Effects of post mortem pH and salting time on Zinc-protoporphyrin content in nitrite-free Serrano dry-cured hams

Zinc-protoporphyrin formation in nitrite-free Parma Ham and its relationship with intrinsic parameters and red color profile of processed hams

A total of 134 fresh hams, assayed for Ferrochelatase (FeCH) activity and ultimate pH (pH48), were processed in compliance with the procedures established for PDO Parma ham and finally, analyzed for salt, moisture, Zinc Protoporphyrin IX (ZnPP), heme, iron and zinc contents, and proteolysis index (PI). The variation in ZnPP content was related to the intrinsic parameters of fresh and matured hams by a Partial Least Square Regression model. The most favorable factors on the formation of ZnPP were total iron content (representative of the initial hemoprotein content), and FeCH activity, demonstrating the main role played by these raw matter-specific predictors in the long matured dry-cured hams. To a lesser extent, zinc content and pH48 were involved with a positive and negative role, respectively. Salt content and PI of matured hams showed an inhibitory and a favorable influence, respectively, toward the ZnPP formation. Principal Component Analysis showed the associations between the sensory red color profile and the physicochemical traits of matured hams. The red color intensity increased in agreement with the red-violet and red-pink hues scores. The formation of a high amount of ZnPP was associated with the increased perception of the red-violet shade, with a lower lightness (L*) and Hue angle (h°). Moisture increase contributed to the shift in color perception to red-pink, while marked progress in PI strengthened the perception of the red-brown shade. ZnPP and final heme favored the red color of matured hams, although a high concentration of these pigments increased in particular the red-violet perception.

Zinc protoporphyrin IX generation by Leuconostoc strains isolated from bulged pasteurized vacuum sliced hams

The colour of meat typically fades as it decays. However, it has been observed that certain vacuum-packaged spoiled hams can maintain a pink colour even when the packaging is bulged. A large amount of Zinc protoporphyrin IX (ZnPP) was found in these hams, compared to fresh red hams or spoiled and grey hams. Combined with high-throughput sequencing and cultural isolation, the potential cultures of Leuconostoc mesenteroides S-13 (LM), Leuconostoc citreum OCLC11 (LC), and Leuconostoc mesenteroides subsp. IMAU:80679 (LS) were selected based on their ability to produce ZnPP. Subsequently, these cultures were introduced into a fermented sausage model to assess their effect on colour conversion. The analysis of absorption and fluorescent spectra showed that Nitrite sausages contained nitrosyl heme pigment, while bacteria-inoculated sausages were predominantly composed of ZnPP. In addition, the a* value of the LS sausage was close to the Nitrite group at the end of fermentation, significantly higher than control, indicating the effect of bacterial metabolism on the redness. Meanwhile, the Ferrochelatase (FECH) activity of LM, LC and LS groups were 140 ± 13, 113 ± 16 and 201 ± 20 U/g sausage, respectively, providing a potential method on compensating for nitrite/nitrate substitution based on the presence of ZnPP in meat products.

UHPLC-MS/MS-based lipidomics for the evaluation of the relationship between lipid changes and Zn-protoporphyrin formation during Nuodeng ham processing

The effects of changes in lipids on the formation of Zn-protoporphyrin (ZnPP) during the processing of Nuodeng ham were analyzed using a lipidomics approach based on UHPLC-MS/MS. The Nuodeng ham samples had a strong fluorescence emission peak at 590 nm, and the fluorescence intensity increased with the processing time. Lipid profiles were mainly affected by processing time. A total of 5 lipid classes were detected, of which glycerophospholipids (GP) and glycerolipids (GL) were the most abundant lipids. Fifty differential lipid compounds were screened, which were mainly GP and GL. Correlation analysis showed that 13 differential lipid compounds were significantly positively correlated with ZnPP content, and they contained more linoleic acid and oleic acid branch chains. Meanwhile, all triglycerides (TG) were negatively correlated with heme content, and they were enriched in stearic acid and palmitic acid branch chains. These findings can deepen the understanding of the relationship between ZnPP and lipids.

Formation of Zn-protoporphyrin during the elaboration process of non-nitrified serrano dry-cured hams and its relationship with lipolysis

This study assessed the ZnPP content, heme content, salt content, and instrumental color in the biceps femoris and semimembranosus muscles during the elaboration of Serrano dry-cured ham manufactured without the addition of nitrate and nitrite for 15 months. The effects of lipolysis and lipid oxidation on the content of Zn-protoporphyrin were also investigated in the biceps femoris. We found that the maximum formation of Zn-protoporphyrin occurred between end of resting and 6 months of processing, which coincides with temperature increase during processing and the end of salt equalization. Zn-protoporphyrin further increased in the biceps femoris until 9 months of processing but remained unchanged in the semimembranosus. Free fatty acid content increased till 6 months and then remained unchanged until the end of the process. These findings and those from an in vitro study reinforced the idea that the release of free fatty acids can promote the activity of the endogenous enzyme ferrochelatase and contribute to the formation of Zn-protoporphyrin from heme. However, the content of Zn-protoporphyrin decreased at the end of the processing, which may be due to the progression of lipid oxidation.

Sodium reformulation and its impact on oxidative stability and sensory quality of dry-cured rabbit legs

The aim of this study was to evaluate the oxidative stability and sensory quality of dry-cured rabbit legs produced with a reduction or replacement of 50% of NaCl by KCl and with the addition of monosodium glutamate (MG). Oxidative stability was evaluated during 90 days of storage at 20 °C by determining pH, redox potential (Eh), and TBARS while overall liking and sensory profile were measured at the beginning of storage. The results indicated that oxidative stability of the dry-cured rabbit legs was not affected by the sodium reformulation. However, TBARS values increased about 15-fold during storage in all treatments. Dry-cured rabbit legs produced with KCl showed lower scores (P < 0.05) for the overall liking and flavor attributes as "astringent flavor", "bitter taste" and "metallic flavor". The addition of MG to products with 50% NaCl reduction provided a liking and a sensory profile similar to the product with 100% NaCl.

Low-sodium dry-cured rabbit leg: A novel meat product with healthier properties

Dry-cured rabbit legs were produced with a 50% reduction or replacement of NaCl by KCl and with the addition of monosodium glutamate (MG). The effect of this reformulation on technological, nutritional, and sensory characteristics was evaluated. The sodium reformulation did not show a great impact on Aw, pH, weight loss, and volatile profile of the samples. The samples presented high protein (31.5 to 36.1%) and low fat contents (3.2 to 5.7%). In addition, all essential amino acids presented an amino acid score greater than 1.0. The reformulated samples showed a sodium reduction of 46.2% while the addition of KCl to the formulations provided a healthy Na/K ratio. Oleic acid was the major fatty acid (FA) (31.3% of total FA) and healthy lipid indexes were observed for all samples. Finally, the addition of MG was effective to compensate for the sensory defects caused by sodium reformulation.