Table of Content

01 July 2021, Volume 44 Issue 4

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Analysis & Detection

Effects of Reconstitution, Storage and Reheating on Vitamin B1 and Vitamin D Contents in Formula Foods for Special Medical Purposes

ZHANG Bin, LI Zengning, GUO Meijuan, WANG Fang, ZHANG Lantian, ZHANG Yan

2021, 44(4):  1-5.  DOI: 10.15922/j.cnki.jdst.2021.04.001

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This research investigated the effects of reconstitution pH value and temperature, storage duration, sunlight exposure and reheating on the contents of vitamin B1 and vitamin D in six different kinds of formula foods for special medical purposes sold on the market. The results showed that the vitamin B1 content decreased with increasing reconstitution pH value and temperature and storage time, but was little affected by reheating. The vitamin D content decreased with storage time in sunlight. pH value and reheating had little effect on the content of vitamin D. The optimum conditions for ensuring the highest utilization ratio of vitamin B1 and vitamin D in formula foods for special medical purposes were reconstitution in acidic water (pH < 7) at 40–60 ℃, storage in darkness and preferably use immediately after reconstitution.

Helicase-Dependent Isothermal DNA Amplification for Rapid Detection of Salmonella in Fermented Milk

WANG Zan, LI Xian, WANG Hui, XU Miaomiao, ZHANG Jie, LIU Shuai, ZHOU Wei, SHI Guohua

2021, 44(4):  6-10.  DOI: 10.15922/j.cnki.jdst.2021.04.002

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A rapid detection method for Salmonella in fermented milk was developed by helicase-dependent isothermal DNA amplification (HDA). In this method, the invA gene sequence of Salmonella was used as the target gene to design specific primers, and the concentrations of UvrD helicase and T4 gp32 in the reaction system were optimized to establish the optimal reaction system. The HDA method was used to directly detect Salmonella in fermented milk, and the amplification products were detected by electrophoresis to verify the specificity of this method. The results showed that the proposed method exhibited high specificity for Salmonella in fermented milk. The optimized reaction system contained 0.10 μg of UvrD helicase and 5.0 μg of T4 gp32 per 50 μL of sample. The amplification product was consistent with the designed sequence length (304 bp). The detection limit was 2.6 × 102 CFU/g. The method can meet the requirements for the rapid detection of Salmonella in fermented milk, and thanks to its high sensitivity and easy operation, it can be used as a basic method for rapid detection of Salmonella in fermented milk.

Applicability of the National Standard Detection Methods for Chlorine to Infant Formula for Special Medical Purposes

WU Hao, ZHANG Bin, LIU Xiaoguang, GUO Meijuan, ZHANG Lantian, ZHANG Yan

2021, 44(4):  11-14.  DOI: 10.15922/j.cnki.jdst.2021.04.003

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The applicability of silver nitrate titration and potentiometric titration, two of the three detection methods for chlorine in food samples specified in the national standard GB 5009.44—2016, for infant formula for special medical purposes was evaluated. The results showed that the spiked recoveries of silver nitrate titration for partially hydrolyzed protein infant formula, extensively hydrolyzed protein infant formula, and amino acid-based infant formula for special medical purposes were 95%–108%, 98%–125% and 100%–106%, respectively, and the relative standard deviations (RSD) for precision were between 12.7% and 32.9%. The results of potentiometric titration was lower than that of silver nitrate titration.

Detection of 3-Chloropropanol Esters and Glycidyl Esters in Infant Formula for Special Medical Purposes

ZHAO Limin, HUANG Yunxia, MENG Zhijuan, NIU Lisha, ZHANG Yali, WANG Teng, DI Pengyue, ZHANG Dongsheng, SUN Wenyi

2021, 44(4):  15-18.  DOI: 10.15922/j.cnki.jdst.2021.04.004

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Using gas chromatography-tandem mass spectrometry (GC-MS), an indirect method was established for the simultaneous detection of 3-chloropropanol esters (3-MCPDE) and glycidyl esters (GE) in infant formula for special medical purposes. The conditions for sample extraction and transesterification/hydrolysis were optimized and stable isotope dilution was used to improve the accuracy and precision of the method. The results showed that the method exhibited good linearity in the range of 0.005–2.000 μg/mL (R2 ≥ 0.999), together with a limit of detection (LOD) of 5 μg/kg and a limit of quantification (LOQ) of 25 μg/kg (both calculated based on the corresponding amount of chloropropanol). The recoveries of the analytes spiked in infant formula for special medical purposes at 25, 125 and 250 μg/kg were 88.5%–104.1%, and the relative standard deviations (RSDs) for six replication determinations were less than 15% (n = 6). The levels of 3-MCPDE and GE in three types of commercial infant formula for special medical purposes were below the maximum limits set by the EU.

Optimization of the Spectrophotometric Determination of L-Carnitine in Infant Formula for Special Medical Purposes

MA Xiaobo, WU Lei, ZHANG Bin, ZHANG Lantian, GAI Lina

2021, 44(4):  19-23.  DOI: 10.15922/j.cnki.jdst.2021.04.005

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In order to establish an efficient method for the determination of L-carnitine in infant formula for special medical purposes, the spectrophotometric method for the determination of L-carnitine in foods for infants and young children and dairy products specified in the national standard GB 29989—2013 was optimized with respect to standard curve preparation, sample pretreatment and enzyme preparation. The results showed that under the following conditions: using the optimized standard curve, enzyme extraction at a rotation speed of no less than 6 000 r/min, and hydrolysis of 5 g of homogeneous milk powder (accurate to 0.000 1 g) with 0.25 g of α-amylase at 50 ℃ for 30 min, the optimized method exhibited high precision and spiked recovery. This method could overcome the problems encountered in the determination of L-carnitine in infant formula for special medical purposes by the traditional method such as cloudy filtrate, the dark color of prepared samples that could interfere with the determination of absorbance and low spiked recovery, being suitable for the large-scale determination of L-carnitine in amino acid-based infant formula, extensively hydrolyzed protein infant formula and partially hydrolyzed protein infant formula for special medical purposes.

