Application of chemical methods for the assessment of beef quality. 3. Methods related to fat spoilage

Various methods for assessing the extent to which the fat has deteriorated in stored beef are considered in relation to various criteria discussed in Part I. From the point of view of routine quality control, the titrimetric determination of free fatty acids (FFA) appears to be the most reliable method. From statistical correlations with odour scores, most meats were considered acceptable provided the FFA did not exceed 1.2% (calculated as oleic acid on the extracted fat). Several of the other fat spoilage methods considered gave values which rose during the storage period to a maximum and then either remained constant or decreased steadily to a very low figure. Most fresh samples gave peroxide values of 0.1-1.0 mequiv./kg (on the extracted fat), but a critical limit of 5 might be applied under practical conditions.     

Application of chemical methods for the assessment of beef quality. IV. Physicochemical and miscellaneous methods

Methods which are used either to assess physicochemical changes during beef spoilage or to measure general effects not necessarily related to the breakdown of protein or fat directly are considered in relation to various criteria discussed in Part I. From the point of view of routine quality control, measurements of the extract-release volume and pH appear to be useful for spoilage assessment, provided that allowance is made for the differing results obtained during the pre-rigor period. From statistical correlations with odour scores most meats were considered acceptable provided that the ERV (extract-release volume, using the standardised method described) was at least 17 ml. The pH of the meat should preferably not exceed about 6.0. The joint use of total volatile nitrogen, free fatty acids, and ERV for deciding upon general acceptability in industrial control is considered.     

Application of chemical methods for the assessment of beef quality. I.—General considerations,sampling and the determination of basic components

This paper introduces a series of contributions covering the application of chemical methods to samples of stored comminuted beef. The criteria to be investigated are outlined, together with the methods employed for sampling, determination of basic composition and assessment of odour.     

Meat quality assessment using biophysical methods related to meat structure

This paper overviews the biophysical methods developed to gain access to meat structure information. The meat industry needs reliable meat quality information throughout the production process in order to guarantee high-quality meat products for consumers. Fast and non-invasive sensors will shortly be deployed, based on the development of biophysical methods for assessing meat structure. Reliable meat quality information (tenderness, flavour, juiciness, colour) can be provided by a number of different meat structure assessment either by means of mechanical (i.e., Warner-Bratzler shear force), optical (colour measurements, fluorescence) electrical probing or using ultrasonic measurements, electromagnetic waves, NMR, NIR, and so on. These measurements are often used to construct meat structure images that are fusioned and then processed via multi-image analysis, which needs appropriate processing methods. Quality traits related to mechanical properties are often better assessed by methods that take into account the natural anisotropy of meat due to its relatively linear myofibrillar structure. Biophysical methods of assessment can either measure meat component properties directly, or calculate them indirectly by using obvious correlations between one or several biophysical measurements and meat component properties. Taking these calculations and modelling the main relevant biophysical properties involved can help to improve our understanding of meat properties and thus of eating quality.     

实时荧光定量PCR结合培养法在细菌学室间质量评价中的应用

目的 评价培养法和实时荧光PCR法在细菌学质控样本中的检测应用.方法 采用培养法和实时荧光PCR法分离鉴定30件质控考核致病菌,探讨快速、准确检测致病菌的理想方案.结果 从鉴定结果和检测完成时间方面具体分析了其中5件质控标本,质控标本1号、2号实时荧光PCR优于培养法,质控标本3号、4号培养法弥补了实时荧光PCR的局限...     

Application of biospeckle laser technique for determining biological phenomena related to beef aging

Among the features of beef quality, color is a major factor that influences marketing since it is the only characteristic consumers can see at the time of purchase, although tenderness is the organoleptic trait that most affects consumer acceptance of beef. Thus, an effective technology to predict meat quality is highly desirable for the meat industry. Among many emerging technologies, optical methods have the greatest potential since they are fast, nondestructive, and generally low cost. This study evaluated the potential application of laser biospeckle technique and its methods of image processing in order to assess and quantify biological phenomena related to beef aging. Samples of muscle Longissimus thoracis were aged for 21 days and underwent biospeckle analysis, objective color and Warner–Bratzler Shear Force (WBSF). According to the results, biospeckle laser parameters may, possibly, assess biological activity resulting from action of endogenous enzymes (calpains and cathepsins) responsible for the aging process through its correlation (R = 0.6146) with analysis of WBSF and of the correlation (−0.7973) with aging time. High correlation of biospeckle analysis, related to traditional out puts and to new proposals, were obtained to color parameters, especially hue angle (h^*) whose R value was 0.7953, redness intensity (R = 0.8120) and percentage of metmyoglobin (MMb) showed that R value of 0.9119, demonstrates the potential of this technique for evaluating quality of meat color.     

