Color Development of Direct Acidified Pork Sausage Containing Alternative Curing and Reducing Agents

Raw materials and processing

Within 7-d postmortem, legs were collected from 1 side of pork carcasses (n = 6) and frozen and stored at −40°C until processing. Prior to processing each batch, 2 legs were thawed at 4°C for 48 h. After thawing, M. biceps femoris and M. semimembranosus were removed from each leg and trimmed of visible connective tissue and fat. Excised muscles were cut into ∼1-cm cubes, and the pieces were mixed by hand for 60 s to help ensure equal distribution of muscles to be used in each treatment. Afterward, the meat was minced through a 10-mm die, followed by a 4.5-mm die, in a grinder (#22 BigBite, LEM, West Chester, OH).

Approximately 18 h prior to thermal processing, the treatments OVERNIGHT at 4°C were prepared. For each batch, 300 g of minced pork were used. All treatments had 2.30% sodium chloride (NaCl) and 1.00% dextrose added. Treatments were prepared in a 3 × 3 factorial design of 3 cure ingredients (sodium nitrite [NaNO₂ (NITRITE)], CELERY, BEET) and 3 cure accelerators (none [NONE], ERYTH, CHERRY). Formulations used are provided in Table S1. Cure ingredients were added to target 125 ppm of ingoing NO₂. This level was chosen over the standard 156 ppm in comminuted products considering the known negative sensory attributes associated with higher concentrations of alternative sources of NO₂ (Redfield and Sullivan, 2015). For NITRITE, this was added in the form of curing salt #1 (6.25% NITRITE, 93.75% NaCl). For CELERY (11-1042, The Sausage Maker, Inc., Buffalo, NY) and BEET (11-1045, The Sausage Maker, Inc., Buffalo, NY), the level of inclusion to achieve 125 ppm of ingoing NO₂ was 0.42% in accordance with the supplier’s specifications. For ERYTH, 547 ppm was included. For CHERRY (11-1048, The Sausage Maker, Inc., Buffalo, NY), 1000 ppm was included in accordance with the supplier’s recommendations.

To prepare treatments, NaCl, dextrose, cure ingredients, and cure accelerators were added to the minced pork with 24.0 mL of ice-cold deionized (DI) water to facilitate distribution. The mixture was mixed in a stand mixer (Professional 600 Series 6 Quart Bowl-Lift Stand Mixer, KitchenAid, Benton Harbor, MI), set to a 2 speed for 180 s. After this, the sides of the bowl were scraped with a rubber spatula, and encapsulated citric acid (G4570700059, Walton’s, Inc., Wichita, KS) was added at a 1.00% inclusion level and mixed for an additional 60 s. A negative control (CONTROL) was prepared including NaCl, dextrose, DI water, and encapsulated citric acid but no cure ingredients or cure accelerators.

After mixing, sausages were stuffed into 1.5 × 12-in prestuck fibrous casings (230256, Walton’s, Inc., Wichita, KS), each weighing approximately 220 g. Approximately 115 g of the mixture was collected for determining raw instrumental color, as later described. Sausages were weighed to determine the initial weight for determining yield, after which they were stored in a 4°C cooler overnight. For preparing the IMMEDIATE treatments, the same procedure was followed utilizing the remaining mince for the OVERNIGHT treatments that had been stored at 4°C overnight. For IMMEDIATE treatments, sausages were prepared, weighed, and held for approximately 1 h after completion of the last treatment at 4°C. For the OVERNIGHT group, the mean duration from mixing to thermal processing was 17 h and 6 min. Within IMMEDIATE, the mean duration was 1 h and 46 min. The order of preparing treatments was rotated among batches to minimize any potential confounding of preparation order. Similarly, placement in the smokehouse was randomized to minimize any impacts on color from sources other than the treatment preparations.

