Meat Science, Vol. 47, No. 314, 259-266, 1997 0 1997 Elsevier Science Ltd
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Technological Suitability of Mutton for Meat Cured Products M. J. Beriain, J. Iriarte, C. Gorraiz, J. Chasco & G. Lizaso Escuela Tknica
Superior de Ingenieros Agkmomos, Universidad PCblica de Navarra, Campus Arrosadia, 3 1006 Pamplona, Spain
(Received 6 March 1997; revised version received 6 May 1997; accepted 15 May 1997)
ABSTRACT A comparative study on the technological suitability of mutton and pork for meat cured products was carried out. One type of cured dry sausages was made of mutton and the other of pork, using the same formulation and technological conditions. Thus, the evolution of physico-chemical and microbiological parameters, as well as colour and texture were measured at three different stages of the process: after mincing, after fermentation and after drying. The sensory parameters were assessed in the final product. Both mutton and pork had a similar technological aptitude during processing of cured dry sausages, with a similar evolution of the pH value, a, and Lactobacilli counts. The main differences between both types of sausage were observed in texture, colour and in the organoleptic characteristics, having mutton sausages greater cohesivity and more stable and redder colour than pork sausages. Besides, mutton sausages showed an aroma,Javour and texture that were not desirable for the panellists. 0 1997 Elsevier Science Ltd. All rights reserved
INTRODUCTION The low trade price of sheep meat and the fact that pork cannot be consumed in many countries because of religious customs, have favoured the development of transformation procedures of meat derivatives involving meat from different animal species such as sheep (Gokalp, 1986; Shaikh et al., 1991). The organoleptic quality of meat products is directly influenced by the lipid composition. Meat flavour is determined by specific aromatic compounds of its lipid fraction, which presents a higher saturated fatty acid percentage in lamb than in pork (Wasserman and Spinelli, 1972; Cramer, 1983). Lamb meat flavour depends on animal feeding systems, and becomes stronger with increasing age of slaughtering (Field et al., 1983). Some authors (Anderson and Guillet, 1974; Brennand and Mendenhall, 1981; Bartholomew and Osuala, 1986) suggest the need of adding beef or pork fat to decrease lamb flavour because lamb products are usually assessed as acceptable only when lamb fat is equal or less than 10% in the mix. Spices and smoking are also used to reach this aim, hiding the unpleasant lamb flavour (Daun, 1979; Bartholomew and Osuala, 1986). A study of Vera y Vega et al. (1976) about ‘chorizo’ made of different proportions of lamb and pork lean meat confirmed that lamb has optimal technological properties for 259
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curing, even if its sensorial assessment is not very satisfactory, due to the intense aroma of this kind of meat. Bandeira de Oliveira et al. (1992) studied the evolution of physicochemical parameters during curing of dry sausages made of goat meat, comparing the final product with current legislation requirements. The aim of this work was to compare the technological aptitude of mutton and pork for being transformed in cured dry products by industrial processing. So, the evolution of physico-chemical parameters, as well as parameters related to colour, texture and sensory evaluation of dry sausages made of mutton and pork, were studied during the technological process.
Sausage preparation and processing Four series (approximately 15 kg serie-‘) from each type of dry sausage were manufactured in a pilot plant. Pork sausage was made of back fat and lean from porks slaughtered at 110 kg live weight and six months old. Mutton sausage was made of perirenal fat and lean from ewes slaughtered at 50-55 kg live weight and 5-6 years old. Slaughter conditions complied with the Spanish Legislation (B.O.E., 1993). Both types of sausage had an average composition of 76% lean and 24% fat in the initial mix. The manufacturing stages started with the mincing of fat and lean in a 15 mm diameter mincer at &5”C. The minced mix was then placed in a vacuum kneading machine together with the following additives and ingredients: common salt (25 g kg-‘), paprika (24 g kg-‘), garlic (6 g kg-‘), sacarose (4 g kg-‘), nitrites (150 ppm), nitrates (150 ppm), sodium ascorbate (1 g kg-‘) and powder milk (20 g kg-i). The initial mix was stored at 2-5°C for 24 hr before casing. The mix was stuffed in pieces of about 300 g in a 30 mm diameter natural sausage casing. Then, they were fermented at 24°C and 60% and 90% relative humidity alternate circles, about 65 hr, just enough for dry sausages to reach a 4.9 pH value. At this moment, they were transferred to a drying chamber at 12-15°C where relative humidity was decreased gradually from 85% to 75%. Samples were taken at three process stages: after kneading and storing the minced mix at 2-SC, after fermentation and in the final product (after drying). Physico-chemical and microbiological parameters Physico-chemical parameters