Near-infrared reflectance spectroscopy for predicting chemical, instrumental and sensory quality of beef

The aim of this study was to assess near-infrared reflectance (NIR) spectroscopy as a tool for determining sensory and texture characteristics of beef. Chemical, instrumental, texture and sensory characteristics were predicted by near-infrared reflectance spectroscopy carried out on longissimus dorsi muscle samples from 190 young bulls. The use of first derivative gave best predictions together with NIR spectra, except for myoglobin and water holding capacity, which had an R(2) of prediction of 0.91 and 0.82, respectively, using visible and NIR spectra. Tenderness was the best-predicted variable (R(2)=0.98) demonstrating the potential of NIR spectroscopy in the prediction of sensory variables. Chemical composition variables and Warner-Bratzler shear force were predicted with an R(2) of prediction of around 0.7, but protein was not predicted with accuracy.     

Development of an indirect α-actinin-based immunoassay for the evaluation of protein breakdown and quality loss in fish species subjected to different chilling methods

α‐Actinin release from the myofibrillar protein fraction to the sarcoplasm can be considered as an accurate proteolysis index in seafood muscle. The main objective of the present study was to develop a specific enzyme‐linked immunosorbent assay (ELISA), based on the use of a monoclonal antibody against α‐actinin to evaluate the degree of proteolysis in two different chilled fish species – European hake (Merluccius merluccius) and turbot (Psetta maxima) – kept under two different storage systems: flake ice and slurry ice. Comparison with sensory assessment, K‐value and sarcoplasmic protein profiles was carried out. A different degree of proteolysis could be observed in both fish species; thus, the immunoassay was shown to be useful in monitoring the protein degradation events in hake muscle especially under flake ice storage. In the case of turbot, as very low proteolysis development could be obtained, the assay was not suitable for assessing quality changes. A different break point of immunoassay values for each fish species is suggested.     

包装方式对宰后牛肉成熟过程中食用品质的影响

以真空包装作为对照,研究托盘包装和气调包装对牛肉宰后成熟过程中食用品质的影响。取6头宰后24h的黄牛左侧背最长肌,切割成大小基本相同的肉块并随机分组进行托盘包装、真空包装和气调包装(2.54cm厚),在4℃下冷藏成熟0,4,7,10d,分别测定颜色、嫩度、贮藏损失、离心损失、蒸煮损失和水分分布状态,评价包装方式对宰后成熟过程中牛肉食用品质的影响。结果表明:与真空包装相比,托盘包装和气调包装牛肉样品的蒸煮损失在宰后成熟过程中无显著性差异(P0.05),而贮藏损失差异显著(P0.05);托盘包装和气调包装牛肉样品的a*值和自由水含量较高(P0.05),而托盘包装和气调包装牛肉样品的嫩度显著低于对照组(P0.05)。说明气调包装和托盘包装有助于改善牛肉的颜色,而对牛肉嫩度和水分分布状态却不具有改善作用。     

Protein quality of some Nigerian feedstuffs. II. Biological evaluation of protein quality

The protein quality of some Nigerian protein concentrates were studied by conventional protein quality techniques using weanling albino rats of the Wistar Strain. The true digestibility of the concentrates were between 90 and 98% for most of the feedstuffs examined, except the cashew nut scrap kernel meals I and II, (84.6 and 84.3%); the African locust bean seed only (75.9%); the African locust bean seed and pulp (81.6%); and the palm kernel meal (74.2%) which showed significantly lower values than the others. The animal protein sources examined (milk powder, casein, fishmeals and egg) were found to show superior p.e.r., n.p.r., p.r.e., n.p.u. and b.v. values to those observed for the cashew nut samples, African locust bean seed, groundnut and palm kernel meal. Blood meal, however, could not support the growth of rats and showed poor protein quality indices: ?2.46, 0.83, 16.1, 18.9 and 19.3 for the p.e.r., n.p.r., p.r.e., n.p.u. and b.v., respectively. The cashew nut scrap kernel meal samples I and II with protein values in the range 0.76 to 1.12, 2.86 to 3.13, 45.7 to 50.1, 41.3 to 46.7 and 48.9 to 55.3 for p.e.r. n.p.r., p.r.e., n.p.u. and b.v., respectively, were poorer compared to the good grade kernel meal with values of 2.01, 4.01, 64.2, 63.0 and 68.6 for p.e.r., n.p.r., p.r.e., n.p.u. and b.v., respectively, probably as a result of more severe heat damage. The African locust bean seed samples could not support the growth of rats, gave negative p.e.r. (?3.19 to ?2.54); low n.p.u. and b.v. (19.8 to 20.9 and 22.3 to 23.7). The palm kernel meal, despite its apparent balance of amino acids showed poor protein quality indices: 1.27, 2.62, 42.0, 44.1 and 56.7 for p.e.r., n.p.r., p.r.e., n.p.u. and b.v., respectively, attributable to its high fibre content and a concomitant lowering of the digestibility.     

