The influence of breed on the organoleptic characteristics of Zamorano sheep’s raw milk cheese and its assessment by instrumental analysis

The aim of this study was to investigate the effects of three different somatic cell count (SCC) values on the sensory characteristics of sheep’s milk cheeses from the Castellana and Churra breeds (allowed for Protected Designation of Origin Zamorano cheese manufacture) and the Assaf breed (foreign), determined by typical consumers and instrumentally. The results show that the sensory characteristics of hardness, intensity of taste, and pungency reflect a significant influence of the SCCs of the original milk whereas breed significantly affects colour intensity and hardness (Warner‐Bratzler maximum shear force; WBSF). The instrumental parameters most closely related to the assessments of the typical consumers were WBSF and the value of a*, for hardness and colour respectively.     

Inspection of lymph nodes for caseous lymphadenitis and its effect on the density of microbes on sheep carcasses

This study aimed to measure the amount of microbial contamination caused by inspecting the lymph nodes of adult sheep carcasses for caseous lymphadenitis (CLA). Surface swabs from carcasses pre-inspection (N=296) and post-inspection (N=296) were obtained for enumeration of indicator organisms at three commercial abattoirs. At the scapular site, inspection doubled the probability of detecting E. coli (Pr before=0.35, Pr after=0.67) and increased the expected count of E. coli from 2cfu/cm(2) to 13cfu/cm(2). Inspection at the rump site increased the probability of detecting E. coli by 1.1 times (Pr before=0.84, Pr after=0.93) and increased the expected count from 32cfu/cm(2) to 45cfu/cm(2). Effects were also observed for Enterobacteriaceae and total viable count. The findings show that routine inspection of adult sheep carcasses for CLA has a detrimental impact on carcass microbiological traits.     

Effects of dietary rosemary extract on lamb spoilage under retail display conditions

A dietary rosemary extract (RE) was tested to extend the shelf life of raw lamb meat. Lambs were supplemented with 0.6 mg kg⁻¹ RE during fattening (from 13 to 25 kg live weight). Meat spoilage (total viable counts, psycrophilic bacteria, Enterobacteriaceae, molds and yeasts), TBARS, CIE L*a*b* color and the sensory traits of lamb cuts were analyzed on days 0, 7, 14 or 21 under retail display conditions (70/30 O₂/CO₂ atmosphere, 2 °C temperature and 1600 lx lighting). Supplementation of the lamb diet with RE was effective (P < 0.05) in prolonging the time chilled-packed lamb cuts could be kept under retail display conditions. Dietary rosemary clearly inhibited lipid oxidation and rancidity, and was moderately efficient in preventing sensory deterioration and microbial spoilage. Although the results concerning meat preservation were limited, the dietary use of rosemary extracts in lambs seems to be promising as a nutritional strategy for improving meat quality.     

Effects in ewe diet of rosemary by-product on lipid oxidation and the eating quality of cooked lamb under retail display conditions

Distilled dietary rosemary leaf (DRL) was tested to prevent lipid oxidation and sensory deterioration of cooked lamb under retail display conditions. Pregnant sheep were fed with a basal diet supplemented by 0%, 10% and 20% DRL. Cooked lamb fillets were stored for 0, 2 or 4 days at a temperature of 4 °C in a display cabinet and re-heated, simulating catering practices. The cooked lamb suffered rapid lipid oxidation and odour and flavour spoilage associated with slight rancidity and warmed-over flavour, and, to a lesser extent, with loss of colour and juiciness. DRL feeding delayed lipid oxidation measured as TBARS and volatile compounds, this being more effective in the first two days of storage. 10% and 20% of DRL provided equal antioxidant capacity. However, DRL feeding hardly prevented sensory deterioration, although incipient rancidity was delayed. Feeding DRL to ewes contributed to extend the shelf life of cooked lamb under retail display conditions.     

