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Fat, composed mainly of triacylglycerols and phospholipids, and protein, composed of amino acids, constitute major components of meat. Carbohydrate, in the form of glycogen, is present in very low amounts. This article describes the main methodologies available for the analysis of these substances, discusses their advantages and disadvantages, and gives recommendations for the choice of methods.

Dry-cured hams are a good source of bioactive peptides, whose stability to gastrointestinal (GI) digestion determines their bioaccessibility and thus their bioavailability to exert beneficial effects. The aim of this study was to evaluate the effect of in vitro GI digestion of dry-cured hams on the peptide profiles and their antioxidant activity. Results showed that the antioxidant activity decreased in the digested samples when measured by DPPH radical scavenging activity and ferric-reducing antioxidant power methods, but increased when assayed by ABTS radical scavenging assay. Chromatographic and mass spectrometry analysis revealed changes in the peptide profiles and evidenced the degradation of proteins, mainly titin, by the digestive enzymes. The study of the peptide profiles before and after digestion of dry-cured hams would help to extend the knowledge about the influence of peptide characteristics on their antioxidant activity and resistance to hydrolysis by digestive enzymes, allowing a better understanding of the bioaccessibility of the bioactive peptides generated in dry-cured hams., Grant AGL2017-89381-R and FEDER funds from the Spanish Ministry of Economy, Industry and Competitiveness are acknowledged.

This study evaluates the effect of dietary selenium (Se) supplementation source (organic, Se-enriched yeast; SY vs. inorganic, sodium selenite; SS), dose (0.2: L vs. 0.4: H mg/kg) and the combination of Se and vitamin E (VITE + SS) for 26 days on drip loss, TBARS, colour changes, myofibrillar protein pattern and proteolysis in pork. The lowest water losses were observed in the SY-H group when compared to the others. SY-H and VITE + SS groups presented lower myofibrillar protein hydrolysis/oxidation. VITE + SS supplementation also resulted in higher PRO, TRP and PHE content at days 2 and 7, whereas the SY group showed increased GLY and CAR and tended to have higher TAU and ANS at day 2. The myofibrillar fragmentation index was not modified by the dietary treatment; however, at day 8, it tended to be higher in groups supplemented with SeY and VITE + SS. The results of the present study might indicate a possible relation between muscle proteolysis and water loss., This research was supported by projects CDTI IDI-20111017 and S2013/ABI-2913-MEDGAN-CAM.

Thornback ray skin gelatin has been hydrolyzed with two different proteases in order to obtain peptides with ACE inhibitory and antioxidant activity. Hydrolysates with protease from Bacillus subtilis A26 (TRGH-A26) displayed ACE inhibitory activity with an IC 50 value of 0.94 μg/μL whereas Neutrase® hydrolysate from Bacillus amyloliquefaciens (TRGH-Neutrase) showed an IC 50 value of 2.07 μg/μL. Regarding antioxidant activity, IC 50 values of 1.98 and 21.2 μg/μL in TRGH-A26 and TRGH-Neutrase, respectively, were obtained using the DPPH radical-scavenging assay. The most active fractions identified by size-exclusion chromatography were further purified by RP-HPLC and analysed using nanoESI-LC–MS/MS to identify the sequence of the peptides. APGAP was the most active peptide inTRGH-A26 for ACE inhibitory activity with an IC 50 value of 170 μM, whereas GIPGAP showed the best ACE inhibitory activity in TRGH-Neutrase sample with an IC 50 value of 27.9 μM. The highest antioxidant activity was identified in peptide AVGAT, showing a 33% of activity at 3 mg/mL using the DPPH radical-scavenging assay. The obtained results proved the potential of thornback ray skin gelatin hydrolysates as a source of bioactive peptides. Statement of significance This study describes a peptidomic approach for the identification of ACE-inhibitory and antioxidant peptides generated from thornback ray gelatin ( Raja clavata ) hydrolysates from Bacillus subtilis A26 and Bacillus amyloliquefaciens Neutrase® enzymes and expose the potential of thornback ray gelatin hydrolysate as a source of bioactive peptides. In this sense, the decrease of systolic blood pressure is one of the main measurements considered in public health for the treatment of cardiovascular diseases, stroke and even end-stage renal disease. Traditionally, synthetic drugs such as captopril and enalapril have been used as ACE inhibitors despite their secondary effects, but the finding of new sources for the generation of natural bioactive peptides such as thornback ray muscle results is very important in the knowledge of less hostile but highly effective antihypertensive peptides as well as the development of new uses for waste and by-products generated from marine products, helping to solve the already existing environmental problem affecting this industry.

