Dry-cured ham flavour: enzymatic generation and process influence

Insight into the Relationship between the Causes of Off-Odour and Microorganism Communities in Xuanwei Ham

To expound on the correlation between the microorganism communities and the formation of off-odour in Xuanwei ham, the microorganism communities and volatile compounds were investigated in the biceps femoris (BF) and semimembranosus (SM) of Xuanwei ham with different quality grades (normal ham and spoiled ham). The single molecule real-time sequencing showed that differential bacteria and fungi were more varied in normal hams than in spoiled hams. Headspace solid-phase microextraction-gas chromatography (HS-SPME-GC-MS) results indicated that aldehydes and alcohols were significantly higher in spoiled hams than those in normal hams (p < 0.05). The off-odour of spoiled hams was dominated by ichthyic, malodourous, sweaty, putrid, sour, and unpleasant odours produced by compounds such as trimethylamine (SM: 13.05 μg/kg), hexanal (BF: 206.46 μg/kg), octanal (BF: 59.52 μg/kg), methanethiol (SM: 12.85 μg/kg), and valeric acid (BF: 15.08 μg/kg), which are positively correlated with Bacillus cereus, Bacillus subtilis, Bacillus licheniformis, Pseudomonas sp., Aspergillus ruber, and Moraxella osloensis. Furthermore, the physicochemical property and quality characteristics results showed that high moisture (BF: 56.32 g/100 g), pH (BF: 6.63), thiobarbituric acid reactive substances (TBARS) (SM: 1.98 MDA/kg), and low NaCl content (SM: 6.31%) were also responsible for the spoilage of hams with off-odour. This study provided a deep insight into the off-odour of Xuanwei ham from the perspective of microorganism communities and a theoretical basis for improving the flavour and overall quality of Xuanwei hams.

The contribution of inoculated probiotics to increased protein-derived volatile flavor compounds

This study aimed to evaluate the contribution and mechanisms of Lactobacillus plantarum and Zygosaccharomyces mellis inoculation to the enhancement of protein-derived volatile flavor compounds (PVFCs) in low-salt dry-cured mackerel (LDCM). The contents of PVFCs (3-methylbutanal and phenylacetaldehyde), intermediates (α-ketoisocaproate and phenylpyruvic acid), precursor (α-ketoisocaproate and phenylpyruvic acid), and key enzyme activities (protease and transaminase) significantly increased (p < 0.05) in probiotic-treated groups. The dominant species in the probiotics-treated groups were the inoculated Lactobacillus plantarum and Zygosaccharomyces mellis, which were the main producer of key enzymes for the generation of PVFCs. Lactobacillus plantarum performed well in protein degradation and amino acid transamination, resulting in generating more 3-methylbutanal and phenylacetaldehyde, while Zygosaccharomyces mellis played a main role in phenylethanol production. The synergistic action of Lactobacillus plantarum and Zygosaccharomyces mellis could promote the formation of 3-methyl-1-butanol.

Effects of Mustard Seed Extract on Physicochemical and Storage Characteristics of Dry-aged Pork Loin Ham

This study investigated the effects of mustard seed extracts on physicochemical and storage characteristics of dry-aged pork loin ham during the aging period. In experiment 1, antioxidant activity was assessed for mustard seed extracted with varying ethanol concentrations and the results showed high antioxidant activity at 25%, 50%, and 75% ethanol concentrations. In experiment 2, pork loin was treated with mustard seed extracts obtained using different ethanol concentrations: not treated (control), 25% (MS25), 50% (MS50), and 75% (MS75). Physicochemical and storage characteristics of pork loin ham were measured in wk 0, 2, 4, and 6. The pH, aw, CIE b*, thiobarbituric acid reactive substances and volatile basic nitrogen values were lower in treated samples compared to the control (p<0.05). In conclusion, applying mustard seed extracts, particularly MS75, in the dry-aged pork loin ham production process could enhance storage stability and improve color attributes without having negative impacts on product quality.

Comparative Quantitation of Kokumi γ-Glutamyl Peptides in Spanish Dry-Cured Ham under Salt-Reduced Production

Salting is a crucial step during the production of dry-cured ham and it is not well known whether it has an impact on the generation of taste-active peptides. The present study focused on the quantitation of kokumi γ-glutamyl peptides in low-salted Spanish dry-cured hams with 12 months of processing. By using mass spectrometry, peptides were quantitated from samples obtained after ethanolic deproteinization-based and non-ethanolic deproteinization-based extraction methods. Peptides γ-EA, γ-EE, and γ-EL registered mean values of 0.31, 2.75, and 11.35 µg/g of dry-cured ham, respectively, with no differences observed between both extraction protocols. However, γ-EF, γ-EM, γ-EV, γ-EW, γ-EY, and γ-EVG presented significantly (p < 0.05) higher concentrations in the ethanolic deproteinized samples showing values of 5.58, 4.13, 13.90, 0.77, 3.71, and 0.11 µg/g of dry-cured ham, respectively. These outcomes reflect the importance of protocols for the extraction of peptides to achieve the most feasible results. In addition, potential precursors for the formation of γ-glutamyl peptides are generated during dry-curing under salt restriction. The kokumi activity of these γ-glutamyl peptides could enhance the sensory attributes countering the taste deficiencies caused by the salt restriction.

