, fabricated and frozen by the Iowa State University Meat Laboratory. The meat was stored frozen at −20°C until use, then thawed at 4.4°C for 2 d and moved into refrigerated storage at 1°C for 24 to 72 h. All treatments were processed separately using the same procedure. Replications were manufactured on separate, consecutive days, and the treatment processing sequence was randomized prior to production. Manufacturing and thermal processing of all treatments occurred on the same day for each replication. The slicing and packaging order of each treatment was conducted in the same order as production.
Beef raw materials were first ground through a 12.7-mm plate (Biro Manufacturing Company, Marblehead, OH). Each formulation consisted of 45.36 kg of meat including 14.97 kg of beef 50s and 30.39 kg of beef 80s. Lean (beef 80s) and fat (beef 50s) portions were mixed separately using a double action mixer (Leland Southwest, Fort Worth, TX) to ensure uniform distribution of fat and lean after grinding and to create a uniform blend of each. The lean ground beef (beef 80s) was then added to a vacuum bowl chopper (Kramer & Grebe GmbH and Co., KG, Biendenkopf-Wallau, Germany) along with salt, curing ingredient, half of the water/ice mixture, spices (A.C. Legg Inc., Calera, AL), and cure accelerator (if needed). For the experimental treatments of CON-CF, CJP-CF, and CJP-NEF, the cure accelerator (sodium erythorbate or cherry powder) was added to the spice blend and mixed prior to use. A cure accelerator was not included in the Natpre T-10 EML Plus S formulation. The mixtures were chopped until the batter temperature reached 4.4°C. The fat trimmings (beef 50s) were then added, along with remaining water/ice mixture, and chopping continued until the batter temperature reached 13°C. The meat batters were then moved to a vacuum stuffer (Handtmann VF 608 Plus, Lake Forest, IL) and stuffed into 14.25 cm × 114.3 cm pre-stuck fibrous casings (Kalle: 6.5 × 45 Fibrous N Clear, Kalle, Wiesbaden, Germany). Each bologna log was individually weighed, placed horizontally on a smoke rack, and moved into a smokehouse (Alkar, The Middleby Corporation, Elgin, IL) for thermal processing, which included application of smoke. All treatments were thermally processed together in the smokehouse for each replication. Thermal processing utilized a standard large-diameter bologna thermal processing schedule with stepwise temperature increases to reach internal product temperature of 71°C (approximately 6 h).
After cooking, the bologna logs were chilled overnight (approximately 19 h) at 1 ± 2°C. Subsequently, bologna logs were weighed for cooked and chilled yield measurements, casings were removed, and the product was sliced (Bizerba, Piscataway, NJ) into 6.35-mm-thick slices and packaged. Four slices were stacked and placed into either conventional vacuum packages (CON-CF, CJP-CF, NT10-CF) (2-mil thick with an oxygen transmission rate of 1.5–3.5 cm3/0.06 m2/24 h/1 atmosphere (atm) at 5°C and 0% relative humidity [RH]; water vapor transmission rate of 0.3–0.6 g/0.06 m2/24 h/1 atm at 38°C and 100% RH; Cryovac, Sealed Air Corporation, Duncan, SC) or nitrite-embedded film vacuum packages (CJP-NEF, NT10-NEF) (7-mil thick with an oxygen transmission rate of < 0.3 cm3/0.06 m2/24 h/1 atm at 23°C and 0% RH; water vapor transmission rate of < 0.5 g/0.06 m2/24 h/1 atm at 38°C and 100% RH; FreshCase, Bemis Company Inc., a division of Amcor Flexibles North America, Oshkosh, WI). The nitrite-embedded film was the same as that approved for use with fresh meat and included 113 mg of sodium nitrite per square meter of film. Both package types (conventional film, nitrite-embedded film) were vacuum sealed (Ultravac UV 2100 vacuum chamber packaging machine, UltraSource LLC, Kansas City, MO) and immediately stored at 1 ± 2°C under continuously lighted (24 h/d) simulated retail display conditions using white fluorescent lights (32W, 120V; Sylvania, Danvers, MA) for the duration of the study. Packages were placed in single layers on shelves, with each shelf having fluorescent lights suspended immediately above the packages. The light source was placed approximately 254 mm from the package surface, and illuminance was 2,200 ± 500 lx. Illuminance was measured using an URCERI Light Meter MT-912 (URCERI, Shenzhen Huanhui E-commerce company, Ltd, Shenzhen, China). Multiple locations throughout the storage area were selected for illuminance measurements. Sample locations were routinely rotated (every 3 wk) to provide uniform light exposure. Product packaging day was considered day 0 of the experiment.