The bacteriological quality of British beef 2. Frozen minced beef

Frozen minced beef was obtained from five commercial wholesale producers, and the aerobic plate count, and counts of coliforms, Escherichia coli type 1 and Staphylococcus aureus, determined. No E. coli O157:H7 or salmonellas were detected. The results were evaluated in relation to: (1) two earlier surveys involving fresh mince purchased from retail butchers and supermarkets in the UK (Roberts et al., 1980; Hudson et al., 1986); and (2) the standards set out in Annex II of the Minced Meat Directive 94/65/EC. In respect to the latter, none of the 99 samples of mince examined was unsatisfactory.     

Rapeseed meal. II. Chemical composition and biological quality of the protein

The chemical composition (moisture, ash, protein, amino acids, ether extract, crude fibre, Ca, P, Fe, thioglucosides, isothiocyanates and oxazolidinethiones) and biological quality (net protein utilisation, available lysine and digestibility) were investigated in 12 samples of presscake meal of rapeseed (Brassica napus) collected from local factories. Crude fibre and mineral contents were comparatively high. Thioglucosides and their hydrolysis products (isothiocyanates and oxazolidinethiones, which are toxic) were found in high concentrations. All samples showed a high protein content and their amino acid patterns corresponded to a good-quality protein with a score of 80, and an adequate level of available lysine. Nevertheless, the biological quality measured as net protein utilisation and digestibility gave low values, which could be explained on the basis of the presence of the toxic factors and the high level of crude fibre, respectively.     

质构仪及其在食品品质检测方面的应用

质地特性是食品特别重要的品质因素,物性质构仪能够较好的反映出食品的这一重要品质因素,已经开始应用于各种食品的品质检测中。通过介绍质构仪的构造及工作原理,介绍其在面制品、肉制品、奶制品和果蔬等不同样品测试时探头的使用,参数的设定以及其他测试条件的设置,给科研工作者提供一定的参考依据。     

Breadmaking quality of ten greek breadheats. II. Relationships of protein,lipid and starch components to baking quality

Protein, lipid and starch components of ten Greek inter bread heats (four poor quality soft milling varieties, and to soft and four hard milling varieties of good quality) ere examined for possible relationships ith bread loaf volume and volumes in sedimentation tests for flour quality. High molecular eight glutenin subunit quality scores ere loer (4, 4, 6, 6) in the poor quality heats than in the good quality heats (6, 6, 6, 6, 8, 10) and ere only roughly correlated ith the other quality parameters. Gliadin electrophoregram patterns ere distinctive for most heats and might be useful for variety identification, but consistent occurrence of γ-gliadin 40, associated ith eakness, and γ-gliadin 43.5, associated ith strength, as not observed. The ratio non-polar/polar free lipids as highly correlated (P < 0.001) ith loaf volumes using both long fermentation and activated (chemical) dough development processes. Starch granule composition, selling and gelatinisation properties, hich ere very similar to those of other heat starches, did not relate to baking quality. A 15-kDa protein on the surface of starch granules associated ith endosperm softness as found in the soft heats.     

Consumption of oxygen by the muscles of beef animals and related species. II. Consumption of oxygen by post-rigor muscle

The oxygen consumption rate (o.c.r.) of post-rigor beef muscle, unlike the pre-rigor o.c.r., is virtually unaffected by the degree of comminution of the muscle. It has a constant enthalpy of activation (ΔH*) of 18.2 ± 0.3 kcal/mol, which is nearly double the value for pre-rigor muscle and is close to the enthalpy of activation of the mitochondrial NAD⁺-linked oxidation of pyruvate (～19 kcal/mol). The latter mitochondrial rate (m.r.) appears to be the step which determines the post-rigor o.c.r., unlike the pre-rigor state where the rate of turnover of ATP (a.t.r.) is rate-determining, except below 15 °C. This is because the potential post-rigor a.t.r. is too high for the mitochondrial electron-transport chain to keep pace with it under the prevailing conditions of low pH. The post-rigor o.c.r. can be doubled at all times of storage up to 6 weeks by addition of an ATP supplement. The o.c.r. declines exponentially from the second day of storage onwards and reaches about 10% of its initial level after about 6 weeks storage of the muscle at 2 °C. This is shown to parallel the decline in the m.r. on storage and is evidently due to partly irreversible impairment of mitochondrial function and not to loss of NAD⁺. The respiratory quotient (r.q.) in the post-rigor state is 1.0 at low pH and falls to ～0.5 on raising the pH to 7.2, due to initial production and subsequent oxidation of α-glycerol phosphate and pyruvate in equal amounts. There are species differences in the magnitude of the post-rigor o.c.r., possibly due to differing mitochondrial contents. The exponential decay of the o.c.r. during storage goes far to explain the increasing depth of penetration of the oxymyoglobin layer which forms on exposing a surface of meat to air or oxygen and which gives the exposed meat an attractive bright red appearance.     

