THE EXTENSIVE PIG QUALITY

A. Fallola, C. Sanabria, E. Sabio, Mª. C. Vidal-Aragón and F. Espárrago Instituto de Tecnología

Agroalimentaria, Aptdo. 217 6800 Badajoz, Spain

Summary

The extensive pig production system in particular areas in the south of Europe is characterised by the use of local genotypes and their crosses and the exploitation of the natural resources common in the sylvopastoral space, among which, the species Quercus and Castaneas stand out due to their importance. The main features of this model of exploitation are the use of adipogenic genotypes, the great functional exercise, and the existence of a period of feeding restriction (pre-pasture) followed by a period of abundance (fattening or pasture). The final result is the production of heavy animal s, with ages from 14 and 18 months, which gives place to the obtaining of a carcass with great adiposity. The geographic distribution is limited mainly to the South-west of the Iberian peninsula and specific areas of the Mediterranean, like the island of Corsica. Likewise, another singular feature of the extensive production is its association to regions which are developing, where this activity makes up one of the most important productions and it contributes, with its existence to the preservation of their ecosystems, from which arises its socio-economic and environmental importance. Besides, it contributes to get a traditional transformed production of high quality and non surpluses within the European Union.

The whole extensive production system is focused on the elaboration of high quality products. The final product quality will depend on the quality of the raw matter (clearly influenced by the genotype and the diet used) and it will also depend on the technological process used. The adipogenic feature presented by the local genotypes and the sort of diet which is digested during the fattening period (acorns and chestnuts), are going to define a raw matter with high contain in coverage and intramuscular fat, providing at the same time, a suitable technological and nutritional quality. The fat composition will influence on the obtaining of high quality products. In this sense, the high degree of monounsaturation (high contain in oleic acid) of the extensive pig fat allows the raw matter to be subjected to a long cured process. This also favours the formation of the aroma and affects in a positive way the organoleptic sensations, providing a healthy nutritional quality from the cardiovascular point of view.

Keywords: Extensive pig, genotype, diet, fatty acids, triglycerides, quality

Introduction

The extensive pig production systems are located in particular areas of Southern Europe such as the west and Southwest of the Iberian Peninsula and certain insular areas of the Mediterranean among which the Island of Corsica stands out notoriously. The extensive pig production is defined by the use of local genotypes or crosses which exploit, through grazing, the natural resources of the sylvopastoral space, particularIy the species of Querccus and Castaneas destined for an elaboration of traditional transformed products of high quality and non-surpluses within the European Union. This particular sort of ecosystem is called "dehesa" specifically in Spain and "montado" in Portugal and it is characterised by its mean altitude of 350-400m and non deep floors which support the oak (Querqus ilex L., ssp. rotundifolia

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(Lamk.) Schwz.) and the cork oak (Q. suber L.) as the most representative trees in the ecosystem and in a lesser degree the gall oak (Q. Lusitánica Lamk) and the chestnut (Castanea sativa Miller) (Martin Bellido, 1989). The weather in the "dehesa" is semiarid Mediterranean (Llano Ponte et a1.1974) with hot and dry summer periods and rather cold and wet winters. The rainfall is between 440 and 660 mm/year, with great variability among years and distributed irregularly among the seasons, allowing the development of grazing lands formed by numerous species. The pasture owns two great productions in autumn and in spring, getting dry at the end of the spring as a result of the lack of rain and high temperatures (Martín Bellido, 1986). The grazing land surface of the "dehesa" area is of more than 5 millions of ha in Spain. In Portugal there is a surface of more than l million of ha and correspond to the Alentejo region. In Corsica the pig production is located in the mountainous areas where the oaks and chestnuts wood are found (30.000 ha), being greater in Corse-du-Sud department (63% livestock) than in the Haute Corse (37% livestock). Therefore, a particular feature of the extensive pig production is its association to developing countries, in which this activity is one of their most important productions and it contributes with its existence to the preservation of their ecosystems, hence its socio-economic and environmental importance. As regards the number of animals dedicated to this kind of exploitation, we find in Corsica about 4,400

mother pigs (Recesenment Génèral agricole, 1992) While in Spain in the area of the Iberian pig production restricted mainly to the peninsular Southwest there is a census of about 103,600 breeding pigs, obtained from the census carried out in 1988 by ACERIBER (Spanish Association of Iberian Pig Breeders) and later updatings in 1989 and 1990, and the one obtained by the Register of Exploitations of the Junta de Extremadura in 1993 (Espárrago et al., 1994). In Portugal the Alentejan pig population presents an irregular dispersion in the Alentejo region. -It is considered that there are a population of Alentejan pig of about 5,000 breeding pigs.

In the year 1994 about 2,000 breeding pigs were registered in "The Book of Breed" thanks to the dynamic efforts done by UNIAPRA (Associations Union of the Alentejan Breed producers) in relation to the genetic features of this breed (Fallola et al, 1996).

