Free amino acids and dipeptides in porcine muscles: differences between `red' and `white' muscles.

Three porcine muscles (m. longissimus dorsi, masseter and trapezius), chosen to represent the three main metabolic types, from 18 carcasses had their free amino acids and dipeptides quantified by reverse-phase high performance liquid chromatography (HPLC) in aqueous extracts derivatized with phenyl isothiocyanate. Of the 25 measured compounds, four amino acids and the dipeptide carnosine were closely related to the metabolic type of the three muscles. Masseter, a red oxidative muscle, had the highest contents of aspartic acid, glutamine and taurine. Longissimus dorsi, a white glycolytic muscle was characterised by the highest contents of ß-alanine and carnosine. Trapezius, an intermediate muscle, had intermediate contents. These results show that free amino acid and dipeptide contents could partly explain differences in taste of muscles from the same species.

Time-related changes in nitrogen fractions and free amino acids of lean tissue of frech dry-cured ham.

The 80 hams of 40 pig carcasses from one slaughter batch were taken on the day after slaughter. The 40 left hams were dry-cured. Groups of 10 hams were taken for analysis at 74 days (end of rest), 81 days (end of heating), 179 days (mid-seasoning) and 273 days (end of seasoning) after the beginning of processing. A slice of about 150 g was taken in the middle of the Biceps femoris and used for analysis of nitrogen fractions and free amino acids by HPLC. Levels of insoluble nitrogen compounds did not vary significantly, while levels of soluble protein nitrogen decreased strongly from 26 to 16% of total nitrogen, with the fastest decrease observed between days 179 and 273. Levels of non-protein nitrogen increased regularly during the processing from 12 to 23% of total nitrogen. Nitrogen of free amino acids ranged from 3·6% in fresh muscle to 16·6% of total nitrogen at day 179, then decreased to 4·4% of the total nitrogen at the end of the processing. The HPLC method allowed the identification of 29 compounds, among which 27 were amino acids and 2 were dipeptides. The average levels of free amino acids of non-protein origin tended to decrease before day 74, then to increase until day 179 and to decrease again. The levels of compounds of protein origin increased or tended to increase from the beginning until day 179, then decreased.

Estimation of the muscle to bone ratio of the bovine pelvic limb using a morphometric method.

Conformation is an indicator of carcass composition. The aim of this study was to derive an equation for estimating the composition of the bovine pelvic limb using morphometric variates. From a mixed group of 38 French bred bovines, the sample was chosen to have a wide range of conformation. The muscle to bone ratio (M B ) was used as an index of composition. The carcasses were weighed and the other variates of the equation were measured on carcass photographs: M B = 6.2 + 0.005W - 0.62EF AB + 12GH with W: carcass weight (kg); GH: medio-lateral diameter of the distal part of the leg (cm); EF AB : medio-lateral diameter of thigh (cm)/leg length(cm); (R(2) = 0.91 and rsd = 0.27).

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.

[Effect of mercuric chloride on the analysis of nitrites in pork products]. / Effet du chlorure de mercure sur le dosage des nitrites dans les charcuteries.

The effect of HgCl2 on nitrite determination was studied. 0,184 mmol/l to 184 mmol/l Hg Cl2 were added during the defecation or only at the time of analysis with an autoanalyser. Hg Cl2 was added to salami, bacon, dry sausage at different time of ripening and cooked ham. An effect was noted only when Hg Cl2 was added at the defecation time. After cold water extraction, the more the added Hg Cl2, the more "titrated" nitrite. After hot extraction with water and borate, the effect of Hg Cl2 was weaker but significant. The role of Hg Cl2 was important for the accurate determination of nitrites during the ripening of some products: in 16 hours old dry sausage the effect was weak (+40%), but became large (+600%) after 2 weeks of ripening. It is proposed to use Hg Cl2 at the concentration of 4 mmol/l for the determination of total nitrites. The free nitrites should be analysed separately without Hg Cl2.