乳制品质量快速检测原理与技术研究进展

乳制品是鲜奶以及所有以奶为主要原料加工制成的产品的总称,乳制品的安全问题是全球关注的热点。为了对乳制品质量进行监控,目前已有的检测标准和方法需要在实验室进行,检测环境条件要求较高,周期较长。研究并开发灵敏、准确、便捷的检测方法十分必要。近年来,一系列新的乳制品质量快速检测技术已经被广泛应用,本文主要介绍了电子学、光谱学和生物学检测技术的原理及其在乳制品质量检测应用中的优缺点,同时展望了乳制品质量检测技术的发展方向,旨在为乳制品质量检测技术的进一步发展提供资料参考和思路。     

Multi-enzyme biosensors with amperometric detection for determination of lactose in milk and dairy products

 In home-made sensors coimmobilizing enzymes in thin-layer plexi-cells on natural protein membranes, three enzyme cells: β-galactosidase and galactose oxidase (A), β-galactosidase and glucose oxidase (B) and β-galactosidase, galactose oxidase and glucose oxidase (C) were built into a flow-injection-analyzer system. The lactose was decomposed and oxidized by the immobilized enzymes and the hydrogen peroxide generated during the enzymatic reactions was determined by amperometric detection. The parameters for biochemical and electrochemical reactions (concentration of buffer, temperature, flow rate) were optimized in each enzyme cell. The pH optima of the lactose measurement was determined in the three enzyme cells mentioned above. The pH optimum of the cells A, B and C were 6.4, 4.5 and 4.8, respectively. The measuring ranges were 1–5 mM, 2–10 mM and 1–5 mM, while the detection limits were 0.5, 1.0 and 0.5 mM, respectively. More than 600, 1000 and 800 samples could be measured with these cells, respectively. Commercial milk and instant dessert powder products were analysed also. Our results showed that the cells B and C were more suitable for the determination of the lactose content of milk. For samples of dairy products containing added glucose, starch and other carbohydrates, enzyme cell A could be used for the efficient determination of lactose in one step. Received: 24 August 1998 / Revised version: 9 November 1998     

Polycyclic aromatic hydrocarbons in milk and dairy products

Polycyclic aromatic hydrocarbons (PAHs) are a group of organic compounds with a structure consisting of carbon and hydrogen atoms that have more than two fused aromatic rings. Most PAHs have carcinogenic effects on animal or humans and induce various cancers. Polycyclic aromatic hydrocarbons are a consequence of environmental pollutants, imperfect burning or pyrolysis of organic substances during industrial processing. Additionally, foods can be contaminated during their processing and preparation through different heat treatments. This review highlights the formation, occurrence and health impacts of PAHs in milk and milk products, and analytical technique used for their determination in dairy products.     

Studies on iodine content in daily diets and selected dairy products

Poland's people have moderate – and in seaside areas mild – degrees of severity of iodine deficiency. A national program has been introduced for obligatory iodine prophylaxis and includes the iodination of household salt to the extent of 30 ±10 mg KI/kg. In order to assess the extent of iodine consumption, analytical studies were carried out on iodine content in average Polish diets. Taking into account the fact that milk formulae are frequently the basic source of iodine for infants, studies were performed on the iodine content in selected dairy products, mainly infant formulae. Iodine concentrations in samples were determined in duplicate by radioactive neutron activation analysis (RNAA). The iodine content in Polish diets without added iodinated kitchen salt was low and insufficient to provide the Polish RDA for this element. The results of the analytical investigations of the daily diets showed higher iodine content in comparison to theoretical calculations. The theoretical values accounted for 71–85% of the analytical ones. Study of iodine content in infant formula demonstrated differences between the analytically determined iodine content in products and that declared by producers. Received: 22 November 1999     

Bioactive peptides in dairy products

Bioactive peptides are hydrolysates with specific amino acid sequences that exert a positive physiological influence on the body. They are inert within the native protein, but once cleaved from the native protein by microbial or added enzymes and/or gastrointestinal enzymes during the digestive process, they apply their beneficial traits. Dairy products, particularly fermented products, are potential sources of bioactive peptides: several of them possess extra‐nutritional physiological functions that qualify them to be classified under the ‘Functional Foods’ label. Biological peptides in milk, the methods of their generation and their prevalence in dairy products are reviewed along with the reported health benefits and safety aspects.     