Determination of 16 Polycyclic Aromatic Hydrocarbons in Infant Formula

CHEN Tongqiang, LI Can, JING Huihua, LIANG Feng, XU Wenyang, TANG Weijie, DENG Ming, LI Kailong

2021, 44(4):  24-28.  DOI: 10.15922/j.cnki.jdst.2021.04.006

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An analytical method was established by gas chromatography-mass spectrometry (GC-MS) for the simultaneous determination of the contents of 16 polycyclic aromatic hydrocarbons (PAHs) in infant formula. This method was applied to survey the levels of PAHs pollution of 45 infant formula samples sold online. The sample pretreatment procedure was optimized and the figures of merit of the method including linearity, precision and spiked recovery were examined. The external standard method was used for quantitation. The linearity of the method was good in the concentration range of 1–100 ng/ mL (r > 0.999), and the limit of detection (LOD) was 0.01–0.10 μg/ kg. The average recoveries at spiked concentration levels of 5, 10 and 50 μg/kg were in the range of 76.2%–103.1%, and the relative standard deviation (RSD) for precision was less than 10%. The detection rate of PAHs was 86.7% from 15 infant formula samples for babies of 0–6 months at levels of 0–1.12 μg/kg. The detection rate of PAHs was 80.0% from 15 infant formula samples for babies of 6–12 months at levels of 0–0.75 μg/kg. The detection rate of PAHs was 60% from 15 infant formula samples for babies of 12–36 months at levels of 0–0.60 μg/kg.

Development of Ready-to-Use Quality Control Samples for the Detection of Salmonella in Formula Foods for Special Medical Purposes Containing Milk

ZHANG Tao, ZHANG Rui, ZHANG Yalun, XU Miaomiao, WANG Hui, CHEN Chen, ZHOU Wei, SHI Guohua

2021, 44(4):  29-33.  DOI: 10.15922/j.cnki.jdst.2021.04.007

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In order to evaluate the application value of ready-to-use Salmonella quality control samples in matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) identification of Salmonella in milk-containing formula foods for special medical purposes, this experiment evaluated the uniformity and stability of the quality control samples. After being stored at 20 ℃ for 0, 14 and 28 days, these samples were identified by mass spectrometry and the VITEK automatic microbial analysis system. The results showed that the quality control samples had good stability and uniformity, and their mass spectra were similar to each other. The VITEK system confirmed their identity as Salmonella. In conclusion, the ready-to-use Salmonella quality control strains can be used for the detection of Salmonella in milk-containing formula foods for special medical purposes.

Applicability of Different Methods for Determination of Selenium in Infant Formula Foods for Special Medical Purpose

GUO Meijuan, ZHANG Bin, ZHANG Chunlin, LI Jundi, ZHANG Lantian, SHI Guohua

2021, 44(4):  34-37.  DOI: 10.15922/j.cnki.jdst.2021.04.008

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In this study, the applicability of hydride generation atomic fluorescence spectrometry (HG-AFS) and inductively coupled plasma mass spectrometry (ICP-MS), methods I and III specified in the national standard GB 5009.93—2017, respectively to detect selenium in infant formula for special medical purposes was researched. Seven laboratories separately determined the selenium content in six samples of 3 types of infant formula for special medical purposes and infant formula quality control samples, and measured the recoveries. The results showed both methods were suitable for the determination of selenium in infant formula, while the applicability for various types of infant formula foods for special medical purposes needs to be further studied.

Determination of Inositol in Formula Foods for Special Medical Purposes by Ion Chromatography

MAO Lian, ZHANG Bin, WANG Qingbo, GUO Meijuan, WANG Liping, ZHANG Lantian, SHI Guohua

2021, 44(4):  38-41.  DOI: 10.15922/j.cnki.jdst.2021.04.009

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Ion chromatography was used to determine the inositol content in formula foods for special medical purposes. The sample was acidified by hydrochloric acid to precipitate proteins, and inositol was dissolved in the supernatant and then detected with an amperometric detector. The results showed that the peak area was linearly related to the concentration of inositol in the range of 0.025 to 40.000 mg/L with a correlation coefficient (R2) of 0.999 9. The detection limit and quantitation limit were 0.125 and 0.5 mg/100 g, respectively. The average recovery of inositol was 83.1%–102.9% at different spiked levels. The method was proved to be simple, sensitive reproducible and suitable for the determination of inositol in formula foods for special medical purposes.

Reviews

Progress in Detection Methods for Degree of Hydrolysis of Cow’s Milk Proteins: A Review

ZHANG Xiangqu, ZHANG Bin, GAI Lina, TIAN Zechen, WANG Yiwei, ZHANG Lantian

2021, 44(4):  42-45.  DOI: 10.15922/j.cnki.jdst.2021.04.010

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Hydrolyzed protein formula not only solves the problem of allergy or intolerance to cow’s milk proteins in infants and young children, but also meets the nutritional needs. Degree of hydrolysis is an important parameter to evaluate hydrolyzed protein formula. However, there are currently no methods available to determine the degree of hydrolysis of hydrolyzed protein formula. This article presents a brief introduction to the basic concepts of hydrolyzed protein formula and its degree of hydrolysis, and summarizes the existing methods for detecting the degree of hydrolysis of proteins. We expect this review to provide a reference for the establishment of detection methods for the degree of proteolysis of hydrolyzed protein formula.