Determination of the fat content of meat using nuclear magnetic resonance

A nuclear magnetic resonance method has been used to measure the fat content of lean meat and the accuracy assessed by comparison with standard chemical methods. There were linear relationships between the nuclear magnetic resonance (n.m.r.) fat content and those determined by two standard chemical methods; the residual standard deviations being 0.2 and 0.16% of the wet weight for total and extractable fat methods, respectively.     

Measurement of the fat content of meat using ultrasonic waves

The velocity of 2·5 MHz ultrasound in muscle, fatty tissue and muscle/fatty tissue mixtures has been measured over the temperature range ?20°C to +40°C. At a set temperature there is a relation between the velocity of ultrasound and the composition of the tissue, and this relation was studied at ?9°C, 0°C and +37°C. Measurements at 37°C appeared to have the best predictive value, and at that temperature, a linear relation existed between the reciprocal of the velocity and the volume fraction of fat. This relation is such that a measurement of the time taken for a pulse to travel through meat consisting of multiple, parallel layers of muscle and fatty tissue of arbitrary fatness could be used to estimate the overall mean volume fraction of fat. This property could be useful in assessing at selected sites the composition of the soft tissue of living animals. Muscles are acoustically anisotropic and the slight difference between velocities along, and parallel to, the fibres has been measured. The effect of dehydration has also been investigated.     

Assessment of meat fat content using dual energy X-ray absorption

Fat content is an essential component of meat quality. Fat content and fatty tissue content were determined by dual energy X-ray absorption on 3 types of meat: pork meat (mixture of longissimus dorsi and fat) and beef meat (longissimus dorsi and pectoralis profondus). The measurements were carried out with a medical densitometer, the SOPHOS L-XRA usually used for osteodensitometry. The results from the dual energy X-ray absorption and the chemical analysis were compared and the correlations were good to very good (R(2) values from 0.7 to 0.97). The residual standard deviations were in the range 2.75-4.89%. The routine use of dual energy X-ray absorption would though suppose a previous calibration.     

富含脂肪食品总糖含量的测定

根据食品中总糖含量的测定原理及食用油脂的化学性质，提出了测定富含脂肪食品中总糖含量时应先去除其含有脂肪的方法。该方法的变异系数是0．62％（n=7），平均回收率是100．5％，具有较好的精密度和较高的准确度，适用于富含脂肪食品中还原糖、蔗糖、淀粉含量的测定。     

Determination of fat,protein, moisture,and salt content of Cheddar cheese using mid-infrared transmittance spectroscopy

The objective of our work was to develop and evaluate the performance of a rapid method for measuring fat, protein, moisture, and salt content of Cheddar cheese using a combination mid-infrared (MIR) transmittance analysis and an in-line conductivity sensor in an MIR milk analyzer. Cheddar cheese was blended with a dissolving solution containing pentasodium triphosphate and disodium metasilicate to achieve a uniform, particle-free dispersion of cheese, which had a fat and protein content similar to milk and could be analyzed using a MIR transmittance milk analyzer. Annatto-colored Cheddar cheese samples (34) from one cheese factory were analyzed using reference chemistry methods for fat (Mojonnier ether extraction), crude protein (Kjeldahl), moisture (oven-drying total solids), and salt (Volhard silver nitrate titration). The same 34 cheese samples were also dissolved using the cheese dissolver solution, and then run through the MIR and used for calibration. The reference testing for fat and crude protein was done on the cheese after dispersion in the dissolver solution. Validation was done using a total of 36 annatto-colored Cheddar cheese samples from 4 cheese factories. The 36 validation cheese samples were also analyzed using near-infrared spectroscopy for fat, moisture, and the coulometric method for salt in each factory where they were produced. The validation cheeses were also tested using the same chemical reference methods that were used for analysis of the calibration samples. Standard error of prediction (SEP) values for moisture and fat on the near-infrared spectroscopy were 0.30 and 0.45, respectively, whereas the MIR produced SEP values of 0.28 and 0.23 for moisture (mean 36.82%) and fat (mean 34.0%), respectively. The MIR also out-performed the coulometric method for salt determination with SEP values of 0.036 and 0.139 at a mean level of salt of 1.8%, respectively. The MIR had an SEP value of 0.19 for estimation at a mean level of 24.0% crude protein, which suggests that MIR could be an easy and effective way for cheese producers to measure protein to determine protein recovery in cheese making.     

脂肪替代品在低脂肉制品中的研究进展

由于低脂肉制品可有效降低脂肪的摄入,且能预防高脂膳食所引起的各种慢性疾病,相关研究领域逐渐成为近年来的研究热点。本文基于国内外低脂肉制品的发展现状,从脂肪替代物、脂肪模拟物和复合型脂肪替代物三个方面综述了各自对低脂肉制品组成成分、组织结构、抗氧化性及感官评价等指标影响的最新研究进展,并就肉制品中脂肪替代物的发展方向进行了展望。      

Simultaneous determination of fat and water content in caramel using time domain NMR

In the production process of caramel mass it would be desirable to determine the contents of water and fat simultaneously in one single analytical step.     