Sausages were smoked and cooked in a commercial smokehouse (Grand Prize II, UltraSource, LLC, Kansas City, MO) in accordance with the schedule provided in Table S2. The cook 2 stage was terminated when the internal temperature of a sausage prepared in a similar manner, but not used in the experiment, reached 69°C. Following this step, the sausages were showered with water until the internal temperature reached 38°C. The mean thermal processing time was 3 h and 56 min. Sausages were allowed to cool in the smokehouse at room temperature (20°C) for 30 min prior to measuring final weight (hot). Yield (hot) was determined as: [final weight (hot)/initial weight] * 100%. After 20 h of cooling at 4°C, final weight (cold) was measured to determine total yield as (final weight (cold)/initial weight] * 100%. Cooler shrink was determined as the percent difference between final weight (hot) and final weight (cold).

pH

The pH of samples was determined in duplicate on raw and cooked (1- and 21-d postprocessing) samples by homogenizing 3.0 g of sausage with 27.0 ml of distilled water. The measurement was obtained using a pH probe (VWR pHenomenal IS2100L, Avantor Inc., Radnor, PA) calibrated with pH 4 and 7 standards.

Residual NO₂ content

The residual NO₂ content was analyzed following the AOAC Method 973.31 (AOAC, 2000). One gram of finely chopped sample was added to a beaker with 60 mL of hot DI water (80°C). Samples were then placed in a shaking water bath set at 95°C for 2 h and stirred every 30 min. After heating, samples were removed from the water bath, cooled to room temperature, and transferred to a 100-mL volumetric flask carefully to avoid transferring meat and fat pieces. The samples were then diluted to 100 mL using DI water, mixed thoroughly, and filtered using Whatman #4 filter paper. Next, 25 mL of the sample was mixed with 2.5 mL of sulfanilamide reagent, 2.5 mL of N-(1-naphthyl) ethylenediamine dihydrochloride reagent, and 20 mL of DI water, following the procedure described in the AOAC protocol. The absorbance of the samples was read at 540 nm using a Biotek Synergy LX plate reader (Agilent Technologies, Inc., Santa Clara, CA) and compared to a NO₂ standard curve to determine residual NO₂ concentration.

Instrumental color analysis

Instrumental color attributes were measured on samples while raw as well as cooked at 1- and 21-d postprocessing. A portable spectrophotometer (MiniScan EZ 4500L, HunterLab, Reston, VA) was used to obtain Commission Internationale de l’Èclairage (CIE) L* (lightness), a* (redness), and b* (yellowness) values. For raw samples, patties measuring approximately 1.5 cm in thickness were prepared by pressing into a handheld patty former with waxed patty paper, and 3 randomly determined locations were scanned. The time of measurement coincided with the start of thermal processing and was taken within a 15-min interval. For cooked samples, three 1.5-cm slices were obtained from the interior of each sausage, and measurements were taken in triplicate. No packaging was used to cover the samples. The conditions used for the measurements were as follows: illuminant A, 10° observer angle, 31.8-mm port size, and 25-mm viewed area. Illuminant A was chosen due to its common use for cured pork sausage (Kim and Shand, 2022). Reflectance spectra were also obtained for determination of cured color intensity via the ratio of reflectance at 650 and 570 nm (R650/570) (King et al., 2023). Chroma (saturation index) and hue angle (discoloration) values were determined in accordance with King et al. (2023).

Semitrained descriptive color panel

At 1-d postprocessing, a semitrained descriptive color panel was conducted. Panelists (n = 7) had passed a Farnsworth-Munsell 100-Hue test with scores less than 50. Samples were presented to panelists with a random 3-digit number in a randomized order. The panelists were instructed to evaluate each sample for cured meat color using an 9-point scale similar to King et al. (2023) with the following modifications to account for the CONTROL. The scale values were as follows: 1, no cured color; 2, light pinkish cured color; 3, pinkish cured color; 4, slight pinkish-red cured color; 5, pinkish-red cured color; 6, reddish-pink cured color; 7, slightly dark red cured color; 8, moderately dark red cured color; and 9, very dark red cured color. Recording to the nearest 0.5 point was acceptable. Photos were taken for qualitative purposes on a smartphone (iPhone 12 Mini, Apple, Inc., Cupertino, CA) with color and gray color separations included in the original images (Q-13, Tiffen, Hauppauge, NY). Qualitative images are provided in Figure 1.

Figure 1.

