Walk down the deli aisle of any American supermarket and you will find packages of ham labeled “uncured” and boasting “no nitrate or nitrite added.” Yet many of those products contain celery juice powder, a vegetable-derived ingredient that converts into nitrite during processing and performs essentially the same chemical role as the synthetic sodium nitrite it replaces. A new study from the University of Nevada, Reno, published in Food Science of Animal Resources, has put this paradox to a rigorous test, and the results carry implications not only for the meat industry but also for the regulators who decide what the word “cured” actually means.
The research team, led by Nadini H. Gamage and Amilton S. de Mello, manufactured thirty-two smoked hams at a USDA-inspected commercial facility using four different brine formulations. The first was a conventional recipe built on synthetic sodium nitrite. The second replaced the synthetic compound with celery powder and added a buffered vinegar antimicrobial called MOstatin V. The third combined celery powder with spices, and the fourth contained no nitrite source at all, relying instead on spices, red wine, and annatto paste to simulate the appearance and flavor of a cured product. Each batch of hams was then split in two: half of the slices were subjected to high-pressure processing at 85,000 psi, roughly 586 megapascals, for two minutes at 5 degrees Celsius, while the other half remained untreated.
The choice of high-pressure processing was no accident. Ready-to-eat meats, despite being fully cooked, remain vulnerable to contamination after processing, most notably by Listeria monocytogenes, a pathogen of serious public health concern. United States regulations under 9 C.F.R. 430.4 require post-lethality treatments to suppress this organism, and high-pressure processing has emerged as one of the most effective options for sliced cured hams. The catch is that earlier studies suggested the treatment could alter texture, tenderness, color, and lipid stability, raising the question of whether the safety benefit comes at a sensory cost.
To answer that question, the researchers tracked the hams through twenty-nine days of refrigerated vacuum display, measuring lightness, redness, yellowness, hue angle, and chroma with a calibrated colorimeter on eight separate days. They also ran texture profile analysis and Warner-Bratzler shear force tests, determined moisture content following AOAC protocols, and recruited 240 consumer panelists across eight sensory sessions, each participant scoring color, odor, flavor, texture, and overall desirability on nine-point hedonic scales. The statistical design was a completely randomized 4 by 2 factorial, with curing treatment as the whole-plot factor and pressure treatment as the split-plot factor, analyzed in SAS using the GLIMMIX procedure.
The chemistry behind the characteristic pink of cured meat explains much of what the team found. During curing, nitric oxide reacts with myoglobin to form nitrosylmyoglobin, which is converted upon heating into nitrosyl hemochromogen, a heat-stable pigment built around a porphyrin ring with a central ferrous iron bound to nitric oxide. This molecule proved remarkably robust under pressure. Hams cured with either synthetic nitrite or celery powder showed comparable color stability, and the pressure treatment had no significant effect on redness at all. Only small shifts in yellowness and hue angle appeared late in the display period among pressurized samples, with a maximum difference of 0.36 in a* and 1.94 in hue angle, changes far too subtle for the human eye to detect under retail lighting.
The uncured hams told a different story. Without nitrite, the annatto paste and red wine added to the brine simply could not reproduce the rosy pink of genuine curing. Annatto’s carotenoid pigments produce orange-yellow to brick-red tones that fade in light, while the anthocyanins in red wine appear to have oxidized during the ten-hour smoking cycle at 108 degrees Celsius. Neither pigment can mimic the specific cool pink generated by the nitrogen-iron bond at the heart of nitrosyl hemochromogen. Instrumental measurements confirmed it: the uncured hams showed the lowest redness values and the highest yellowness, hue angle, and chroma, and panelists rated their color the least desirable of all four treatments.