Factors whieh affeet the extensive pig quality

The whole productive extensive system is focused on the elaboration of high quality products. The final product quality will depend on the raw material quality (clearly influenced by the genotype and the diet followed) and the technological process used. The adipogenic feature presented by the local genotypes and the sort of diet taken in its fattening period (acorn or chestnut), will define a raw material with high content in coverage and intramuscular fat providing at the same time a proper technological and nutritional quality.

Raw matter quality

The raw matter quality is influenced by many factors, some intrinsic ones as the breed, sex or age and some extrinsic ones like the diet and management.

Intrinsic factors

Among the intrinsic factors, the genotype is one of the most influential element on the raw material quality. Although there can be differences in the protein percentage, in the muscular fibber diameter and texture; the greater variations are observed in the fatty content, which is usually bigger in animals subjected to a lesser genetic selection (de Pedro 1989). This is the case of the extensive pig because the determining factors of exploitation, adaptation to the

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environment and the particular features of the raw matter limit the genetic improvement systems applied to the white pig, since it is possible to affect in a negative way the raw matter quality, rusticity level and the own survival of these extensive pig breeds. Therefore, the pig dedicated to the extensive production can be defined by the following descriptions: adipogenic, early and rustic, with all the connotations this means. Nevertheless, the extensive production has not been dctached from the introduction of crossing practices with foreign breeds, with the goal of getting a better profitability from its productions, through the increase of the numerical productivity in the crossed fernales, getting a daily increase in the mean profits during the fattening period and the improvement of the industrial yield by means of obtaining carcasses with smaller fatty basin and greater percentage in noble pieces. So, the crossing with Duroc is used in the Iberian pig production which allows to get animals of the 50% and 75% of purity in Iberian blood. In Corsica The crossing practice is carried out using traditionally as male the Large White and the Pietrain and less frequent the Landrace 8 (Molenat and Casabianca, 1979). Another important feature, typical of this sort of genotype is the high level of monounsaturation in its adipose tissue. In table 1 the adipose tissue composition in fatty acids of the Iberian and Large- White fed with commercial fodder, is shown and this table also shows the high content in oleic fatty acid of the Iberian pig versus the Large- White (51, 12 vs 44,53) and the smaller content in palmitic fatty acid (23,35 vs 26,23). Likewise, the triglyceride composition and, therefore, its properties will depend on the content in fatty acids in the pig adipose tissue which is conditioned by the genotype among other factors. It is shown in table 2 that there are remarkable quantitative and qualitative differences between Iberian and Large- White breeds; and this shows the composition of the triglycerides of the subcutaneous fat in both breeds. It also can be noticed that whereas the POO represents the 45,75% in Iberian pig, in Large- White is only the 27,9%. In this last breed the triglyceride percentage is more distributed, without being so prominent as in the Iberian pig. Besides, it is noticed that whereas in the Iberian pig fat all the triglycerides have oleic acid (C 18: 1) in the position Sn-2, in the Large- White fat PPO and EEO appear; It should be pointed out that this difference is mainly due to genetic reasons.

Table I.Mean values ofthe adipose tissue composition in fatty acids in Iberian pigs and Large- White fed with commercial fodder

C12:0 C14:0 C16:0 C16:1 C18:0 C18:1 C18:2 C18:3

Iberian 0.11 1.53 23.35 3.53 10.83 51.12 8.62 1.05

Large- white 0.16 1.52 26.23 2.45 14.53 44.73 9.830 0.56

Table 2. Composition in percentage of the subcutaneous fat triglycerides of the Iberian Pigs and Large- White fed with commercial fodder

OOL POL OOO POO POP EOO POE PPO EEO

Iberian 3.8 11.1 7.6 45.7 7.3 5.1 18.9 - -

Large- White - 13.6 7.8 27.9 - - 17.3 8.0 5.0

With regard to sex, castration of female and male pigs destined to fattening is imposed in the exploitation of the lberian pig, affecting therefore meat quality, contributing to a greater cluster of fat in the tissues of the castrated animals (León, 1992).

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As a result of the exploitation system, these animals are slaughtered at the late ages of about 15 and 18 months, with alive weights of about 150-160kg for the Iberian pigs, and 110-130kg for the pigs from Corsica. According to Leseigneur-Meynier and Gandemer (1991), the animal age indicates the red and white fibber proportion in the muscle. The red fibbers are mainly aerobic and they use the lipids as energetic substratum. This is the reason why the red fibbers have greater quantity of muscular pigment and a more developed vascular system. So, the extensive pig meat colour is intenser than the one in the improved pig breeds. As well, due to the high proportion of red fibbers, this sort of meat is more aromatic and tasty, by creating the metabolised lipids a great variety of chemical substances of great intensity with regard to smell and taste (León, 1992).

