Concentrations in beef and lamb of taurine, carnosine, coenzyme Q(10), and creatine

Levels of taurine, carnosine, coenzyme Q(10), and creatine were measured in beef liver and several muscles of beef and lamb and in cooked and uncooked meat. The amino acid taurine has numerous biological functions, the dipeptide carnosine is a buffer as well as an antioxidant, coenzyme Q(10) is also an antioxidant present within mitochondria, and creatine along with creatine phosphate is involved with energy metabolism in muscle. Large differences were shown for all compounds between beef cheek muscle (predominantly red fibres) and beef semitendinosus muscle (mainly white fibres), with cheek muscle containing 9.9 times as much taurine, and 3.2 times as much coenzyme Q(10), but only 65% as much creatine and 9% as much carnosine. Levels in lamb relative to beef semitendinosus muscles were higher for taurine but slightly lower for carnosine, coenzyme Q(10) and creatine. Values for all the compounds varied significantly between eight lamb muscles, possibly due in part to differences in the proportion of muscle fibre types. Slow cooking (90 min at 70?°C) of lamb longissimus and semimembranosus muscles led to significant reductions in the content of taurine, carnosine, and creatine (P<0.001), but a slight increase in coenzyme Q(10). There was also a four-fold increase in creatinine, presumably due to its formation from creatine. It is concluded that biologically, and possibly nutritionally, significant levels of taurine, carnosine, coenzyme Q(10), and creatine are present in beef and lamb, but that these levels vary between muscles, between animals, and with cooking.     

Muscle and Adipose Tissue Aminopeptidase Activities in Raw and Dry-Cured Ham.

Free amino acids have been analyzed in biceps femoris muscle and adipose tissue from raw and dry-cured ham. A high increase was observed for all amino acids except glutamine and taurine. Major increases were in glutamic acid, arginine, alanine, valine, leucine, and lysine. A survey of five aminopeptidase activities of muscle and adipose tissue from raw and dry-cured ham was performed by using 7-amino-4-methylcoumarin derivatives of five amino acids (Leu, Arg, Ala, Tyr and pGlu) as substrates. Optimum activity was found at neutral pH and around 37°C, except the leucyl hydrolyzing activity which was 45°C. High recoveries of activity (25–75%) were obtained in the dry-cured ham. These enzymes might be responsible for free amino acids increasing during dry-curing.     

Biochemical changes during processing of traditional Jinhua ham

Jinhua ham is the most famous traditional meat product of China and one of the most famed dry-cured hams in the world. Its processing consists of six stages: green ham preparation, salting, washing and sun-drying and shaping, ripening, and post-ripening. Intense proteolysis and lipolysis occur during processing period. As a result, the content of free amino acids in final ham products is 14-16 times that of green ham, and 191 volatile compounds have been identified during processing, which make a major contribution to the flavor of Jinhua ham.     

Contribution of muscle aminopeptidases to flavor development in dry-cured ham

The activity of muscle aminopeptidases (alanyl, arginyl, leucyl and pyroglutamyl aminopeptidases) have been assayed along the processing of dry-cured ham. The generation of free amino acids resulting from aminopeptidase action on N-terminal of proteins and peptides has been also analyzed. The assayed aminopeptidases, except pyroglutamyl aminopeptidase, showed good stability. Alanyl and arginyl aminopeptidases have optimal neutral pH near the pH in ham and, in addition, their spectrum of activity against terminal amino acids is in coincidence with the observed release of free amino acids in ham. So, both aminopeptidases appear to be the main contributors to the generation of free amino acids during the processing of dry-cured ham.     

