液相色谱法检测与乳制品中甲醛的含量

为了建立一种快速准确检测乳与乳制品中甲醛含量的方法,本文采用沉淀蛋白的方法,然后对处理样品利用2,4-二硝基苯肼对甲醛进行衍生,通过液相色谱仪检测,回收率在90．64～108．41％之间,均能满足仪器法检测乳与乳制品甲醛含黾的要求。     

Evaluation of analytical methods for the determination of free formaldehyde on textile substrate

Release of formaldehyde from durable press-treated fabrics is a problem for human health and safety because formaldehyde is suspected to be carcinogenic. The accuracy of the standard test method for the free formaldehyde determination, Japan Law 112, depends on the formaldehyde content of the sample. The detection of low formaldehyde contents is particularly important in fields, like children clothing, so the application of high-performance liquid chromatography was evaluated. The results obtained by the standard test method, Japan Law 112, where UV/Vis spectrometer was used, were compared with the results obtained by HPLC method in which separation was performed on an RP C18 column with water–methanol as a mobile phase. It was shown that the detection limit and limit of quantification were improved using the HPLC method.     

Alcohol oxidase- and formaldehyde dehydrogenase-based enzymatic methods for formaldehyde assay in fish food products

For Gadoid fishes, formaldehyde can be generated in tissues in huge amounts during endogenous enzymatic degradation of natural osmoprotectant trimethylamine-N-oxide. This paper describes two enzymatic methods for assay of formaldehyde in fish food products using alcohol oxidase (AOX) and formaldehyde dehydrogenase (FdDH) isolated from the thermotolerant methylotrophic yeast Hansenula polymorpha. AOX-based method exploits an ability of the enzyme to oxidise a hydrated form of formaldehyde to formic acid and hydrogen peroxide monitored in peroxidase-catalysed colorimetric reaction. In FdDH-based method, a monitored coloured formazane is formed from nitrotetrazolium salt during reduction by NADH, produced in formaldehyde-dependent reaction. It was demonstrated an applicability of both methods for assay of formaldehyde in fish products. The optimal protocols for analysis procedures have been elaborated and analytical parameters of both enzymatic methods have been established. The both methods were demonstrated that some fish products (hake and cod) contain high formaldehyde concentrations (up to 100 mg/kg wet weight).     

高效液相色谱法检测西药制品中甲醛残留的 方法研究

目的针对西药制品建立一种基于高效液相色谱(HPLC)的甲醛残留检测方法。方法西药中甲醛经2,4-二硝基苯肼衍生化得到2,4-二硝基苯腙后,采用高效液相色谱进行分析,以乙腈-水(60:40,V:V)为流动相进行等度洗脱。并对高效液相色谱条件进行优化。考察所建方法的线性关系、检出限、精密度、回收率、专属性、耐用性、样品及标准溶液的稳定性。结果甲醛在2.38~14.28 mg/L内呈现良好的线性关系,回收率为92.21%,相对标准偏差(RSD)为1.897%。结论该方法具有较强的专属性和耐用性,可用于西药制品中甲醛残留的实际检测。     

Validation of UPLC method on the determination of formaldehyde in smoked meat products

The study was carried out to establish a formaldehyde (FA) detection method in smoked meat products with ultra-performance liquid chromatography (UPLC) method. The high-performance liquid chromatography method was developed by using steam distillation as extraction method and then derived by2,4-dinitrophenylhydrazine (DNPH). The final optimum conditions of derivatization for UPLC method were determined as follows: DNPH dosage of 0.3 mL, derivatization temperature of 60°C, derivatization time of 60 min, and twice extraction. This method was further applied to determine the content of FA in the smoked meat products from five companies. The internal FA in the smoked meat products ranged from 25.55 mg/kg meat to 49.20 mg/kg meat, and the surface FA was 34.04 mg/kg meat to 165.25 mg/kg meat. Thus, this study establishes a simple, fast, and reliable method for the analysis of FA in smoked meat products.     

Kinetics and products of photolysis and reaction with OH radicals of a series of aromatic carbonyl compounds