Extrinsic factors

The diet determines, a great deal, the final features of the animal carcass, from the qualitative as well as the quantitative point of view (de Pedro, 1989). Being the pig a monogastric animal suffers modifications in the composition of its lipids if certain fats are introduced in its diet, since the fatty acids are eliminated without suffering any important structural modification (Wood, 1984). In this sense, it is noticed that the Iberian pig fat fed with grass and acorn presents a more tender and oily texture, as well as a particular composition in fatty acids (Montero de Espinosa et al., 1992).

The acorn components in immediate principIes, as well as its profile in fatty acids versus such a fodder and cereal like the triticale appear reflected in table 3. It is seen in this table that the acorn is richer in water than fodder, so the caloric contribution by kilogram is smaller. Besides, the acorn is very rich in fat and fairly low in protein and carbohydrates, compared to the cereals and fodders used in the fattening process. Since the raw matter from the Iberian pigs fed with pasture and acorn, as well as the hams elaborated with them reach a higher price in the market.

Table 3. Mean composition of the acorn vs. fodders (%) C16: C16:1 C18: C18:1 C18:2 C18:3 FAT PROTEIN CARBO- MOIS-

0 0 HYDRATE TURE

Triticale 14.2 0.3 0.1 20.5 57.6 5.3 1.5 (1.7)* 11.6 (12.9)* 70 (77.7)* 10

Fodder 12.6 0.2 2.3 24.6 56.7 3.4 2.8 (3.1)* 14.8 (16.5)* 65.6 (72.8)* 10

Acorn 14.2 0.3 2.4 . 63.1 16.2 1.1 3.3 (6.6)* 4 (8)* 25.4 (50.8)* 10

With regard to the animals fed with fodder, it is relevant to point out, from an objective view, the different categories found in the market. For this purpose a great deal of studies have been carried out; studies on the description of Iberian pig in relation to the diet. The most common methods for the elaboration of these studies have been the description of the composition in fatty acids and triglycerides of the subcutaneous fat. Other methods used apart from the classical ones (fusion point, sliding point, Iodo index) have been the NIR and the description of isotopes C12-C13. in table number 4 we can see the effect of the diet based on pasture and acorn on the Iberian pig versus the Large-White fed with commercial fodder which is characterised by the greatest content in oleic fatty acid (58,23 vs. 44,73) and the smallest content in palmitic acid (19,20 vs. 26,23). Therefore, with the acorn diet effect, the composition in fatty acids, which had been checked before, is reinforced. In table 1 you can notice how a great degree of unsaturation is produced when the pig consumes greater amount of acorn. This high percentage of monounsaturation is present thanks to the high content in oleic, which is the case of the subcutaneous fat closely related to the diet based on acorn (table 3).

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Table 4. Mean values of the adipose tissue cOmposition in fatty acids in lberian pigs fed \Vith acorn and Large- White fed with cOmmercial fodder

C12:0 C14:0 C16:0 C16:1 C18:0 C18:1 C18:2 C18:3

Iberian 0.07 1.10 19.20 2.01 9.35 58.23 9.33 0.71

Large- white 0.16 1.52 26.23 2.45 14.53 44.73 9.830 0.56

As regards the composition in triglycerides, table 5 presents the current differences between the Iberian pig

and the Large- White fed with pasture, acorn and commercial fodder respectively. lt can be seen that in both breeds the POO keeps showing itself as the predominant triglyceride (41, 7 vs 27,9) although decreasing its percentage in relation to the Iberian pig fed with fodder (41,7 vs. 45,7). Likewise, an increase ofthe 100% is noticed in the composition of the triglyceride 000, in the Iberian pig fed with acorn (15,1) versus the Large-White (7,8) and the Iberian pig fed with fodder (7,6). We still notice that in Large-White the percentage of triglycerides is more distributed than in Iberian pig and in this last one all the

triglycerides have oleic fatty acid in the Sn-2 position and there is not any with the palmitic or stereatic acid in the Sn-2 position like in the case of the Large- White.

Table 5. COmposition in percentage of the subcutaneous fat triglycerides of lberian pigs fed with acorn and Large- White fed with cOmmercial fodder

OOL POL 000POO POP EOO POE PPO EEO

Iberian 7.8 12.3 15.1 41.7 4.3 6.1 12.8 -

Large- White - 13.6 7.8 27.9 - - 17.3 8.0 5.0 In this sense, it is known that during the fattening period there is an important elimination of the fat coming

from the diet in the animallipid tissues. This process is named exogenous lipid synthesis. In this process of exogenous synthesis the diet triglycerides are hydrolyzed by the pancreatic lipase in the terminal esters links (Sn-l and Sn-3) giving place to the formation of the esterificated monoglyceride in the Sn-2 position and two free fatty acids. Later, within the enterocite the triglyceride is regenerated quickly (Mataix and Martinez, 1988). Like it can be seen, the Sn-2 position remains immutable during the exogenous synthesis of the triglycerides. Therefore, a diet rich in acorn, in which the majority triglyceride is the OOO, contributes to the presence of the triglycerides with oleic acid in the Sn-2 position.