Role of Enzymatic Reactions in Meat Processing and Use of Emerging Technologies for Process Intensification

Meat processing involves different transformations in the animal muscle after slaughtering, which results in changes in tenderness, aroma and colour, determining the quality of the final meat product. Enzymatic glycolysis, proteolysis and lipolysis play a key role in the conversion of muscle into meat. The accurate control of enzymatic reactions in meat muscle is complicated due to the numerous influential factors, as well as its low reaction rate. Moreover, exogenous enzymes are also used in the meat industry to produce restructured products (transglutaminase), to obtain bioactive peptides (peptides with antioxidant, antihypertensive and gastrointestinal activity) and to promote meat tenderization (papain, bromelain, ficin, zingibain, cucumisin and actinidin). Emerging technologies, such as ultrasound (US), pulsed electric fields (PEF), moderate electric fields (MEF), high-pressure processing (HPP) or supercritical CO₂ (SC-CO₂), have been used to intensify enzymatic reactions in different food applications. This review aims to provide an overview of the enzymatic reactions taking place during the processing of meat products, how they could be intensified by using emerging technologies and envisage potential applications.

Influence of meat sample geometry on dehydration dynamics during dry-aging of beef

Meat geometry may impact on the dehydration kinetics during dry-aging influencing the drying rate and, potentially, aspects of meat quality. In this study, three meat geometries (slices, steaks and sections) were prepared from three bovine Longissimuss thoracis et lumborum at 3 days post-mortem and were dry-aged at 2 °C, 75% relative humidity with an airflow of 0.5-2.0 m/s for 22 days (slices), 48 days (sections) and 49 days (steaks). Weights were recorded during dry-aging and drying curves were obtained for the three geometries, with the larger sections showing limited dehydration due to internal resistance to moisture migration from the core to the surface. Seven thin-layer equations were fitted to the dehydration data in order to model the drying kinetics during dry-aging. Thin-layer models described reliably the drying kinetics of the three geometries. In general, reduced k values (h^-1) reflected the lower drying rates as thickness increased. The Midilli model provided the best fit for all geometries. Proximate analyses of the three geometries and bloomed colour of sections were measured at the start and the end of the dry-aging period. Moisture loss during dry-aging led to the concentration of protein, fat and ash contents; while no significant differences were found for L*, a* and b* values of sections before and after the dry-aging process. In addition, moisture content, water activity (a_w) and LF-NMR measurements were taken at different locations within beef sections to further explore water dynamics during dry-aging.

A proteomic study of "Coppa Piacentina": A typical Italian dry-cured Salami

Coppa Piacentina is considered a peculiar dry cured salami, since it is manufactured by the entire neck muscles stuffed and matured in natural casings, the same as dry cured ham and fermented dry cured sausages. In this work the proteolysis of external and internal portions was investigated by a proteomic approach and by amino acids analysis. Samples of "Coppa Piacentina" were analyzed at 0 days and after 5 and 8 months of ripening through mono- and two-dimensional gel electrophoresis. Image analysis of 2D electrophoretic maps indicated a more intense enzyme activity on the external part, mainly due to endogenous enzymes. They favored, respectively, myofibrillar or sarcoplasmic proteins at 5 or 8 months of ripening. Free amino acids determination proved that lysine and glutamic acid were the most represented ones, followed by a free amino acids sequence like that of dry cured ham. The peculiarities of "Coppa Piacentina" were characterized by a slow proteolysis, due to sacking and binding of the whole cut of the pork neck.

Bioactive and Sensory Di- and Tripeptides Generated during Dry-Curing of Pork Meat

Dry-cured pork products, such as dry-cured ham, undergo an extensive proteolysis during manufacturing process which determines the organoleptic properties of the final product. As a result of endogenous pork muscle endo- and exopeptidases, many medium- and short-chain peptides are released from muscle proteins. Many of them have been isolated, identified, and characterized, and some peptides have been reported to exert relevant bioactivity with potential benefit for human health. However, little attention has been given to di- and tripeptides, which are far less known, although they have received increasing attention in recent years due to their high potential relevance in terms of bioactivity and role in taste development. This review gathers the current knowledge about di- and tripeptides, regarding their bioactivity and sensory properties and focusing on their generation during long-term processing such as dry-cured pork meats.