Surface color and internal color of the stacks of slices were measured in 2 ways using Commission Internationale de l’Eclairage (CIE) L*a*b* color space (L* = lightness; a* = redness; b* = yellowness). For in-package color, measurements were done with the packaging film in place on the products. Unpackaged color was measured on the products after opening the packages and removing the packaging film. In both cases, color measurements were done on days 1, 6, 13, 27, 41, 55, 69, 83, 97, 111, and 125 following packaging. All color measurements were taken at a 10° observer angle, using illuminant D65 (daylight at 6,500 K), and a 2.4-cm aperture size, with a HunterLab MiniScan EZ 4500L colorimeter (Hunter Associates Laboratory Inc., Reston, VA). For unpackaged color measurements, a standard instrument calibration (with no film covering the black or white tiles) was used, and measurements were conducted by placing the HunterLab MiniScan EZ instrument nose cone directly onto the product surface. For the in-package surface measurements, a modified colorimeter standardization procedure was utilized, in which the white calibration tile was covered with the respective packaging material (conventional film or nitrite-embedded film). Product measurements were then taken by placing the nose cone of the HunterLab MiniScan EZ instrument directly onto the package. This process was used to more accurately measure the visual color of the packaged product as observed by consumers.
For unpackaged products, both surface and internal color were measured. One package per treatment (5), per sample day (11), per replication (2) was randomly selected for both surface and internal color measurement for a total of 110 packages measured during the display period. Measurements were done by opening the package, removing the slices, and subsequently measuring the surface of the top slice (slice directly exposed to light source) for unpackaged surface color as well as measuring the color at the interface of slices 2 and 3 of the 4-slice stack for the internal color measurement.
For in-package surface color (with the packaging film intact), 22 packages of each treatment and each replication were selected for repeated measurement of the same designated packages on each sample date for the duration of the display period. This generated a total of 220 measurements (22 packages × 5 treatments × 2 replications) of in-package color on each sampling day of the 125-d display period. The mean of the 3 measurements on each of the 220 packages for both in-package and unpackaged products was calculated and used to represent the color values of each package at each time point of the display period.
Residual nitrite analysis was done in accordance with AOAC Method 973.31 (
Residual nitrate analysis was conducted by Hormel Laboratories (Division of Hormel Foods, LLC, Austin, MN) using AOAC Method 993.30 (
Duplicate samples of raw batters and cooked products from each production batch were finely chopped using a food processor (KitchenAid, St. Joseph, MI) for measurement of fat, moisture, and protein content. Fat content was analyzed by the CEM ORACLE System (
Samples of raw batters and cooked products from each treatment were finely chopped using a food processor, as done for the proximate composition measurements. Ten grams of each sample were weighed into a beaker, and 90 mL of ambient-temperature distilled water were added. The meat and water were mixed thoroughly by hand with a glass stirring rod for 1 min, after which a filter paper disc (Whatman Grade 1, GE Health Care Life Sciences, Pittsburgh, PA) was folded and submerged into the sample. The pH of the filtered solution was measured with a Mettler Toledo SevenMulti pH meter (Mettler Toledo, Columbus, OH). Duplicate measurements of raw batters were done on the day of production, whereas the cooked products were measured in duplicate on day 14 following thermal processing and chilling of the products. The pH of some of the nonmeat ingredients included in the formulations was measured by first dispersing 5 g of each ingredient in 90 mL of distilled water, then measuring the pH as described previously.