The other formation process of the lipid reserves is the exogenous synthesis. Inside it, the greatest part of the digested immediate principIes, mainly the carbohydrates, are metabolised to Acetil-CoA. This compound works as sustrate for the synthesis of the fatty acids (Rérat,1978 and 1981). The first fatty acid formed on the way of the synthesis of the carboxylic acids is the palmitic (C 16:0), which will turn partly into esteric (C 18:0) by the action of an enlogasa. Finally, the estearic acid is transformed into oleic acid (C18:1) by the action of a deshydrogenasa enzyme. The lack of a proper enzymatic system in the mammals interrupts the formation process of linoleic acids (C 18:2). therefore, in the pig, all the linoleic acids present in the fat comes from the exogenous synthesis.

To conclude, it can be said that the diet components will make good to any process of synthesis. So, Diets rich in fats will favour the exogenous synthesis, whereas the ones rich in carbohydrates stimulate the endogenous lipid synthesis, favouring the presence of palmitic acid in the animal fat

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Vidal-Aragón (1996) in a study carried out about the composition of the triglycerides in the lberian pig subcutaneous fat according to the diet followed (fodder and different level of replacement in pastures), finds out (table 6) that the POP and the POO increase their concentration, as the quantity of digested fodder also increases during the fattening process. This is due to the major presence of endogenous synthesis. Likewise, when the replacement kilograms are increased in the pastures, the concentration of trioleine (OOO) increases, since the lipid synthesis moves to the exogenous process, by having the acorn a greater content in fat.

Besides, the exploitation system, that is the extensive pig management during the fattening period, forces the animals to do muscular exercise. This, together with, the movement during the acorn and chestnut grazing impose a functional modification of the muscular fibbers towards more aerobic forms, which originates, together with the age, a greater proportion of red fibbers and, therefore, a greater intensity in the flavour.

Table 6. Composition in percentage of the subcutaneous fat triglycerides of Iberian pigs fed with different level of acorn in pasture

OOL POL OOO POO POP EOO POE

Iberian-acorn 58 kg 7.8 12.3 15.1 41.7 4.3 6.1 12.8

Iberian-acorn 46 kg 7.7 13.0 14.4 42.1 4.5 5.5 12.2

Iberian-acorn 35 kg 8.6 . 15.3 12.9 41.0 5.7 4.8 11.5

Iberian-acorn 23 kg 6.4 13.9 11.5 43.6 6.5 5.0 13.0

Iberian- fodder 3.8 11.1 7.6 45.7 7.3 5.1 18.9

Technological quality

The technological process adjusting is, together with the raw matter, one of the most influent factors on the final product quality. In table 7 it can be seen in a schematic way the differences according to the proceeding, of the most important hams within the Mediterranean context. The fundamental stages in the Iberian ham elaboration are the following:

i.- Obtaining hams. ii.- Selection and classification. iii.- Salting. iv.- Post-salting. v.- Drying. vi.-Ripening in cellar.

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i- Obtaining hams

This stage covers, among others, the slaughter operarions and the pig quartering, followed by the outlined and bleeding of the posterior extremities. During the whole stage the hygienic conditions must be overdone to reduce, as much as possible, the risk of microbian infection. In this sense, it is necessary to control the temperature correctly, keeping it between 5 and 8°C and so to avoid the multiplication of the polluting micro-organisms.

Before doing the outline of the pieces the pH is measured to eliminate those carcasses which present irregular values, as it happens in the cases of the DFD and PSE meats. The incidence of DFD and PSE meat depends, a great deal, on the previous conditions to the slaughter. The PSE meats are not suilable for the elaboration of cured hams because they become dehydrated quickly giving place to a finished product of great fibrosity due to the reduced water holding capaciLy which present this sort of meat (Díaz,1994). The DFD is not suitable for the elaboration of this sort of product either due to its high pH values, which allow the growing of altering micro-organisms and potentially pathogenen. In addition, the drying process of these meats is affected in a negative way by their own high water holding capacity. In the Iberian pig, the presence of PSE carcasses is very strange, but the one of DFD can be found due to the animals arrival at the slaughterhouse, in some cases their energetic reserves run out because of the constant exercise done during the grazing and the inadequate conditions of transport.

The outline consists of the elimination of certain fat, skin and muscles of the posterior extremity to get a piece of certain proportions. In the Iberian pig the cut is in V form.

Once outlined the piece, the bleeding is done to eliminate the left blood in the ham, which could favour Lhe microbian alteraLion during the procedure. This operation is usualIy done by hand, pressing from the inferior part to the superior one, following the way of the femaral and sapene arteries (De Prado, 1988).

ii- Selection and classification

Those pieces whose pH cover from 5,3 and 6,2 are selected, so the non suitable ones for the ripening are left out. In the Iberian pig the pH is frequently superior to 6 (León et al. 1988). Of course the broken pieces and the ones with bruises or cracks are rejected.

