RESUMO

The objective of this study was to determine if pasture or grain diets affect oxidative/antioxidative status and the color stability of beef during retail display. Ten crossbreed steers were fed on pasture. Five of them were randomly assigned to remain on this diet, and the other five were finished on feedlot system (grain diet) during 110days until slaughter. Slices of Psoas major steaks were randomly distributed among retail display times (1, 3, 5, 7 and 9days). Lipid and protein oxidation were higher in Psoas major steaks from grain diet than in pasture diet (P<0.05). After 3days of display, lipid oxidation increased in meat from grain diet, whereas in meat from pasture diet the first evidence was after 7days (P<0.05). Protein oxidation was higher in meat from grain diet than in meat from pasture diet at day 9 of display (1.15±0.92 vs. 1.91±0.70µg/g, respectively; P<0.05). Antioxidant vitamins, α-tocopherol and ß-carotene were higher at time=0 in pasture Psoas major steaks (P<0.05) and were differentially reduced throughout storage. While α-tocopherol decreased 41% and 57% for pasture and grain beef respectively (P<0.05), ß-carotene levels remained practically unaffected in grain beef. After 7days of display "a" value was higher for Psoas major steaks from pasture diet (P<0.05). Besides, "L" parameter showed higher values for samples from grain diets but it was no affected by display time. No differences were observed between both treatments for "b" value, but a significant decrease (P<0.05) was observed along storage. Superoxide dismutase and catalase activity was stable throughout storage, while glutathione peroxidase activity decreased significantly (P<0.05). The results in this study demonstrated that the higher initial level and synergistic action (under light and air) of α-tocopherol and ß-carotene found in pasture-finished animals improved the oxidative and color stability of beef, as showed by a better retention of redness at the end of retail display.

RESUMO

Steers of varying genotypes (Aberdeen Angus, Charolais x AA and Argentine Holstein) in four feeding systems were evaluated. Feeding systems were: S1=a diet based on pastures only; S2=a similar forage base as S1 plus a daily supplementation with cracked corn, at 0.7% of l.w./head/day; S3=a similar forage base as S1 plus a daily supplementation with cracked corn, at 1.0% of l.w./head/day; and S4=a regular feedlot diet. Tenderness and marbling were not affected by the feeding system. Feedlot meat showed an n-6/n-3 ratio significantly higher than meat produced with the diets based on pastures (S1=2.1; S2=3.1; S3=4.5; S4=14.2) (P<0.05), whereas CLA content had an inverse behavior, showing S1 (0.67%) and S2 (0.64%) higher concentrations than S3 (0.55%) and S4 (0.28%) (P<0.05). Diet based on pastures plus a low level of supplementation produced meat with better nutritional characteristics than other productive alternatives, without significant effects of the biotypes.

RESUMO

Fatty acid (FA) composition of intramuscular fat (IMF) in M. Longissimus dorsi (LD) was measured in 72 steers from Angus (A), Charolais×Angus (CHA×A) and Holstein Argentine (HA) breeds. The steers were allotted to four dietary treatments of six animals each: T1, steers grazed on pasture; T2, steers supplemented with cracked corn grain (0.7% of live-weight) daily and free access to pasture; T3, steers supplemented with cracked corn grain (1% of live-weight) daily and free access to pasture; and T4, feedlot (concentrate based on corn, alfalfa hay and soybean meal without access to pasture). At slaughter weight, samples of LD at the 11th rib were used for intramuscular lipid analysis. The diet was shown to be more important than breed in determining FA composition. Pasture beef had higher percentages of saturated fatty acids (SFA), n-3 polyunsaturated fatty acids (PUFA) and conjugated linoleic acid (CLA) and lower percentages of IMF, monounsaturated fatty acids (MUFA), n-6 PUFA and n-6/n-3 ratios than feedlot beef. HA beef presented lower percentages of SFA and more MUFA with a higher n-6/n-3 ratio than A and CHA×A. Comparing grass and feedlot beef the amounts of FA in muscle (mg/100g) were, respectively 18:3 n-3 (44 vs. 11mg), CLA (20 vs. 12mg), 20:5 n-3 (20 vs. 11mg), 22:5 n-5 (20 vs. 11mg), 22:6 n-3 (12 vs. 6mg) and n-3 PUFA (84 vs. 32mg). Feedlot beef has more SFA (1372 vs. 1081mg), MUFA (1574 vs. 1078mg), PUFA (350 vs. 227mg) and n-6 PUFA (318 vs.143mg).