Preparation and functional properties of protein coprecipitate from sheep milk

The optimum conditions for the production of coprecipitate from sheep milk were studied. The best percentage of calcium chloride added to milk was 0.2%, which resulted in a recovery of 97.5% of milk proteins. At low pH (4.5–5), the recovery of protein was low, but it increased at higher pH values (5.5–6.5); recovery was greatest at pH 6.5. The optimum heating temperature to obtain coprecipitate from sheep milk was 85–95°C. The functional properties of the sheep milk coprecipitate were studied. At pH values higher than 6, there were no differences between the solubility of sheep milk coprecipitate and sheep milk sodium caseinate, but the solubility of coprecipitate at pH values lower than 5 was relatively higher than those of the caseinate. At pH ≥6, the emulsion activity index (EAI) for emulsions of sheep milk coprecipitate and caseinate increased as pH increased; at all pH values, the EAI of the coprecipitate was higher than that of the caseinate. Sheep milk coprecipitate showed higher foaming ability and stability than sheep milk sodium caseinate.     

Relative Availability of Tannin- and Terpene-containing Foods Affects Food Intake and Preference by Lambs

The availability of different forages varies across landscapes, but little is known about how proportional consumption of different foods affects food intake and the use of landscapes. The relative amounts of nutrients and plant secondary metabolites (PSM) consumed by herbivores may influence forage intake and animal fitness in landscapes dominated by plants with PSM. Our objective was to determine if the relative availability of nutritious foods that contain PSM affected food preference and intake by lambs. Lambs in three treatments (eight lambs/treatment) were offered two PSM-containing foods at different relative availabilities: treatment 1—ad libitum terpene- and 100-g tannin-containing food, treatment 2—ad libitum tannin- and 100-g terpene-containing food, and treatment 3—ad libitum access to both tannin- and terpene-containing foods. We measured intake of individual foods and total intake of PSM-containing foods during conditioning and a preference test, where animals were offered both PSM-containing foods ad libitum. When lambs were fed 100 g of the tannin-containing food, they ingested more terpene and total PSM (P < 0.05) than when both PSM were offered ad libitum, but limiting terpenes did not affect intake of tannin or total intake of PSM (P > 0.10). During preference tests, all groups preferred tannins over terpenes, but lambs in the treatment fed 100 g of tannin had a higher preference for terpenes than did lambs in the other two treatments (P < 0.10). These results support the notion that the relative amounts of PSM consumed affects intake and preference for PSM-containing foods by herbivores.     

Eating quality of commercially processed hot boned sheep meat

The aim of this work was to establish consumer perceptions of the eating quality of commercially processed hot boned sheep meat. The eating quality scores for tenderness, flavour, juiciness, and overall liking of grilled m. longissimus thoracis et lumborum (LL) were derived from untrained consumers. The animals used in this experiment were sourced from three different properties and were of various ages, breed, and sex, and had been on various quality pastures. All carcases were subjected to immobilisation, spinal discharge and high voltage electrical stimulation and boned within 2 h of slaughter. All LL samples were frozen after boning according to the system applied at the abattoir and samples kept for consumer assessment and measurement of meat quality. The results showed, on average carcases entered rigor at high temperatures with a pH of 5.95 at 29.3 °C. With an average sarcomere length of 1.68 μm, some shortening was evident and there was a significant difference between lots in sarcomere length (P < 0.05). A large percentage (82%) of samples had a pH greater than 5.8 at the time of freezing. All samples taken for shear force analysis exceeded a recommended threshold for acceptable table meat of 49 N and there was no significant difference between lots (P > 0.05). Only 13.5% of the samples met the ‘good everyday’ requirement following sensory assessment and there were significant differences between lots for eating quality traits (P < 0.05). This work clearly shows that the application of effective electrical stimulation is not sufficient to ensure that hot boned sheep meat will be suitable as a table meat. These findings highlight the need for the inclusion of other intervention techniques.     

The effect of feeding system in the expression of genes related with fat metabolism in semitendinous muscle in sheep

The effect of feeding system on the expression of LPL, ACACA, FASN, FABP4, DGAT1, SCD, CPT1B, PRKAA2, LEP, SREBP1, PPARG, PPARA and CEBPB genes in semitendinous muscle was studied. Forty-four single born male lambs of the Rasa Aragonesa breed, allocated to four different dietary treatments, were used: grazing alfalfa, grazing alfalfa with supplement for lambs, indoor lambs with grazing ewes and drylot. Significant differences were found in the expression of genes LPL, ACACA, FASN, FABP4, CPT1B and SCD. Genes related to adipogenesis (LPL, ACACA, FASN, FABP4, and SCD) are up-regulated in the intensive groups. In grazing groups CPT1B gene expression, related to β-oxidation process, is up-regulated. The relative expression of CPT1B was 1.54 fold higher in ALF+S, and 0.43 and 0.37 fold lower in IND- GRE and IND, respectively. The results support the hypothesis that changes in fatty acid profile due to feeding system implicate changes in the mRNA expression level of genes related with fat metabolism. Feeding strategy is an important tool to manipulate intramuscular fatty acid profile in meat through altering gene expression of enzymes related with fat metabolism.     