The classification is carried out as regards weight and the ham size with the purpose of being the time in the following phases as homogeneous as possible, particularly the salting time.

iii- Salting

The objective of this phase is to help the cured salts reach at the inner part of the ham so that a dehydration and stabilisation of the pieces can be produced, inhibiting the growing of altering and pathological micro-organisms.

The salting is done by rubbing the hams with sodium chloride (NaCl) and little quantities of nitrites and nitrates, as well as, in certain occasions, sugars and antioxidants. Then the pieces are piled in the special refrigerator for salted meat, alternating a layer of salt and other of hams, up to a non superior height of 8 pieces, to avoid an excessive pression on the pieces placed at the bottom. The temperature in these refrigerators must be about 3 and 5°C and they have a relative humidity of the 90 to the 95%. It is convenient to keep relative environmental humidities during the salting, in order to favour the formation of saturated salt solutions favouring, in this way, their penetration through diffusion and capillary in the muscular fibbers (Nicolau).

The pieces stay covered in salt from 0,65 to 2 days per kg. of the piece weight. The current tendency is to keep them as less as possible in salt, since the consumers' taste has changed

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towards products poor in salt. This reduction is possible thanks to the current control of the technological process, which make possible the use of low temperatures until the ham stabilisation. This aspect is very important because the salt content not only affects the taste of the final product, but it is also a determining factor in the own enzymatic activity of the aroma and the muscular tissue and this takes part in the reactions of the generation of the responsible compounds of the tlavour and smell during the tasting.

Once ended this phase of salting, the hams are washed and brushed to eliminate the superficial salt. Later on, they are placed in drain refrigerators, in which the temperatures must be risen to favour the washing water elimination.

iv- Post salting

This is a resting or stabilisation stage, in which the objective is to get an homogeneous distribution of the salt around the whole piece. The salt and the hydration concentration produced during the salting as well as during the post-salting, produce a decrease of la aw, or non mixed water quantity, therefore the risk of a microbian growth decreases, producing as a consequence, the piece stabilisation (Buscailhon, 1992).

The post-salting is carried out in refrigerators to a temperature that at the beginning is of 5°C to increase gradually up to about 13°C and relative humidity in progressive fall, from the 90% up to the 80%. The duration of this phase varies according to the pieces size, it normally covers between 40 and 80 days (Díaz, 1994). In the case of the Iberian ham, this phase is frequently lengthened up to 90 days, due to the presence of the high fat contents, and this fact makes the dehydration and the salt diffusion difficult.

In this stage as in the previous one, processes of protein and lipids hydrolysis (proteolysis and liposis respectively) are being produced. In the proteolysis, the proteins break themselves in peptides, which can be also fragmented, setting free little peptides and free aminoacids. These ones constitute the fundamental protein units. As regard with the lipolisis, the hydrolysis of the triglycerides esters links and phospholipids gives place to the appearance of monoglycerides, diglycerides and derived from the phospholipids and free fatty acids. In both processes the structural degradation should affect the muscular enzymes (endogenous) or the ones coming from micro-organisms (exogenous).

The low molecular weight peptides as well as the free aminoacids, and the free fatty acids and their salts, have the defined sapides features, this means that they are able to activate the nervous tasted receptors. Moreover, some of these compounds act as flavour potentials (ex. sodium monoglutamate) or emulgent (ex. monoglycerides).

Beside proteolytic and lipolytic processes, oxidising degradations of the set free components are produced, fatty acids as well as aminoacids, giving place to the formation of numerous volatile compounds. The great majority of these volatile compounds own smell, this means, they are aromatic from the sensorial point of view, not from a chemical point of view.

v - Drying

In the drying phase, the hams are exposed to higher temperatures and lower relative humidities, with the purpose of intensifying the proteolysis and lipolisis biochemical phenomena, favouring in this way the reactions which will give place to the responsible components of the aroma and flavour.

By the way, being higher the temperature, the fat melts and it impregnates the muscular fibbers acting as a real solvent of the volatile compounds, avoiding the loss of themselves. In this process part of the subcutaneous fat is lost in the known dripping of the "ham sweating".

This stage is carried out in natural drying sheds, where the regulation of the temperature and

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the relative humidity are reached by the opening and closing of windows, according to the environmental climatic conditions. With the summer arrival, the temperatures goes from 16 to 30°C, and the relative humidity is between the 60 and 80%. There are systems of temperature and relative humidity regulation in the industries, which usually work in case the conditions mentioned before are not reached in a natural way; although there are cases of drying sheds totally artificial, in which the parameters are always controlled.