RESUMO

The main goal of the present work was to determine the overall antioxidant status in fresh meat from animals fed different diets and to differentiate them through their odour profiles. Attributes were evaluated in beef from pasture or grain-fed animals with (PE and GE) or without supplementation (P and G) with vitamin E (500UI/head/day). Fresh meat produced on pasture (P and PE) had higher total ferric reducing antioxidant power (FRAP) levels than meat from grain fed-animals (G and GE) (P<0.05). However, no differences were found on their ability to reduce ABTS(+) (2,2'-azino-bis-(3-ethylbenz-thiazoline-6-sulfonic acid)), indicating that total antioxidant activity was preferentially due to the reduction potential than to the quenching capacity of tissue homogenates. Two-fold glutathione (GSH and GSSG are the reduced and oxidised forms, respectively) levels were found in the P+PE group respect to G+GE meat (P<0.001). In addition, meat from pasture-fed animals presented a higher glutathione redox potential compared to grain-fed animals (-156.1±6.1 and -158.1±6.5 vs. -148.1±13 and -149.8±14.6 for P, PE G and GE, respectively), showing that the antioxidant status in fresh meat was affected by diet. Enzymatic activity of catalase and glutathione peroxidase were equivalent for all dietary groups. Only superoxide dismutase activity was slightly higher (P<0.05) in the P+PE group than in G+GE samples. Odour profile analysis was performed in relationship to antioxidant parameters. Significant linear correlation coefficients (P<0.05) were found for a set of sensors and the FRAP values. E-nose methodology successfully discriminated the odour characteristics of samples corresponding to pasture- or grain-based diet. Hence, it was possible to describe an analytical relationship between the odour profile and the antioxidant power of fresh meat.

RESUMO

Argentine meat has been traditionally produced on pasture. However, to comply with some market requirements, grain finishing is becoming more common among producers. The main goal of the present work was to study lipid oxidation in fresh meat from animals fed different diets in relationship with their antioxidant vitamin status. Attributes were evaluated in beef from pasture or grain-fed animals with (PE and GE) or without supplementation (P and G) with vitamin E (500 UI/head/day). Fresh meat produced on grain (G and GE) had higher fat (4.0±1.6 and 4.7±1.4 g/100 g) and cholesterol content (51.0±3.0 and 52.0±4.0 mg/100 g) than meat from pasture (P and PE) fed animals (2.7±1.2 to 2.9±1.1 g/100 g and 48.0±5.0 to 49.0±4.0 mg/100 g of intramuscular fat and cholesterol respectively). Fatty acid composition was clearly affected by diet. Beef from pasture-fed cattle had higher percentage of linolenic acid, less linoleic acid and, overall, higher percentage of polyunsaturated fatty acids than beef from grain-fed animals (P<0.05). Thiobarbituric acid reactive substances number and volatile levels of hexanal, pentanal, heptanal, octanal and 3-methylbutanal were higher in grain than in pasture samples (P<0.05). P+PE meat had higher content of antioxidant vitamins than G+GE samples (P<0.001). Values ranged from: 15.92±3.48 (G) to 17.39±4.29 (GE) and 25.3±10.0 (P) to 21.98±5.11 (PE) µg/g of ascorbic acid; from 1.05±0.73 (G) to 1.76±0.97 (GE) and 3.08±0.45 to 3.91±0.74 µg/g of α-tocopherol; and from 0.06±0.03 (G) to 0.05±0.01 (GE) and 0.45±0.21 (P) to 0.63±0.27 (PE) µg/g of ß-carotene. In addition, principal component analysis clearly separated grain from pasture samples regardless of their supplementation with vitamin E. This level of supplementation did not improve the antioxidant status of fresh meat (P>0.05). We conclude that pasture diet contributes natural antioxidants in sufficient amounts and is an efficient way to prevent lipid oxidation in fresh beef.

RESUMO

An improved method for the analysis of phospholipids by normal-phase HPLC is described. Addition of methanol and acetonitrile to a gradient based on 2-propanol/hexane/water promoted a rapid separation of major classes of bovine surfactant phospholipids (PL) by using a conventional silica column. The use of an ELSD permitted an accurate analysis of a mixture of PL. Calibration curves were linear within the range of 5-40 microg with detection limits below 1 microg for PE and PC, and CV ranged from 0.6 to 9.6%. PL present in surfactant homogenates were separated by a solid-phase extraction (SPE) procedure before HPLC analysis. This methodology gave a recovery of 95% and combined SPE-HPLC and quantification of biological PL within a 30-min run. The use of ELSD detection of the eluted compounds was precise, linear, and sensitive.

Assuntos

Cromatografia Líquida de Alta Pressão/métodos , Fosfolipídeos/análise , Calibragem , Fosfolipídeos/química , Fatores de Tempo

RESUMO

The ability of an electronic nose, comprising 32 conducting polymer sensors, to identify and classify warmed-over flavour (WOF) aroma in bovine semitendinosus muscle, processed by vacuum cook-in-bag/tray technology (VCT) and storage under refrigerated conditions, was evaluated. The VCT process employed low temperature-long time (50°C-390 min) thermal treatments. Multivariate analysis showed that VCT processed beef aroma profiles were sorted into two groups, one included samples stored for up to 20 days and the other included samples with 34 to 45 days of storage. WOF odour standard samples were recognised to have similar aroma as samples of the second group. Lipid oxidation results, measured by thiobarbituric acid reactive substances, showed an increment in oxidation level for samples stored for 34 days or more (P<0.05). This study shows that electronic nose technology can be applied to WOF odour identification and classification in VCT beef meat, complementing chemical and sensory techniques used in this field.