Effect of incorporation of dairy products in chevon nuggets

This paper presents the different ways of incorporating various coprecipitates obtained from milk in chevon nuggets. The chevon was obtained from a rare but popular breed called Black Bengal goat. Milk coprecipitates of varying composition were in the formulations. Emulsion stability, yield, moisture and protein contents were not affected significantly, whereas shear force, pH, various organoleptic properties were found to be affected significantly. This method may potentially lead to the development of new emulsion-based nuggets.     

浅析乳制品中脂肪酸类营养强化剂检测方法

本文将乳制品经酸水解后,利用乙醇-乙醚-石油醚提取脂肪酸,在碱性条件下进行甲基化反应,用气相色谱-质谱法测定出添加的7种脂肪酸类营养强化剂。本检测方法前处理简单快捷,易于操作,方法重现性良好,其RSD可达0.82%～1.78%;回收率可达89.9%～103.6%;灵敏度高,检测限为0.1 mg/kg。     

Amperometric determination of hydrogen peroxide residue in beverages using a Nafion modified palladium electrode

Hydrogen peroxide (H₂O₂) residues are not permitted in food due to health concerns. An amperometric sensor based on a Nafion modified palladium (Pd) electrode was developed for the rapid determination of the H₂O₂ residue in aseptically packaged beverages. A prepared Pd electrode shows a slowly increasing reaction upon repeating the procedure of adding the same concentration of H₂O₂ into the reaction cell unless pretreating the electrode with cyclic voltammetry to obtain reproducible surfaces, whereas a Nafion modified Pd electrode can reach stable reaction to H₂O₂ without any pretreatment. The interference level of ascorbic acid (the ration of electrochemical response to ascorbic acid to the electrochemical response of H₂O₂) was calculated as 0.0004 for the Nafion modified Pd electrode. Interference (99.5%)from ascorbic acid was diminished by Nafion membrane. The response of the sensor to H₂O₂ in distilled water is linear over the range of 0.25–15 μM (r ² = 0.9956). The sensor developed in this study can efficiently determine H₂O₂ residues in commercial beverages with good linear correlation between spiked H₂O₂ concentration and detected H₂O₂ concentration, for winter melon-flavored drink, r ² = 0.9904 in the range of 0.25–15 μM and for lemon-flavored tea, r ² = 0.9927 in the range of 0.25–25 μM.     

乳制品中乳酮糖的测定

采用高效液相色谱法测定乳制品中的乳酮糖。该方法简单易行,应用示差折光检测器。最低检测限为1.82×10-7g,变异系数（CV％）为1.74,回收率为94.0％～98.5％。     

Survey of aflatoxin M1 in milk and dairy products consumed in Burdur,Turkey

The aim of this study was to investigate the occurrence of aflatoxin M₁ (AFM₁) in dairy product samples in Burdur city. A total of 315 samples of dairy products were collected during 2008. Of the 315 samples analysed, AFM₁ in 246 samples (78.1%) was found to range from 5.5 to 800 ng/kg. In addition, AFM₁ levels of 16 raw milk, two pasteurised milk, only one milk powder and three white cheese samples were above the Turkish Food Codex. It is concluded that the occurrence of AFM₁ in dairy products may be considered as a possible hazard for public health.     

A review of the analytical methods coupled with chemometric tools for the determination of the quality and identity of dairy products

There is an increasing demand of the consumers and actors of the food industry sector to have means of measurement allowing the characterisation of raw materials or food. Dairy products (milk, ice cream, yogurt, butter, cheese, etc.) are in considerable demand, command premium prices and are, therefore, vulnerable to economic adulteration. Authenticity of these products is an important issue for food processors, retailers, regulatory authorities and consumers. It is also valuable for ensuring fair competition and as a mean of protecting consumers against fraud due to mislabelling. Conventional chemical methods are not able to determine the regional provenance of dairy products unambiguously. Therefore, alternative techniques such as spectroscopic techniques i.e., near infrared (NIR), mid infrared (MIR), front face fluorescence spectroscopy (FFFS), stable isotope and nuclear magnetic resonance (NMR)-coupled with chemometric tools have many potential advantages as tools for the evaluation of the identity of such products. This review article discusses the potential of destructive and non-destructive techniques for the determination of the quality and the authenticity of dairy products.     