Microbial populations of aerobic bacteria and of lactic acid bacteria on the products were monitored utilizing a shelf life procedure in which all treatments and replications were stored at 1°C ± 2°C. The analyses were conducted on days 0, 7, 14, 30, 60, 90, and 120. Eleven grams of sample was aseptically removed from each package, and 99 mL of 0.1% peptone water (Hardy Diagnostics, Category Number D299, Santa Maria, CA) was added, creating a 1:10 dilution. The samples were then placed into a WhirlPak filter stomaching bag (Nasco, Ft. Atkinson, WI), homogenized in a stomacher with the peptone water for 1 min, and serially diluted, with the first 10-fold dilution coming from the stomaching bag and the remaining dilutions (to extinction) consisting of 1 mL into 9 mL of 0.1% peptone water. Subsequently, total aerobic bacterial populations were enumerated in duplicate on Aerobic Count Petrifilm (3M Health Care, St. Paul, MN) following the manufacturer’s instructions. Petrifilms were incubated aerobically at 21°C for 72 h to assess total aerobes, and populations were determined following the manufacturer’s instructions. For lactic acid bacteria populations, enumeration was conducted anaerobically on the same days as the total aerobic populations and followed the procedure previously described, but with 0.1 mL of homogenized sample surface plated onto DeMan, Rogosa and Sharpe (MRS) agar (Becton, Dickinson and Company, Sparks, MD) in duplicate. Plates were incubated anaerobically at 31°C ± 2°C for 72 h before counting.
Due to the low bacterial growth observed during conventional storage at 1°C, an additional accelerated shelf life analysis was conducted to test the impact of the packaging environment on potential growth of spoilage bacteria. To achieve this, a spoilage inoculum of lactic acid bacteria was isolated from samples of commercial bologna. To create the inoculum, packages of 5 different commercial bologna products were purchased from retail stores. Two slices (approximately 60 g) were removed from each package, added to a bag with 1 L of tryptic soy broth (Becton, Dickinson and Company), and allowed to incubate at 20°C for 72 h. After incubation, 1 mL of broth was removed, added to 9 mL of MRS broth (Becton, Dickinson and Company), and incubated at 30°C for 48 h; 1 mL of the inoculated broth was then transferred to an additional 9 mL of MRS broth and again incubated at 30°C for 48 h. This bacterial transfer process was repeated 4 times. Finally, 1 mL of culture was added to 40 mL of MRS broth and incubated at 30°C for 48 h. Serial dilutions (to extinction) were made from the final culture and plated onto MRS agar to enumerate the population of the lactic acid bacteria inoculum. The culture was held at 1°C during this time. The culture was then diluted to achieve an approximate inoculation population of log103 colony-forming units (CFU)/g in the packages. The packages were inoculated with 1 mL of the spoilage inoculum by aseptic injection through a self-closing foam adhesive septum placed on each package. The inoculated packages were held at 10°C for the duration of the inoculation study. Inoculation occurred on day 158 post processing of the previously described products. For the inoculation study (denoted as I), day 158 post processing was designated as day 0(I). Analyses were conducted on days 0(I), 3(I), 6(I), 9(I), 12(I), 18(I), and 21(I) of storage at 10°C ± 2°C.
All microbiological data (conventional and inoculated shelf life) were collected and reported logarithmically as CFU/g.
The study was replicated twice, with replications produced on separate but consecutive days. The experiment was designed as a randomized complete block design with treatment (CON-CF, NT10-CF, CJP-CF, NT10-NEF, CJP-NEF) and replication as whole-plot factors and day as subplot factor, with factors arranged in a (2 × 2) + 1 arrangement. The data were analyzed using a mixed model with SAS version 9.4 (SAS Institute Inc., Cary, NC) in which treatment and day were fixed factors and replication was a random factor and the interaction of treatment × day was investigated. In addition, a Tukey-Kramer pairwise adjustment was included for repeated measures. Statistical significance was determined at
Means for raw and cooked proximate composition and yields of bologna treatments
Raw | Cooked | ||||||
---|---|---|---|---|---|---|---|
% Moisture | % Fat | % Protein | % Moisture | % Fat | % Protein | % Yield | |
60.9 | 21.8 | 13.6 | 57.6 | 24.7 | 16.8 | 92.3 | |
59.9 | 23.0 | 13.4 | 56.6 | 25.8 | 16.1 | 91.6 | |
59.9 | 23.0 | 13.4 | 57.0 | 25.0 | 16.1 | 91.6 | |
60.3 | 21.5 | 13.7 | 56.6 | 25.8 | 15.9 | 91.6 | |
60.3 | 21.5 | 13.7 | 56.5 | 25.1 | 16.4 | 91.6 | |
0.01 | 0.01 | 0.00 | 0.01 | 0.00 | 0.00 | 0.00 |
Means in the same column with different letters are significantly different (
CON-CF = control, conventionally cured and vacuum packaged in conventional film.