Water activity (uw), drip point method, using a water activity meter CX-2 AQUALAB; moisture, (IS0 1442-1973a); pH, (IS0 R2917-1974); total protein by the KJELDAHL method, (IS0 937-1978); Texture profile analysis (TPA) (Boume, 1978); total fat by the SOXHLET method, (IS0 1443-19736); lipid extraction (Bligh and Dyer, 1959); methylation (Eichhorn et al., 1985); methyl esters were analysed on a Hewlett-Packard chromatograph (HP-5890) equipped with a hydrogen flame ionization detector (FID); separations were effected with a HP-FFAP (cross-linked) column (25m lon x0.2mm i.d. x0.3 mm) under the following conditions: (a) carrier gas: helium at 1 mlmin-‘; (b) oven temperature: 18&21O”C at 3°C min-‘, 210°C for 5 min, 210-255°C at 5”Cmin-‘, 9min at 225°C; (c) injector temperature: 230°C; (d) detector temperature: 240°C. On injection, the stream of helium and the injected sample’s volume were split (1:24). Methyl ester standards of fatty acids (Matreya Inc.) were used for the peaks identification; Study of reflectance spectrum-pigment nitrosation index (R560/R500) (Giddey, 1966) and colour parameters (L’, a*, b’) (CIE, 1976), Chroma (C’) and Hue (H’) with a MINOLTA
Technological suitability of mutton for meat cured products
CM2002 spectrophotometer ‘standard observer’.
using a D65 type light source and a 10” position of the
Microbiological parameters Lactobacillus: Lactobacilli MRS Broth ([email protected]
), Bacto-Agar ([email protected]
); Staphylococcus aureus: Baird-Parker (Difco@) with Egg Yoke Tellurite Enrichment; Escherichia coli: Petrifilm (Microbiology Products 3M Health Care); Salmonella: Peptone water ([email protected]
Selenito-Cistina Broth (Difcom), Green Brilliant Red Phenol Agar ([email protected]
), Triple Sugar Iron (Difcoa). Sensory analysis Fermented sausages were assessed by a trained lo-member sensory panel using a 5-point scale. Samples were evaluated for ripeness (0 = low intensity; 5 = high intensity), shape, appearance and colour (0 = not acceptable; 5 = very acceptable) in the final product; and fat content (0 = low; 5 = high), residual flavour intensity (0 = low intensity; 5 = high intensity), aroma, flavour, residual flavour, texture and overall acceptability (0 = not acceptable; 5 = very acceptable) in the slices. Samples were served in isolated taste panel booths using full lighting. Statistical analysis Each type of sausage was processed in four replications (four batches produced at different times). All sample analyses, except colour (in nine replicates), were performed in triplicate. Data were analysed by analysis of variance and mean separation by Tuckey test. Data analysis were performed using the Statgraphics 7.0 (1993).
The nature and composition of fat and meat, used as ingredients in the manufacturing process of dry sausages, and their transformations during drying have a direct influence on sausage flavour, and, so, they have repercussions on the acceptability of the final product (Bartholomew and Osuala, 1986; Gokalp, 1986; Mellett, 1991). In the present work, the same proportions of fat and lean, and the same ingredients and processing conditions were used in the two types of sausage. Therefore it could be confirmed that differences between both types of dry sausages were due to the influence of the composition of the raw materials (pork and mutton) in the biochemical reactions that took place during fermentation and drying. The drying stage went on for nine days in mutton sausages and 15 days in pork sausages. The duration of this stage in each type of sausage was controlled by the loss of moisture, until the suitable curing rate and consistency for each type of dry sausage was reached. Over this period, the initial moisture content decreased up to 37.66% (pork) and 43.88% (mutton) (Table 1). The a, decreased all over the process from O-965 in pork sausage and 0.967 in mutton sausage to 0.896 and O-914, respectively. Water content changes in dry sausages were influenced by the pH decrease during fermentation, because when getting close to the isoelectric point of proteins, dry sausages have a lower water holding capacity, that would accelerate dehydration (Girard, 1991). These data agree with results in dry sausages from other authors (Serrano, 1979; Gokalp, 1986; Mellet, 1991). pH value decreased during fermentation, increasing slightly in the final product. This effect might be due to the proteolysis phenomena (Potthast, 1987; Roncales et al., 1989)
