Effects of cooking methods and temperatures on nutritional

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Effects of cooking methods and temperatures on nutritional and quality characteristics of meat lamb

Effects of cooking methods and temperatures on nutritional and quality characteristics of meat lamb fed on the Algerian pastures Nabila Berrighi 1*, Louiza Belkacemi 1, Kaddour Bouderoua 1, Maria Khossif 2, Gaspar Ros 2, Gema Nieto 2 1 Laboratory 2 Department of Food Technology and Nutrition. Mostaganem University. Algeria of Food Technology, Nutrition and Food Science, Veterinary Faculty University of Murcia, Campus de Espinardo. Spain. Abstract: In this contribution we assessed the effect of the cooking methods and temperatures on their meat quality especiallay on fatty acids composition and colour characteristics of meat lamb fed on the Algerian pastures. The investigation was carried out in spring 2014 on two groups of lambs (Rumbi breed) feeding either on pasture supplemented with hay in a highland area or on pasture supplemented with concentrate in a steppe area, with a free access to water. After slaughter, samples of the Longissimus thoracis have been removed, cooked and subjected for further analysis. The results showed more fat in the meat from the steppe group than in the highland one (respectively 11. 78% vs. 7. 70%, p<0. 001). The polyunsaturated fatty acid (PUFA) levels of meat from lambs raised in the steppe were higher compared to the highland group. The n-3 PUFA and C 18: 3 n-3 (ALA) levels were significantly higher in the tissue from the steppe group, but there was no significant difference between the highland the steppe lamb meat with regards to C 18: 2 n-6 (LA) levels. The LA/ALA and n-6/n-3 ratios reached 9% and 5. 67% for highland steppe animals, respectively (P<0. 001) and 3. 45% and 3. 01% for the steppe-bred animals and highland (P<0. 001). Keywords: aroma compound; feeding; GC–olfactometry; lamb meat. 1. INTRODUCTION • In Steppe, sheep farming is one of the most traditional agricultural activities and occupies a very important place in domain of animal production and is the first red meat provider. Ruminant meat is an important source of nutrients and is also of high sensory value. However, the importance and nature of these characteristics depend on ruminant nutrition. Several previous studies (Wood et al. , 2008; Prache et al. , 2011) have suggested that the nutritional quality of meat is influenced by its lipid component, and healthy fatty acid concentrations increase with the copious consumption of herbs. In addition to providing a favourable healthy value for humans, healthy fatty acids deposited in meat usually provide more intense flavour. Moreover, the flavour of meat is one of the most important sensory attributes, which can be used to identify animal species (Matsuishi et al. , 2004). The concept of lamb flavour quality varies from one region to another (Font i Furnols et al. , 2009 and 2011), with the degree of the typical flavours of meat and fat, which depend on the animal’s growth rate and age at slaughter (Priolo et al. , 2002). To lend weight to this idea, a quantitative and qualitative experiment was carried out to determine the effects of the rearing system (feeding diets in the steppe and the highlands) on animal performance, fatty acids and meat flavour from the two diets. 2. OBJECTIFS • Evaluation of the Algerian steppe and highland feeding systems effect on a local lamb meat flavour. • Intense flavour in the steppe lamb meat is due to the presence of aromatic plants and their antioxidant effect. • The Algerian steppic ecosystem is very interesting in generating a typical flavoured lamb meat considered as a label. 3. MATERIELS ET METHODES v. Sampling: Twenty 7 month-old lambs, with an average body weight (W) of 32. 2± 2. 38 kg, were divided into two groups (n=10). The first group of lambs was put out to pasture from 21 March to 21 June in 2014 on a highland farm and the second group was raised on a steppe farm. The lambs were allowed to graze freely on young spring grass until the haymaking season, with free access to water. Samples (3 -4 kg) of grass, plants and hay (highland) and grass, plants and concentrate (steppe) were taken for analysis. After 92 days, the lambs were slaughtered (body weights of 42. 06± 2. 95 and 49. 72± 3. 22 kg, respectively). They were processed and eviscerated in a local commercial slaughterhouse. Samples of the longissimus thoracis were removed from each carcass and placed on ice in isothermal boxes while they were transported to the laboratory. The dissected muscles were trimmed, minced in a meat grinder and stored at -20°C for further analysis. v. Mesurement analysis: The aroma profile of the meat lamb has been studied by sensory analysis, quantitative gas chromatography–olfactometry (GC–O) and gas chromatography–mass spectrometry (GC–MS). The odour active of compounds is evaluated in a dynamic headspace-solid phase extraction (DHS-SPE). The statistical calculations were carried out using a monofactorial variance analysis (ANOVA), followed by a comparison of the means according to the Newman- Keuls test. The results are presented in terms of p values, with a level of significance p<0. 05. © The concentrate was composed of 15% corn, 10% soybean meal, 4% brain and 1% minerals. 4. RESULTATS ET DISCUSSION The effects of volatile compounds (hexanal, 2 -methyl-3 -furanthiol, nonanal and 1 octen-3 ol) on lamb were more pronounced in the steppe meat than in the highland meat, while others (4 - bis 1, 1 dimethylphenol, heptanal and 1 penten-3 - ol) were higher in highland meat due to the presence of aromatic plants in the corresponding diet. All of the volatile compounds analysed showed significant differences (p<0. 05) between steppe meat and highland meat, especially those resulting form lipid oxidation, amino acids or Maillard reaction products (Priolo et al. , 2001). All of the aldehydes analysed (hexanal, heptanal and nonanal) contribute to the emergence of unpleasant flavour notes due to their high rate of formation and low flavour threshold (Ullrich and Grosch, 1987). Diet has also been implicated in the formation of branched chain fatty acids, which are regarded as the main contributors to “mutton” flavour. In addition, cooking plays a vital role in the development of flavour, and can affect the acceptability of the volatile flavour components of meat (Sañudo et al. , 2000). . According to SH Reurs et al, 2007, 2, 3 -octanedione formation is linked to the lipoxygenase enzyme and linolenic acid, both of which are abundant in green leafy tissue. It is known that the odour/flavour of meat from sheep is specifically linked to branched fatty acidsn ans Skatol (3 methyl This is probably exacerbated by pasturederived 3 -methylindole and alkyl phenols. In the steppe group, there was a high level of 2 -methyl-3 -furanthiol compared to the highland samples (8. 88 vs. 7. 45 µg/kg, res 0 pectively, p<0. 05), and the odour was described as boiled meat. However, the presence of many other odorants from different chemical families revealed the existence of numerous processes for aroma generation (Ahn et al. , 2007). 5. CONCLUSION With regard to the volatile compounds, many of the volatile substances were characterized by aromatic hydrocarbons, alcohols and aldehydes, including: nonanal, hexanal, heptanal and 1 -octen-3 -ol. These chemical compounds are mainly responsible for the flavour characteristics of the cooked lamb meat both from the steppe and highland groups. Overall, the impact of the feeding regime on the lamb flavour was higher in the lambs grazing on pasture and concentrated feed. REFERENCES BIBLIOGRAPHIQUES