Salmonella risk in imported fresh beef, beef preparations, and beef products

Additional guarantees (AGs) for Salmonella in imported defined animal-derived foods were agreed on for Finland when it was admitted to the European Community. The aim of this project was to evaluate the impact of these AGs on the prevalence of Salmonella in the Finnish beef supply and the adequacy of their scope. According to the quantitative Bayesian model, the efficacy of AGs was mainly dependent on the proportions of different beef categories imported and the true prevalence in the countries of origin. According to the model, AGs were able to reach their target in the referred year 1999 and kept the true Salmonella prevalence of beef imports below 1% with quantified uncertainty. The extension of AGs to all imported fresh beef would have reduced the Salmonella prevalence of beef imports from three- to fourfold, whereas expanding the implementation of AGs to all imports of fresh beef, beef preparations, and beef products would have resulted in a sixfold decrease. If current AGs targeting fresh beef intended to be sold as fresh or to be processed by the Finnish industry with processes not achieving 70 degrees C were not implemented, the 95% credible interval of Salmonella prevalence in the Finnish beef supply would be 0.2 to 1.3% (mean, 0.6%) instead of 0.1 to 1.2% (mean, 0.5%). However, if the prevalence in the exporting countries were to rise or the main import countries and/or magnitudes were to change, AGs would be of greater importance.     

不同浓度环孢菌素A处理对牛肉宰后成熟过程中品质及细胞凋亡因子的影响

为研究环孢菌素A(Cs A)对牛肉宰后成熟过程中品质及细胞凋亡发生的影响,以4种不同浓度(0.10、0.20、0.25及0.30 mol/L)环孢菌素A处理的牛肉背最长肌为研究对象,分别在成熟时间点12、24、48、96和144 h测定处理组及对照组肉样在成熟过程中的pH值、肉色、保水性、嫩度等品质评价指标及胞浆细胞色素C(Cytochrome C,Cyt-c)含量、细胞凋亡酶-9,3(Caspase-9、3)活性等细胞凋亡评价指标的变化。结果表明,牛肉宰后成熟72 h内,处理组L*值和a*值均高于对照组,b*值低于对照组;宰后48 h内,处理组pH值、蒸煮损失及剪切力均高于对照组;同时,处理组肌原纤维小片化指数(MFI)均低于对照组;在宰后48 h内,处理组胞浆Cyt-c含量高于对照组;在宰后24 h内,处理组Caspase-9活性低于对照组,且宰后48 h变化与之相反;两组Caspase-3活性均呈先上升后下降的变化,且宰后48 h,处理组Caspase-3活性均高于对照组。以上研究表明,Cs A处理对宰后肌肉品质有较大影响,且各品质指标的变化均呈浓度依赖趋势变化,同时Cs A可能抑制宰后肌肉细胞凋亡的发生进而影响肌肉品质。     

Marbling fat in beef

The growth and distribution of intramuscular fat was studied in 62 carcases from four beef genotypes, Angus, Hereford, Friesian and Charolais x Illawarra.

Relative to dissected side fat weight, ether extract weight of side muscle was deposited in a similar manner in all four genotypes. At high levels of side fatness (45 kg) Herefords had significantly less ether extract than the other genotypes. Ether extract percentage (of side muscle) was greater in the Angus than in the other genotypes at low side fatness levels (20 kg, 30 kg or 20%). Relative to dissected fat percentage ether extract percentage of side muscle, initially lower in the Friesians and Charolais x Illawarra than in the Angus and Herefords at low levels of carcase fatness, was not significantly different from them over 27% dissected fat.

With increasing carcase fatness marbling fat was deposited differentially among the primal cuts, with few major between-breed differences.

A study of the muscle weight distribution of the primal cuts confirmed the cutting technique as a useful method for examining the commercial importance of marbling.     

Cooking tenderizing in beef

Heating tenderzes meat in three distinct phases. Up to 65°C aging occurs through proteolysis at specific sites in the myofibrils. From about 70°C the collagen of the connective tissue is denatured and melts. Above about 100°C the myofibrils begin to break down again presumably from non-specific high-temperature hydrolysis. The rate of cooking tenderizing above 70°C increases sharply with temperature and at 100°C is equal to the maximum aging rate at 60°C. However the collagen becomes more resistant to breakdown with animal age since the time to achieve maximum tenderizing of m. sternomandibularis at 80°C increases from 4 h for young calves to greater than 15 h for old bulls. There is little overlap in the temperature ranges of aging and cooking tenderizing above 70°C with a minimum tenderizing temperature of 67°C. The merits of tenderizing meat by holding it below or above this temperature are discussed.     