Fat deposition, fatty acid composition and meat quality: A review

This paper reviews the factors affecting the fatty acid composition of adipose tissue and muscle in pigs, sheep and cattle and shows that a major factor is the total amount of fat. The effects of fatty acid composition on meat quality are also reviewed. Pigs have high levels of polyunsaturated fatty acids (PUFA), including the long chain (C20-22) PUFA in adipose tissue and muscle. The full range of PUFA are also found in sheep adipose tissue and muscle whereas cattle ‘conserve’ long chain PUFA in muscle phospholipid. Linoleic acid (18:2n − 6) is a major ingredient of feeds for all species. Its incorporation into adipose tissue and muscle in relation to the amount in the diet is greater than for other fatty acids. It is deposited in muscle phospholipid at a high level where it and its long chain products eg aracidonic acid (20:4n − 6) compete well for insertion into phospholipid molecules. Its proportion in pig adipose tissue declines as fat deposition proceeds and is an index of fatness. The same inverse relationships are not seen in ruminant adipose tissue but in all species the proportion of 18:2n − 6 declines in muscle as fat deposition increases. The main reason is that phospholipid, where 18:2n − 6 is located, declines as a proportion of muscle lipid and the proportion of neutral lipid, with its higher content of saturated and monounsaturated fatty acids, increases. Oleic acid (18:1cis − 9), formed from stearic acid (18:0) by the enzyme stearoyl Co-A desaturase, is a major component of neutral lipid and in ruminants the same enzyme forms conjugated linoleic acid (CLA), an important nutrient in human nutrition. Like 18:2n − 6, -linolenic acid (18:3n − 3) is an essential fatty acid and is important to ruminants since it is the major fatty acid in grass. However it does not compete well for insertion into phospholipid compared with 18:2n − 6 and its incorporation into adipose tissue and muscle is less efficient. Greater biohydrogenation of 18:3n − 3 and a long rumen transit time for forage diets also limits the amount available for tissue uptake compared with 18:2n − 6 from concentrate diets. A positive feature of grass feeding is that levels of the nutritionally important long chain n − 3 PUFA are increased ie EPA (20:5n − 3) and DHA (22:6n − 3). Future research should focus on increasing n − 3 PUFA proportions in lean carcasses and the use of biodiverse pastures and conservation processes which retain the benefits of fresh leafy grass offer opportunities to achieve this. The varying fatty acid compositions of adipose tissue and muscle have profound effects on meat quality. Fatty acid composition determines the firmness/oiliness of adipose tissue and the oxidative stability of muscle, which in turn affects flavour and muscle colour. Vitamin E is an essential nutrient, which stabilises PUFA and has a central role in meat quality, particularly in ruminants.     

PCR identification of meats from chamois (Rupicapra rupicapra), pyrenean ibex (Capra pyrenaica), and mouflon (Ovis ammon) targeting specific sequences from the mitochondrial D-loop region

A polymerase chain reaction (PCR) assay was developed for the identification of meats from chamois (Rupicapra rupicapra), pyrenean ibex (Capra pyrenaica), and mouflon (Ovis ammon) by using oligonucleotides targeting mitochondrial D-loop sequences. A D-loop region (700–1000 bp) was firstly amplified and sequenced from various game and domestic meat DNAs, and three primer sets were then designed on the basis of nucleotide multialignment of the generated D-loop sequences. As expected from sequence analysis, PCR amplification of the targeted D-loop fragments was successfully achieved from chamois (88 bp), pyrenean ibex (178 bp), and mouflon (155 bp) meats, showing adequate specificity and reproducibility against a number of game and domestic meats. Mouflon and sheep meats were amplified together in accordance to the high nucleotide identity of their mt D-loop sequences. In this work, satisfactory amplification was also accomplished in the analysis of experimentally pasteurized (72 °C for 30 min) and sterilized (121 °C for 20 min) meats, with a detection limit of 0.1% for each of the targeted species. The proposed PCR assay represents a rapid and straightforward method for the detection of possible adulterations in game meat products.