We have investigated the photolysis and OH radical reactions of phthaldialdehyde, 2-acetylbenzaldehyde, and 1,2diacetylbenzene, atmospheric reaction products of naphthalene and alkylnaphthalenes, and of phthalide, a photolysis product of phthaldialdehyde. Using a relative rate method with 1,2,4-trimethylbenzene and 2,2,3,3-tetramethylbutane as reference compounds, measured rate constants for the gas-phase OH radical reactions (in units of 10(-12) cm3 molecule(-1) s(-1)) were as follows: phthaldialdehyde, 23 +/- 3; 2-acetylbenzaldehyde, 17 +/- 3; 1,2-diacetylbenzene, < 1.2; and phthalide, < 0.8. Blacklamp irradiation showed that phthaldialdehyde and 2-acetylbenzaldehyde photolyze, and, combined with absorption spectra measured in n-hexane solution, average photolysis quantum yields of 0.19 and 0.21, respectively, were derived (290-400 nm). No evidence for photolysis of 1,2-diacetylbenzene or phthalide by blacklamps was obtained. The major atmospheric loss process of phthaldialdehyde and 2-acetylbenzaldehyde are estimated to be by photolysis, with photolysis lifetimes of 1.4-1.5 h for a 12-hr average NO2 photolysis rate of 0.312 min(-1). Phthalic anhydride was the major observed product from the OH radical-initiated reactions of all four compounds and was also formed from photolysis of phthaldialdehyde and 2-acetylbenzaldehyde. The major photolysis products observed were phthalide from phthaldialdehyde and 3-methylphthalide from 2-acetylbenzaldehyde.     

乳制品中游离甘氨酸的测定

建立了高效液相色谱法测定乳制品中甘氨酸质量浓度的方法。采用色谱柱为waters氨基酸色谱柱,流动相缓冲液A和缓冲液B,流速为0．4mL／min,激发波长338nm,发射波长425nm。结果表明,甘氨酸的最低检出限为0．03mg／L,回收率为99．88％,变异系数（CV％）为0．42。     

Evaluation of advanced glycation end products and carbonyl compounds in patients with different conditions of oxidative stress

Advanced glycation end products (AGE) and dicarbonyl compounds accumulate in serum and tissues of patients with diabetes and chronic renal failure. Pentosidine, free pentosidine, glyoxal and methylglyoxal have been evaluated in plasma of diabetic patients with poor metabolic control at baseline and after the improvement of glycemic levels, and in plasma and peritoneal dialysate of patients with renal failure before and after 12 h of peritoneal dialysis. In diabetic patients, acceptable metabolic control was unable to normalize levels of pentosidine (after 2 and 10 months), glyoxal and methylglyoxal (after 2 months). In patients with end-stage renal disease, mean values of pentosidine, free pentosidine, glyoxal and methylglyoxal decreased in plasma after dialysis. No pentosidine or free pentosidine were present in the peritoneal dialysate at time 0, but were found after 12 h of peritoneal dialysis; glyoxal and methylglyoxal decreased after 12 h of dialysis. So, glyoxal and methylglyoxal, already present in the dialysis fluid, can react with the peritoneal matrix protein, giving a reason for the gradual loss of peritoneal membrane function often observed in patients undergoing long-term peritoneal dialysis.     

Rapid determination of formaldehyde and sulfur dioxide in food products and Chinese herbals

Simple, sensitive and rapid methods for the determination of formaldehyde and sulfur dioxide were developed. The formaldehyde determination is based on the reaction between formaldehyde and acetylacetone solution, producing yellow 3,5-diacetyl-l-1,4-dihydrolutidine. Sulfur dioxide was detected as the deoxidize of sulfurous acid by zinc in acidic medium, which produces sulfureted hydrogen that make lead acetate paper blackening due to lead sulfide formation. The detection limits were 0.8 μg mL⁻¹ and 6.0 μg mL⁻¹ for formaldehyde and sulfur dioxide, respectively. The linear range were 0.8–20.0 μg mL⁻¹ for formaldehyde and 6.0–100.0 μg mL⁻¹ for sulfur dioxide determination. The main advantages of the new analytical procedure are the low background level, high selectivity, and very little sample preparation for on-site analysis of formaldehyde and sulfur dioxide in food or Chinese herbal samples with reference color card for qualitative or semi-quantitative determination. The results from these methods correlated well with those obtained from the standard methods.     

HPLC法测定乳制品中的结合型羟甲基糠醛

5-羟甲基糠醛来源于食品的热处理加工过程,分游离型和结合型两种。通过对Amadori产物水解和还原糖异构化可获得该化合物,它可作为一种评估食品中蛋白质发生质量损伤程度的有效标志物。采用三氯乙酸沉淀法对婴幼儿配方食品进行蛋白质沉淀,通过对获得的Amadori产物酸水解,最终测定发生于美拉德反应过程中的羟甲基糠醛含量。结果表明:Amadori产物水解的最优条件为:草酸浓度1.07 mol/L;22.22 mL草酸/g蛋白质;水解240 min。该方法的检出限为0.045μg/mL,变异系数为7.9%,回收率为92.2%。通过对市售样品分析发现,蛋白质质量热损伤程度不同的乳制品中B-HMF差别较显著。     

Antioxidant activity of oligochitosan Maillard reaction products using oligochitosan as the amino or carbonyl groups donors

