The measurement uncertainty was estimated for the determination of 1-oleic-2-palmitic-3-linoleic acid triglyceride (OPL) content in milk powder by gas chromatography (GC). According to the Measurement and Expression of Uncertainty in Measurement (JJF 1059.1—2012) and the Guidance on Quantifying Uncertainty in Chemical Analysis (CNAS-GL 006: 2019), a mathematical model was established to analyze the sources of measurement uncertainty. The major factors affecting the measurement uncertainty were evaluated. Results showed that the average OPL content of six milk powder samples was measured to be 1.172 g/100 g. The relative expanded uncertainty (urel) was 0.023 6 with a coverage probability of approximately 95%. The standard uncertainty arising from sample preparation was the main source of uncertainty.

A high performance liquid chromatographic (HPLC) method was developed for the determination of naringin in milk and dairy products. Samples were extracted with methanol, and the analytes were separated on a C18 column using a mobile phase consisting of 0.1% acetic acid aqueous solution and acetonitrile (75:25, V/V), detected by a diode array detector at 284 nm and quantified by an external standard method. The results showed that the linearity of this method was good in the concentration range of 5–500 μg/mL with a correlation coefficient of 0.999 9. The recoveries of powdered and liquid milk power and yogurt spiked at 0.02, 0.04, and 0.08 g/100 g were 96.2%–103.2%, 96.3%–103.7%, and 99.7%–104.1%, respectively, with relative standard deviations (n = 6) of 1.12%–2.31%, 1.25%–1.85%, and 1.24%–1.66%, respectively. The reported method is simple, rapid, accurate, repeatable, and suitable for the determination of naringin in milk and dairy products.

A gas chromatographic (GC) method for the determination of 1-oleic-2-palmitic-3-linoleic-triglyceride (OPL) in milk powder was established. The samples were extracted with ether and petroleum ether, and the extract was concentrated to near dryness, re-dissolved in n-heptane, separated on a CP-TAP CB elastic quartz capillary column, detected by a hydrogen flame ionization detector, and quantified by an external standard method. The column temperature was programmed to rise. The inlet temperature was set at 330 ℃. The samples (1.0 μL) were injected using the split mode (1:10). The detector temperature was set at 360 ℃. Nitrogen was used as the carrier gas. The makeup flow rate (nitrogen) was 25 mL/min. The recovery of OPL from spiked milk powder at 1–6 g/100 g ranged from 95.2% to 101.9%, and the relative standard deviations (RSDs) for precision ranged from 1.289% to 1.998%. The limit of detection (LOD) and limit of quantitation (LOQ) of the proposed method were 0.2 and 1.0 g/100 g, respectively. This method, therefore, is simple, accurate, repeatable, and suitable for the determination of OPL in milk powder.

A gas chromatographic (GC) method to determine the contents of 16 trans fatty acids in ice cream was established. The 2.0 g samples were pretreated sequentially with 8 mL of hydrochloric acid and 10 mL of anhydrous ethanol, separated on an SP-2560 capillary column, detected by GC with a flame ionization detector (FID) and quantified by the peak area normalization method. Under optimized chromatographic conditions, the limit of detection and limit of quantification of the proposed method were 0.012% and 0.024%, respectively, and it allowed effective separation of trans fatty acid methyl esters from cis fatty acid methyl esters and saturated fatty acid methyl esters.

Iodine is an important index of the nutritional quality of milk. Milk and dairy products are important dietary sources of iodine for humans, which has always aroused extensive concern. With the continuous exploration of nutrients in foods, research on iodine in milk has been increasingly intensified and refined. This paper reviews the recent literature on the factors that affects the iodine content of milk and the analytical methods that have been applied to determine it, which is expected to provide a reference for researchers in this industry and also provide a theoretical basis for the labelling of iodine in infant formula preparation.