CJP-CF = alternatively cured with cultured celery juice powder and vacuum packaged in conventional film.
CJP-NEF = alternatively cured with cultured celery juice powder and vacuum packaged in nitrite-embedded film.
NT10-CF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in conventional film.
NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in nitrite-embedded film.
SEM = standard error of mean.
Mean treatment effects on proximate composition of raw and cooked bologna in addition to cooked yields (
Dependent Variable | Treatment | Day | Treatment × Day |
---|---|---|---|
Raw fat, % | — | — | |
Raw moisture, % | — | — | |
Raw protein, % | 0.133 | — | — |
Cooked fat, % | 0.162 | — | — |
Cooked moisture, % | 0.083 | — | — |
Cooked protein, % | — | — | |
Yield, % | — | — | |
Raw pH | 0.115 | — | — |
Cooked pH | — | — | |
In-package surface color L* | |||
In-package surface color a* | |||
In-package surface color b* | |||
Unpackaged surface color L* | 0.542 | 0.908 | |
Unpackaged surface color a* | |||
Unpackaged surface color b* | 0.760 | ||
Internal color L* | 0.172 | 0.957 | |
Internal color a* | |||
Internal color b* | |||
Surface residual NO2 ppm | |||
Internal residual NO2 ppm | |||
Surface residual NO3 ppm | 0.794 | ||
Internal residual NO3 ppm | 0.955 | ||
LAB | 0.673 | 0.234 | 0.535 |
LAB | 0.409 | ||
TAB 120-d growth | 0.059 | ||
TAB inoculated 21-d growth | 0.176 |
Alpha level of 0.05 used for statistical significance.
LAB = Lactic Acid Bacteria.
TAB = Total Aerobic Bacteria.
ppm = parts per million.
For cooked products, fat, moisture, and protein content in samples of the treatment groups followed trends similar to those of the raw product composition. Because there was relatively little numerical difference between treatments for raw or cooked composition, the composition was not expected to affect the outcome of this study. Cooked and chilled yield results were all within approximately 1% among the treatments, though the Natpre T-10 EML Plus S treatments resulted in a small but significant reduction of the cooked yield for those products.
Means for raw and cooked pH for bologna treatments at day 14 post processing
Raw pH | Cooked pH | |
---|---|---|
6.16 | 6.19 | |
6.19 | 6.17 | |
6.19 | 6.17 | |
6.15 | 6.09 | |
6.15 | 6.07 | |
0.03 | 0.11 |
Means in the same column with different letters are significantly different (
CON-CF = control, conventionally cured and vacuum packaged in conventional film.
CJP-CF = alternatively cured with cultured celery juice powder and vacuum packaged in conventional film.
CJP-NEF = alternatively cured with cultured celery juice powder and vacuum packaged in nitrite-embedded film.
NT10-CF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in conventional film.
NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in nitrite-embedded film.
SEM = standard error of the mean.
Means for in-package surface color values for bologna treatment effects during 125-d lighted display
L* | a* | b* | |
---|---|---|---|
65.09 | 13.76 | 16.21 | |
64.24 | 13.56 | 17.11 | |
63.99 | 14.44 | 16.09 | |
65.73 | 7.34 | 20.70 | |
65.71 | 12.02 | 16.82 | |
1.70 | 0.84 | 0.09 |
Means in the same column with different letters are significantly different (
CON-CF = control, conventionally cured and vacuum packaged in conventional film.
CJP-CF = alternatively cured with cultured celery juice powder and vacuum packaged in conventional film.
CJP-NEF = alternatively cured with cultured celery juice powder and vacuum packaged in nitrite-embedded film.
NT10-CF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in conventional film.
NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in nitrite-embedded film.
SEM = standard error of the mean.
In-package surface a* value for bologna treatment × day effects during lighted display. CON-CF = control, conventionally cured and vacuum packaged in conventional film; CJP-CF = alternatively cured with cultured celery juice powder and vacuum packaged in conventional film; CJP-NEF = alternatively cured with cultured celery juice powder and vacuum packaged in nitrite-embedded film; NT10-CF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in conventional film; NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in nitrite-embedded film. Error bars represent ± standard error of the mean (SEM; 0.87). a–cMeans from the same day with different letters are significantly different (
The results for unpackaged surface and internal CIE L*, a*, and b* measurements for treatment effects are shown in
Means for unpackaged surface and internal color values for bologna during 125-d lighted display
Unpackaged Surface | Internal | |||||
---|---|---|---|---|---|---|
L* | a* | b* | L* | a* | b* | |
63.34 | 13.74 | 15.79 | 64.45 | 13.77 | 14.78 | |
63.12 | 13.05 | 16.67 | 63.79 | 13.82 | 15.45 | |
62.64 | 14.06 | 16.14 | 63.52 | 13.91 | 15.34 | |
64.49 | 7.09 | 19.43 | 66.49 | 7.19 | 17.99 | |
64.53 | 11.43 | 16.77 | 65.62 | 10.41 | 16.17 | |
1.68 | 0.83 | 0.26 | 1.54 | 0.60 | 0.13 |
Means in the same column with different letters are significantly different (
CON-CF = control, conventionally cured and vacuum packaged in conventional film.
CJP-CF = alternatively cured with cultured celery juice powder and vacuum packaged in conventional film.
CJP-NEF = alternatively cured with cultured celery juice powder and vacuum packaged in nitrite-embedded film.
NT10-CF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in conventional film.
NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in nitrite-embedded film.
SEM = standard error of the mean.
Unpackaged surface a* values for treatment × day effects are displayed in
Surface a* values for unpackaged bologna treatment × day effects during 125-d lighted display
Day 1 | Day 6 | Day 13 | Day 27 | Day 41 | Day 55 | Day 69 | Day 83 | Day 97 | Day 111 | Day 125 | |
---|---|---|---|---|---|---|---|---|---|---|---|
14.50 | 14.35 | 14.46 | 14.32 | 14.11 | 14.25 | 13.67 | 13.15 | 12.96 | 12.71 | 12.68 | |
14.33 | 14.29 | 14.25 | 14.11 | 13.61 | 13.59 | 13.15 | 12.52 | 11.84 | 11.18 | 10.68 | |
14.68 | 14.56 | 14.23 | 14.23 | 14.33 | 14.20 | 13.85 | 13.85 | 14.08 | 13.32 | 13.35 | |
6.59 | 7.31 | 7.00 | 7.06 | 7.17 | 7.02 | 7.22 | 7.34 | 7.21 | 7.07 | 7.05 | |
9.94 | 11.75 | 12.43 | 12.99 | 12.50 | 12.08 | 10.96 | 11.20 | 11.10 | 10.82 | 9.99 |
Means in the same column with different letters are significantly different (
Means in the same row with different letters are significantly different (
CON-CF = control, conventionally cured and vacuum packaged in conventional film.
CJP-CF = alternatively cured with cultured celery juice powder and vacuum packaged in conventional film.
CJP-NEF = alternatively cured with cultured celery juice powder and vacuum packaged in nitrite-embedded film.
NT10-CF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in conventional film.
NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in nitrite-embedded film.
SEM = standard error of the mean (0.91).
Visual appearance of the unpackaged surface of NT10-CF and NT10-NEF treatments opened at day 1 or day 41 of lighted display storage. NT10-CF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in conventional film; NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in nitrite-embedded film.
