Table of Content

01 May 2023, Volume 46 Issue 3

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Basic Research

Analysis of Amino Acid Composition in Infant Formula

LI Linyao, CHU Xiaojun, HUA Jiacai, SU Xiaofang, KANG Qiaojuan, GAO Chao

2023, 46(3):  1-6.  DOI: 10.7506/rykxyjs1671-5187-20230331-014

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The composition and content of amino acids in infant formula sold in China were investigated in comparison with human milk at different lactation stages. An amino acid analyzer was used to detect the contents of free and hydrolyzed amino acids in commercial infant formula, and total amino acid content and the proportion of individual amino acids were calculated. The results showed that free amino acids were detected in some of the 12 samples, while hydrolyzed amino acids were detected in all these samples. The average concentration of most amino acids was close to that of human milk at 1 to 60 d of lactation, and higher than that of human milk at 61 to 180 d. The average ratio of essential to total amino acids was 46.43%, which was close to that of human milk. The proportions of methionine and tryptophan to total amino acids were higher than those of human milk, the proportions of arginine and cystine to total amino acids were lower than those of human milk, and the proportion of other amino acids to total amino acids was close to that of human milk. This study reveals the difference in amino acid content between commercial infant formula and human milk.

Comparative Study of Nutrient Composition of Yak Milk from Qinghai Plateau Yak in Different Seasons

JIA Hongxin

2023, 46(3):  7-11.  DOI: 10.7506/rykxyjs1671-5187-20230423-020

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This study analyzed the effect of season on the nutrient and fatty acid composition of yak milk. Yak milk samples from the Qinghai-Tibet Plateau in summer and winter (n = 18, each) were selected for this study. Results showed that the contents of protein, lactose, non-fat milk solid, ash, vitamin A and main trans fatty acids (trans-9 C18:1 and trans-9,12 C18:2 n-6) were significantly lower in winter than in summer (P < 0.05), while the contents of fat and main fatty acids (C16:0, C17:0, C18:0, cis-9 C16:1, cis-9 C18:1 and cis-9,12 C18:2 n-6) in yak milk were significantly higher in winter than in summer. This suggests that the nutrient and fatty acids composition of yak milk from the Qinghai-Tibet Plateau are influenced by season.

Analysis & Detection

Determination of Six Quaternary Ammonium Disinfectant Residues in Food for Special Medical Purposes by Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

SUN Lei, ZHANG Mingxing, ZHAI Hongwen, MA Junmei, ZHANG Chunlin, REN Xiaowei, CAO Meirong

2023, 46(3):  12-16.  DOI: 10.7506/rykxyjs1671-5187-20230517-026

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An ultra-high performance liquid chromatography tandem triple quadrupole mass spectrometry (UPLC-MS/MS) method was established for the determination of six quaternary ammonium disinfectant residues in milk-containing food for special medical purposes. The sample was extracted with 80% acetonitrile in water and the extract was separated on a RRHD Eclipse Plus C18 column, detected in the positive ion mode using an electrospray ionization source with multiple reaction monitoring (MRM), and quantified by matrix-matched standard calibration. The calibration curves for the six quaternary ammonium disinfectants was linear in the concentration range of 0.1–5.0 ng/mL with correlation coefficient higher than 0.996 0. The limit of detection (LOD) was 0.5 μg/kg and the limit of quantification (LOQ) was 1 μg/kg. The recoveries were 72.8%-102.3% for spiked solid matrix samples, and 71.8%–100.8% for spiked liquid matrix samples with relative standard deviations (RSDs) in the range of 0.25%–3.88% and 0.19%–2.51%, respectively. The proposed method is simple, efficient, rapid, sensitive, and suitable for the qualitative and quantitative analysis of quaternary ammonium disinfectant residues in food for special medical purposes.