Coenzyme Q10 (CoQ10) or ubiquinone (2,3-dimethoxy-5-methyl-6-multiprenyl-1,4-benzoquinone) is an endogenous hydroxybenzoquinone liposoluble compound which plays important physiological roles that makes it to be considered as a bioactive compound that may be used for clinical practices and as food supplement. The purpose of this work was to analyse CoQ10 in three muscles with different oxidative patterns and determine its variability in different animal species (pork, beef, lamb and rabbit). The content of CoQ10 ranged from 4.3 to 30.9μg/g meat with the highest content in those muscles with oxidative pattern. So, more specific data on type of meat cut and proportion of muscles must be given for this nutrient when reporting its content in food composition databases., Grant PROMETEO/2012/001 from Conselleria d'Educació, Formació i Ocupació of Generalitat Valenciana (Spain) is fully acknowledged.

Pork meat is generally recognised as a food with relevant nutritional properties because of its content in high biological value proteins, group B vitamins, minerals especially heme iron, trace elements and other bioactive compounds. But pork meat also contributes to the intake of fat, saturated fatty acids, cholesterol, and other substances that, in inappropriate amounts, may result in negative physiologically effects. However, there are relevant factors affecting the content of many of these substances and somehow such variability should be taken into consideration. So, genetics, age and even type of muscle have a relevant influence on the amount of fat and the contents in heme iron. Also the composition in fatty acids of triacylglycerols is very sensitive to the contents of cereals in the feed; for instance, polyunsaturated fatty acids may range from 10% to 22% in pork meat. The content of other nutrients, like vitamins E and A, are also depending on the type of feed. Some bioactive substances like coenzyme Q10, taurine, glutamine, creatine, creatinine, carnosine and anserine show a large dependence on the type of muscle. This manuscript describes the main factors affecting the composition of pork meat nutrients and how these changes may affect the general food composition databases. (C) 2012 Elsevier Ltd. All rights reserved., Grant AGL2010-16305 from the Spanish Ministry of Science and Innovation (Madrid, Spain) and FEDER Funds and collaboration of Vaquero Foundation for R+D on Pork Meat (Madrid, Spain) are acknowledged. Grant PROMETEO/2012/001 from Generalitat Valenciana (Spain) is also acknowldeged. Work prepared within the Unidad Asociada IAD (UPV)-IATA (CSIC) framework.

This work is focused on the determination of compounds of nutritional interest that are naturally present in pork meat and how they are affected during the processing of dry-cured ham. Such compounds are creatine, creatinine, coenzyme Q(10), glutathione, carnosine, anserine, carnitine, taurine, cystine, cysteine and the essential amino acids. Their antioxidant and antyhipertensive functions were evaluated. Of all the assayed substances, only glutathione decreased totally during processing. Carnosine, creatinine, anserine and glutathione showed antioxidant, while cysteine, glutathione and carnosine showed antyhipertensive activity. So, dry-cured ham constitutes an excellent source of essential amino acids (all essential amino acids exhibited a large increase during processing) and other nutritionally interesting compounds such as cystine, cysteine, carnosine, anserine, taurine, carnitine and coenzyme Q(10).

This study is focused on the characterization of the proteolysis occurred during the processing of Pastırma, a traditional Turkish dry-cured meat product, which is responsible for its final characteristics. Thus, the evaluation of naturally generated free amino acids and peptides present at 0, 2, 5, 10, and 21 days of processing and the bioactivity of peptide fractions have been approached. Peptides were examined by MALDI-TOF and results showed differences in the amount of generated peptides at different times of processing, and a total of 29 peptides were newly generated at Day 21 in comparison with Day 2 during processing. The water soluble fraction of Pastırma at the end of the curing period (Day 21) was also analyzed by size-exclusion chromatography and some of the collected fractions demonstrated strong ACE-inhibitory and antioxidant activities. In fact, Pastırma showed an ACE inhibitory activity higher than 86% from 220 to 270 mL corresponding to molecular masses between 900 and 1500 Da, and also a DPPH radical-scavenging activity above 60% at 250 to 300 mL corresponding to molecular masses between 700 and 2000 Da. Thus, Pastırma represents a good source of natural ACE-inhibitory and antioxidant peptides which might be due to the proteolysis occurred by endogenous enzymes and the contribution of the çemen paste used in production., Grant AGL2014-57367-R from MINECO (Spain) and FEDER funds and JAEDOC-CSIC postdoctoral contract of L.M. cofunded by European Social Funds are acknowledged. The research fellowship grant provided by Erasmus + KA1 Student Mobility Programme for Higher Education for the author Ebru Deniz is also gratefully acknowledged.