The purpose of this study was to evaluate the influence of oligochitosan (COS) as amino (–NH₂) or carbonyl group (–C=O) donors on the antioxidant activities of COS Maillard reaction (MR) products. Two kinds of COS MR products (COS MRPs) were prepared by using COS and glucose/α-alanine, respectively. Their structures were characterized by Fourier transform infrared spectroscopy (FT-IR), their molecular weights (Mws) were measured by gel permeation chromatography, and the –NH₂ contents of COS MRPs were determined. The antioxidant activities of COS MRPs were evaluated by measuring the scavenging activity of superoxide anion radical (O₂^?), 1,1-diphenyl-2-picrylhydrazyl radical, and the reducing power. The result showed that C=N absorbance can be observed in CG (MRPs of COS and glucose) and CA (MRPs of COS and α-alanine). The Mw of COS increased after MR. CG and CA showed dramatically enhanced antioxidant activity compared to COS, and the antioxidant activity of CG was better than that of CA. In other words, MR is an efficient way to enhance the antioxidant activity of COS. Moreover, it is a more efficient way to enhance the antioxidant activity of COS by using COS as amino group donor involved in MR. The results may provide some references to the modification and application of COS.     

Promoting dairy products through the web: The case of Pecorino Siciliano PDO during the COVID-19 pandemic

This study analyses the digital marketing tools that companies producing Pecorino Siciliano with a protected designation of origin (PDO) are implementing on the web through their corporate website and their brand page on Facebook. It aims to verify whether companies are adapting (or not) to new trends in web marketing and e-commerce. The quality of corporate websites was assessed during the COVID-19 pandemic in terms of usability and amount of activity on Facebook brand pages by Pecorino Siciliano PDO-producing companies. Analysed data show that the companies producing Pecorino Siciliano PDO fell short in developing their web-marketing tools, demonstrating their poor adaptation to the new digitalisation trends driven by the COVID-19 pandemic.     

Assessment of aflatoxin M1 levels in selected dairy products in north‐western Iran

The purpose of this survey was to evaluate the natural occurrence and content of aflatoxin M_1, AFM_1, in dairy products marketed in Urmia. During September 2007, 40 samples of pasteurised milk, 40 samples of ultra high temperature‐treated (UHT) milk, 40 samples of creamy cheese and 40 samples of Iranian Feta cheese were collected from different supermarkets in Urmia city. AFM₁ contents were determined by the competitive enzyme‐linked imunosorbent assay (ELISA) technique. All milk samples analysed showed a mean of AFM₁ concentrations lower than the permissible level of 50 ng/kg in Iran (23.22 and 19.53 ng/kg in pasteurised milk and UHT milk respectively). The mean levels of AFM₁ contamination were 43.31 ng/kg in Feta cheeses and 21.96 ng/kg in creamy cheeses. The potential risk of human exposure to aflatoxin M₁ via consumption of milk and milk products is well known. Dairy products must therefore be evaluated for aflatoxin and kept free from fungal contamination as much as possible.     

乳品中维生素K1的测定

在奶粉样品中加入适量的脂酶，酶解后用NaOH皂化，用正己烷萃取，蒸干后用甲醇乙酯混合注溶解；用甲醇作流动相；用液相色谱法测定维生素K1，此法成功地提取了乳粉中的维生素K1，回收率达87．8％，变异系数CV为1．147％。     

水产品中甲醛HPLC测定的前处理方法探讨

为了探讨前处理方法对水产品甲醛检测的影响,本文比较了三氯乙酸结合超声提取法(超声+TCA法)、三氯乙酸提取法(TCA法)、蒸馏水提取法、水蒸气蒸馏法四种前处理方法的高效液相色谱法(HPLC)测定甲醛。结果显示,水蒸气蒸馏和三氯乙酸超声提取平均回收率分别为109.06%和103.62%,而蒸馏水提取的回收率低于40%。经优化后的三氯乙酸超声提取条件优化为超声时间25min,10%TCA加入量10mL。因此,三氯乙酸超声提取具有稳定性较好,操作简便,与水蒸气蒸馏法前处理效果相当,是一种适合用于大多数鲜活和冷冻水产品甲醛含量检测的前处理方法。     

Monitoring of biogenic amines in cheeses manufactured at small-scale farms and in fermented dairy products in the Czech Republic

The aim of the study was the monitoring of six biogenic amines (histamine, tyramine, phenylethylamine, tryptamine, putrescine, and cadaverine) and two polyamines (spermidine and spermine) in 112 samples of dairy products purchased in the Czech Republic, namely in 55 cheeses made in small-scale farms and in 57 fermented dairy products. The products were tested at the end of their shelf-life period. Neither tryptamine nor phenylethylamine was detected in the monitored samples; histamine was found only in four cheese samples containing up to 25 mg/kg. The contents of spermine and spermidine were low and did not exceed the values of 35 mg/kg. Significant amounts of tyramine, putrescine, and cadaverine occurred especially in cheeses produced from ewe’s milk or in long-term ripened cheeses. In about 10% of the tested cheeses, the total concentration of all the monitored biogenic amines and polyamines exceeded the level of 200 mg/kg, which can be considered toxicologically significant. In fermented dairy products, the tested biogenic amines occurred in relatively low amounts (generally up to 30 mg/kg) that are regarded safe for the consumer’s health.     