The internal a* values for treatment effects are also presented in
Internal a* values for treatment × day effects also did not differ among CJP-NEF, CJP-CF, CON-CF, or NT10-CF treatments during the display period (125 d) (
Internal a* values for bologna treatment × day effects during 125-d lighted display
Day 1 | Day 6 | Day 13 | Day 27 | Day 41 | Day 55 | Day 69 | Day 83 | Day 97 | Day 111 | Day 125 | |
---|---|---|---|---|---|---|---|---|---|---|---|
13.84 | 14.04 | 13.67 | 13.79 | 13.79 | 13.79 | 13.75 | 13.56 | 13.96 | 13.70 | 13.59 | |
13.91 | 13.80 | 13.81 | 14.00 | 13.74 | 13.69 | 13.82 | 13.73 | 13.73 | 13.90 | 13.87 | |
13.83 | 14.24 | 13.85 | 13.90 | 13.76 | 13.76 | 14.01 | 13.80 | 14.10 | 13.82 | 13.94 | |
6.42 | 7.12 | 6.96 | 7.44 | 7.34 | 7.53 | 7.38 | 7.23 | 7.11 | 7.56 | 7.01 | |
6.86 | 7.70 | 9.43 | 10.37 | 11.04 | 11.36 | 11.24 | 11.48 | 11.47 | 11.86 | 11.75 |
Means in the same column with different letters are significantly different (
Means in the same row with different letters are significantly different (
CON-CF = control, conventionally cured and vacuum packaged in conventional film.
CJP-CF = alternatively cured with cultured celery juice powder and vacuum packaged in conventional film.
CJP-NEF = alternatively cured with cultured celery juice powder and vacuum packaged in nitrite-embedded film.
NT10-CF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in conventional film.
NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in nitrite-embedded film.
SEM = standard error of the mean (0.65).
There were no differences between NT10-CF, NT10-NEF, CON-CF, or CJP-CF for unpackaged external surface L* value treatment effects (
Unpackaged surface b* value (
Unpackaged surface and internal L* values for treatment × day effects during lighted display showed no difference (
Slices that were in direct contact with the packaging material (slices 1 and 4 of each package) and internal slices that were in the center of each package (slices 2 and 3) were analyzed separately for residual nitrite. Slices 1 and 4 were combined to represent the residual nitrite in the surface slices, while slices 2 and 3 were combined to represent the internal residual nitrite concentration.
Surface residual nitrite values for treatment × day effects are displayed in
Residual nitrite (parts per million [ppm]) for bologna treatment × day effects under retail display. (A) Surface residual nitrite. (B) Internal residual nitrite. CON-CF = control, conventionally cured and vacuum packaged in conventional film; CJP-CF = alternatively cured with cultured celery juice powder and vacuum packaged in conventional film; CJP-NEF = alternatively cured with cultured celery juice powder and vacuum packaged in nitrite-embedded film; NT10-CF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in conventional film; NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in nitrite-embedded film. Error bars represent ± standard error of the mean (SEM): (A SEM = 2.00), (B SEM = 2.10). a–cMeans from the same day with different letters are significantly different (
Internal residual nitrite concentrations as a result of treatments are shown in
Means for external surface and internal residual nitrite concentrations for bologna treatment effects under 125-d lighted display
Surface Residual NO2 ppm | Internal Residual NO2 ppm | |
---|---|---|
16.4 | 16.3 | |
13.5 | 12.8 | |
15.9 | 15.0 | |
6.6 | 6.6 | |
7.7 | 7.2 | |
1.66 | 1.80 |
Means in the same column with different letters are significantly different (
CON-CF = control, meat conventionally cured and vacuum packaged in conventional film.
CJP-CF = alternatively cured with cultured celery juice powder and vacuum packaged in conventional film.
CJP-NEF = alternatively cured with cultured celery juice powder and vacuum packaged in nitrite-embedded film.
NT10-CF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in conventional film.
NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in nitrite-embedded film.
SEM = standard error of the mean.
Surface and internal residual nitrate for each treatment are shown in
External surface and internal residual nitrate concentrations for bologna treatment effects during 125-d lighted display
Surface Residual NO3 ppm | Internal Residual NO3 ppm | |
---|---|---|
40.2 | 39.1 | |
46.6 | 46.3 | |
45.5 | 46.0 | |
33.6 | 33.4 | |
38.6 | 39.1 | |
2.25 | 2.48 |
Means in the same column with different letters are significantly different (
CON-CF = control, meat conventionally cured and vacuum packaged in conventional film.