Endogenous skeletal muscle antioxidants

Skeletal muscle is susceptible to oxidative deterioration due to a combination of lipid oxidation catalysts and membrane lipid systems that are high in unsaturated fatty acids. To prevent or delay oxidation reactions, several endogenous antioxidant systems are found in muscle tissue. These include α‐tocopherol, histidine‐containing dipeptides, and antioxidant enzymes such as glutathione peroxidase, superoxide dismutase, and catalase. The contribution of α‐tocopherol to the oxidative stability of skeletal muscle is largely influenced by diet. Dietary supplementation of tocopherol has been shown to increase muscle α‐tocopherol concentrations and inhibit both lipid oxidation and color deterioration. Dietary selenium supplementation has also been shown to increase the oxidative stability of muscle presumably by increasing the activity of glutathione peroxidase. The oxidative stability of skeletal muscle is also influenced by the histidine‐containing dipeptides, carnosine and anserine. Whereas carnosine and anserine are affected by diet less than α‐tocopherol and glutathione peroxidase, their concentrations vary widely with species and muscle type. In pigs, beef, and turkey muscle, carnosine concentrations are greater than anserine, while the opposite is true in rabbit, salmon, and chicken muscle. Anserine and carnosine are found in greater concentrations in muscle high in white fibers, with chicken white muscle containing over fivefold more anserine and carnosine than red muscle. Anserine and carnosine are thought to inhibit lipid oxidation by a combination of free radical scavenging and metal chelation.     

The Role of Muscle Proteases and Lipases in Flavor Development During the Processing of Dry-Cured Ham

The processing of dry-cured ham is very complex and involves numerous biochemical reactions that are reviewed in this article. Muscle proteins undergo an intense proteolysis, resulting in a great number of small peptides and high amounts of free amino acids. The enzymes responsible of these changes are proteinases (cathepsins B, D, H, and L and, to a less extent, calpains) and exopeptidases (peptidases and aminopeptidases). Muscle and adipose tissue lipids are also subject to intense lipolysis, generating free fatty acids by the action of lipases that, in a second stage, are transformed to volatiles as a result of oxidation. Sensory profiles of dry-cured ham are strongly affected by these enzymatic reactions. In addition, the activity levels of the muscle enzymes significantly depend on the properties of raw ham, such as age and crossbreeding as well as the process conditions such as temperature, time, water activity, redox potential, and salt content. Thus, the control of the muscle enzyme systems, mainly proteases and lipases, is essential for the standardization of the processing and/or enhancement of flavor quality of dry-cured ham.     

Generation of volatile flavour compounds as affected by the chemical composition of different dry-cured ham sections

The composition of different dry-cured ham sections has been determined in order to study their contribution to flavour generation. The proteins, free amino acids, free fatty acids and volatile compounds were analysed in different sections of dry-cured hams with 7 and 12 months of processing. The main differences among sections were detected in free amino acids and volatile compounds. To sum up, there was a higher concentration of free amino acids in the centre section than in the butt and shank sections. However, after 12 m of ripening the difference among sections was lower and only the butt was the one with the lowest concentration. Similar results were obtained in the content of volatile compounds, the centre part of the hams contained a higher proportion of volatile compounds after 7 m of ripening than the shank and butt sections. Nevertheless, in 12 months dry-cured hams there are changes in the proportions of volatile compounds being the centre section the one with the highest proportion of volatile compounds due not only to the higher concentration of free amino acids but also to the oxidation of unsaturated fatty acids.     

Creatine and creatinine evolution during the processing of dry-cured ham

Dry-curing of ham involves many biochemical reactions that depend on the processing conditions. The aim of this study was to evaluate the effect of the dry-cured processing on the concentration of creatine, creatinine and the creatinine/creatine ratio. Dry-cured hams under study were salted using three different salt mixtures (100% NaCl; NaCl and KCl at 50% each; and 55% NaCl, 25% KCl, 15% CaCl₂ and 5% MgCl₂) in order to observe its influence on creatinine formation but no significant differences were found between them at any time of processing. However, significant differences between different post-salting times (20, 50 and 80 days) and the ripened hams (7, 9 and 11 months of ripening) were observed. Results showed that creatine and creatinine remain stable once the ripening period is reached. These results were confirmed when analysing dry-cured ham samples submitted to extreme conditions of temperature and time (20, 30, 40 and 70 °C during 0, 20, 40 and 60 min) as well as commercial dry-cured hams with more than 12 months of processing.     