In this stage the growth of molds in the piece surface starts. The influence of these microorganisms in the development of this product typical features is not cIarified correctly, although it seems that they own an antioxidant effect, by having enzymes which are able to destroy preoxids and protect the ham surface from light. It is frequent in this proceeding stage, to put pig butter on the ham surfaces to fill in cracks and little interstices through which mites, diptereans, cleopterans and even molds can penetrate.

vi- Ripening in cellar

When the summer is over, the hams are moved to the cellars where the temperature and relative humidity are more constant and less dependent on the external climatic conditions. The temperature ranges between 10 and 15 °C in winter and between 15-22°C in summer. Likewise, the relative humidity ranges between the 60-70% depending on the season of the year. The duration of this stage is about one year. It is the typical phase of the Iberian pig ham elaboration. In this stage the organoleptic features of this product are going to developed, overall the aroma and flavour.

Quality controls of hams

Once the process of cure ends, it is necessary to elaborate a control of the final product to guarantee the consumer the quality of it.

Starting from a suitable raw matter and following the whole technological process correctly, it can be supposed that an apt product for the consumption is to be obtained. However, sometimes there are failures during the proceeding, either a deficient raw matter breaks, getting altered hams. These alterations produce important economical losses to the industry because they mean modifications of the organoleptic features (colour, aroma, texture and flavour) which make possible the sale and distribution of these pieces (Ventanas and Córdoba, 1994).

With the finished product control, the purpose is to eliminate the cured hams which present alterations of any procedence. So, the alterations in the surface are sensosrially detected with the touch, the sight, the smell and analytic determinations in the laboratory. The anomalies inside the ham like the deep putrefaction are detected without spoiling the piece through the sample slice. This test is done by an expert pricking with a bone in the coxophemoral and phermorotibiorrotuline articulation and smelling the bone surface afterwards. The hams with funny smells are analysed to study the sort of alteration produced.

For a correct quality control of the cured ham it is also necessary to evaluate the organoleptic features which really define the product: flavour, aroma, colour, juiciness and fibroid character. This is carried out through the sensorial analysis done by a group of trained tasters who are able to appreciate little modifications in any of the analysed parameters.

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Technological quality of fat

The fat found in the transformed and elaborated products from the extensive pig is a component of great importance within the product qualities, since its composition allows a raw matter adaptability to the long elaboration process, affecting, likewise and in a positive way to the organoleptic sensations, because the great majority of the volatile compounds responsible for the aroma are formed from the fat.

The intluence of the fat quality over the meat quality is focused on the fat quality, its stability, its features and its adecuation to the elaboration.

The fat quantity can be controlled through the animal genetic, producing animal s with greater or smaller subcutaneous and intramuscular fat content (Díaz and García, 1994), although in the extensive pig case and particularly in the Iberian pig this aspect is less controlled because of the genetic conditions and the management carried out in this sort of exploitations. So, in Iberian pigs, the high alometric coefficients of the pieces and fat deposits show that the greatest growing of the carcass, with regard to the alive weight, is consequence of its greasing. This greasing is mainly due to the elimination of subcutaneous and loin fat since the inter and intramuscular fat have an earlier development (de Pedro 1987). This same author shows, in relation to the ham weight, in the same sense that the weight increase of the piece is a consequence of the high fat deposal, mainly of the subcutaneous type.

The composition of fatty acids as their localisation within the glycerol molecule have a direct influence on the characteristics of the fat and on its stability and, therefore, this condition its adecuation for the elaboration of the meat products. The unsaturated fatty acids, with low point of melting, are responsible for the soft consistence of the fat , and the saturated, for its stability. According to Enser (1984), the stearic acid (C 18:0) is the one with greatest influence on the fat consistency, although this also depends on the conjunctive development. As regard with stability, the fats with high fatty polyunsaturated acids contents are very sensible to the oxidation, whereas the one with greater quantities of saturated and monosaturated fatty acids are more stable. The use of very polyunsaturated fats could give place to the appearance of rancid smell, originating in this way a quality loss of the product (Fulimoto et al., 1990). In the case of Iberian pigs, the particular characteristic of the fat, concerning to its composition in fatty acids (high content of monounsaturated and low polyunsaturated) and the position which occupy in the glycerol, condition the ham quality with regard to flavour, aroma, juiciness and resistance to the process of oxidation. This aspect is very important, since being the fat mainly monounsaturated it can be subdued to the long periods of cure needed in the Iberian ham elaboration, without detriment to the quality due to the rancidity problems.

Aromatic compounds of the Iberian pig ham

In a study carried out by Vidal-Aragón (1996) about the Iberian pig ham volatile fraction, the following conclusions can be established.

The technique used in the volatile fraction analysis allows to isolate and identify in Iberian pig ham 45 volatile compounds, which have molecular weights between 30 and 150. These compounds belong to the following chemical families: aldehyde (12), ketone (7), sters (3), alcohols (4), n-alcanes (S), aromatic hydrocarbons (4), terpenes (3), sulphurate compounds (3), sters (l), phurane(1) and chlorate compounds (2).