猪血球胃蛋白酶水解物抗氧化活性的研究

以脂质氧化抑制力(LA)、亚铁离子螯合能力(FICP)、二苯代苦味酰肼(DPPH)自由基清除能力(DRSA)为测定指标,探讨了猪血球胃蛋白酶水解物(PDPH)的抗氧化活性。结果表明,PDPH具有极好的亚油酸脂质氧化抑制力(P<0.01)、一定的FICP(P<0.05)和DRSA(P<0.05)。PDPH的脂质氧化抑制力在10μg/mL时为α-生育酚的4.38倍,100μg/mL时为5.50倍;金属离子螯合能力在100μg/mL样品浓度,50μmol/L FeCl2时的螯合率约为10μmol/L EDTA的1.23倍;在10-100μg/m L样品浓度时基本无DRSA,但在500μg/m L的DR-SA为53.8%。     

牛肉香气成分的分析及其香精的开发

本文介绍了牛肉挥发性成分的提取方法、牛肉香气成分组成以及牛肉香精的开发.常用的分析方法有气相色谱-质谱联用技术(GC-MS)和气相色谱-嗅觉检测技术(GC-O).采用甲硫醇、呋喃硫醇、吡嗪、反-2,4-壬二烯醛和呋喃酮等主要的牛肉香气成分香原料,可以调配出香气逼真的炖牛肉香精.     

Differentiation between fresh beef and thawed frozen beef

In order to prevent meat retailers offering thawed, imported frozen beef as fresh domestic beef, the method of Gottesmann and Hamm for differentiating between fresh and frozen/thawed meat is recommended. The principle of this method is based on the fact that freezing and thawing of meat results in a release of the enzyme β-hydroxyacyl CoA-dehydrogenase (HADH) from the mitochondrion into the sarcoplasm; an elevated HADH activity in the muscle press-juice indicates freezing and thawing of tissue. The HADH colour test of Gottesmann and Hamm was modified by replacing the electron-transmitter meldolablue by resazurin which results in a much higher colour stability after reaction with fresh meat extracts.     

新疆褐牛不同部位分割肉块品质差异研究

为了研究育肥新疆褐牛不同部位分割肉块品质的差异,实验选取了11头育肥新疆褐牛,对其肩肉、辣椒条等10个部位肉进行了营养指标和理化指标的测定。结果显示,不同部位分割肉块间的蛋白质含量、脂肪含量、水分含量、蒸煮损失、剪切力、p H和肉色L*、b*值均存在差异;肩肉和臀肉的脂肪含量仅次于高档部位肉,但与高档部位肉存在显著差异(p<0.05);除大黄瓜条和小黄瓜条外,其余部位肉剪切力均低于4.39kg。可见,育肥新疆褐牛的肉质因部位不同而有所差异,且总体较嫩,为今后各部位的加工利用和品质改进提供依据。      

Antioxidative activity of carnosine in gamma irradiated ground beef and beef patties

The activity of carnosine as a natural antioxidant in gamma irradiated ground beef and beef patties was studied. Samples of ground beef, in the absence and presence of 0.5% or 1.0% carnosine, as well as raw and cooked beef patties prepared with 1.5% salt (NaCl), in the absence and presence of 0.5% or 1.0% carnosine, were gamma irradiated at doses of 0, 2, and 4 kGy. The extent of oxidation in irradiated and non-irradiated samples of ground beef and raw beef patties was then determined during refrigerated (4 ± 1 °C) and frozen (−18 °C) storage, while determined for cooked beef patties during refrigerated storage only. Moreover, the determination of metmyoglobin (MetMb) accumulation and sensory evaluation for the visual color were carried out for samples of ground beef and raw patties. The results indicated that salt or salt and cooking accelerated the oxidative processes and significantly increased the peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) in the prepared non-irradiated samples. However, salt slowed down the accumulation of MetMb in raw patties. Irradiation treatments and storage in the absence of carnosine significantly (P < 0.05) increased the PV and TBARS in samples, at higher rates in salted or salted and cooked beef. Moreover, irradiation and storage significantly (P < 0.05) increased the formation of MetMb in ground beef and raw patties in the absence of carnosine. Addition of carnosine significantly (P < 0.05) reduced the oxidative processes and MetMb formation (proportionally to the used concentration) in samples post-irradiation and during storage. Furthermore, carnosine exerted significant efficacy in maintaining an acceptable visual red color post-irradiation and during storage of ground beef and raw patties. These results demonstrate that carnosine can be successfully used as a natural antioxidant to increase the oxidative stability in gamma irradiated raw and cooked meat products.     