Contribution of a selected fungal population to proteolysis on dry-cured ham

The proteolytic changes taking place in dry-cured hams lead to increases in free amino acids. Such free amino acids not only contribute to flavour, but also serve as precursors of volatile compounds. Several months of ripening time are required to allow the particular flavour to develop. The fungal population allowed to grow on the surface of some types of dry-cured could play a key role on proteolysis, as it has been shown for dry-cured sausages. The purpose of this work was to study the possible contribution of fungi to proteolysis in dry-cured ham. For this, a strain each of non-toxigenic Penicillium chrysogenum (Pg222) and Debaryomyces hansenii (Dh345), selected for their proteolytic activity on myofibrillar proteins, were inoculated as starter cultures. Changes in the high ionic strength-soluble proteins of an external muscle (adductor) revealed in only 6 months higher proteolysis in the inoculated hams when compared to non-inoculated control hams. Proteolytic strains among the wild fungal population on non-inoculated control hams prevented from obtaining similar differences at the end of processing. However, inoculation with Pg222 and Dh345 led to higher levels for most free amino acids at the external muscle in fully dry-cured hams. In addition, the concentration for some of the more polar free amino acids (i.e. Asp, Glu, Ser and Gln) in inoculated hams was higher at external than at internal (biceps femoris) muscles. These promising results deserve further studies to know the impact of a selected fungal population on the volatile compounds and sensory properties of dry-cured ham.     

Composition and some quality characteristics of the longissimus muscle of reindeer in Norway compared to farmed New Zealand red deer

Norwegian reindeer of Finnmark county live under harsh conditions on extensive feed sources. Thus the meat may have special qualities. M. longissimus lumborum from 30 animals was investigated with respect to carcass and meat quality and compositional/nutritional characteristics. Meat from calves had a higher myofibrillar fragmentation index and tenderness, and had lighter, redder and more yellow colour than meat from adult reindeer. Regarding nutritional compounds the meat from calves had lower antioxidant capacity, and higher taurine levels than adults, while the levels of iron, carnosine, anserine, and vitamin E were similar. Carcass weights of the adult reindeer were lower than the weights reported for Swedish reindeer and New Zealand farmed red deer. Reindeer muscles had higher antioxidant capacity, shorter sarcomeres, smaller muscle fibre diameters, higher n−6/n−3 ratios of fatty acids in the intramuscular fat and higher muscle taurine levels relative to values for the same muscle of New Zealand farmed red deer.     

金华火腿传统工艺过程挥发性风味物质的分析研究

通过对金华火腿传统工艺过程晒后、中温发酵、高温成熟、成熟下架样品中挥发性风味物质的分析测定,研究传统工艺过程中挥发性风味物质的发展规律,结果表明:共有78种挥发性风味物质检出,醛、羧酸、醇、酯、酮、脂肪族和芳香族碳氢化合物、含硫化合物、吡嗪是主要成分;工艺工程中醛和酮的相对含量随温度的升高而逐渐降低,羧酸、酯、吡嗪和含硫化合物的相对含量逐渐增加。金华火腿的高温成熟工艺使来自于美拉德反应的羧酸有显著增加,这是金华火腿与地中海地区干腌火腿最显著的区别,也是金华火腿具有其独特风味的主要原因。     

Small peptides (<5kDa) found in ready-to-eat beef meat

Dietary proteins can have biological properties, many attributed to bioactive peptides (2–50 amino acids). Since little is known about peptides in meat, we investigated the postmortem occurrence of low molecular weight peptides (<5 kDa) in bovine Pectoralis profundus muscle, after 14 days storage at 4 °C and vacuum cooking for 90 min at 75 °C. The study combined quantitative (amino acid analysis) and qualitative approaches (mass spectrometry). Eighty-nine percent of peptidic amino acids in fresh muscle corresponded to carnosine, anserine and glutathione. Levels of these compounds were lower in cooked meat compared to fresh muscle. Concomitantly, numerous larger compounds, most probably peptides, were generated in a very reproducible manner during ageing and even more during cooking of meat. Seven peptides (fragments of troponin T, nebulin, procollagen and cypher proteins) were identified in cooked meat extracts.     