The chemical family of the aldehydes is the most important, from the quantitative as well as the qualitative point of view, in the Iberian pig ham, being the hexanal the most abundant, with great difference over the rest. This result has a very important practical interest since these compounds present a great aromatic intensity.

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The great abundance of aldehydes in the Iberian ham is due to the quantitative point of view as well as to the raw matter features such as the technology used in its elaboration. So, the Iberian ham is rich in intramuscular fat, and this is the origin of many aldehydes, particularly of the lineal ones. Besides, the Iberian ham elaboration process is characterised by the use of temperatures superior to the ones used for other sort of ham during the drying period and of very long ripening times ( 18 months). Both factors favour the proteolysis and lipolysis processes, which lead to the apparition of fatty acids and free aminoacids, which are the forerunners of many aldehydes.

Nutritional quality

Nowadays there is a growing interest, from the scientific as well as from the consumers point of view, in knowing the composition of the fat digested in the diet, due to its nutritional implications related to the health.

In the last years, this interest has turned into another of the marketing elements. Although the extensive pig ham is not a product of high consumption, it is obvious that the data provided about the nutritional quality of this product will always be of great interest. In this sense, the fatty acids composition plays an important part in the nutritional-health quality, since this sort of products have a very suitable lipid profile by presenting a high proportion of monounsaturated fatty acids versus a low tax of saturated fatty acids, being very different this profile from the one shown in the products derived from the intensive white pig.

So, in a study carried out recently by García Rebollo (Ortiz et al. 1996) to value the influence on the plasmatic lipids from the Iberian pig ham (fed with acorn) consumption, the following conclusion, among others, was reached:

The total cholesterol, the triglycerides and the LDL cholesterol in blood had a relevant decrease after a dietetic period (which included acorn Iberian hams) with regard to the basal values.

This study is the first one about the dietetic interventions which include acorn lberian ham, and it allows to state (in spite of the limitations) that in the context of a diet low in saturated fats , the acorn Iberian ham, even consuming a great deal of it daily, has not got harmful effects on the plasmatic lipid profile.

Sensorial quality

A lot of studies have been carried out by the Agroalimentarian Department of Technology about the sensorial analysis of the Iberian pig ham. The attributes done have been the following: colour, graining, smell like Iberian ham fed with acorn pasture. other smells, flavour like Iberian ham fed with acorn pasture, salting, intensity of fIavour, persistence of fIavour, fluidity of the fat, juiciness, tenderness and acceptability or global evaluation. The smell and fIavour like Iberian ham fed with acorn pasture refers to the typical smell and fIavour of the elaborated ham from Iberian breed pigs which have been bred in an extensive regimen and which have been fed with grass and acorn during the fattening period previous to slaughter. With the attribute "other colours", the purpose is to evaluate the presence of smells strange to this product such as the acid, putrefaction, rancidity, etc, indicating normally the existence of greater or smaller degree of any alteration. The used technique has been the quantitative descriptive analysis for which the multiscalars tests were chosen. The scales scored from l to 10. The conclusions which can be drawn from the obtained results are the following: The diet provided to the animal during the fattening period influences on all the analysed sensorial attributes, except on the colour.

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In all the cases the animal group fed with fodder is the one which present the lowest mean values, except in the attribute "other colours", which is remarkably superior in this group and can be related to the obtained data in the analysis of volatile compounds, where a greater concentration of sulphurate compounds and steers were found.

The attributes flavour to acorn pasture, fluidity of the fat, juiciness, tenderness and global acceptability follow a quadratic variation with the kilograms of replacement that the animal suffers during the acorn fattening phase, similar to the one found for the triglycerides.

The variables of smell like acorn pasture, flavour intensity, persistency of the flavour and tenderness increase at the same time as the replacement kilograms becoming independent of the diet from the 35 replacement in pastures. However, the acorn pasture variables, the fat fluidity and juiciness keep on increasing progressively during the whole interval of the studied replacement (0-60 kg).

With regard to the global ham acceptability, this has an intermediate behaviour, appearing a very high maximum to replacement values, close to 60 replacement kilograms in pasture.

The study of main components shows that the genotype has a clear effect on the organoleptic features of the Iberian ham. This analysis points out that pure Iberian animals make up a group differentiated, in general, from the animals of the 75% and the 50% by having a greater value of smell and flavour like pasture, flavour intensity and flavour, juiciness, fat fluidity, colour, tenderness and the product global acceptability.

Economic importance

The breeder production costs

The animals prices are conditioned by the different quality of the carcasses and production costs, which depend on the duration of the productive cycle (12-20 months), slaughter weight (140-180 kg) and in certain periods, feeding with acorn, which requires the existence of an extensive exploitation system in the pasture, the efficiency of the manpower and the sucking pigs value (Espárrago et al., 1994).