In order to develop a new method to determine nitrite and nitrate in milk and milk products, some improvements were made on the ion chromatography method specified in the national standard GB 5009.33-2016 Determination of Nitrite and Nitrate in Food. Samples were extracted with ultra-pure water and added with acetic acid to precipitate proteins before being chromatographed on AS11-HC column and detected with a conductivity detector. Under the above conditions, the calibration curves for nitrite and nitrate were linear with correlation coefficients greater than 0.99. The limit of quantitation (LOQ) for nitrite and nitrate was 0.25 and 0.8 mg/kg in milk, and 1 and 5 mg/kg in milk powder, respectively. The recoveries for spiked samples of milk powder and milk were from 80% to 110%. The improved method was simple to operate and cheap with ideal recovery and high precision. It could avoid potential problems encountered in the use of the traditional method and allow for more rapid and accurate detection of low contents of nitrite and nitrate in milk and milk products.

A method for the determination of zeaxanthin in milk powder was developed using high performance liquid chromatography (HPLC). The sample was saponified with potassium hydroxide solution to release zeaxanthin, extracted with a mixed solvent of ethyl ether, n-hexane and cyclohexane and frozen for degreasing. The chromatographic separation was performed on a C30 column with gradient elution. The analyte was detected with an ultraviolet detector and quantified by an external standard method. The limit of quantification was 100 μg/100 g and the limit of detection was 30 μg/100 g for zeaxanthin in milk powder. The method recoveries at spiked concentration levels of 90–811 μg/100 g were 85.8%–102.2%, with relative standard deviations ranging from 1.43% to 2.76%. This method was accurate, repeatable, precise and sensitive.

A reversed-phase high performance liquid chromatography (RP-HPLC) method for the simultaneous quantitative determination of vanillin, methyl vanillin, ethyl vanillin and coumarin in milk and dairy products has been established. Vanillin compounds from samples were extracted with acetonitrile, blown to dryness under nitrogen, and then cleaned up with n-hexane. The chromatographic separation was achieved using a mixture of 20 mmoL/L ammonium acetate (pH 5.6), acetonitrile and methanol as the mobile phase with gradient elution on a C18 column. The analysis was carried out using a UV detector at a wavelength of 267 nm and the analytes were quantified by an external standard method. Good linear relationships in the range of 0.05–5.00 μg/mL were observed for all analytes. The limit of quantification was 0.2 mg/kg and the limit of detection was 0.06 mg/kg for the four analytes in liquid milk, milk powder, yogurt, lactic acid fermented beverage, ice cream, and cheese. The recoveries for vanillin, methyl vanillin, ethyl vanillin and coumarin in these samples at spiked concentration levels of 0.2–2.0 mg/kg were 80.6%–110.0%, 80.1%–109.6%, 80.4%–109.5% and 80.1%–105.9%, with relative standard deviations of 1.87%–7.70%, 1.45%–9.80%, 1.66%–9.52% and 1.16%–9.52%, respectively. This method was rapid, accurate, repeatable and simple and could be applied to determine vanillin compounds in milk and dairy products.

A method for the determination of lactose in low-lactose milk and lactose-free milk by using ion chromatography was developed. Lactose from samples was extracted with 3% acetic acid as a protein precipitator. The method was performed on a CarboPacTM PA20 column by gradient elution. The analyte was detected with an electrochemical detector and quantified by an external standard method. The limit of quantification was 100 mg/kg and the limit of detection was 50 mg/kg for lactose in milk. The recoveries at spiked concentration levels of 100–500 mg/kg were 92.3%–103.4%, with relative standard deviations between 1.44% and 4.43%. This method proved to be rapid, accurate, repeatable, sensitive and simple.