不同来源和年份诺邓火腿的理化和呈味性质

为研究市售常见诺邓火腿的差异,对具有地域特色的诺邓火腿进行综合评价。以洋三元白猪、诺邓黑猪为原材料,按照诺邓火腿工艺加工1、3 年火腿,测定其理化指标、质构特性和游离氨基酸含量,并用电子舌分析其滋味特性差异。结果表明：4 组火腿质地存在明显差异;4 组火腿中均分离出18 种游离氨基酸,精氨酸含量最丰富,亮氨酸、赖氨酸和谷氨酸次之;洋三元白猪火腿（W组）的游离氨基酸含量高于诺邓黑猪火腿（B组）,B组的鲜味氨基酸相对含量高于W组,氨基酸的释放量可明显将1 年和3 年的火腿区分开;电子舌结果表明,B1组的滋味丰富性最大,B3组的咸味最大但鲜味最小,W1组的鲜味较大但丰富性较小,W3组的咸鲜味和丰富性适中。综上,鲜味、丰富性和咸味是诺邓火腿重要的味觉指标,诺邓黑猪火腿滋味较为丰富,B3组硬度、咸味最大,加工过程中要控温控湿。     

Effect of Penicillium chrysogenum and Debaryomyces hansenii on the volatile compounds during controlled ripening of pork loins

During ripening of meat products such as dry-cured ham, the moulds and yeasts that proliferate on the surface may contribute to flavour development. However, their contribution to volatile components of dry-cured meat products is not known. One strain each of Penicillium chrysogenum and Debaryomyces hansenii, selected from dry-cured ham by their proteolytic activity, were tested to determine their effect on the volatile compounds during ripening. Sterile pork loins were inoculated and ripened for 106 days. Volatile compounds collected with a Solid Phase Micro-Extraction (SPME) fibre were analysed by GC/MS. Inoculation of pork loins with P. chrysogenum lead to a decrease in compounds attributed to lipid oxidation and to an increase of compounds derived from free amino acids. Inoculation with D. hansenii seemed to favour the formation of complex alcohols.     

Relations between compositional traits and sensory qualities of French dry-cured ham

The left hams of 20 pig carcasses were processed by dry-curing for either 179 (n = 10) or 273 days (n = 10). The Biceps femoris was taken at the end of the processing and submitted to chemical and sensory analyses. The following chemical traits were determined: pH, moisture, salt content, fatty acid content and composition of lipid classes (triglycerides, phospholipids, free fatty acids), nitrogen fractions (soluble and insoluble protein, non-protein nitrogen, free amino acids) and volatile compounds. Sensory analysis was performed by a panel of 12 trained members, who scored texture traits (firmness, dryness, fibrousness, mellowness), taste (salty, acid), intensity of aromas (typical of dry ham, fresh meat, fat, cured meat, rancid, metal), persistence of dry ham aroma, persistence of taste after deglutition, persistence of astringency, persistence of metallic taste. The sensory qualities of dry-cured ham showed noticeable changes between days 179 and 273. Firmness, dryness and intensities of aromas typical of dry-cured ham and cured meat were enhanced with time. Neither pH, moisture nor salt content played a noticeable role in determining the sensory quality of dry-cured ham. Among the volatile compounds, the levels of several ketones and 1-butanol were significantly correlated with the aromas of dry ham and cured meat, while rancid aroma was related to aldehydes, ethylacetate, 2,3-pentanedione and nonane. Therefore, the aromas of dry ham and cured meat appeared to be determined mainly by the products of lipid oxidation. However, they were related also to unidentified volatile compounds, whose identification would be of particular interest.     

Cooking temperature effects on the forms of iron and levels of several other compounds in beef semitendinosus muscle