Determination of Dicamba Residues in Milk by High Performance Liquid Chromatography-Tandem Mass Spectrometry

ZHANG Lijia, LIU Lijun, BAI Yanmei, WANG Yang, MO Nan, GAO Yujie, LI Cuizhi

2023, 46(3):  17-22.  DOI: 10.7506/rykxyjs1671-5187-20230407-017

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The objective of this study was to establish a method for detecting the residue of dicamba in cow milk by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The sample was extracted with 0.5% formic acid in acetonitrile, and the extract was purified by sodium chloride salting out, and separated on an Acquity UPLC BEH C18 column (100 mm × 2.1 mm, 1.7 μm) by gradient elution using a mobile phase composed of acetonitrile and 0.01% formic acid aqueous solution. Identification and quantification were achieved using an electrospray ionization source in the negative ion mode with multiple reaction monitoring (MRM). Under optimized pretreatment and instrumental conditions, good linearity was observed in the concentration range of 5.0–250.0 μg/L with correlation coefficient (r) more than 0.999. The limit of detection (LOD) and limit of quantification (LOQ) of the proposed method were 5 and 10 μg/kg, respectively. The recoveries of dicamba at spiked concentration levels of 10, 20 and 200 μg/kg were 104.3%, 101.5% and 96.2% with relative standard deviations (n = 6) of 3.0%, 2.0% and 1.5%, respectively. This method is simple, accurate, repeatable, and suitable for the rapid detection of dicamba in milk.

Optimization of Extraction Method for the Analysis of Nitrite in Milk Powder

LI Yongjuan, HUANG Ke, ZHANG Jing, SUN Wenyi

2023, 46(3):  23-26.  DOI: 10.7506/rykxyjs1671-5187-20230423-021

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This study aimed to select and optimize a sample extraction method for the determination of nitrite from milk powder. The absorbance of the experimental water stored for different periods of time was detected by three extraction methods, heat extraction, ultrasonic extraction and ultrasonic decolorization. The color and spiked recoveries of the filtrates from the three methods were evaluated. The nitrite content of quality control samples was determined by ultrasonic decolorization and the limit of detection (LOD) of this method was investigated. The results indicated that storage time did not affect the absorbance of the experimental water. The recoveries of the ultrasonic decolorization method were over 90%, with relative standard deviations (RSD) less than 10%. and the measured results of the quality control samples were within the characteristic value range with LOD of 0.4 mg/kg, which meets the laboratory quality control requirements. The ultrasonic decolorization method has good accuracy and accuracy, and it is recommended that it be used for the decolorization of colored substances in the national standard method.

Determination of Residual Solvents in Sucrose Fatty Acid Esters

FU Changyu, YANG Dan, CHENG Zhixiang

2023, 46(3):  27-31.  DOI: 10.7506/rykxyjs1671-5187-20230228-012

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A headspace gas chromatography (HSGC) method was established for the determination of residual methanol, isopropanol, methyl ethyl ketone, ethyl acetate and isobutanol in sucrose fatty acid esters. Samples were directly injected into the headspace. The chromatographic analysis was performed on a DB-1 column (60 m × 530 μm, 1 μm) equilibrated for 40 min at 80 ℃. The results showed that the calibration curves for the five solvents were linear in the range of 0.05–10.00 μg, with correlation coefficients greater than 0.999, and the limits of quantitation (LOQ) for methanol, isopropanol, methyl ethyl ketone, ethyl acetate and isobutanol were 0.024 4, 0.019 7, 0.022 7, 0.024 5 and 0.019 2 mg/kg, respectively. The average recoveries for all analytes were in the range from 81.7% to 96.8%, and the relative standard deviation (RSD) for precision ranged from 1.90% to 4.52%. The pretreatment method was simple and rapid, with good recovery and precision, and was suitable for the analysis of the five residual solvents in sucrose fatty acid esters. A total 20 lots of of sucrose fatty acid ester samples were detected by the proposed method. The residues of three solvents in 17 of them met the requirements of the Joint FAO/WHO Expert Committee on Food Additives (JECFA). The detection rate of methanol was highest (80%), and methanol was the major solvent retained in the lipophilic samples at a level up to 9.42 mg/kg. More solvents were detected in the hydrophilic samples at lower levels.