牛肉香气成分的分析及其香精的开发

本文介绍了牛肉挥发性成分的提取方法、牛肉香气成分组成以及牛肉香精的开发.常用的分析方法有气相色谱-质谱联用技术(GC-MS)和气相色谱-嗅觉检测技术(GC-0).采用甲硫醇、呋喃硫醇、吡嗪、反-2,4-壬二烯醛和呋喃酮等主要的牛肉香气成分香原料,可以调配出香气逼真的炖牛肉香精.     

卤牛肉与牛肉高汤联合生产技术

主要阐述卤牛肉与牛肉高汤联合生产工艺,分析了产生的经济效益。     

Intramuscular variation in beef tenderness

Intramuscular variation of beef tenderness was investigated in three muscles: Semitendinosus (ST), Triceps brachii (TB) and Rectus femoris (RF). The aim of the study was to evaluate a French process (called "affranchi") used to improve meat tenderness. Two groups of 72 muscles (24 ST, 24 TB and 24 RF) aged 10 and 14 days respectively, were assessed for tenderness by sensory analysis and compression measurements. For all three muscles, sensory evaluation showed a significant intramuscular variation in tenderness with a longitudinal gradient. Compression measurements on the raw meat showed similar results but of reduced accuracy. It appears that the process "affranchi" which consists in removing a part of the muscle, is very useful to improve meat tenderness and could be used by meat processors. The low relationship between compression measurements and sensory evaluation suggest compression measurements on raw meat are not suitable to predict meat tenderness as perceived by consumers.     

Microbiological contamination of raw beef trimmings and ground beef

To survey the microbiological quality of beef trimmings and final-ground beef, samples were collected from eight commercial grinding facilities, including trimmings from fed-cattle, culled-beef cows, culled-dairy cows, imported-beef trimmings and finished-ground products. Trim samples (core and purge) and ground product samples (n=586) were evaluated for aerobic plate (APC), total coliform (TCC), Escherichia coli (ECC) and Staphylococcus aureus counts and the presence of Salmonella spp. and Listeria monocytogenes. As fat content in the trimmings increased, APC also increased. Trimmings from fed-cattle had higher (P<0.05) APC and TCC than trimmings from culled-beef cows, culled-dairy cows and imported trimmings. Purge samples produced higher (P<0.05) APC, TCC and ECC than core samples, but there were no difference (P>0.05) across fat percentages in APC, TCC, ECC or S. aureus counts. Final-ground beef samples had a 13.6 and 1.5 % incidence of L. monocytogenes and Salmonella spp., respectively. The results of this study indicate specific areas of potential that ground beef processors could capitalize upon to further improve the microbiological quality of their finished product. Ground beef processors should focus their efforts on reducing the microbial counts on incoming raw materials, especially those containing large proportions of subcutaneous fat, and processors should no longer incorporate the purge component of raw materials into ground beef. From this study, it is also apparent that ground beef processors should implement sanitation and manufacturing procedures that address L. monocytogenes contamination.     

Temperature-dependent cooking toughness in beef

Toughness development in beef sternomandibularis muscle during cooking has been measured by a tenderometer, cleaving samples at right angles to the fibre direction. Since the muscles had been set in rigor mortis in an unshortened state, such toughening was not related to that induced by pre-rigor contraction. Two distinctly separate phases of toughening develop with increasing cooking temperature. A three- to fourfold toughening occurs in the first cooking phase between 40 and 50 ºC, followed by a further doubling in the second phase between 65 and 75 ºC. The first phase is associated with loss of myosin solubility, presumed to indicate denaturation in the contractile system. The second is closely associated with collagen shrinkage. This apparently induces shortening along the meat fibre, forcing out meat juice.     