Insight into Ultrasound-Induced Modifications of the Proteome and Flavor-Related Proteins of Unsmoked Bacon by Applying Label-Free Quantitation Technology

The aim of this study was to investigate the modifications of the proteome and flavor-related proteins in unsmoked bacon resulting from ultrasound treatment with the application of label-free quantitation technology together with bioinformatics analysis. Results showed that the expression levels of 137 proteins were markedly affected by ultrasound with most of them being significantly upregulated. The proteins distributed in the cytoplasm and the cytosol, the mitochondrion, and the nucleus were more susceptible to ultrasound treatment. Meanwhile, 20 flavor-related proteins, mostly myofibrillar proteins and metabolic enzymes mainly involved in the metabolic pathways of signaling and cellular processes and environmental information processing, were screened out. In addition, the differential expressions of flavor-related proteins induced by ultrasound were verified by western blotting. This study displayed insightful information from the proteomics perspective for a better understanding of the influential effect of ultrasound treatment on meat flavor.

Influence of Fermented-Moutai Distillers' Grain on Growth Performance, Meat Quality, and Blood Metabolites of Finishing Cattle

The present study evaluated the effect of dietary supplementation with fermented-Moutai distillers' grain (FMDG) on the growth performance, meat quality, amino acid composition and blood metabolites of finishing cattle. Thirty cattle (2 years old; 237.55 ± 10.72 kg) were randomly assigned to one of three dietary supplementations: 0% FMDG (control), 15% FMDG (R1) and 30% FMDG (R2) [dry matter (DM) basis]. After 60 days, the inclusion of FMDG had no significant (p > 0.05) effects on the growth performance indices (dry matter intake, average daily gain and feed efficiency), meat quality (cooking yield, shear force, L^*, a^*, and b^* values) or bovine blood biochemical indicators (except albumin and immunoglobulin A). Cattle fed R1 had the lowest (p = 0.001) loin eye area. Supplementation with FMDG significantly (p < 0.05) increased the beef contents of various amino acids (except isoleucine and arginine) compared with the control diet. Specifically, R2 significantly increased (p < 0.05) the total amino acid, essential amino acid, non-essential amino acid and umami amino acid contents in beef, while the difference in bitter amino acid content between different treatments was not significant (p = 0.165). These results suggest that it is feasible to include FMDG at up to 30% DM without affecting the growth performance, meat quality or blood metabolites of finishing cattle.

Quantification and in silico analysis of taste dipeptides generated during dry-cured ham processing

Small peptides such as dipeptides contribute to a great extent to the characteristic taste of dry-cured hams. In this study, hydrophilic interaction liquid chromatography (HILIC) combined to tandem mass spectrometry was used to separate, identify, and quantify seven dipeptides in dry-cured hams sampled at different processing times (6, 12, 18, and 24 months). Results showed an increased concentration of dipeptides DA, DG, EE, ES, and EV with the length of processing, obtaining values up to 23 μg/g of dry-cured ham, which suggests an intense action of muscle enzymes dipeptidyl peptidases during the process. The dipeptide VG significantly decreased from 7 to 4 μg/g of dry-cured ham as the processing increased from 6 to 24 months, whereas the dipeptide PA showed low values between 380 and 550 ng/g of dry-cured ham at all the sampling times. Additionally, in silico analyses reported the sensory characteristics of the studied dipeptides, mostly giving bitter and umami taste, and predicted their allergenicity, toxicity, and physicochemical properties. These results could be useful for further studies related to the pleasant taste of dry-cured hams.

The Influence of the Type of Dry-Cured Italian PDO Ham on Cathepsin B Activity Trend during Processing

Cathepsin B activity was measured during processing in hams originating from the main Italian prosciutto PDOs: Parma, San Daniele and Toscano. Sixty-five heavy pig thighs, from sixty-five Italian large white x Italian Landrace pigs bred and slaughtered in the same conditions were considered. Five thighs represented the post-mortem control time. The other 60 were distributed one plant per PDO, following a balanced plan. The thighs were sampled at the biceps femoris in groups of four per plant in the following ripening phases: salting, resting, drying, greasing, end of curing. The activity of the Cathepsin B (U/g protein) was determined by means of fluorescence measurements. The Cathepsin B ripening trend of the various PDOs was significantly different, particularly during the initial and mid-curing stage. This activity correlates with the proteolysis index through a PDO dependent pattern, indicating that different processing conditions can influence the quality of prosciutto, since they determine its biochemical development.

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.