Qualitative images of direct acidified pork sausage when (A) OVERNIGHT, raw; (B) IMMEDIATE, raw; (C) OVERNIGHT, cooked at 1-d postprocessing; and (D) IMMEDIATE, cooked at 1-d postprocessing. BEET refers to beet powder at 125 ppm of ingoing NO₂. CELERY refers to celery powder at 125 ppm of ingoing NO₂. CHERRY refers to cherry powder at 1000 ppm. CONTROL refers to the negative CONTROL group. ERYTH refers to sodium erythorbate at 547 ppm. IMMEDIATE refers to ∼1.75 h of holding at 4°C prior to processing. NITRITE refers to NaNO₂ at 125 ppm. NONE refers to no cure accelerator. OVERNIGHT refers to ∼17 h of holding at 4°C prior to thermal processing.

Texture profile analysis

After 21 d of holding at 4°C in vacuum bags, texture profile analysis was conducted in triplicate using a TA.XT plusC Texture Analyzer (Stable Micro Systems, Ltd., United Kingdom) equipped with 50 kg load cell and TA-25 probe. For each replicate, a 2.0-cm thick slice was collected. A twice compression test (50% compression, 10 mm distance) was conducted in accordance with the parameters described by Tuell et al. (2020).

Statistical analysis

Data were analyzed using the PROC GLIMMIX procedure of SAS (9.4, SAS Institute, Inc., Cary, NC). For the experiment, 3 independent replications were conducted, thus batch (n = 3) served as the experimental unit. A model was created to analyze the fixed effects of cure ingredient (NITRITE, CELERY, BEET), cure accelerator (NONE, ERYTH, CHERRY), holding period (OVERNIGHT, IMMEDIATE), and their interactions. Least-squares mean differences were determined by the LSMEANS statement and Tukey-Kramer adjustment. The CONTROL was not included in the analysis, but images are included to support that NO₂ did not cross-contaminate among treatments during storage or thermal processing. Differences in means were considered significant at P < .05, and trends were defined as .05 ≤ P < .10.

Yield

As expected, across treatment groups, sausages had a similar initial weight (Table 1; P > .05), and hot and cold weights of sausages were not affected (P > .05). Yield (hot) measured 30 min after the completion of the shower stage was 83.6% in IMMEDIATE compared to 81.8% for OVERNIGHT (P < .05). Similarly, yield (cold) measured 20 h after storage at 4°C was greater at 80.4% in IMMEDIATE than OVERNIGHT at 77.8% (P < .01). There was a tendency (P = .073) of OVERNIGHT sausages losing more weight (5.0%) than IMMEDIATE (3.8%) in the cooler. No significant effects of cures or cure accelerators were observed for any measures of yield.

Kim and Shand (2022) reported that pork bologna prepared with powdered BEET would have similar proximate composition and emulsion stability relative to conventionally cured controls. Jin et al. (2014) reported that emulsion sausages prepared with powdered BEET would have greater moisture content, attributed to the high pH of the powder improving protein functionality. The study by Jin and Kim (2023) found that pork emulsions with CELERY would have similar purge loss after 2 wk of storage, whereas BEET would be slightly elevated. Similarly, Ozaki et al. (2021) reported that dry sausages prepared with BEET would have similar proximate composition compared to conventionally cured controls; however, greater moisture loss would be experienced during the drying process. This study found no differences in yield among types of cure, which could be due to the differences in product types. As shown in Figure 1A, it appears that some premature release of citric acid occurred prior to thermal processing, indicated by patches of nitrosyl hemochrome formation. The relationship of pH, protein denaturation, and water-holding capacity is well-established (Warner, 2023), helping explain the findings that the denaturing conditions created in OVERNIGHT would result in poorer yields. It may also be that the poorer yields could be related to the 16 h of storage at 4°C, which IMMEDIATE was not exposed to, thus allowing time for evaporative moisture loss to 17 h of storage. The initial weight for OVERNIGHT was taken prior to storage, and a weight immediately before thermal processing was not collected. However, the trend of OVERNIGHT losing more moisture in the cooler does support that protein functionality and water-holding capacity would be impaired due to longer exposure to denaturing conditions.

pH

The pH of sausages formulated with encapsulated citric acid ranged from 4.78 to 4.82 while raw with no significant treatment effect (Table 2). An interaction was observed for pH at 1-d postprocessing between cure ingredient and cure accelerator (P < .05). In general, BEET with NONE or CHERRY and CELERY with NONE had elevated pH compared to other treatment combinations. This continued throughout storage where a 3-way interaction was observed for pH at 21 d (Figure 2; P < .01). The greatest pH (5.06) was found in the treatment combination of BEET with NONE held OVERNIGHT. In general, the values for pH at 21 d were relatively close, ranging from 4.89 to 5.06.