The effects of amino acid composition and peptide molecular mass on ACE-inhibitory and antioxidant activities of protein fragments obtained from tomato waste fermented using Bacillus subtilis were evaluated. The addition of B. subtilis increased the relative amounts of aromatic and positively-charged amino acids which have been described to influence the biological activities of peptide fragments. IC50 values of hydrolysates for ACE-inhibitory and 2, 2′-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities were found to be 1.5 and 8.2 mg/mL, respectively. Size-exclusion chromatography (SEC) pattern of the hydrolysate indicated the breakdown of parent proteins to smaller peptides with molecular weights mainly below 1400 Da. MALDI-TOF mass spectrometry analysis revealed that the highest ACE-inhibitory activity was due to peptides showing molecular mass range 500–800 Da, while the most active antioxidant peptides were found to be mainly at the two different peptide weight ranges 500–800 Da and 1200–1500 Da., This study was funded by Grant of Ministry of Science, Research and Technology of Iran and Emerging Research Group Grant from Generalitat Valenciana in Spain (GV/2015/138). Also, a JAEDOC-CSIC postdoctoral contract was cofunded by the European Social Fund to Dr. Mora.

Amino acids are natural constituents of proteins and peptides present in foods that are known to contribute to many relevant functions in an organism. The knowledge of the amino acid profile or the essential amino acids contents in foods and the limiting amino acids in a protein is very important for the characterization of their biological value and how their nutritional benefits may be affected by food processing or during storage. There are many available methods for the analysis of amino acids in foods that are summarized in this article.

Histidine-containing dipeptides carnosine, anserine, and balenine are natural constituents in mammalians, which are known to contribute to relevant bioactive functions during postmortem processing of muscle foods. The knowledge of the content of these dipeptides in meat, poultry, and seafood is very important for the characterization of its biological value in different muscles and cuts and how its antioxidant benefits may be affected by processing or during the storage. This article is describing the importance for health, the availability, and the occurrence of histidine-containing dipeptides in meat, poultry, and seafood as well as the description of the main available methods for their analysis in foods.

Several muscle compounds (creatine, creatinine, hypoxanthine, inosine, inosine 5' monophosphate, xanthine, adenosine monophosphate, guanosine, and uridine) were studied as possible biological markers of a minimum dry-cured ham processing time. A correlation between the concentration of the compounds and the time of processing was found. The ratios for some of them were calculated to study their behaviour during processing. The Hx/Ino ratio substantially increased up to 5 months of curing and then remained constant (p

Hydrophilic interaction chromatography has been used to investigate the retention characteristics of a group of polar compounds typically present in meat like carnosine (Car), anserine (Ans), creatine (Cr), creatinine (Cn), glutathione oxidised (GSSG), glutathione reduced (GSH) and nicotinamide adenine dinucleotide (NADH). These compounds were separated using four polar stationary phases composed by bare silica, amide and zwitterionic groups bound to porous silica and zwitterionic groups attached to a polymeric bead. Ammonium acetate salt used in the mobile phase was found to provide the best results in selectivity and reproducibility. The effect of salt concentration together with pH and acetonitrile (ACN) content of the eluent on the retention of the different polar stationary phases was also studied. A linear gradient of ACN from 80% to 30% with 10 mM ammonium acetate at neutral pH values (pH 6.0 and pH 7.8) offered retention factors k ≤ 10 while keeping a resolution higher than 1.5 for all the assayed compounds in bare silica and amide columns. The separation of NADH from GSSG was not possible under the studied conditions at any salt concentration using zwitterionic columns.