Review: Pork quality attributes from farm to fork. Part II. Processed pork products

Pork is often consumed in a very wide variety of products, processed from integral cuts or minced meat using different conservation methods (curing, smoking, cooking, drying, fermenting). Quality of pork products results from a combination between the properties of the raw material and the processing conditions to elaborate the final products. The influence of primary production factors, slaughtering and carcass processing on the quality of fresh pork has been reviewed (part 1), considering quality as an integrative combination of various attributes: commercial, organoleptic, nutritional, technological, convenience, and societal image, the latter denotes cultural, ethical (including animal welfare) and environment dimensions related to the way pork is produced, processed, and its geographical origin. This review (part 2) focuses on the influence of primary production factors and processing techniques on the quality of two important and economically significant processed pork products issued from contrasting processing techniques: cooked ham and dry-cured ham. As with fresh pork, many factors influence the quality of processed products, and one factor can affect several attributes. Moreover, in the case of processed products, numerous factors in both animal production and processing steps interact to determine their quality attributes. The quality of cooked ham depends on the properties of the raw material (in particular pH, colour, water holding capacity, presence of destructured meat defect, etc.) which are determined by pig husbandry practices (especially the genotype), pre-, postslaughter and processing conditions including the composition of curing mixture (ingredients, additives), salting, mixing and heat treatment. Processing techniques of cooked ham aim at homogenising the product quality within a given quality category (e.g. 'standard' or 'superior') or brand. Therefore, the variability of raw material is problematic for the cooked ham processing industry, which generally seeks uniformity and homogeneity of fresh hams. Likewise, pig husbandry conditions exert even greater impact on dry-cured ham quality. Indeed, the properties of raw material (including weight of fresh ham, fat thickness, pH, intramuscular fat and antioxidants content, fatty acid profile, etc.) that result from combined effects of primary production factors (genotype, feeding, production system, etc.) interact with processing conditions (salting, drying, ripening conditions and duration, etc.) to elaborate the quality attributes of the final products. Synergies can be sought between the primary production factors and processing techniques leading to specific organoleptic characteristics (texture, taste, aroma, flavour, etc.) that can be valued by quality labels. Quality of products is thus built along the whole chain from farm to fork.

Drying dynamics of meat highlighting areas of relevance to dry-aging of beef

Drying of foods is a processing step, which has a variety of outcomes from improving shelf life and product stability, to reducing weight, or to achieving a targeted product eating quality. Drying is key step in the manufacturing of some dried meat products, such as jerky. It is also a major event that occurs when beef is dry-aged, where beef is exposed to air under defined conditions for an extended aging period. Although the conditions typically used to produce dried meat products are significantly different from those that prevail during dry-aging, both involve a gradual removal of water from muscle. As there is a paucity of research on the kinetics of the dehydration process occurring during dry-aging of beef, this paper comprehensively reviews models used to describe drying kinetics in other beef products, in order to gain insights regarding the key factors that impact water removal from meat. Consideration is given as to how the specific conditions during dry-aging such as air flows used (approximately 2 m/s), high air relative humidity, low temperature, and meat geometry will influence the kinetics of the drying. With regard to modeling, equations derived from Fick's second law of diffusion (e.g., thin-layer models) have been used to describe the drying kinetics of small-sized meat products. However, to apply Fick's law to dry-aging, some different considerations may need to be evaluated such as: tridimensional geometry (i.e., whole muscle); uniform initial moisture content; isotropic diffusion; negligible shrinkage;and a combination of internal and external resistances.

Characterization of Umami Dry-Cured Ham-Derived Dipeptide Interaction with Metabotropic Glutamate Receptor (mGluR) by Molecular Docking Simulation

Dry-cured ham-derived dipeptides, generated along a dry-curing process, are of high importance since they play a role in flavor development of dry-cured ham. The objective of this study was to analyze the residues of the less-studied metabotropic glutamate receptor 1 (mGluR1) implicated in the recognition of umami dry-cured ham dipeptides by molecular docking simulation using the AutoDock Suite tool. AH, DA, DG, EE, ES, EV, and VG (and glutamate) were found to attach the enzyme with inhibition constants ranging from 12.32 µM (AH) to 875.75 µM (ES) in the case if Rattus norvegicus mGluR1 and 17.44 µM (VG) to 294.68 µM (DG) in the case of Homo sapiens, in the open–open conformations. Main interactions were done with key receptor residues Tyr74, Ser186, Glu292, and Lys409; and Ser165, Ser186, and Asp318, respectively, for the two receptors in the open–open conformations. However, more residues may be involved in the complex stabilization. Specifically, AH, EE and ES relatively established a higher number of H-bonds, but AH, EV, and VG presented relatively lower Ki values in all cases. The results obtained here could provide information about structure and taste relationships and constitute a theoretical reference for the interactions of novel umami food-derived peptides.