Figure 2.

Interaction of cure ingredient (C), cure accelerator (A), and holding period (H) on pH at 21-d postprocessing of direct acidified pork sausage (n = 3). ^A–EIndicate means are statistically different within the treatment group at P < .01. BEET refers to beet powder at 125 ppm of ingoing NO₂. CELERY refers to celery powder at 125 ppm of ingoing NO₂. CHERRY refers to cherry powder at 1000 ppm. ERYTH refers to sodium erythorbate at 547 ppm. IMMEDIATE refers to ∼1.75 h of holding at 4°C prior to processing. NITRITE refers to NaNO₂ at 125 ppm. NONE refers to no cure accelerator. OVERNIGHT refers to ∼17 h of holding at 4°C prior to thermal processing.

Jin et al. (2014) found that unfermented red BEET at a level of 0.5% and 1.0% would increase the pH of emulsified pork sausage from 6.06 to 6.21 and 6.30, respectively. Typically, however, fermented CELERY (Hwang et al., 2018) and BEET (Hwang et al., 2018; Ozaki et al., 2021) decrease pH values of pork sausage owing to the acidic pH achieved during fermentation. Other studies have reported no effect on pH due to the inclusion of fermented vegetable extracts (Terns, et al., 2011a; Redfield and Sullivan, 2015). Regardless, the pH values of all formulations were within the expected range for the level of encapsulated citric acid inclusion. The magnitude of difference in pH across product formulations was slight overall and likely not of practical importance considering all formulations were below a pH of 5.3 following thermal processing (US Department of Agriculture Food Safety and Inspection Service, 2023).

Residual NO₂

Residual NO₂ was similar across treatments while raw (Table 2; P > .05). However, an interaction between cure ingredient and cure accelerator was observed at 1- and 21-d postprocessing (P < .01). At 1 d, the greatest residual NO₂ was found in CELERY with NONE, followed by NITRITE with NONE, and BEET with NONE. The inclusion of a cure accelerator resulted in lower residual NO₂, regardless of cure ingredient. This pattern was mostly similar at 21 d; however, NITRITE with NONE maintained greater residual NO₂ to CELERY with NONE and BEET with NONE (P < .05). Inclusion of ERYTH and CHERRY decreased residual NO₂ in NITRITE (P < .05). By 21 d, no differences were detected by inclusion of a cure accelerator or not for CELERY and BEET (P > .05), with the exception of CELERY with CHERRY having lower residual NO₂ than CELERY with NONE (P < .05).

The finding of a cure accelerator reducing the amount of residual NO₂ is in line with previous literature both with conventional and alternative ingredients. Posthuma et al. (2018) reported that ERYTH would decrease residual NO₂ in beef emulsions prepared with NITRITE, and CHERRY would decrease residual NO₂ in those prepared with CELERY. In agreement with the present study, the greatest amounts of residual NO₂ were found in sausages containing NITRITE with NONE. Inclusion of a cure accelerator, regardless of it being conventional or alternative, favors a decrease in the amount of residual NO₂ and cured meat pigmentation to be greater (Posthuma et al., 2018).