CJP-CF = alternatively cured with cultured celery juice powder and vacuum packaged in conventional film.
CJP-NEF = alternatively cured with cultured celery juice powder and vacuum packaged in nitrite-embedded film.
NT10-CF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in conventional film.
NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in nitrite-embedded film.
ppm = parts per million; SEM = standard error of the mean.
The total aerobic bacterial populations (log CFU/g) in conventional shelf life conditions (1°C) showed essentially no growth in any of the treatments during the 120 d of storage (data not shown). However, there was a treatment effect at day 30, with NT10-NEF being significantly higher for total aerobic counts than CON-CF but not significantly different from NT10-CF, CJP-CF, or CJP-NEF. Given that this does not reoccur after day 30, this was most likely due to sampling error or some other procedural effect rather than a treatment effect. Lactic acid bacteria populations (log CFU/g) for conventional shelf life conditions also showed no measurable counts for any of the treatments (data not shown).
Mean lactic acid bacteria populations (log CFU/g) for inoculated bologna treatment × day effects during 21-d display
log CFU/g | |
---|---|
6.53 | |
6.47 | |
6.49 | |
6.10 | |
6.10 | |
0.09 |
Means in the same column with different letters are significantly different (
CON-CF = control, conventionally cured and vacuum packaged in conventional film
CJP-CF = alternatively cured with cultured celery juice powder and vacuum packaged in conventional film.
CJP-NEF = alternatively cured with cultured celery juice powder and vacuum packaged in nitrite-embedded film.
NT10-CF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in conventional film.
NT10-NEF = alternatively cured with Natpre T-10 EML Plus S and vacuum packaged in nitrite-embedded film.
CFU = colony-forming units; SEM = standard error of the mean.
Proximate composition of the bologna used in this study confirmed that formulation was consistent among treatments with only minor differences observed for fat, moisture, and protein content. The small differences observed, though statistically significant, are not likely large enough or consistent enough to be truly impactful on the primary objectives of this study. The cooked yield of the Natpre T-10 EML Plus S formulations in both packaging treatments was lower than for the other formulations, likely due to the reduced pH of about 0.1-pH unit in that cooked product. However, the range in the cooked yield was just 0.69% from high to low. Natpre T-10 EML Plus S was the alternative cure replacement ingredient in the NT10-CF and NT10-NEF treatments; this ingredient contains fruit and spice extracts, and our analysis showed that it had a pH of 4.76, which could account for the lower product pH compared to the other formulations. For comparison, Modern Cure and sodium erythorbate used as curing ingredients for the control product had pHs of 7.84 and 7.50, respectively. Additionally, there were no buffering ingredients (such as phosphates or carbonates) included in the formulations; therefore, an impact on pH from other ingredients such as curing ingredients and/or reductants would be more likely.
Products packaged in nitrite-embedded film resulted in greater in-package external a* values (greater redness), which demonstrated the potential role for nitrite-embedded film to affect cooked, cured meat color. This suggests that the nitrite from the film is providing nitric oxide for the heat-denatured (cooked) myoglobin to generate improved cured color (redness). In fresh meat, the innate reducing capacity of fresh meat has been shown to reduce nitrite to nitric oxide and generate nitric oxide myoglobin (
In this study, in-package surface a* values over time show that the NT10-NEF treatment performed similar to CJP-CF with regard to color stability during the display period despite considerably less ingoing nitrite (21 ppm vs. 99 ppm) in the product formulation. Further, comparing NT10-NEF to NT10-CF for in-package surface a* value highlights the fact that NT10-NEF a* value increased relative to NT10-CF during the display period. This again suggests that nitric oxide generated from nitrite in the film is resulting in additional formation of cured meat pigment in the product.
The increase in unpackaged surface a* value in NT10-NEF compared to NT10-CF over the first 27 d of display (
Greater in-package surface b* values in the NT10-CF relative to the other treatments suggests greater discoloration (yellowness) in the NT10-CF (conventional film) product compared to NT10-NEF. However, NT10-NEF was similar to CJP-CF for surface b* values, which means that the nitrite-embedded film package provided for less discoloration in the low nitrite product, making the color stability of the low nitrite product similar to that of the products with celery juice powder that contained a greater amount of ingoing nitrite. Internal b* values decreased in the NT10-NEF treatment during display (b* value of 17.87 on day 1 to 15.62 on day 125), but NT10-CF showed the greatest discoloration (greatest b* value) throughout the display period.
