Ángela Jurado

Effect of ripening time and rearing system on amino acid-related flavour compounds of Iberian ham

The evolution of free amino acids and amino acid-derived volatile compounds during the ripening of Iberian ham from pigs reared in a Montanera system (outdoor-based, with acorn and pasture available) and a Pienso system (indoor-based, with a high oleic acid concentrate) was studied. Ripening time influenced significantly all the free amino acids detected (p<0.05) except for threonine and tyrosine. The total free amino acid content increased significantly from day 120 to day 230 (drying stage) and then the concentration remained almost steady. This marked increase in the free amino acid content matched an increase in the amino acid-derived volatile compounds. The volatile compounds also increased after day 230. Conversely, rearing system had a weak effect on the free amino acid content and on the amino acid-derived volatile compounds. Only glutamic acid was significantly influenced (p=0.027), and a slight effect on proline and aspartic acid was found (p=0.051 and p=0.084, respectively), concentrations being larger in Montanera hams than in Pienso ones. With regard to the amino acid derived volatile compounds, only a significant influence of rearing system on acetaldehyde and on the coelution of 2,6-dimethylpyrazine+dihidro-2(3H)furanone was found. The small differences caused by rearing system confirm the great importance of concentrate formulation.

Quality traits in muscle Biceps femoris and back-fat from purebred Iberian and reciprocal Iberian × Duroc crossbred pigs

The present study evaluated the physico-chemical characteristics of muscle biceps femoris and back-fat from purebred Iberian (PBI) pigs and reciprocal crossbred Iberian×Duroc pigs (IB×D pigs: Iberian dams×Duroc sires; D×IB pigs: Duroc dams×Iberian sires). Muscles from PBI pigs contained significantly higher amounts of IMF, heme pigments and iron than those from crossbred pigs. In addition, muscles from PBI pigs were darker (lower L(∗)-values) and redder (higher a(∗)-values) and exhibited a more intense colour (higher chroma value) which was closer to the true red axis (lower hue value) than muscles from crossbred pigs. Back-fat from PBI pigs had significantly higher percentages of monounsaturated fatty acids (MUFA) and significantly smaller percentages of polyunsaturated fatty acids (PUFA) than those from crossbred pigs. Regarding the fatty acid profiles of the muscle lipid fractions, the genetic background particularly affected the composition of the polar lipid (PL) fraction. PL in muscles from PBI pigs contained significantly higher proportions of oleic acid and total MUFA and significantly lower amounts of arachidonic acid, certain long-chain PUFA (ω-6 and ω-3 fatty acids) and total amount of PUFA than PL in muscles from crossbred pigs. The results obtained indicate that tissues from PBI pigs would be more suitable for the production of dry-cured meats than those from cross-bred pigs. The position of the dam or the sire in reciprocal Iberian×Duroc crosses had no clear effects on meat quality.

Subcutaneous and intermuscular fat characterisation of dry-cured Iberian hams.

The fatty acid composition of the triacylglycerols and free fatty acids of subcutaneous (internal and superficial layers) and intermuscular fat and the contribution of these fatty acids to the formation of volatile compounds were determined in dry-cured Iberian ham. The profile of the fatty acids and volatile compounds showed that lipolytic and oxidative processes occur more intensively in subcutaneous than intermuscular fat, however, few differences were found compared to those found in ham lean.

Note: Effect of Crossbreeding and Rearing System on Iberian Ham Volatile Compounds

Several volatile compounds from Iberian ham trapped from the headspace were analysed to research the effect of crossbreeding (Iberian vs. Iberian Duroc 50% pigs) and rearing system (Montanera system vs. Pienso system) on them. Thirty-four Iberian hams grouped following a factorial treatment structure were analysed. A two-way analysis of variance with interaction was applied to the data from 46 volatile compounds identified. The effect of crossbreeding was negligible on the studied volatile compounds, which was in agreement with the effect on fatty acid percentages of subcutaneous fat. On the contrary, the effect of rearing system was significant in most of the fatty acid percentages used to classify the hams into the current commercial grades of Iberian ham (16:0, 18:0 and 18:1, p<0.001). However, a slight effect on the volatile compounds was found, and only a limited number of compounds were significantly affected. Results for the effect of crossbreeding and rearing system on headspace volatile compounds agreed with the sensory data for odour of hams.

Characterisation of the most odour-active compounds of bone tainted dry-cured Iberian ham.

The most odour-active compounds of different bone tainted dry-cured Iberian hams were researched using the detection frequency method. Most of the odourants identified were found in all the Iberian hams (spoiled and unspoiled). Some compounds (ethyl butanoate, dimethyl disulfide, phenylacetaldehyde, acetic, propanoic, butanoic, 3-methylbutanoic and pentanoic acids) were identified in the spoiled hams as Iberian ham odourants for the first time. The detection frequency (DF) values for the spoiled and the unspoiled hams were markedly different. The main differences were found for 2-methylpropanal, ethyl-2-methylpropanoate, ethyl-2-methylbutanoate, phenylacetaldehyde and methional (the lowest DF values were found in the unspoiled ham) and hexanal (the largest DF value was found in the unspoiled ham). Spoiled hams with a different global odour had different DF values.

MADURACIÓN DEL JAMÓN IBÉRICO: EVOLUCIÓN DE ÍNDICES BASADOS EN COMPUESTOS VOLÁTILES IBERIAN HAM RIPENING: EVOLUTION OF VOLATILE COMPOUND-BASED INDICES

Abstract The aim of this work was to know the evolution of several summatories and indices (calculated using volatile compound data) during the ripening stage of Iberian ham. Several summatories and indices experienced significant changes through ripening, and therefore they could be used as indicators of the ripening time of Iberian ham. Furthermore, for most variables a significant equation of simple linear regression (including one variable and ripening time) was found, which could help to predict ripening time. With regard to the summatories, the best result was found for the equation including time and the sum of 2-methylpropanal, 2-methylbutanal, 2-methyl-1-butanol and dimethyldisulfide (R2 = 0.610). With regard to the indices, the best result was found for the equation including time and the percentage of lipid oxidation-derived compounds (R2 = 0.632). Resumen El objetivo de este trabajo fue conocer la evolución de distintos sumatorios e índices (calculados a partir de los compuestos volátiles) durante la maduración del jamón ibérico. Distintos sumatorios e índices experimentaron cambios significativos durante la maduración, por lo que podrían ser utilizados como indicadores del grado de maduración del jamón ibérico. Además, en la mayoría de los casos se obtuvo una ecuación de regresión lineal simple significativa incluyendo uno de los índices y el tiempo, lo cual podría permitir predecir el tiempo de maduración. En cuanto a los sumatorios, el mejor ajuste se obtuvo con la suma de 2-metilpropanal, 2-metilbutanal, 2-metil-1-butanol y dimetildisulfuro (R2 = 0,610). En cuanto a los índices, el mejor ajuste se consiguió con el porcentaje de compuestos volátiles procedentes de la oxidación respecto al total (R2 = 0,632). Palabras clave: Jamón Ibérico, maduración, compuestos volátiles