Color

A₁₀ instrumental color attributes of raw sausages are presented in Table 3. For CIE L*, significant main effects were observed for cure, cure accelerator, and holding period with no interactions. Raw patties prepared with BEET had lower CIE L* than NITRITE and CELERY (P < .05). Patties with NONE were lighter than ERYTH and CHERRY (P < .01). OVERNIGHT holding resulted in patties with a darker color relative to IMMEDIATE (P < .01). Significant interactions were observed between cure accelerator and holding period in CIE a*, CIE b*, and chroma values of raw patties. IMMEDIATE processing with NONE resulted in patties that had lower CIE a* and greater CIE b* compared to other treatment combinations (P < .05). ERYTH and CHERRY within the IMMEDIATE group had lower CIE a* and greater chroma than OVERNIGHT treatments (P < .01), but CIE b* was similar (P > .05) with the exception of OVERNIGHT NONE being lower (P < .05). Greatest CIE a* and chroma values were found in ERYTH and CHERRY within the OVERNIGHT group (P < .01) followed by OVERNIGHT NONE. OVERNIGHT holding, regardless of cure or cure accelerator, had decreased hue angle (indicative of discoloration) at 40.3 relative to IMMEDIATE at 54.8 (P < .01). Similarly, both ERYTH (45.6) and CHERRY (46.4) had lower hue angle than NONE (50.6; P < .01) across cures and holding periods. These findings support that both ERYTH and CHERRY were effective at reducing MMb-NO₂/NO-MMb to NO-Mb during the holding period, though sufficient time was not provided in the IMMEDIATE group.

For cooked sausages at 1-d postprocessing, BEET maintained lower CIE L* compared to NITRITE and CELERY (Table 4; P < .05). CIE b* and hue angle were also greater in BEET (P < .01). CELERY had a similar (P > .05) CIE b* to NITRITE; however, hue angle was slightly elevated to NITRITE but less than BEET (P < .01). There was a tendency (P = .053) of BEET having more saturated color compared to NITRITE and CELERY. For cure accelerators, ERYTH and CHERRY were similar in producing sausages with greater CIE a*, chroma, and R650/570 nm compared to NONE (P < .01). IMMEDIATE processing resulted in sausages that had lower CIE L* and greater CIE a*, chroma, and R650/570 nm values compared to OVERNIGHT (P < .05). For CIE b* and hue angle, a significant interaction was observed between cure accelerator and holding period. In general, CHERRY elevated CIE b* compared to NONE and ERYTH within each respective holding period (P < .05). Similarly, hue angle was increased in CHERRY compared to NONE and ERYTH within OVERNIGHT (P < .05). For IMMEDIATE, CHERRY (35.2) had similar (P > .05) hue angle to NONE (35.4), while ERYTH had decreased hue angle (34.6; P < .05). In general, these patterns were observed at 21 d for instrumental color with BEET appearing darker and more yellow than NITRITE and CELERY as well as ERYTH and CHERRY exhibiting greater redness, saturation, and cured color (Table 5; P < .05).

The semitrained descriptive color panel for cured color intensity found significant main effects of cure accelerator and holding period (Figure 3A, 3B). ERYTH had more intense cured color than NONE (P < .05), while CHERRY was intermediate to the others regardless of cure or holding period (P > .05). IMMEDIATE processing resulted in sausages with more intense cured color compared to OVERNIGHT (P < .05). Type of cure neither influenced cured color intensity, nor were any interactions observed among treatments (P > .05).

Figure 3.

Main effects of cure accelerator (A) and holding period (H) on cured color intensity (1-9) evaluated by semitrained panelists (n = 7) of direct acidified pork sausage (n = 3) at 1-d postprocessing. The scale values were as follows: 1, no cured color; 2, light pinkish cured color; 3, pinkish cured color; 4, slight pinkish-red cured color; 5, pinkish-red cured color; 6, reddish-pink cured color; 7, slightly dark red cured color; 8, moderately dark red cured color; and 9, very dark red cured color. ^a,bIndicate means are statistically different within the treatment group at P < .05. CHERRY refers to cherry powder at 1000 ppm. ERYTH refers to sodium erythorbate at 547 ppm. IMMEDIATE refers to ∼1.75 h of holding at 4°C prior to processing. NONE refers to no cure accelerator. OVERNIGHT refers to ∼17 h of holding at 4°C prior to thermal processing.