The effects of curing agents on the proteolysis and lipid oxidation of pastırma produced by the traditional method

In the study, the effects of nitrate and/or nitrite (150 mg/kg KNO₃, 300 mg/kg KNO₃, 150 mg/kg NaNO₂, and 150 mg/kg KNO₃ + 150 mg/kg NaNO₂) on proteolytic changes (free amino acid composition, SDS-PAGE) in pastırma were investigated. Pastırma samples were also analyzed in terms of some qualitative (pH, a_w, TBARS, residual nitrite, salt) properties. The lowest total free amino acid content (1818.3 mg/ 100 g DM) was observed in the combination of 150 mg/kg KNO₃ + 150 mg/kg NaNO₂, while the highest content (2847.49 mg/ 100 g DM) was observed in 150 mg/kg KNO₃. Although the pastırma groups generally exhibited similar SDS-PAGE profiles, differences were detected at some band intensities. The lowest TBARS value (22.24 μmol MDA/kg) was observed in 150 mg/kg KNO₃ + 150 mg/kg NaNO₂. As a result, the use of 150 mg/kg KNO₃ in the pastırma curing process causes more intense proteolysis.

Formation of amino acid-derived volatile compounds in dry-cured mackerel (Scomberomorus niphonius): Metabolic pathways involving microorganisms, precursors, and intermediates

This study focuses on the formation mechanism of amino acid-derived volatile compounds (AAVC) in dry-cured mackerel (Scomberomorus niphonius) (DCM) during the process. Three kind of AAVC (3-methylbutanal, 3-methylbutanol, and phenylacetaldehyde) were detected in DCM. The content of 3-methylbutanal (14.6 mg/kg) was higher than that of phenylacetaldehyde (12.9 mg/kg), and part of which was reduced to 3-methylbutanol (5.15 mg/kg). While the corresponding intermediate, α-ketoisocaproate (156 μg/kg), was lower than that of phenylpyruvic acid (271 μg/kg), indicating its decarboxylation was limited. Five strains (Bacillus, Enterobacter, Staphylococcus, Macrococcus, and Lactobacillus) that can produce the relative transaminases and decarboxylases were involved in the production of AAVC. The most dominant strain, Bacillus (81.9%), was only involved in the production of 3-methylbutanal. The relative abundance of Staphylococcus, the sole phenylpyruvate decarboxylase-producing bacteria, was low, resulting in low product conversion. These results indicated that the production of AAVC is determined by specific microorganisms in the products.

Investigating the Features of PDO Green Hams during Salting: Insights for New Markers and Genomic Regions in Commercial Hybrid Pigs

Protected Designation of Origin (PDO) dry-cured hams production is greatly dependent on raw meat quality. This study was performed to identify genetic markers associated with the quality of dry-cured ham. Carcass traits of 229 heavy pigs belonging to three commercial genetic lines were registered (weight, EUROP classification). Phenotypic traits (Semimembranosus muscle ultimate pH, ham weight and lean meat content, adsorbed salt) of the corresponding thighs, undergone PDO ham process in three different plants, were measured, using a fast and non-invasive technology. Green ham weight and lean meat percentage influenced the estimated salt content and the weight loss during salting, even if the processing plant greatly affected the variability of the measured ham traits. The genomic data were obtained with the GeneSeek Genomic Profiler (GGP) 70k HD Porcine Array, using the slaughter day and the sex of the animals in the statistical analyses. The phenotypic traits were associated with the genotypes through GenAbel software. The results showed that 18 SNPs located on nine porcine chromosomes were found to be associated with nine phenotypic traits, mainly related to ham weight loss during salting. New associations were found between markers in the genes Neural Precursor Cell Expressed Developmentally Down-Regulated 9 (NEDD9, SSC7), T-Cell Lymphoma Invasion and Metastasis 2 (TIAM2, SSC1), and the ham quality traits. After validation, these SNPs may be useful to improve the quality of thighs for the production of PDO dry-cured hams.

Effect of storage temperature on volatile marker compounds in cured loins fermented with Staphylococcus carnosus by brine injection

In this study, the influence of low (5 °C), intermediate (15 °C) and high (25 °C) storage temperatures on the profile of volatile compounds of North European cured loins fermented with Staphylococcus carnosus strains was investigated. In this context, proteolytic activity, bacterial growth, key volatile compounds and sensory attributes were studied. In conclusion, storage temperature significantly affected the volatile marker compounds. A multiple regression indicated significant effects of seven volatile compounds (acetophenone, benzaldehyde, butanone, 3-methylbutanal, 1-octen-3-ol, nonanal and pentanone) on the overall odor (R2 = 95.9%) and overall flavor (R2 = 81.1%). The sum of the marker volatiles aldehydes, ketones and alcohol increased with rising temperatures and the highest amounts of the odor active 3-methylbutanal up to 155 and 166 ng/g meat were detected in high temperature-stored loins. Moreover, the addition of S. carnosus strain LTH 3838 showed maximum effect at 5 °C-storage temperature in comparison to the control.