M. J. Beriain et al.
Changes in Physico-chemical Parameters during Pork (P) and Mutton (M) Sausage Drying Process Parameters
PH a, Moisture (%) Total protein (%) Total fat (%)
P M P M P M P M P M
5.78f 0.11” 5.75 f 0.07” 0.965f O.OOOO’ 0.967&0.000u2 59.26f 1.49”’ 62.20f 0.62”2 17.14f0.57O’ 16.26f 0.32a2 18.27kO.87” 20.18f 0.28O
Fermentation 5.01 f 0.076 5.09 l 0.086 0.945 f 0.00061 0.952 f O.OlOb2
53.86f 0.62b’ 55.72f 3.03b2
Final product 5.43 * 0.08’ 5.35ItO*Ol’ 0.896 f 0.010”
0.914*0.010c2 37.66&3.47” 43.88f 1.48c2 21.90f0.20b’ 20.66f 0.22b2 31.43f 1.28b 33.09* 1.346
Means f standard error. Any two means followed by different superscripts are significantly different (p < O-05).Letters compare among the different phases of the process, numbers between both types of sausage.
which would involve a rise in the content of basic nitrogen compounds and, thus, the partial neutralization of the acidity (Flores et al., 1985). The acidification of the mix and the solubility that proteins (specially myofibrillar) acquire by the addition of salts could be the reason for the ingredients of the sausage to become blended (Ketelaere et al., 1974). During fermentation, micro-organisms that metabolise carbohydrates develop, giving lactic acid (Demeyer et al., 1986; Flores et al., 1985) and causing the pH evolution. Lactobacillus microbial counts were similar in pork and mutton sausages (3.3 1 lo9 cfu g-’ and 3.38 lo9 cfu g-i, respectively) after fermentation. The decrease of pH involved as well the Enterobacteriaceae counts decrease in both types of sausage (Bacus and Brown, 1981). Moreover, 12 and 30 cfu g-i of E. coli were obtained in both final products in pork and mutton sausages, respectively, and there was absence of S. aureus and Salmonella, complying with the microbiological Spanish Legislation for cured dry sausages (B.O.E., 1977). The colour of cured products depends mainly on heme pigments modifications caused by their reactions with curing salts (nitrites and/or nitrates). Sausage processing involves nitrosomyoglobin formation, giving meat products their characteristic cured red colour (Giddey, 1966; Hunt et al., 1991; Chasco et al., 1996). The CIE colour parameters, measured at each phase of the technological process, showed that colour evolved in a different way over curing in the studied sausages (mutton and pork) (Table 2). Although mutton sausage was darker than pork sausage after mincing both types of sausage reached a similar lightness (L’) in the final product. Pagan et al. (1992) and Chasco et al. (1996) also found a peak in Lightness during drying; a’, b’ and C’ also showed similar values in both of the final products, but while these three parameters decreased gradually in pork sausage throughout the process, they decreased until fermentation in mutton sausage, remaining constant during drying. Regarding Hue (H’), a lower value was observed in the final product than after mincing, giving both types of sausage a darker red hue. Pigment Nitrosation Index (NJ.: Mb/NOMb) is of great interest in the study of sausage colour evolution because it yields direct information on the relative proportions of myoglobin and nitrosomyoglobin (Giddey, 1966). This index followed the same trend of a*, b’ and C’ values, decreasing in pork sausages through the process and in mutton sausages during fermentation, remaining constant until the end. This decrease indicated an increase in the nitrosomyoglobin relative percentage in both sausages. Mutton sausages showed lower
Technological suitability of mutton for meat cured products TABLE 2
Changes of Physical Colour Parameters during Pork (P) and Mutton (M) Sausage Drying Process Parameters Lightness (L’) Redness (a’) Yellowness (b’) Chroma (C’) Hue (H’) Pigment Nitrosation
P M P M P M P M P M P M
40.15+0.51a’ 3594 f 0.48a2 29.94 f 0.36”’ 31.05&0.32”* 26.33 f 0.77”’ 20.81 f 0.56”2 39.9 1 f 066O’ 37,88 f 0.4502 41.01 ltO.85“’ 34.06 f 0.87”2 2.40 f 0.08”’ 1.87 f 0.04”2
44.71 f 0.48b’ 40.68 f 0.27b2 26.23 f 0. 17b’ 2464 f 0.23b2 22.19*0.30b1 16.12*0.27b2 34.37 + 0.25b’ 29.53 *0,31b2 40.00 f 0.38”’ 32.76 f 0.40ab2 1.94 f 0.026’ 1.51+0.02b2
39.80 f 0.27” 39.64 hO.30” 25.03*0.18” 24.37 f 0.20b2 16.37 f 0.24” 15.33 f 0.25b2 29.97 f 0.24”’ 28.79 zt 0.26b2 33.08 f 0.36b’ 31.9750.3562 1.67 f 0.02” 1.56*0.01b2
Means f standard error. Any two means followed by different superscripts are significantly different (p < 0.05). Letters compare among the different phases of the process, numbers between both types of sausage.