6 pages.-- Review article., [EN] Potassium and sodium salts of nitrite (E 249 and E 250) and nitrate (E 251 and E 252) are authorised for use under certain levels in several foodstuffs such as non-heat-treated, cured and dried meat products, other cured meat products, canned meat products and bacon. The key point in the use of nitrate and nitrite as preservatives is to find a balance between ensuring the microbiological safety of the ham and keeping as low as possible the level of nitrosamines in the final product. Nitrites and nitrates are authorised as additives for dry-cured ham in the Directive 2006/52/EC of 5 July 2006 that modifies previous Council Directive 95/2/EC on food additives other than colours and sweeteners. The effect of nitrate and its reduction to nitrite in controlling the lipid oxidation process during the ham ripening is very important for the development of the characteristic cured flavour. The main benefits and drawbacks of the use of nitrites and nitrates in dry-cured ham and how these levels may affect its flavour are discussed in this manuscript., [ES] Las sales sódica y potásica del nitrito (E249 y E250) y del nitrato (E251 y E252) están autorizados para su uso en los productos cárnicos, secos, curados y no tratados por el calor, otros productos cárnicos curados, productos cárnicos enlatados y bacon. El punto esencial en el uso de nitrato y nitrito como conservantes consiste en encontrar un balance entre el aseguramiento de la seguridad microbiológica del jamón y mantener el nivel de nitrosaminas tan bajo como sea posible. Los nitratos y nitritos están autorizados como aditivos en el jamón curado según la Directiva Europea 2006/52/EC de 5 de Julio de 2006 que modificaba la previa Directiva Europea 95/2/EC de aditivos alimentarios distintos a los colorantes y edulcorantes. El efecto del nitrato y su reducción a nitrito para controlar la oxidación de los lípidos durante la maduración del jamón es muy importante para el desarrollo del característico flavor a curado. Se presentan en este manuscrito los principales beneficios y problemas del uso de los nitratos y nitritos en el jamón curado así como sus efectos en el sabor., Grant AGL2007-65379-C02-01/ALI from the Spanish Ministry of Science and Innovation and FEDER funds is fully acknowledged.

All rights reserved. In this study, a peptidomic approach has been used in the identification of naturally generated peptides during a dry-curing process, showing methionine (Met) oxidation in their sequence. A total of 656 peptides derived from major myofibrillar proteins in Protected Designation of Origin (PDO) Teruel dry-cured ham have been identified by nanoliquid chromatography coupled to tandem mass spectrometry (nLC-MS/MS), including 120 peptides showing methionine oxidation. The percentage of oxidised peptides in the studied proteins ranged from 6% to 35%, being peptides derived from nebulin, titin, myosin heavy chains, and troponin I proteins, those showing the highest number of oxidised methionine. The identification of the peptide sequence incorporating the oxidised amino acid provides valuable information of neighbouring amino acids, degree of hydrolysis of the sample, and characteristics of the peptide, which might be very useful for a future better understanding of the oxidation mechanisms occurring in dry-curing processing., Grant AGL2013-47169-R from MINECO (Spain) and FEDER funds and FPI Scholarship BES-2011-046096 from MINECO (Spain) to M.G. are fully acknowledged. JAEDOC-CSIC postdoctoral contract and support from European Social Funds to L.M. are also acknowledged.

Peptidomics is a necessary alternative in the analysis of naturally generated peptides in dry-fermented processing. The intense proteolysis occurred during the processing of dry-fermented sausages is due to the action of endopeptidases and exopeptidases from both, endogenous muscle origin and lactic acid bacteria (LAB) added in the starter. Sodium caseinate is frequently used as an additive in this type of products because of its emulsifying properties, and consequently influences the protein profile available during the proteolysis. In this study, a mass spectrometry approach has been used to determine the impact of added sodium caseinate in the final peptide profile as well as to analyse its possible influence in the presence of certain previously described casein-derived bioactive peptides.

The effects of nutrient sources and growth phase of Debaryomyces hansenii on the protease (PrA and PrB) and aminopeptidase (prolyl-[PAP] and arginyl-[AAP] aminopeptidases) activities were investigated. These activities were also monitored during growth on a whole sarcoplasmic muscle protein extract (WSPE) and on an equivalent medium but free of compounds under 10 kDa (SPE>10 kDa). The levels of specific protease and aminopeptidase activities were higher when cells were grown in urea and dipeptides than when grown in either ammonium or free amino acids as nitrogen sources. The level of each aminopeptidase (PAP or AAP) activity was preferentially induced by its own substrate (ProLeu or LysAla), suggesting a role in the utilization of exogenous peptides. Higher specific activities for all proteolytic enzymes were detected when using acetate as carbon source. The time course experiments carried out on urea or sarcoplasmic protein-containing media revealed an increase in all activities during transition and advanced stages of stationary phase of growth. In muscle protein extracts, the absence of low molecular mass nutrients (SPE>10 kDa) initially induced the production of PrA, PrB, and AAP activities, possibly involved in the breakdown of muscle oligopeptides.