Determination of added fat in meat paste using microwave and millimetre wave techniques

By evaluating the sensitivity of measurement parameters such as dielectric constant and microwave loss to fat content, several microwave and millimetre methods were compared to identify optimal frequency measurement bands. The results showed that the optimum frequency range lay between 8 and 20GHz where these parameters vary linearly, by up to a factor of 8, as fat is increased to 50% volume. A narrowband waveguide sensor cell was designed and constructed for this optimum range. The imaginary part (ε') of the complex permittivity demonstrated a better measurements resolution for determining fat content than the real part (ε'). The waveguide method has excellent repeatability as indicated by low relative standard deviation (RSD<4.88%). Temperature and sample density had minimal impact on the accuracy, repeatability and robustness of the final measurement system. A method of mixtures model for complex permittivity was shown to be a useful predictor of fat content.     

紫外分光光度法检测山楂总黄酮方法的建立

以芦丁为标准品,根据现有条件对硝酸铝显色-分光光度法进行改进,利用果胶酶将山楂果肉中的果胶分解后,再进行黄酮的含量分析,减少果胶对检测黄酮的影响,建立起更加精确的紫外分光光度法山楂总黄酮分析系统,旨在为山楂总黄酮的定量及生物功能评价提供检测方法。     

Water/moisture and fat analysis by time-domain NMR

Time-domain nuclear magnetic resonance (TD-NMR) is widely used within food industries for QC/QA applications. Precise determination of moisture and water is of fundamental interest. To determine moisture and water in the presence of lipids, the minispec makes use of differences in their respective NMR relaxation properties. The minispec applications analysing bound water are well-known and have become International standard methods. Different methods to analyse food samples with high water content or free water, like some dairy products, are addressed in this paper. Explicitly, the well-known pre-drying methods are compared to NMR diffusion experiments and a combined relaxation time analysis. Finally the single-sided NMR approach is discussed to analyse packages food.     

Determination of ash content in meat products

Various procedures for determining 'ash' content of meat products have been compared. The ISO method gave significantly higher results than the other methods tested. The standard method (IAS 2-043) gave lower recoveries and, in one of the experiments, lower results for ash content, than the other methods tested. The AOAC and Lees' methods gave high recoveries, but their results for ash content were significantly lower than those of the ISO method. All four methods showed good precision and repeatability. The differences between them although small were statistically significant. The ISO method is recommended on account of its speed, accuracy and reliability.     

午餐肉中食盐含量的测定

采用直接沉淀滴定法测定午餐肉中的食盐含量,结果表明,所测样品中食盐含量为1.36g/100g,该方法简单、快速、准确度高,适用于午餐肉中食盐含量的测定。     

火腿肠中水分和食盐含量的测定

采用直接干燥法和直接沉淀滴定法分别测定火腿肠中水分和食盐的含量,结果表明,所测样品中水分和食盐的含量分别为63.0g/100g和1.69g/100g,该方法简单、准确度高,适用于火腿肠中水分和食盐含量的测定。     

应用低场核磁共振技术快速鉴别冻融肉

目的 利用化学计量学方法结合低场核磁共振（LF-NMR）对冻融肉的快速鉴别进行研究。方法 利用LF-NMR选择CPMG序列对111个长白猪里脊肉样品采集核磁信号,通过对核磁信号数据的反演,将获得的12个变量采取主成分分析方式提取出4个主成分,并建立判别研究模型。结果 模型按照鲜肉组、微冻融肉组和冻融肉组分析,使用回代法验证的正确率为95.5%,使用交叉验证的正确率为94.6%。结论 LF-NMR具有简单、快速的优点,可用于冻融肉的判别分析,为监管部门提供了可靠有效的依据。     

午餐肉罐头中铅含量的测定

采用石墨炉原子吸收光谱法测定午餐肉罐头中铅的含量,结果表明,所测样品中铅的含量为0.083mg/kg,该方法简单、快速、准确度高,适用于午餐肉中铅含量的测定.     

午餐肉罐头中砷含量的测定

采用原子荧光光谱分析法测定午餐肉罐头中砷的含量,结果表明,所测样品中砷的含量为0.0125mg/kg,相对标准偏差为1.18%,检出限为0.0018ng/mL,回收率为98%～102.6%,该方法简单、快速、准确度高,适用于午餐肉中砷含量的测定。     

午餐肉罐头中锡含量的测定

采用原子荧光光谱分析法测定午餐肉罐头中锡的含量,结果表明,所测样品中锡的含量为0.443 mg/kg,相对标准偏差为1.32％,检出限为0.026ng/mL,回收率为95.3％～103.5％,该方法简单、快速、准确度高,适用于午餐肉中锡含量的测定.