Texture results reinforced nitrite’s functional necessity. The uncured hams recovered their shape less effectively after compression, showing reduced springiness compared with the conventional and spiced celery-powder hams. The researchers hypothesize that lower sodium chloride levels in the uncured formulation reduced salt-mediated protein solubilization, leaving muscle fibers more swollen and water-laden. Notably, moisture content itself did not differ among treatments, hovering around 63 to 65 percent, which suggests other brine ingredients contributed to the textural deficit. High-pressure processing, meanwhile, produced only one measurable textural change, a slight reduction in deformation, and left hardness, shear force, chewiness, and cohesiveness untouched. The authors attribute this resilience to the fact that the hams were already cooked: their proteins were thermally denatured before pressurization and did not undergo further transformation during the brief two-minute treatment.
The sensory panel delivered the most commercially significant verdict. Hams cured with synthetic nitrite and those cured with celery powder plus the buffered vinegar antimicrobial received the highest flavor and overall desirability scores, and they were statistically indistinguishable from each other. Panelists clearly preferred the traditional cured flavor profile over the seasoned alternatives, and the spiced formulations of both the celery-powder and uncured hams scored lower on flavor, odor, and overall appeal. The equivalence of the two nitrite-cured products indicates that the source of the nitrite, whether synthesized in a factory or extracted from celery, leads to the same flavor and color development during processing.
One interaction between curing source and pressure treatment stood out. In the celery-powder hams containing the buffered vinegar antimicrobial, high-pressure processing actually reduced off-flavor intensity, consistent with earlier work showing that buffered vinegar improves flavor perception in restructured beef. In the uncured hams, however, pressure treatment increased off-flavor intensity. The researchers point to lipid oxidation as the likely culprit: pressures above 400 megapascals are known to markedly accelerate lipid oxidation in uncured pork, while nitrite protects against oxidation by stabilizing heme iron and preventing the release of catalytic pro-oxidants. Vacuum packaging, which removes oxygen before storage, appears to have shielded the nitrite-cured hams from this effect entirely.
The study’s conclusions cut in two directions. For manufacturers, the message is reassuring: naturally sourced nitrite performs equivalently to synthetic nitrite in maintaining quality, and high-pressure processing does not compromise the attributes of nitrite-cured ready-to-eat hams. For regulators, the findings sharpen an existing dilemma. Because the USDA does not recognize celery powder as an equivalent curing agent, products made with it can be labeled “uncured” even though the ingredient functions as nitrite once converted. The authors argue that this labeling convention deserves reconsideration, noting that the similarity between naturally and synthetically cured products in their study supports regulatory recognition of naturally cured hams. They also acknowledge the study’s limits: lipid oxidation and residual nitrite were not directly measured, and future work should examine how different nitrite sources interact with pressure treatment to affect food safety indicators, including Listeria contamination. Until then, the humble slice of deli ham remains a surprisingly rich case study in how chemistry, consumer perception, and labeling law collide on the supermarket shelf.
Subject of Research: Effects of natural versus synthetic nitrite curing sources and high-pressure processing on the quality of smoked ready-to-eat hams
Article Title: Effects of curing sources and high-pressure processing on quality attributes of smoked hams
Article References: Gamage, N. H., Ewasko, D., Yeh, Y., & de Mello, A. S. (2026). Effects of curing sources and high-pressure processing on quality attributes of smoked hams. Food Science of Animal Resources, 46(1), Article 63. https://doi.org/10.1007/s44463-026-00063-y
Image Credits: AI Generated
DOI: 10.1007/s44463-026-00063-y
Keywords: nitrite, celery powder, high-pressure processing, smoked ham, clean label, meat science, Listeria monocytogenes, lipid oxidation, sensory evaluation, cured color, ready-to-eat meat, food regulation
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Tags: celery powdercelery powder as nitrite substituteclean labelcomparison of synthetic sodium nitrite and vegetable-derived nitratesconsumer perceptions of uncured versus cured meatscured coloreffectiveness of celery powder in antimicrobial preservationfood regulationfood safety of vegetable-based nitrates in processed meatsfood science research on meat curinghigh-pressure processingimpact of celery juice powder on cured meat qualityindustry standards for “curedlipid oxidationListeria monocytogenesmeat sciencenatural curing methods in meat processingnitriteready-to-eat meatregulatory implications of natural curing agentsrole of spices and red wine in meat curing processessensory evaluationsmoked hamsmoked ham preservation