The present work is focused on the use of the relative amounts of carnosine and anserine for detecting the presence of proteins of mammalian origin in feeds for ruminants. The methodology is cheap and simple and may serve for the rapid screening of feeds. Animal protein additions to feeds as low as 0.5% can be easily detected based on the cation exchange HPLC determination of the carnosine and/or anserine dipeptides. Furthermore, the molar ratio of these dipeptides was found to be characteristic of the animal species and could be used to discriminate between mammalian and non-mammalian species eventually added to feeds. Feeds having carnosine/anserine molar ratios higher than 0.3 were strongly suspected of containing banned mammalian proteins. Those suspicious feeds might be later confirmed by more specific techniques. The exact source of feeds containing mixtures of animal proteins from different species could not be identified by this method even though the method was able to detect its mammalian origin.

A simple methodology, consisting in cation exchange HPLC separation combined with OPA postcolumn detection, has been succesfully applied to the analysis and detection of histidine dipeptides in feeds. The use of the proposed methodology, which is very simple and relatively fast, allows the detection of 2.63 ppm and 0.58 ppm of carnosine and anserine, respectively, in cattle feed. As balenine (3-methylhistidine) was not commercialy available, it was isolated from pork muscle and used as standard for its quantitation in feeds. These dipeptides have shown good stability against intense heat treatments, even at temperatures as high as 120 °C for 20 min. So, these histidine dipeptides can be feasible used as markers of animal protein content in feeds.

The processing of dry-cured ham results in an intense proteolysis that leads to the generation of peptides of different sizes and composition, which have been shown to be biologically active. In this study, a total of ninety-three peptides mainly derived from actin, β-enolase, myosin heavy chain, and creatine kinase proteins have been identified from a size-exclusion chromatography (SEC) fraction that resulted as antioxidant by using matrix-assisted laser desorption/ionisation time-of-flight (MALDI-ToF) and nESI-ion trap mass spectrometry. Several of the identified peptides have been synthesised and their antioxidant activity tested in vitro by using DPPH radical-scavenging assay and reducing power analysis. The peptide with sequence SNAAC showed the best results with an IC50 of 75.2μM in DPPH radical-scavenging assay and 205μM in ferric-reducing antioxidant power analysis, very good when comparing with the positive control 2,6-di-tert-butyl-4-methyl phenol (BHT) that showed an IC50 of 358.5μM and 90.3μM, respectively, in the different assays. These results suggest that Spanish dry-cured ham represents an important source of powerful antioxidant peptides which due to their natural characteristics may represent a highly valuable alternative in human health., HEFCE infrastructure funding is acknowledged for MS equipment to PDF. LM and PDF are grateful to the EU-FP7 Marie Curie IEF scheme (FOOSAF project) for the financial resources. FPI Scholarship from Spanish Ministry of Science and Innovation to E.E. and grant AGL2010-16305 from Spanish Ministry of Economy and Competitiveness and FEDER funds are fully acknowledged.

The content of nucleotide metabolites in the muscle L.dorsi from 9 exudative and 9 acceptable quality pork carcasses was determined during 7 d of aging in order to establish a period postmortem for detecting exudative meats. Hypoxanthine and inosine levels in exudative meats were different (p < 0.05) from those of normal meats up to 3 days of aging, while 5′-inosine monophosphate (IMP) and 5′-adenosine triphosphate (ATP) contents only differed during the 1st 4 and 6 h postmortem, respectively. The IMP/ATP ratio was only different (p < 0.05) at 2 h. Thus, 2 h postmortem is proposed as the optimal sampling time for the detection of exudative pork meats.