The color of cured meats is determined by the formation of nitrosyl hemochrome through the addition of NO₃ and NO₂ (King et al., 2023). During the curing process, NO₂ reacts with deoxymyoglobin to form MMb-NO₂ (Rivera et al., 2019). This pigment form has a gray/brown appearance due to oxidation of heme into the ferric state (King et al., 2023). As this occurs, NO₂ is reduced to NO, forming NO-MMb. This pigment is further reduced to NO-Mb (dark red), which then forms nitrosyl hemochrome upon exposure to denaturing conditions of heat and/or acidic pH (King et al., 2023). In this study, sausages in the IMMEDIATE group appeared to be in the MMb-NO₂ state at the time of thermal processing as evidenced by decreased redness and color saturation relative to OVERNIGHT. In the OVERNIGHT group, reduction to NO-Mb had sufficient time to occur, resulting in greater redness, saturation, and lower hue angle. Within OVERNIGHT, the inclusion of ERYTH and CHERRY as cure accelerators favored the reduction of MMb-NO₂ and NO-MMb to NO-Mb.

Interestingly, despite appearing in a reduced state at the start of thermal processing, the OVERNIGHT group had less intense cured color relative to IMMEDIATE, evident through decreased redness, chroma, and R650/570 nm in OVERNIGHT, regardless of cure accelerator. These findings were supported by semitrained panelists who found the IMMEDIATE sausages to have more intense cured color than OVERNIGHT as well as ERYTH having a more intense color than NONE. Posthuma et al. (2018) found that holding beef emulsion sausages from 120 min would increase CIE a* over those held 5, 15, and 30 min. Sindelar et al. (2007) reported that pork hams prepared with cultured vegetable juice powder would have similar color attributes relative to conventionally cured controls regardless of a prior incubation time of 120 min or none. Conversely, it has also been found that incubation at 37.8°C for 90 min of pork emulsion sausages with vegetable juice powder would improve redness relative to those that were immediately processed (Terns et al., 2011a). The findings of the present study are likely related to the premature release of citric acid into the sausage during the storage period prior to thermal processing. Nitrosyl hemochrome is known to form when proteins denature due to heat or acid (King et al., 2023). As shown in Figure 1A, there are patches of nitrosyl hemochrome formation in the OVERNIGHT group that are not apparent in the IMMEDIATE group in Figure 1B. As the patties were stored at 4°C, this would indicate some premature breaking of the encapsulation, thus creating the acidic conditions required for nitrosyl hemochrome formation. Supporting this, for sausages in the OVERNIGHT group, a strong negative correlation was observed between raw CIE L* and cooked CIE a* (Table S3; r = −0.85; P < .01), chroma (r = −0.89; P < .01), and R650/570 nm (r = −0.84; P < .01). As nitrosyl hemochrome is formed in protein denaturing conditions through exposure of the porphyrin ring, it is not clear why OVERNIGHT had less intense cured color than IMMEDIATE following thermal processing. It may be that the simultaneous release of acid and application of heat is ideal for the formation of nitrosyl hemochrome, but this would warrant further study.

Jin et al. (2018) found CELERY would result in sausages with elevated CIE a*, CIE b*, chroma, and hue angle values compared to conventional NITRITE. Jin and Kim (2023) reported that cultured CELERY would result in emulsion sausages with mostly similar color to NITRITE, which would be maintained during storage. However, others have found that cultured CELERY would result in pork sausages with lower CIE a* and greater CIE b* relative to conventionally cured controls (Hwang et al., 2018; Posthuma et al., 2018). The findings of this study agree with Jin and Kim (2023), as color was largely similar between NITRITE and CELERY groups. Red BEET has been shown to decrease CIE L* relative to pork emulsions prepared with NITRITE (Jin et al., 2014; Kim and Shand, 2022), but the opposite (Jin and Kim, 2023) or no trend (Hwang et al., 2018) has also been found. Similarly, varying influences on other color attributes have also been reported, where BEET has been shown to increase (Jin et al., 2014; Kim and Shand, 2022) and decrease (Hwang et al., 2018; Jin and Kim, 2023) redness relative to conventional NITRITE. The present study found BEET to have similar redness and cured color intensity to NITRITE, which is likely due to the culturing process resulting in high levels of NO₂. However, the study by Hwang et al. (2018) also applied a fermented BEET and observed similar CIE a* values to a CONTROL group and considerably lower than the positive control including NITRITE. Jin and Kim (2023) reported emulsions prepared with uncultured BEET would have inferior redness, likely owing to lower concentrations of NO₂ relative to cultured CELERY that performed similarly to conventional NITRITE. Similar findings were reported for uncultured CELERY, which resulted in lower concentrations of residual NO₂ and considerably lower cured pigmentation (Ramachandraiah and Chin, 2021) Other differences could be due to the relative absence of betalain pigments, as Jin et al. (2014) reported that CIE a* would be considerably increased in pork emulsions prepared with powdered BEET owing predominantly to a high concentration of betalain pigments. Inclusion of unfermented red BEET at a level of 0.5% and 1.0% increase CIE a* values from 7.1 in emulsified pork sausage formulated with 75 ppm ingoing NITRITE to 21.0 and 27.4, respectively (Jin et al. 2014). Considering the overall lack of difference in redness in BEET relative to NITRITE in the present study as well as for residual NO₂ while raw and after thermal processing, it is unlikely endogenous pigments are considerably influencing color. This is supported by a lack of change in redness upon addition of the alternative curing agents to the raw mixture. It may also be that betalains present in the preconverted BEET may help to offset any relative ineffectiveness in meat curing. Jin et al. (2014) reported that unfermented BEET and NITRITE would synergistically influence redness, with greatest CIE a* in sausages prepared with 1.0% BEET and 75 ppm NITRITE. The present study did not measure cured meat pigmentation directly, making it partly unclear what effect other pigments may have had on color development.