Technologically important characteristics of Enterococcus isolates from milk and dairy products

Enterococcus faecium (54 strains), E. faecalis (40 strains), and E. durans (14) were isolated from various dairy products (raw milk, cream, butter and fermented milk products) during a previous study (Wessels et al., 1988). In this article various characteristics of these isolates, which may have a bearing on their significance in dairy products, have been studied. A large percentage of the identified strains of all three species were able to grow at 7°C. Seventy-six percent of the E. faecium strains, 62% E. faecalis and 50% E. durans strains also showed proteolytic activity at psychrotrophic temperatures. The fact that proteolytic activity could be detected within 2 days at 7°C is significant, since bulk cooled milk is normally held for 3 to 4 days at temperatures between 4 and 7°C at farms or factories prior to processing. This examination confirmed that enterococci are proteolytic rather than lipolytic.     

Investigation of a multienzyme based amperometric biosensor for determination of sucrose in fruit juices

Determination of sucrose content is one of the most important routinely performed tests for quality control in the beverage industry. Thus, it is rather important to have a fast, simple and sensitive method that can be used for determination of sucrose in sweet-drink processing. The biosensor investigated was based on a thin layer enzyme cell in which glucose oxidase, invertase and mutarotase were immobilized on a protein membrane. Hydrogen peroxide as the product of the consecutive enzyme reaction was detected by amperometric technique. The optimum enzyme composition of invertase, mutarotase, and glucose oxidase for immobilisation was found to be 8498, 672, and 120 U using 2.2 mg BSA as protective agent dissolved in 200 μL phosphate buffer solution. To achieve the best measuring technique, changes in several parameters such as pH value, temperature and flow rate were studied. Having found the optimum conditions, the statistical parameters of the analysis were established. The linear range of the determination was between 1.0 × 10⁻⁴ and 2.5 × 10⁻³ mol/L with a correlation coefficient of 0.99. The sucrose content of several fruit juices was determined with this sensor, and the results were compared with an enzymatic reference method. The correlation between the two sucrose determination methods was found to be 0.97.     

Capabilities of automated Karl Fischer titration combined with gas extraction for water determination in selected dairy products

The water content of different types of butter, processed cheeses and hard cheese was determined by classical oven drying, manual Karl Fischer titration and a combination of water release by heating and transferring the released water in a dried air stream into a Karl Fischer titration cell. This technique is also referred to as gas extraction of the water or combined method.     

乳制品中脂溶性维生素检测的前处理方法研究进展

脂溶性维生素是维持身体健康所必需的一类有机化合物,对人体生长发育、新陈代谢有极其重要的作用,如果长期缺乏或过量某种脂溶性维生素,就会引起生理机能障碍或某种疾病。脂溶性维生素品种丰富、结构类似;稳定性差,在光、氧、酸、碱等条件下易降解;不同类型脂溶性维生素极性不同、且在食品基质中含量差异大,因此多目标物高效前处理、有效分离、降低基体干扰等关键技术是脂溶性维生素准确定量面临的挑战。本文综述了液液萃取、固相萃取等传统及新型QuEChERS萃取、超临界流体萃取等提取与净化技术在乳制品及婴幼儿配方奶粉中脂溶性维生素的分析应用,分析了液相色谱、液相色谱串联质谱、超临界流体色谱以及酶联免疫等检测技术的特点,并展望了其发展趋势。     