The content of nucleotide metabolites in the muscle L. dorsi was analyzed for the detection of pale, soft and exudative (PSE) pork meats at just 2 h postmortem. PSE meat was characterized by significantly lower (p < 0.05) amounts of adenosine 5′-triphosphate (ATP) and higher adenosine 5′-monophosphate (AMP), inosine 5′-monophosphate (IMP), inosine (ino) and hypoxanthine (hyp) than normal meat. IMP and ino classified all the samples from both groups with statistical significance (p < 0.05). The K0 value, R′ value and IMP/ATP ratios were also useful indicators for full distinction of PSE meats. Thus, the assay of any of these nucleotide metabolites may allow a good detection of PSE meats at very short, only 2 h, postmortem time.

This work describes the correlation found along 10 days between potentiometric measurements obtained by using an electronic tongue and the variation in certain physicochemical, microbial and biochemical parameters measured on a whole piece of pork loin stored under refrigeration. The electronic tongue consists of a set of six electrodes made of Au, Ag, Cu, Pb, Zn and C, and a reference electrode. Through the use of various multivariate analysis techniques, such as: PCA and two types of artificial neural networks (i.e. multilayer perceptron (MLP) and fuzzy ARTMAP) it was found that it is possible to determine the time elapsed in relation to the degradation of the loin by using simple potentiometric measurements. Additionally, in the same pork sample used to measure redox potentials with the electronic tongue, the following parameters were also determined; pH, microbial count, concentrations of inosine 5'-monophosphate (IMP), inosine (Ino) and hypoxanthine (Hx). Through the use of PLS analysis, it was found a rather good correlation between pH and the potentiometric data. Also a remarkable correlation was observed between the measures carried out with the electronic tongue and the so-called K-index that simultaneously measures the variation in the adenosine triphosphate (ATP) degradation products. These results suggest that this simple, or a similar electronic tongue, could be useful for the undemanding qualitative or semi-quantitative evaluation of freshness in meat samples in a wide range of situations. © 2010 Elsevier Ltd. All rights reserved., We would like to thanks the Spanish Government for support (Project CTQ2006-15456-C04-01/BQU and AGL2007-65379-C02-01 and 02/ALI). This work has been partially carried out under Associated Unit framework between IIAD (UPV) and IATA (CSIC).

A metallo arginyl aminopeptidase (EC 3.4.11.6) activated by Co(2+) was isolated from Debaryomyces hansenii CECT 12487. The enzyme was purified after precipitation with protamine sulphate, followed by a weak anion exchange chromatography, gel filtration chromatography and a strong anion exchange chromatography. The arginyl aminopeptidase (AAP) was purified 337 folds, with a 18% recovery. The AAP appeared to be a dimer with a molecular mass of 101 kDa. The enzyme was active in the pH range from 6 to 9. The optimal activity was detected at pH 7.0 and at 37 degrees C. AAP activity was inhibited by typical aminopeptidase inhibitors (puromycin and bestatin), reducing agents (DTT), chelating agents (EDTA, EGTA and phenantroline) and sulphydryl groups reagents (iodoacetate). Ca(2+), Mn(2+) and Co(2+) activated the enzyme, while Cu(2+), Cd(2+), Hg(2+) and Mg(2+) inhibited it. The K(m) values calculated for Arg-AMC (7-amido-4-methylcoumarin) and Leu-AMC were 0.071 and 0.094 mM, respectively. The enzyme showed maximum specificity for basic amino acids (Arg and Lys), but was also able to hydrolyze non-charged amino acids (Leu, Met and Ala) and, at a minor rate, aromatic amino acids (Phe and Tyr). AAP showed higher activity when an acid residue was located at the C-terminal position of dipeptides. The described purification of an arginyl aminopeptidase from the yeast D. hansenii can contribute to the lack of knowledge about the exopeptidase activity in one of the yeasts more frequently isolated in sausage and to understand its role during the ripening of a fermented sausage.

Twenty pork carcasses were classified in different pork meat qualities: red, firm and non-exudative (RFN), pale, soft and exudative (PSE), red, soft and exudative (RSE) and dark, firm and dry (DFD) meat. The content of peptides and free amino acids during the ageing process was analysed and compared within quality classes. Four peptide fractions were isolated through cation-exchange and reverse-phase chromatography. The main significant differences among qualities were obtained for peptide fractions 3 and 4. Peptide fraction 3 at 4 days and peptide fraction 4 at 2 h postmortem were higher in the ideal pork quality (RFN) than in the other quality classes. The ageing of pork meats produced a general increase in all free amino acid concentrations for the studied quality classes except for Gln, β-Ala, Taurine and Orn and the dipeptides carnosine and anserine. The DFD class showed higher increases in Lys, Ala and Met probably due to the activation of neutral aminopeptidases.