Application of toxicological risk assessment principles to the chemical constituents of cigarette smoke

Data sources: International Agency for Research on Cancer Monographs; California and US Environmental Protection Agency cancer potency factors (CPFs) and reference exposure levels; scientific journals and government reports from the USA, Canada, and New Zealand.

Study selection: This was an inclusive review of studies reporting yields of cigarette smoke constituents using standard ISO methods.

Data extraction: Where possible, the midpoint of reported ranges of yields was used.

Data synthesis: Data on 158 compounds in cigarette smoke were found. Of these, 45 were known or suspected human carcinogens. Cancer potency factors were available for 40 of these compounds and reference exposure levels (RELs) for non-cancer effects were found for 17. A cancer risk index (CRI) was calculated by multiplying yield levels with CPFs. A non-cancer risk index (NCRI) was calculated by dividing yield levels with RELs. Gas phase constituents dominate both CRI and NCRI for cigarette smoke. The contribution of 1,3-butadiene (BDE) to CRI was more than twice that of the next highest contributing carcinogen (acrylonitrile) using potencies from the State of California EPA. Using those potencies from the USEPA, BDE ranked third behind arsenic and acetaldehyde. A comparison of CRI estimates with estimates of smoking related cancer deaths in the USA showed that the CRI underestimates the observed cancer rates by about fivefold using ISO yields in the exposure estimate.

Conclusions: The application of toxicological risk assessment methods to cigarette smoke provides a plausible and objective framework for the prioritisation of carcinogens and other toxicant hazards in cigarette smoke. However, this framework does not enable the prediction of actual cancer risk for a number of reasons that are discussed. Further, the lack of toxicology data on cardiovascular end points for specific chemicals makes the use of this framework less useful for cardiovascular toxicity. The bases for these priorities need to be constantly re-evaluated as new toxicology information emerges.

     

Application of immersion vacuum cooling to water-cooked beef joints - Quality and safety assessment

Immersion vacuum cooling (IVC) was compared against air blast cooling (AB) and vacuum cooling (VC), to establish its applicability to cool water-cooked beef joints. Process parameters (cooling time and cooling loss) and quality parameters (proximate; physical; sensory and microbial analysis) were compared. Results showed IVC samples have lower cooling losses and improved quality properties compared to VC, while generally comparable to AB samples. IVC cooling times were slower then VC, but faster than AB. Sensory results showed no preference between samples (P > 0.05), even though differences in tenderness and juiciness were detected. Cooling methods had no significant effect on thermoduric spore survival or heat activation in the case of Bacillus atrophaeus and Geobacillus stearothermophilus spores. Results confirmed IVC is capable of combining rapid process times and lower mass losses producing microbiologically safe beef joints of overall high quality in terms of sensory, physical and composition characteristics.     

Comparing two internal check measurement methods for wood drying quality assessment

Internal checks that are created in the interior of lumber during or after timber drying seriously affect the quality and value of timber used for the production of high value wood products. This study compared two different methods of assessing wood drying quality, by using either an image analysis ImageJ or Digital Calliper technique, to determine the percentage loss of cross section due to internal checking. The study revealed that there was a significant difference in the total area of internal checks, but the overall timber quality classes determined from both techniques were identical based on the Australian and New Zealand standard for timber quality assessment.     

不同烹调方法对牛里脊营养和感官品质的影响

以牛里脊为研究对象,分别采用水煮、油煎和真空低温烹调三种烹调方法对牛里脊进行烹调,研究了不同烹调方法对牛里脊营养成分及感官品质的影响。结果表明,采用三种烹调方法烹制的牛里脊的菌落总数和大肠杆菌数均符合国家熟肉制品卫生要求,而采用真空低温烹调方法烹制的牛肉营养损失率和脂肪氧化程度最低,色泽和嫩度等感官品质最佳。综上所述,真空低温烹调方法作为一种新型的烹调方法,较传统烹饪方法而言,能更好地保留牛肉的营养成分和风味成分,具有较高的市场推广价值。