A surprising observation in this study was that internal color showed an improvement over time in nitrite-embedded-film-packaged product, presumably from penetration of nitrite/nitric oxide from the film into the product interior. It is important to note that all slices were 6.35-mm thick and the internal color was measured at the most interior slice surface (between slices 2 and 3), which was 12.7 mm from the contact point with the film. This is particularly noteworthy given the very low (21 ppm) ingoing nitrite in the Natpre T-10 EML Plus S treatments where this degree of internal color improvement was not expected.
The lighter color of the Natpre T-10 EML Plus S products relative to the celery juice powder treatments was probably due to the celery juice powder. A previous study conducted by Usinger et al. (
The CIE L*, a*, and b* values observed in the present study over time are consistent with previous research that reported decreased a*, increased b*, and reduced L* during respective display periods (
Residual nitrite in the surface slices of the bologna showed that Natpre T-10 EML Plus S treatments both had considerably less residual nitrite than the control or the celery juice powder products, as expected. More importantly, the nitrite-embedded film did not result in greater measurable nitrite in the product than in the product packaged in conventional film. Further, the film type (conventional film or nitrite-embedded film) did not have a significant impact over time during the display period, with one exception in that CJP-CF was lower than CJP-NEF at day 6. Thus, the nitrite-embedded film provided for improved cured color stability without affecting measurable residual nitrite concentrations.
As expected, the present study confirmed that residual nitrite in typical formulations decreased over time. Reduction in residual nitrite during storage has been well documented in previous research studies (
Surface residual nitrate results for treatment effects showed that nitrate was detected in the control formulation (CON-CF), even though only nitrite was included in the formulation. This can be expected because, during the curing process, some of the nitrite forms nitrate by means of a mildly acidic environment (
In the inoculated products, bacterial growth during elevated temperature storage (21 d) was achieved as expected. Anaerobic lactic acid bacterial populations were not different between control and celery juice powder treatments and there was no effect of nitrite-embedded film on bacterial growth. However, NT10-NEF and NT10-CF treatments showed lower bacterial populations compared to all other treatments. Both of these treatments contained Natpre T-10 EML Plus S, which includes fruit and spice extracts that may include microbial inhibitors such as organic acids, as well as other antimicrobial compounds.
The results from the present study demonstrate that nitrite-embedded film has potential to extend the color stability of alternatively cured meat products. Nitrite-embedded film improved both surface and internal redness in alternatively cured meat products, especially those that contained low concentrations of ingoing nitrite. In the present study, a* value was used as an indicator for cooked, cured meat pigment, and—based on the improvements in a* value for treatments with low ingoing nitrite in nitrite-embedded film packaged products—it appears that additional cured pigment (nitrosylhemochrome) was formed in these cooked products following thermal processing. This means that the film not only has the potential to improve retail display color but also provides a means of generating cured color, post thermal processing. The mildly acidic conditions surrounding cooked, cured products in an anaerobic package environment are conducive to nitric oxide formation from nitrite. The generated nitric oxide can then bind to heme iron to generate nitrosylhemochrome pigment as well as replace the nitric oxide that dissociates from the pigment during color fading. Further research should be conducted to clarify the proposed mechanism for nitrosylhemochrome formation following thermal processing and pigment denaturation, in addition to the impact of nitrite-embedded film technology on the safety, quality, and sensory impact in nitrite-free and alternatively cured, cooked meat products.
The authors thank Dan Siegel and Matt Peterka with Bemis Company, Inc. (a division of Amcor Flexibles, North America) for supplying nitrite-embedded film for this project; Hormel Foods, LLC, in particular Dr. Kevin Myers and his analytical team specialists Aaron Asmus and David Cole, for making residual nitrate testing possible; Wenda America, Inc. and Florida Food Products, Inc. for providing alternative curing ingredients; and Steve Niebuhr for his expertise and scientific knowledge in microbiology sampling techniques. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.