A method for the determination of deoxynivalenol (DON) and its derivatives 3-acetyl-deoxynivalenol (3-ADON) and 15-acetyl-deoxynivalenol (15-ADON) in dairy products, cereal flour and dairy cow feed was developed using high performance liquid chromatography (HPLC). Samples were extracted with ultrapure water, and the extract was cleaned up by immunoaffinity column chromatography and detected by HPLC with ultraviolet detection (HPLC-UVD). The limit of quantitation of the method was 100 μg/kg for all three analytes in dairy products, cereal flour and feed. Recoveries from these three sample matrices spiked at concentration levels ranging from 100 to 500 μg/kg were higher than 90% for DON and higher than 80% for 3-ADON and 15-ADON. This method proved to be simple, fast, sensitive, highly selective, and suitable for the simultaneous analysis of DON, 3-ADON and 15-ADON in dairy products, cereal flour and feed.

An high performance liquid chromatographic (HPLC) method for the determination of four sweeteners and one preservative in fermented milk and jam was developed in this paper. Water was used as the extraction solvent. The chromatographic separation was performed on a reversed phase C18 column using a mobile phase composed of a mixture of 20 mmol/L ammonium acetate buffer solution (pH 4.6) and methanol by isocratic elution. The ratio between mobile phase A and B was 85:15 (V/V) for the detection of benzoic acid and sorbic acid and 95:5 (V/V) for the detection of saccharin sodium and acesulfame K. The analytes were detected using an ultraviolet detector at 254 nm and quantified by an external standard method. The recoveries for benzoic acid, sorbic acid, saccharin sodium and acesulfame K in fermented milk at spiked levels of 1–20 mg/kg were 92.0%–102.4%, and the recoveries in jam at spiked levels of 5–20 mg/kg were 92.3%–105.8%. The limit of quantification (LOQ) for all analytes was 1 and 5 mg/kg in fermented milk and jam, respectively.

A method for the determination of eight colorants, new red, amaranth, allura red, ponceau, tartrazime, sunset yellow, indigotine and brilliant blue in fermented milk by high performance liquid chromatography was developed. The analytes were extracted from samples with weakly alkaline water at 7.7–7.9 and cleaned up on a polyamide solid phase extraction cartridge. The analysis was performed on a C18 column with gradient elution using 0.02 mol/L sodium acetate solution-methanol as mobile phase. The results showed that the recoveries of seven colorants other than indigotine at spiked concentration levels of 0.5–5.0 mg/1 000 g in fermented milk were higher than 90%, while the recovery of indigotine was around 80%. The limit of detection of the method was 0.5 mg/kg. The repeatability relative standard deviation was less than 5%, indicating good precision. With the advantages of accurate results, simplicity and good repeatability, this method is suitable for the analysis of colorants in fermented milk.

A method for determination of hippuric acid and benzoic acid in dairy products by high performance liquid chromatography (HPLC) is described.The protein samples was precipitated by adding lead acetate and centrifuged,and then the analytes were separated on a C18 column with a mobile phase consisting of ammonium acetate and methanol solution and detected with a UV detector at 230 nm.The results showed that hippuric acid and benzoic acid displayed a good linearity relationship in the concentration range of 1-100 mg/kg.The recovery rate was 95.3％-103.6％.The method proved to be simple,accurate and repeatable.

A method for the determination of nucleotides in milk powder by high performance liquid chromatography (HPLC) was developed. Nucleotides were extracted with water, deproteinated with 0.5% acetic acid and cleaned up by an SAX solid phase extraction (SPE) column. The analysis was performed on C18 column using 0.1 mol/L phosphate as the mobile phase. The recoveries of spiked samples at three levels ranging from 0.3 to 50 mg/100 g were higher than 90%. The limit of quantification was 0.3 mg/100 g. This method was accurate, simple, reproducible, and suitable for the analysis of nucleotides in milk powder.

A method for the determination of fructooligosaccharides in modified milk by high performance liquid chromatography (HPLC) was developed. Fructooligosaccharides were extracted with water. The analysis was performed on a NH2 column using 70% acetonitrile in water as the mobile phase. The recoveries of fructooligosaccharides at four spiked levels between 20 and 500 mg/100 g ranged from 80.2% to 107.1%. The limit of quantification was 20 mg/100 g. This method is accurate, simple and suitable for the analysis of fructooligosaccharides in modified milk.