Ice morphology in frozen beef

A histological study was made of pieces of meat which had been frozen from one side, in conditions where the direction of the heat flux was approximately unidirectional and perpendicular to the muscle fibres. The morphology of the ice crystals in tissue frozen under various conditions was studied, and the range of freezing velocities over which no intracellular ice existed, was established. The average diameter D , of ice crystals, measured in different experiments and at different levels in the same piece of meat was related to the characteristic freezing time t _c, by the equation:
D = a + b log t _c     

Consumer attitudes towards beef and acceptability of enhanced beef

The objective of this study was to evaluate consumer quality characteristics of enhanced steaks and roasts derived from cattle supplemented with vitamin E during finishing, and to assess the attitudes of these consumers towards beef. Twelve steers were fed either a control (E-) diet or a diet supplemented with dl-alpha tocopheryl acetate (E+). Paired strip loins and rounds were either used as controls (C) or were pumped (P) to 110% of raw weight to contain 0.4% sodium chloride and 0.4% sodium tripolyphosphate in the final product. Consumers (n=103) evaluated roasts and steaks for juiciness, tenderness, saltiness, and overall acceptability on a 9-point hedonic scale. Enhanced steaks and roasts were more acceptable than non-enhanced controls; E+ steaks were less acceptable than E- steaks. A beef quality questionnaire revealed that color, price, visible fat and cut were the most important factors underlying beef steak purchase, while tenderness, flavor and juiciness were weighted most heavily with regard to eating satisfaction.     

A modified hot processing strategy for beef: functionality of electrically-stimulated and hot-boned meat preblended with different NaCl concentrations

Chucks from 20 electrically-stimulated hot-boned (HB) and cold-boned (CB) beef carcasses were preblended with different concentrations of NaCl (0, 0·5, 1·0, 1·5 and 2·0% w/w). Preblends were analysed for pH, 2-thiobarbituric acid (TBA) values, protein extraction and emulsifying capacities. Bologna (with and without added sodium tripolyphosphate) and ground meat patties prepared from these preblends were also evaluated for cooking yield, color and texture parameters. Ultimate pH values of HB preblends increased with increasing NaCl concentration. At 1% NaCl, HB had higher ultimate pH than CB preblends (P ≤ 0·05) but preblending HB meat with 2% NaCl reduced TBA values (P ≤ 0·05) because the pH was maintained above 6·0. Higher amounts of protein were extracted from HB than from CB preblends (P ≤ 0·01), but boning and salting treatments did not affect their emulsifying capacities (P > 0·05). Two percent NaCl was required to fully achieve the prerigor salting effect. At this concentration, cooking yields of bologna prepared from HB preblends and phosphate containing bologna prepared from CB preblends were not different (P > 0·05) and were higher than those of bologna without added phosphate made from CB preblends (P ≤ 0·05). No meaningful effects were observed on color and texture parameters. Cooking losses were lower in patties made from HB than CB preblends (P ≤ 0·05) independent of NaCl concentration, but boning and salting treatments had no further effects on color or textural parameters (P > 0·05). Therefore, the superior functional properties of electrically stimulated prerigor meat can be maintained by the addition of 2% NaCl up to 2 h post-mortem.     

Transverse anisotropy in beef muscle

In beef sternomandibularis muscles, a variety of treatments—tetanic contraction, cold shortening, cooking shortening and swelling in alkali—caused dimensional changes which differed markedly with the direction chosen within a plane perpendicular to the fibre direction. In all cases a marked increase (up to twice) occurred in the narrow dimension of the muscle, with little change in the wide dimension. In the cooked meat, shear force across the fibre was independent of the transverse direction chosen whether the muscle was relaxed or cold shortened. The effects were also seen in rectus abdominis and psoas, but not in longissimus dorsi muscles. It is suggested that anisotropy is a result of differing organisation of connective tissue in the two directions, although there was little histological evidence. The force to shear parallel to the fibres varied with direction in a manner consistent with this view.