In table 8 it can be noticed how in the 93/94 campaign, due to the low prices, all kind of productions provide losses, standing out in addition the smaller cost of the pasture for that year. By contrast with the cost of this campaign, the high profit per pig obtained during the 86/87 campaign can be seen. These data show that the obtained costs and the price evolution have a great variability in the breeder's profitability, with losses when the price cycIe reaches the minimum values, and moderate high profitability on the contrary case. Nevertheless, The high cost of the pasture does not impute, overall in the exploitations with own trees. The same happens with the financial costs in the profitable exploitations, which can invest in (sucking pigs and fodder mainly), without adding financial profitability costs to the invested capital. The sucking pig cost is also amortised in the exploitations which follow the whole cycle. So, apparently, some exploitations can present very high profits and profitability, which favours an offer expansion and, therefore, a greater oscillation of the prices (Espárrago et al. 1994).

Economic assessment of the Iberian pig carcass

It is shown in table 9, the quartering yield of an lberian pig of 158 kg carcass. It is noticed that the noble products in fresh (hams, shoulders and loins) have a yield over the carcass of the 14,78% 10,04% 3,l0% representing the 27,92% of the carcass weight. Likewise, in relation to the mean market prices for the year 1996 (year of limited pasture) of the fresh products of this quartering we can see that the noble parts represent the 67,77% of the carcass quartering

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sale va1ue. So, according to the market prices reflected in this tab1es a margin of 2.331 pts of gross benefit per pig is obtained by the sale in fresh of the Iberian pig products.

Table 9. Quartering yield of Iberian pig

Concept kg/pig Percentage Pts/kg Price (pts)

Carcass weight 128.46

2 Hams 18.99 14.78% 825 15663

2 Shoulders 12.90 10.04% 550 7094

2 Loins 3.98 3.10% 2100 8353

2 Sirloins 0.57 0.45% 1400 801

2 Top loin 2.96 2.30% 750 2221

Lean 1ª 8.03 6.25% 650 5220

Cheek 0.32 0.25% 350 111

Dew lap 4.71 3.67% 140 660

Head 4.60 3.58% 21 97

Back fat 21.78 16.96% 130 2832

Fat without pork rinds 12.54 9.76% 50 627

Fat with pork rinds 21.25 16.54% 44 935

Raw lard 6.24 4.86% 44 275

Spines 2.68 2.09% 35 94

Ribs 4.05 3.16% 150 608

Kidneys 0.27 0.21% 50 13

Loss (2%) 2.57 2.00%

Total 128.44 99.98%

Tongue 0.30 250 75

Heart 0.30 70 21

Liver 3.00 70 210

0.25

Total products 45908 Pts

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Table 9a. Assessment of the pig alive

Assessment of the pig alive

Weight in kilograms (kg) 158.00

Weight in arrobas (@) 13.74

Price: ptas/@ 2850

Price: pts/kg 247.83

Sale price 39157 Pts

Slaughter Expenditures (28 pts/kg) 363 l Pts

Transport Expenditures(5 pts/kg) 790 Pts

Gross profit/pig 2331 Pts

1@ =1 1,5 kg

Elaborated products and their price

The transformed product prices shown in table 10 have been obtained from the studies carried out in Extremadura by Espárrago et al., (1994 and 1996). It is important to point out that the majority of the incomes are due to the value of the noble products (hams, shoulders and loins) representing the 76% and the 68% for the products of acorn and fodder respectively.

The transformer industry transfers to the final consumer, throughout the price, the different costs of its raw matter purchase and the financial ones motivated by the immobilisation time needed for its elaboration.

The prices are not homogeneous among the different products, varying according to the raw matter origin. In hams, the prices have reached mean values of 3.144 pts/kg and 2.091 pts/kg for the ones of pasture and fodder respectively. The differences of prices in this product are greater in the shoulders and loins, while in cold meat the differences are not relevant.

Besides, in this table, the most relevant cost for the industry have been determined: the raw matter purchase, elaboration costs, financial ones, auxiliar materials and transport. It can be noticed that the gross margin (incomes minus direct costs) is high, being superior in the products from animals fed with acorn. Nevertheless, the margin is quite conditioned by the variability in the raw matter oscillations.

Together with this cost, which is the main one, the financial cost should be pointed out, associated to the long elaboration period). In spite of all this, the profitability is high.

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Conclusions

The quality of the extensive pig productions (Iberian) is the result of the existence of a breed, an animal-pasture production system and a transformer industry. The final consumer asks for products for which he is ready to pay high prices, although non in a uniform way, being maximum this difference for hams and less or hardly nonexistent in cold meat.

The industry transfers the product prices in a homogenous way to the value of the different animal categories. The obtained margins by the industry are high, although capable of suffering remarkable variations derived from the cyclic oscillations in the cattle prices.

The current quality regulations (guarantee of origin) is contributing to impose the regulations which guarantee the quality, and this will favour the sector.

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