Effect of ultrasound on proteolysis and the formation of volatile compounds in dry fermented sausages

Ultrasound (US) is an emerging technology capable of affecting enzymes and microorganisms, leading to the release of amino acids and the formation of volatile compounds. The effect of different exposure times (0, 3, 6, and 9 min) of US (25 kHz, 128 W) on the proteolysis and volatile compounds of dry fermented sausages during processing (day 0 and 28) and storage (day 1 and 120) was investigated. Lower alanine, glycine, valine, leucine, proline, methionine, and tyrosine levels were observed at the beginning of manufacture for the sample subjected to 9 min of US (p < 0.05) when compared to the control. During the storage period, the samples subjected to US exposure for 3 and 6 min exhibited higher free amino acid levels. A greater formation of hexanal, pentanal, and hexanol was observed in the US-treated samples when compared to the control (p < 0.05), as well as other derivatives from the oxidation reactions during the storage. The use of US (25 kHz and 128 W) in the manufacture of dry fermented sausages can affect the proteolysis and the formation of compounds derived from lipid oxidation during the storage.

Effects of microbial fermentation on the flavor of cured duck legs

In this study, fermentation with Lactobacillus plantarum and Saccharomyces cerevisiae was applied to improve the flavor of cured duck leg meat. Odor and taste evaluations, lipid oxidation, volatile flavor substances, and protein degradation were determined to investigate the effects of microbial fermentation on flavor improvement. The results showed that the utilization of L. plantarum represented the most significant effect on lipid peroxidation inhibition (the lowest value of thiobarbituric acid reactive substances and the highest content of polyunsaturated fatty acids) and also enhanced the generation of volatile flavor substances than nonfermented duck meat. Microbial fermentation accelerated protein degradation in duck meat. S. cerevisiae could produce glutamate to promote the umami taste flavor of cured duck leg meat, and L. plantarum significantly improved the sweet taste by releasing alanine. Meanwhile, mixed fermentation with the two microbial species resulted in the combination of both of their advantages. These findings not only indicate the potential application of microbial fermentation in characteristic duck meat but also indicate that fermentation improves sensory properties of duck products significantly.

Challenges to reduce or replace NaCl by chloride salts in meat products made from whole pieces - a review

NaCl is fundamental for the development of the physico-chemical, sensorial and microbiological stability in meat products made from whole pieces such as dry-cured lacón, loin, ham, bacon, jerked beef, and pastirma). The substitution of NaCl by other chloride salts (KCl, CaCl₂ and MgCl₂), in order to minimize changes in the processing steps and insertion of new ingredients, is a major challenge for the elaboration of salted meat products in the context of increasing awareness among consumer about sodium consumption and health. This review aims to discuss the potential use of binary, ternary and quaternary salting mixtures in the processing of salted meat products and their effects on microbiological evolution and safety, sensory properties, oxidative reactions on proteins and lipid, and proteolysis and lipolysis reactions. More specifically, the substitution of NaCl by other chloride salts can influence the growth of microorganisms, the formation of toxic compounds, progression of enzymatic and oxidative reactions, and the sensory attributes. Scientific evidences from a food technological point of view, support the use of KCl to partially replace NaCl while major advances/more sophisticated strategies are still necessary to effectively introduce CaCl₂ and MgCl₂ as NaCl replacers. Moreover, further studies regarding the shelf-life and economic problems of the alternatively salted products are still necessary.

Physicochemical and microstructural attributes of marinated chicken breast influenced by breathing ultrasonic tumbling

Currently, the conventional atmospheric pressure-based and vacuum-based tumbling processes have a limited improvement on the chicken characteristic attributes during the marination process. In view of this, through a breathing (pressure change) tumbling strategy, ultrasonication (40 kHz, 140 W) was applied to improve tenderness, taste, and microstructure of chicken by a redesigned tumbler. The results showed that the tumbling with the breathing action and ultrasonication significantly enhanced the marinating absorptivity, tenderness and taste, and accelerated the degradation of myosin light chain. Free peptides (from 1465.9 ± 34.6 to 4725.7 ± 43.2 μg/mL) and amino acids (from 1.503 ± 0.096 to 2.593 ± 0.109 mg/mL) rose evidently for the control and the breathing tumbling treatment assisted by ultrasound respectively. Raman analysis revealed that strength of disulfide bonds declined from 0.731 ± 0.006 to 0.607 ± 0.011 a.u. and the conversion from α-helix (decreased by 67.23%) into β-fold (increased by 1573%) conformation occurred. Low field NMR analysis indicated that the content of immobilized water increased from 77385 ± 14 to 137011 ± 106 au·ms by integral calculus. Scanning and transmission electron microscopies clearly showed a prospective rupture of myofibers, myofibrils, and lysosomes. Overall, as a potential alternative, the breathing ultrasonic tumbling means improved the marinating efficiency and characteristics of marinated chicken breast.