HPLC-MS/MS法快速测定乳制品中90种兽药的残留量

目的 建立高效液相色谱-串联质谱法（HPLC-MS/MS）测定乳制品中十大类90种兽药残留的检测方法。方法 试样用0.2%甲酸乙腈溶液提取,经Waters Prime HLB固相萃取柱净化,用Waters XBridge BEH-C18色谱柱洗脱分离,并使用电喷雾电离源,正负离子切换扫描模式进行检测,外标法定量。结果90种兽药在1 ng/mL～20 ng/mL范围内呈现良好的线性相关性,相关系数均大于0.995。90种兽药的方法检出限为0.3 ?g/kg,方法定量限为1 ?g/kg。在添加量为1 ?g/kg、2 ?g/kg和10 ?g/kg的加标回收实验下,90种兽药的加标回收率范围分别为66.0%～134.8%,64.0%～122.4%和62.4%～118.3%。同时做了方法精密度验证,有69%的兽药RSD<5%,有28%的兽药RSD在5%～10%,有3%的兽药RSD在10%～20%。结论 该方法简单、快速、高效且能同时准确定性和定量检测乳制品中十大类90种兽药的残留量。     

Electrochemical determination of glucose using polyaniline electrode modified by glucose oxidase

Polyaniline (PANI) enzyme electrode was formed by immobilisation of Glucose oxidase (GOx) via glutaraldehyde into electrochemically polymerised PANI on graphite electrode. Electrochemical polymerisation of PANI on graphite was performed from aqueous solution of 1.0 mol dm⁻³ HCl and 0.25 mol dm⁻³ aniline at constant current density of 2.0 mA cm⁻². Hronopotentiometric curves of the PANI enzyme electrode obtained at current density of 10 μA cm⁻² were recorded in different glucose concentrations. The linearity response range was between 1.0 and 5.0 mmol dm⁻³ of glucose concentration. The estimated apparent Michaelis–Menten constant, was K_m^′ = 0.30 mmol dm⁻³, which is significantly lower than that of free enzyme.     

泰安市售塑料包装奶制品双酚A含量检测及膳食风险评估

目的调查泰安市售奶制品中双酚A(bisphenol A,BPA)含量,并对泰安市居民进行BPA膳食风险评估。方法从泰安市各大市场随机抽取奶制品(包括牛奶、酸奶及奶饮料等),采用超高效液相色谱-质谱联用法(ultra performance liquid chromatography-mass spectrometry,UPLC-MS)测定BPA含量,用SPSS 22.0进行统计分析并通过点评估法对泰安市居民BPA膳食风险进行评估。结果泰安市售奶制品中BPA污染十分普遍,但均不超过国家要求范围,其中普通聚乙烯(polyethylene,PE)材料包装奶制品BPA含量高于高密度聚乙烯(high density polyethylene,HDPE)材料包装奶制品(P0.05),普通人群暴露的BPA来源于乳制品的量为0.007~0.035μg/(kg·bw/d),占暴露量占可耐受每日摄入量(tolerable daily intake,TDI)的0.171%~0.878%。结论泰安市市售的奶制品中BPA的污染比较普遍但污染程度较轻,对泰安市市民的健康尚不构成很大的威胁。     

乳粉中脂肪含量测定的不确定度评定

目的评定碱水解法测定乳粉中脂肪含量的不确定度评定的方法。方法根据GB 5413.3-2013《食品安全国家标准婴幼儿食品和乳品中脂肪的测定》和JJF 1059.1-2006《测定不确定度的评定与表示》建立不确定度模型,运用《测量不确定度评定与表示指南》,分析该方法测定中各不确定因素,对乳粉中脂肪含量的不确定度进行评定。结果乳粉中脂肪含量为21.2 g/100 g,不确定度为0.34 g/100 g,脂肪含量表示为:(21.2±0.34)g/100 g,k=2。结论通过分析各分量的相对不确定度,找出检测过程中的关键环节,对实验进行优化,能有效提高检测工作的质量和效率,帮助检验人员确定测定结果的可靠程度,确保测定结果准确可靠。     

Experimental study of hydrodynamics in a flat ohmic cell—impact on fouling by dairy products

This study highlights the link between hydrodynamics and fouling phenomena in a continuous rectangular ohmic cell. The hydrodynamic study was carried out using flow visualisation techniques and particle image velocimetry (PIV). The distribution of deposits in the ohmic cell was investigated by heating an aqueous solution of β-lactoglobulin-xanthan gum mixture. Experimental results show that the deposit distribution on the electrode surfaces is directly related to the flow structures in the ohmic cell.