Uncertainty Evaluation for the Microbiological Determination of Biotin in Infant Formula

ZHAO Pan, ZHANG Rui, ZHANG Yalun, FAN Sufang, WANG Zan, GUO Limin

2023, 46(3):  32-37.  DOI: 10.7506/rykxyjs1671-5187-20230331-016

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An uncertainty evaluation method for the microbiological determination of biotin in infant formula was developed in order to control the quality of test results and improve the detection accuracy, a method for uncertainty evaluation of milk powder by method was established. According to the requirements of the Evaluation and Expression of Uncertainty in Measurement (JJF 1059.1—2012) and the Guide to the Evaluation and Expression of Uncertainty in Measurement (GB/T 27418—2017), the uncertainty components were estimated for the determination of biotin in infant formula by the method specified in the National Food Safety Standard Determination of Biotin in Foods (GB 5009.259—2016). It was found that the greatest uncertainty resulted from standard curve fitting and repeatability test. The uncertainty for the biotin content of three infant formula samples was as follows: sample A (19.87 ± 2.84) μg/100 g, B (30.35 ± 4.41) μg/100 g, and C (53.15 ± 7.15) μg/100 g (in the 95% confidence interval, coverage factor (k) = 2). As the content of biotin in samples increased, the expanded uncertainty also increased.

Reviews

Research Progress on Intervention Strategies of Probiotics for Autoimmune Diseases

YANG Yang, HONG Qing, LIU Zhenmin

2023, 46(3):  38-45.  DOI: 10.7506/rykxyjs1671-5187-20230411-018

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Probiotics are living microorganisms that provide health benefits to the host when consumed in certain amounts. Autoimmune diseases including systemic lupus erythematosus, multiple sclerosis, and rheumatoid arthritis are immune diseases that cause tissue and organ damage due to immune dysfunction in the body. Patients with autoimmune diseases often suffer from intestinal flora disorders. Probiotic intervention can restore intestinal microecological balance, avoiding the toxic side effects of medications, so it provides a new strategy for the prevention and treatment of autoimmune diseases. This article reviews the recent progress in research on autoimmune diseases and presents the current status and future prospects of the application of probiotic intervention strategies in autoimmune diseases.

A Review of Technologies for Aflatoxin Detection in Milk and Dairy Products

YANG Fan, HUANG Jianhui, CHEN Chen, GUAN Shuhui, LIU Guangpeng, ZHANG Yan

2023, 46(3):  46-51.  DOI: 10.7506/rykxyjs1671-5187-20230331-015

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Aflatoxins (AFTs) is a group of secondary metabolites produced by Aspergillus flavus and Aspergillus parasiticus, which has stable physicochemical properties. Aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1), aflatoxin G2 (AFG2), aflatoxin M1 (AFM1), and aflatoxin M2 (AFM2) are the common analogues of AFT, with AFB1 being the most toxic and widespread one. The International Agency for Research on Cancer (IARC) under the World Health Organization has classified AFB1 as a Group 1 carcinogen. When cows eat contaminated feedstuffs such as peanut, corn, rice, soybean and wheat, some of the AFTs are converted in the body into AFM1, and AFM2, which can exist in milk and dairy products. This paper compares the difference between Chinese and international limits for AFTs in foods, and summarizes the methods for detecting aflatoxin in milk and dairy products such as thin-layer chromatography (TLC), mass spectrometry (MS), spectroscopy, electrochemistry, and rapid test strips. This paper analyzes the advantages and limitations of these methods and predicts future directions in the development of aflatoxin detection technology in milk and dairy products. It is hoped that this review will help in the development of a more convenient, specific, and sensitive detection method for aflatoxin in milk and dairy products.

A Review of Methods for Determination of Vanillin in Formulas for Special Medical Purpose Intended for Infants

GUO Meijuan, ZHANG Lantian, SHI Guohua, ZHANG Yan, WANG Chenyuan, ZHANG Xiangqu, MA Yuechao, ZHANG Bin

2023, 46(3):  52-58.  DOI: 10.7506/rykxyjs1671-5187-20230517-025

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Vanillin is a flavor widely used in the food industry. This paper discusses the application of vanillin in the food industry, worldwide limits for the use of vanillin, the characteristics of the production technology and the possible risks brought by vanillin for foods, and it also summarizes the methods for vanillin detection in dairy products, infant formulas and formulas for special medical purposes intended for infants including gas chromatography (GC), liquid chromatography (LC), gas chromatography-tandem mass spectrometry (GC-MS/MS), liquid chromatography-tandem mass spectrometry (LC-MS/MS), and spectroscopy with special attention to their advantages and limitations. This review is expected to provide a basis for the detection and further research of vanillin in infant formulas for special medical purpose.