Potential Antioxidant and Angiotensin I-converting Enzyme Inhibitory Activity in Crust of Dry-aged Beef

Antioxidant activity, angiotensin I-converting enzyme (ACE) inhibitory activity, and protein profile of crust (the dried surface of dry-aged beef) were evaluated compared to unaged, wet-, and dry-aged beef. Antioxidant activity was determined using 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-di-(3-ethylbenzthiazoline sulfonate) radical scavenging activities, ferric reducing antioxidant power, and ferrous ion chelating activity. The crust samples showed the greatest (P < 0.05) ACE inhibitory and antioxidant activity resulting from the three different mechanisms of action (radical scavenging, non-radical redox potential activity, and metal chelating) among the treatments. Small molecular weight protein bands and small peptides (<3 kDa) indicating potent bioactivity were evident in the myofibrillar protein profile of crust samples. The lowest (P < 0.05) ACE inhibitory activity was observed in unaged beef. The results indicate that crust could be utilized in various areas as a functional ingredient possessed antioxidant and ACE inhibitory activity instead of being discarded. In addition, dry aging can use for generation of functional ingredient from beef as the regime.

Substituting sodium by various metal ions affects the cathepsins activity and proteolysis in dry-cured pork butts

Salt contents and compositions are crucial parameters to enzyme activity and might even affect the proteolysis and quality of dry-cured meat. However, the metal ions significantly vary with geographic origin, which would be a determinant in the dry-cured meat manufacture. Therefore, the main salt compositions of KCl, CaCl₂, MgCl₂ and ZnCl₂ were therefore used to partially substitute NaCl while additionally assessing and regulating their function during the dry-cured pork butts processing. Physiochemical properties, cathepsins activity, proteolysis and sensory evaluation were investigated. The results indicated that partial substitution of sodium prevented the dehydration, and accelerated the pH reduction. CaCl₂ and MgCl₂ partial substitution moreover exerted some promoting effect on cathepsin activity whereas ZnCl₂ was a subtle inhibitor. The proteolysis index of CaCl₂ and MgCl₂ substitution were superior to the rest. The metal ions partial substitution reduced saltness, while the presence of KCl and MgCl₂ enhanced bitterness. Further correlation analysis was performed to better understand the interactions between those parameters.

Interrelationship between myoglobin oxidation and lipid oxidation during the processing of Cantonese sausage with d-sodium erythorbate

BACKGROUND

Pork is used as raw material to produce Cantonese sausage, and 0.5 or 1 g kg^-1 of d-sodium erythorbate is added to the pork meat. In this study the myoglobin oxidation rate, relative metmyoglobin content, heme iron content, redness, pH, free radical content and thiobarbituric acid reactive substance (TBARS) value were measured at different processing times and different content of d-sodium erythorbate.

RESULTS

It was found that d-sodium erythorbate significantly reduced the free radical content and myoglobin and lipid oxidation rates and increased heme iron levels. When d-sodium erythorbate was added to the sausage, the absorption peak of myoglobin porphyrin shifted left, migrating from 414 to 405 nm. At 72 h, with an increase in the d-sodium erythorbate content, a significant negative correlation was identified between heme iron and the degree of redness (P < 0.01).

CONCLUSION

During sausage processing, there are strong correlations among TBARS values, free radical content, metmyoglobin levels, heme iron levels, a* and pH at the same d-sodium erythorbate level. At the same processing time, adding d-sodium erythorbate can slow the rate of myoglobin and lipid oxidation and prevent the discoloration of sausage. © 2019 Society of Chemical Industry.