Free amino acids and natural dipeptides, have been analyzed in pork muscles having different metabolic type (masseter, trapezius, semimembranosus and longissimus dorsi). Carnosine and anserine showed significantly higher (p < 0.05) concentrations with the glycolytic activity of the muscle while taurine and glutamine were significantly higher in the oxidative muscles. Non-essential free amino acids also showed significant (p < 0.05) increased content in the oxidative muscles.

Proteolytic events taking place during prok meat ageing and curing processes are described. Muscle cathepsins and calpains provide suitable substrate for muscle peptidases and aminopeptidases which ultimately generate small peptides and free amino acids. The levels of small peptides and free amino acids in all meats are higher after processing than before as a result of intense action of those proteases. Increases of the free essential amino acids such as valine, methionine, isoleucine, leucine, phenylalanine, tryptophan and lysine are observed along the conditioning of meat and are especially large in the processing of dry-cured ham. Thus, aged meat but very especially dry-cured ham have an important nutritional significance when the energy intake is low or in poor nutritional quality diet.

The effect of curing agents (salt, nitrite, nitrate, ascorbic acid, glucose and polyphosphates) on the main pure aminopeptidases involved in the release of amino acids during the processing of cured meat products has been studied. Salt strongly inhibited alanyl aminopeptidase and pyroglutamyl aminopeptidase: about 40–50% of their original activities were recovered in the presence of 4–5% salt, the typical concentration in dry-cured meat products, while leucyl aminopeptidase was not affected. However, arginyl aminopeptidase was activated to 2–3 times its control level. Nitrate and nitrite did not affect aminopeptidase activity. Ascorbic acid (500 mg/l) slightly inhibited arginyl, alanyl and pyroglutamyl aminopeptidases whereas glucose (20 g/l) activated (to almost 5 times its control level) leucyl aminopeptidase activity. Polyphosphates inhibited (25%) alanyl and arginyl aminopeptidases.

An enzyme sensor employing diamine oxidase from porcine kidney in combination with an oxygen electrode has been developed and optimised to estimate the content of total amines in dry-fermented sausages. The enzyme DAO was immobilised on a preactivated Immunodyne membrane using glutaraldehyde as cross-linking agent. The enzymatic determination was based on the measurement of the consumed O2 in a platinum electrode poised at −600 mV versus Ag/AgCl. The reaction was started by the direct injection of either the standard or meat extract on the enzymatic membrane. The immobilised enzyme could be used up to 30 analyses along the day without significant loss of sensitivity and could be stored at 4 °C showing good stability for at least 6 weeks. A good correlation was observed when comparing data obtained with the enzyme sensor to those obtained with a standard HPLC method. Thus, this sensor may be a reliable screening method to detect the presence of biogenic amines in dry-fermented sausages that can constitute a useful tool for quality control in the meat industry.

The effect of biogenic polyamines (agmatine, cadaverine, putrescine, spermidine, and spermine) on the activity of pork muscle aminopeptidase and alanyl aminopeptidase was investigated. Agmatine (5 mM) showed a powerful inhibitory effect for both enzymes (more than 50% inhibition). Cadaverine and less intensely putrescine showed similar inhibitory effects for both enzymes. All assayed polyamines inhibited activity of both aminopeptidases except spermine and spermidine which did not affect aminopeptidase B. Thus, one of these inhibitors could be used to avoid the interference of alanyl aminopeptidase when assaying aminopeptidase B in muscle extracts.

The effect of endogenous dipeptides (carnosine and anserine) and peptidic fractions from meat extracts on aminopeptidase activity, alanyl and arginyl aminopeptidases purified from porcine skeletal muscle, was studied. Carnosine inhibited the activity of porcine arginyl aminopeptidase (RAP); the inhibition being stronger with the purified form of the enzyme than in the muscle extract. The RAP inhibition was competitive. One of the peptidic fractions isolated from meat extracts inhibited RAP activity But the degree of inhibition depended on the extent of purification. The major aminopeptidase present in muscle, alanyl aminopeptidase (AAP), was neither inhibited by natural dipeptides nor arty of the peptidic fractions. The study of meat inhibitory peptides provides a better understanding of the action of proteolytic enzymes during meat processing.