The influence of final cooked temperature on the form of iron present and on the concentration of taurine, carnosine, coenzyme Q(10) and creatine was investigated in surface and inner parts of 30-mm thick steaks from beef semitendinosus muscle (n=6). The use of a fast, dry-heat cooking method with a Silex clam cooker (set at 200 °C) led to cooking times ranging from 5.6 to 8.6 min for final internal temperatures of 60 and 85 °C, respectively. The proportion of iron as soluble haem iron decreased from 65% in uncooked meat to 22% when cooked to 60 °C and then decreased more gradually with increases in final cooked temperature. The proportion of insoluble haem iron increased in a reciprocal manner, while changes in the proportions of soluble and insoluble non-haem iron were relatively small, but increases in the percentage of insoluble non-haem iron with increasing final temperature were significant (P<0.01). Changes in the forms of iron with cooking generally took place more rapidly in surface samples than inner samples. On a dry-matter basis, concentrations of taurine, carnosine, coenzyme Q(10), and creatine all decreased with cooking, but the decreases were greatest for taurine and creatine. Losses of creatine were at least partly due to conversion to creatinine, and, along with the other compounds, probably included some loss in cooking juices. It is concluded that despite these changes with cooking, beef semitendinosus muscle remains a good source of iron and a useful source of the potentially bioactive compounds taurine, carnosine, coenzyme Q(10) and creatine.     

Improvement of Lactic Acid Production in Ultrafiltered Milk by the Addition of Nutrients

In 4 h at 32°C, mesophilic lactic acid bacteria produced .74% acidity in 3.3:1 retentate of ultrafiltration diluted to 2:1 with permeate. When diluted with distilled water instead of permeate, .56% acidity was produced. In 2.4:1 retentate containing .5% yeast extract, .95% acidity was produced compared with .84% in the control (retentate without yeast extract). The B vitamins, lactose, and minerals (NaCl, MgSO₄, FeSO₄, and MnCl₂) had little or no effect. With another lactic starter, 22 amino acids together at .04 mg/g each in 2:1 retentate improved acid production (.72% compared with .61% for the control). Nonessential amino acids as a group were more stimulatory than essential amino acids. Cysteine and cystine at .04 mg/g each were as stimulatory as all amino acids together and all amino acids minus cysteine and cystine. Reducing agent dithiothreitol at .05 mg/g was as stimulatory as cysteine and cystine. Sulfur-containing compounds (methionine and Na₂SO₄) had no effect, suggesting that the stimulatory effect of amino acids is via the reducing power of cysteine and cystine as well as nutritive value of other amino acids.     

Changes in the forms of iron and in concentrations of taurine, carnosine, coenzyme Q(10), and creatine in beef longissimus muscle with cooking and simulated stomach and duodenal digestion

Longissimus muscle samples from 31 Angus-cross heifers finished on either a high-concentrate feedlot diet or pasture were used to evaluate the effects of cooking (71°C) on the concentration and forms of iron in the meat, and also on concentrations of the bioactive compounds taurine, carnosine, coenzyme Q(10), creatine and creatinine. For a sub-sample of 15 the effects of pepsin and pancreatin digestion were assessed. For iron, cooking resulted in some overall loss together with a major change from soluble haem and non-haem iron to the insoluble forms, but solubility was regained to a significant extent following digestion. Total haem iron percentage, however, decreased at each step from an initial 88% to a final 61% of total iron. For the bioactive compounds, cooking led to a reduction in taurine, carnosine, coenzyme Q(10), and creatine. The effects of digestion on the bioactive compounds varied. No clear differences were shown in the way in which beef from pasture-finished and feedlot-finished cattle responded to cooking and digestion.     

Effects of high pressure application (400 and 900 MPa) and refrigerated storage time on the oxidative stability of sliced skin vacuum packed dry-cured ham

The effect of high pressure processing at 400 MPa and 900 MPa on the oxidative stability of sliced and vacuum packaged commercial dry-cured ham was determined by analyzing the antioxidant enzyme activities, TBARS levels (thiobarbituric acid reactive substances), vitamin E content and physicochemical characteristics during refrigerated storage for 50 days in different light conditions. In dry-cured ham pressurized at 400 MPa color changes and sensory analyses were also assessed. The high pressure process at 900 MPa produced a decrease in superoxide dismutase (SOD) and glutathione peroxidase (GSHPx) activities and increased vitamin E content. In contrast, pressurization at 400 MPa, increased SOD activity, and showed no effect on vitamin E content and GSHPx activity. In general the physicochemical parameters determined (fat, moisture and collagen) were unaffected by pressurization. Treatment at 400 MPa increased the instrumental color measurement of lightness (L* values, CIELAB). This level of pressure also modified the hardness, chewiness, saltiness and color intensity. These changes of the sensory attributes in dry-cured ham were significant, but small.