Changes in Lipase and Antioxidant Enzyme Activities during Processing of Cantonese Sausage with D-Sodium Erythorbate

Pork was used as raw material to produce Cantonese sausage, with additions of 0.05% or 0.1% D-sodium erythorbate. The oxidation indices (peroxide value, TBARS value, carbonyl value, and conjugated dienes value) and enzyme activity (total phospholipase, acid lipase, neutral lipase, superoxide dismutase, and glutathione peroxidase) were measured in the sausages at different processing periods. The results showed slowed lipid oxidation in the presence of D-sodium erythorbate, inhibition of total phospholipase, acid lipase, and neutral lipase activities, and increased superoxide dismutase activity, with little change in glutathione peroxidase activities. When increasing D-sodium erythorbate, the superoxide dismutase activity was negatively correlated with the peroxide value at 5 h (P<0.01), the neutral lipase activity was positively correlated with the conjugated dienes value at 15 h (P<0.01), and the total phospholipase activity was positively correlated with the peroxide value at 30 h (P<0.01). This study explored the antioxidant effect of D-sodium erythorbate and provides a theoretical foundation to improve the quality of Cantonese sausage.

Automatic ham classification method based on support vector machine model increases accuracy and benefits compared to manual classification

The thickness of the subcutaneous fat (SFT) is a very important parameter in the ham, since determines the process the ham will be submitted. This study compares two methods to predict the SFT in slaughter line: an automatic system using an SVM model (Support Vector Machine) and a manual measurement of the fat carried out by an experienced operator, in terms of accuracy and economic benefit. These two methods were compared to the golden standard obtained by measuring SFT with a ruler in a sample of 400 hams equally distributed within each SFT class. The results show that the SFT prediction made by the SVM model achieves an accuracy of 75.3%, which represents an improvement of 5.5% compared to the manual measurement. Regarding economic benefits, SVM model can increase them between 12 and 17%. It can be concluded that the classification using SVM is more accurate than the one performed manually with an increase of the economic benefit for sorting.

Correlation between skeletal muscle fiber type and free amino acid levels in Japanese Black steers

Free amino acids are important components of tastants and flavor precursors in meat. To clarify the correlation between muscle fiber type and free amino acids, we determined the concentrations of various free amino acids and dipeptides in samples of different muscle tissues (n = 21), collected from 26-month-old Japanese Black steers (n = 3) at 2 days postmortem. The proportions of the myosin heavy chain (MyHC), slow (MyHC1) and fast (MyHC2) isoforms were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The contents of free amino acids and dipeptides were measured by high performance liquid chromatography (HPLC). The MyHC isoform composition varied among the tissue samples. The MyHC1 proportion ranged from 6.9% ± 3.9% to 83.3% ± 16.7%. We confirmed that there was a strong positive correlation between MyHC1 composition and total free amino acid concentrations, including those for two dipeptides. Among the 31 measured free amino acids and dipeptides, 11 showed significant positive correlations and five showed significant negative correlations with MyHC1 composition. These results suggest that a high MyHC1 content induces high free amino acid contents in bovine muscles possibly because of greater oxidative metabolism. This high level of free amino acids could contribute to the intense flavor of meat that is rich in slow-twitch fibers.

Role of moisture evaporation in the taste attributes of dry- and wet-aged beef determined by chemical and electronic tongue analyses

The role of moisture evaporation in the taste attributes of dry- and wet-aged beef was determined in this study. A total of 30 striploins (longissimus lumborum) were dry or wet aged for 28 days and analyzed for moisture content, taste-active compounds [free amino acids (FAAs), inosine 5'-monophophate (IMP), and reducing sugars], and taste attributes by an electronic tongue. After the completion of aging process, higher amounts of FAAs and reducing sugars were found in dry-aged beef (P < .05) in negative correlations with moisture content (r² = -0.9 and - 0.9, respectively), which were not detected in wet-aged beef. However, the different taste attributes of dry- and wet-aged beef were observed by the electronic tongue from day 14, whereas their moisture content was significantly different only at day 28. Consequently, although the moisture evaporation during dry aging process contributed to the increased flavor of dry-aged beef, there are other factors affecting flavor development including microbial activity on the surface crust.

Effect of breed on proteolysis and free amino acid profiles of dry-cured loin during processing

Non-protein nitrogen (NPN) and free amino acids (FAA) were analysed in dry-cured loin obtained from the native pig breed Chato Murciano (CM) during processing. In addition, a comparison was drawn between the NPN and FAA values obtained in CM and those obtained in dry-cured loin from a modern crossbreed pig genotype (CG) at commercialisation times (between 30 and 60 days of processing). Processing time affected NPN, total FAA concentration, and all FAA studied, except arginine, histidine and lysine. The breed affected both NPN and total FAA, as superior values were observed in CM at Day 30. From this moment onward, proteolysis was more intense in CG than in CM. At Day 30, the concentration of most amino acids, except for lysine and arginine, was higher in CM. Whereas the concentration of all amino acids, except serine, histidine and methionine + tryptophan, was higher in CG at Day 60. The breed affected proteolytic activity in dry-cured loin. The results suggested that, from the point of view of proteolysis, the optimum processing time for CM dry-cured loin is 45 days.