The use of carbon dioxide in the processing and packaging of milk and dairy products: A review

The upswing in consumer demand for fresh and high quality preservative‐free foods has led to the development of modified atmosphere packaging (MAP). Increasingly, MAP is being used with high carbon dioxide (CO₂) concentration as well as CO₂/N₂ gas mixes. Modified atmosphere packaging or ‘gas flushing’ as it is also known is an increasingly popular technique used to extend the shelf life (both quality and safety) of a number of dairy products. Carbon dioxide is an active constituent of MAP, naturally present in freshly drawn raw milk. Addition of CO₂ to raw milk or flushing the package headspace has proved to be a simple and cost‐effective method, depending upon the initial microbiological quality of the food product. Carbon dioxide addition through MAP or direct injection as an economically affordable shelf life extension strategy is used commercially worldwide for some dairy products. The development of food packaging machines with integrated gas flushing capabilities and the supply of ‘food grade’ gases allow dairy foods manufacturers to enhance the quality of their products. This review presents a broad spectrum of current research and the current trends with respect to CO₂ as a natural microbial hurdle with special focus on its precise mechanism and its role in quality improvement of dairy products.     

几种常见食品中甲醛本底值的调查研究

为了解唐山市居民日常饮食中甲醛的本底值，用乙酰丙酮比色法检测了唐山市出售的来自全国10个省市自治区的75份食品的甲醛含量。75份食品包括腐竹12份，粉丝、粉条16份。水发海产品17份，面粉13份，白糖9份，竹笋罐头4份，其他4份。75份样品全部检出甲醛。69份含量小于4．0mg／kg，占样品总数的92％，5份样品含量较高，8～35mg/kg，还有1份食品高达464mg/kg。由于食品原料、包装材料、加工方法、检验方法等因素的影响，食品中可能会存在一定量的甲醛或产生甲醛反应的物质。从本次检验结果看，低于4．0mg/kg的甲醛含量可被看作是本底值。而6份甲醛含量在8～464mg／kg的样品可以认定是在食品中非法使用了甲醛。     

Simultaneous determination of B-group vitamins in enriched Brazilian dairy products

In addition to serving as good natural sources of vitamin B(2), milk and milk products are currently being enriched with the vitamins B(1), B(2), B(6), and nicotinamide in Brazil. The objective of this research was to evaluate the levels of enrichment of these products according to their availability in supermarkets in the Campinas (SP, Brazil) region. The separation of the vitamins was carried out on a C 18 column with gradient elution with acetonitrile and aqueous phase. Detection of vitamins was effected in the ultraviolet region and quantification by an external standard. The levels of vitamin B(2) determined in powdered whole milk, skimmed milk powder, and one brand of flavored lactic beverage, were practically double those stated on the packages. The same occurred with vitamins B(6) and PP (nicotinic acid + nicotinamide), when determined in the same lactic beverage and with vitamin B(6), determined in acidified milk. The high levels of vitamin B(2), naturally present in whole milk, and the predominance of the free form, allowed for the determination of this vitamin in non-enriched milk.     

Screening of strains of Lactococci isolated from Egyptian dairy products for their proteolytic activity

A collection of cocci isolates (293) obtained from traditional Egyptian dairy products collected from four Egyptian regions yielded 151 lactic acid bacteria (LAB) cocci isolates. Among them, 24 isolates were characterised as highly proteolytic. SDS–PAGE showed that 6 isolates were the most proteolytically active, which were classified into Enterococcus faecalis HH22 (4 isolates) and Enterococcus faecium DO623 (2 isolates). The proteolytic activity of E. faecalis was higher than that of E. faecium (particularly on β-casein). The maximal degradation of milk proteins was achieved at pH 6.5–7.2 (E. faecalis) or pH 6.5 (E. faecium) and at 42 °C for both strains. The proteolytic activities of the two strains were inhibited mostly by the presence of EDTA, showing that their proteases belong mainly to metalloproteases. A slight inhibition of proteolysis by PMSF in the case of E. faecalis HH22 suggests a limited inclusion of serine proteases in its protease system.