values in the initial mix that could indicate a higher initial nitrosation. This fact might be explained by the higher concentration of total pigments in mutton (Bandeira de Oliveira et al., 1992; Beriain et al., 1993). The loss of a, and moisture, and the acidification that takes place during drying determine the texture of dry sausages (Ketelaere et al., 1974) which is also helped by the formation of a gel due to proteins denaturation (Potthast, 1987). The variation of texture instrumental parameters during the manufacturing process was different in both types of sausage (Table 3). These values showed that dry sausages became tougher, specially in pork, and less cohesive, but while in pork sausages chewiness and gumminess (energy needed to separate particles) increased, mutton presented less gumminess after fermentation. The drying chamber caused a slight decrease in chewiness as well as an increase in the gumminess of mutton sausages. The differences in texture in both cured dry products could be explained by the fat used in each type of product, since perirenal fat was used in
Changes of Textural Parameters during Pork (P) and Mutton (M) Sausage Drying Process -After mincing Final product Parameters Fermentation Type Hardness Cohesivity Gumminess Chewiness
P M P M P M P M
26.3 7 14.49“’ 45.01 + 2.23”2 0.32 f 0.09” 0.35 l 0.03” 8.38 f 2.59”’ 16.14* 1.9702 1.61 *0.28” 3.65 f 0.29”
38.24 f 5.42” 33.90*2.19” 0.24i0.01b 0.22 zt 0.026 9.09 f 1.27a 7.62 +0.87b 18.73 i 3.92b 16.96 f 3.05b
82.67 f 6.1 3b’ 62.59 f 2.80b2 0.25 f 0.00’ 0~26*0.01” 21.04 i 1.65b’ 16.50 f 0.8702 23.63 f 3.95b 11.86rt 1.86b --
Means f standard error. Any two means followed by different superscripts are significantly different (p < 0.05). Letters compare among the different phases of the process. numbers between both types of sausage.
M. J. Beriain et al.
mutton sausages and back fat in pork sausages. The chemical composition of fat, especially the saturated/unsaturated ratio, determines the consistency and texture properties of cured products. The fatty acid composition of the minced mix is also very important in the development of the taste and the aroma in cured dry sausages. Lipolytic phenomena imply changes in the lipidic compounds (Cantoni et al., 1966; Demeyer et al., 1974; Shamberger et al., 1977) which will determine the characteristics of the final product. Fermentation is one of the most decisive and delicate phases of the process (Mendoza et al., 1983) because of volatile carbonyl compounds formation (Demeyer et al., 1974; Leon et al., 1985; Lois et al., 1987). Mutton sausages had a higher saturated/unsaturated fatty acids ratio in the minced mix (l-04 vs 0.66) that was scarcely different during the process. In pork sausages this ratio increased over curing due to the decrease in linoleic (Cis:z) and linolenic (Cis:s) fatty acids (from 12.16 to 10.11; and from 1.63 to 0.97, respectively). This fact could be explained by the higher susceptibility of these fatty acids to lipidic autooxidation, giving short chain volatile compounds (Fernindez et al., 1995). These results might confirm that the nature and composition of the raw material had a direct influence on lipolytic and oxidative phenomena, determining a characteristic texture and aroma. Finally, the sensory profile allowed to establish the differences between both sausages (Fig. 1). Trained panellists scored pork sausages as having better texture, colour (external and when sliced), aroma and flavour, and more persistent and pleasant residual flavour than mutton sausages. Thus, the overall acceptability was higher in pork sausages than in mutton sausages. Owing to the fact that the same technological procedure was used in both products, it was unlikely to find differences regarding shape, appearance or fat content in the studied pieces. It can therefore be concluded that, in agreement with results from other authors (Anderson and Gillet, 1974; Brennand and Mendenhall, 1981; Bartholomew and Osuala, 1986) the peculiar flavour of mutton and the characteristics
/ FA All
Sensory profile of pork and mutton sausages.
Technological suitability of mutton for meat cured products
of the fat determined the development of an aroma, flavour and texture disliked by the panellists. The results from this paper suggested that mutton had a good technological aptitude for meat cured products. This was evidenced by its stable cured colour and its high dehydration rate during ripening. However, it would be necessary to use lambs instead of ewes and/or to replace ewe fat by beef or pork fat, in order to decrease the undesirable aroma and flavour of these products. Further research should be addressed in this way.
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