The findings for cure accelerators are in line with previous research showing the ability of ERYTH to exhibit strong reducing ability and improve redness of sausages (Jin et al., 2015; Posthuma et al., 2018; Shang et al., 2020). It has been reported that inclusion of CHERRY at 0.20% would result in slightly decreased CIE a* and increased CIE b* relative to controls for emulsified pork sausage (Terns et al., 2011b). The present study found that CHERRY would increase CIE a*, chroma, and R650/570 nm similarly to ERYTH over NONE. However, cured color intensity would be similar to both ERYTH and NONE, in agreement with the consumer sensory panel for internal color conducted by Terns et al. (2011b). Fu et al. (2022) reported that CHERRY would increase CIE a* and CIE b* of pork sausages, in agreement with the present study. However, the concentrations used were considerably greater at 1, 3, and 5%, as well as of another species (Prunus cerasus L. vs. Malpighia emarginata) (Fu et al., 2022).

Regarding the relationship between raw and cooked color, Kim and Shand (2022) reported that inclusion of BEET would result in pork emulsions with increased CIE a* when raw, but the differences would be slight after thermal processing. Hwang et al. (2018) found that raw sausages including fermented CELERY or BEET would have mostly similar CIE a* values compared to both positive (including NITRITE) and negative (NITRITE-free) CONTROL groups. However, CIE a* would be considerably lower in the sausages prepared with alternative sources of NO₂ compared to the positive control group. While not statistically comparing raw and cooked sausages, the present study found CIE a* to increase during thermal processing for all cure ingredients. Differences may be due to the considerably different formulations used in the present study which used entirely pork M. semimembranosus and M. biceps femoris trimmed of external fat, whereas Hwang et al. (2018) prepared sausages including 25% backfat and 25% ice to 50% of lean pork leg.

Texture profile

No significant impact on texture profile attributes was found for cure ingredient (Table S4). An interaction was observed between cure accelerator and holding period for cohesiveness, springiness, and chewiness (P < .05). OVERNIGHT with CHERRY was less cohesive and chewy than OVERNIGHT with ERYTH (P < .05), while OVERNIGHT with CHERRY was less springy than IMMEDIATE with NONE (P < .05). Fu et al. (2022) reported that CHERRY (Prunus cerasus L.) would decrease hardness, springiness, and chewiness of fermented pork sausage at 0 d of storage, but minimal differences would be found by 30 d. Ganhão et al. (2010) found that emulsified beef patties prepared with antioxidative fruit extracts would have altered texture compared to controls, but the magnitude of the difference would depend on which extract was used and the storage duration. In the present study, texture was assessed at 21 d only, thus it is unclear whether texture would be altered throughout storage. However, considering there were no differences between formulations within IMMEDIATE, this is likely not of practical concern.