Table of Content

01 March 2024, Volume 47 Issue 2

Previous Issue    Next Issue

Basic Research

Responses of Microencapsulated Lactiplantibacillus plantarum L3 Added in Yoghurt to Storage Environments

GAO Jiaxu, QI Fuling, SUN Qingshen

2024, 47(2):  1-8.  DOI: 10.7506/rykxyjs1671-5187-20240415-025

Asbtract ( )   HTML ( )   PDF (5399KB) ( )  

Related Articles | Metrics

Fermented milk with water-in-oil-in-water (W/O/W) Lactiplantibacillus plantarum L3 microcapsules prepared with modified low methoxyl pectin (mLMP) and a commercial starter culture was stored 4 ℃ for 0, 7, 14 or 21 days prior to simulated gastrointestinal digestion. To investigate the stress response of L. plantarum L3 to fermentation, storage and simulated gastrointestinal environments, viable count was measured, cee morphology was observed, and the fatty acid composition of the cell membrane and intracellular amino acid composition were analyzed. Results showed that after storage for 21 days and simulated gastrointestinal digestion, the viable count was maintained at about 9.74 (lg(CFU/mL)) and the cell structure remained intact and clear. Alanine, glutamic acid and aspartic acid were the most abundant amino acids in microencapsulated L. plantarum L3 at all storage periods. The ratio of unsaturated to saturated fatty acids in the cell membrane increased firstly and then decreased with storage time, but was always higher than that of free L. plantarum L3. In conclusion, W/O/W microencapsulation can improve the survival rate of L. plantarum L3 in adverse environments such as yoghurt, cold storage, gastric acid, bile fluid and intestinal fluid, which provides a scientific basis for the application of functional strains in food carriers.

Analysis of Flavor Substances of Mongolian Cheese and Establishment of a Model for Evaluating Its Flavor Intensity

JIA Zhibin, QIAO Xiangyu, WANG Caiyun, ZHANG Xiuxiu, LIU Lu, LI Xiaodong, HAN Renjiao

2024, 47(2):  9-14.  DOI: 10.7506/rykxyjs1671-5187-20240415-020

Asbtract ( )   HTML ( )   PDF (2127KB) ( )  

Related Articles | Metrics

The volatile flavor substances of 5 representative Mongolian cheese samples collected from different regions of Inner Mongolia were determined by headspace purge and trap (PT) coupled with triple quadrupole gas chromatography (QqQ-GC), and a flavor intensity evaluation model was constructed based on principal component analysis (PCA). The results showed that a total of 86 volatile substances were identified in Mongolian cheese, among which 24 were the main volatile substances. The flavor intensity evaluation model (F = 0.353 51F1 + 0.280 46F2 + 0.198 46F3 + 0.167 56F4) showed that the cumulative contribution rate of the first four principal components was 100.000%, which included ethyl caprylate, n-hexanol, ethyl decanoate, n-decanoic acid, acetic acid, and acetaldehyde, ect. They could reflect the original data accurately. In addition, the sensory evaluation results of the 5 cheese samples were consistent with the scores from the flavor intensity evaluation model, which indicated that the constructed model could effectively evaluate the flavor of Mongolian cheese, providing a new method for the evaluation of the flavor of Mongolian cheese.

Screening, Identification and Culture Condition Optimization of Lactiplantibacillus plantarum RT-6 Producing a High Amount of Exopolysaccharide

HUANG Xiaoyu, HAN Jin, YU Wenhui, WU Zhengjun

2024, 47(2):  15-23.  DOI: 10.7506/rykxyjs1671-5187-20240409-019

Asbtract ( )   HTML ( )   PDF (3445KB) ( )  

Related Articles | Metrics

Exopolysaccharides (EPS) from Lactiplantibacillus plantarum have been found to possess a variety of biological activities such as antitumor and antioxidant, but few studies on the synthesis of EPS by L. plantarum in skim milk have been reported. The aim of the present study was to screen L. plantarum with high EPS production capability in skim milk, which will be great significance to the application of L. plantarum in dairy products. L. plantarum RT-6 (CGMCC No. 26778), with a high capability of producing EPS, was isolated from homemade yogurt collected in Guilin, Guangxi, China by the colony thread-drawing method. Its EPS producing capability was compared with that of other L. plantarum strains. The culture conditions for EPS production by L. plantarum RT-6 were optimized using one-factor-at-a-time (OFAT) method and response surface methodology (RSM). It was found that among all tested L. plantarum strains, RT-6 exhibited the highest EPS yield when cultured in reconstituted skim milk, whereas most other strains grew slowly or even could not grow. The optimal culture conditions were determined as 39 h, 32 ℃, 101 mg/mL and 1.488 mmol/L for fermentation time, fermentation temperature, skim milk concentration and concentration of mixed essential amino acids, respectively. Under the optimized conditions, the yield of EPS was 241.1 mg/L, 2.6 times higher than that before optimization.

Analysis & Detection

Determination of 21 Veterinary Drugs in Cow and Goat milk and Milk Powder by QuEChERS Combined with Ultra Performance Liquid Chromatography-Quadrupole/Orbitrap Mass Spectrometry

ZHANG Shenping, QIN Yu, GU Yingjuan

2024, 47(2):  24-29.  DOI: 10.7506/rykxyjs1671-5187-20240409-018

Asbtract ( )   HTML ( )   PDF (2755KB) ( )  

Related Articles | Metrics

A method for the determination of 21 veterinary drugs in cow and goat milk and milk powder was established by the QuEChERS (quick, easy, cheap, effective, rugged, safe) sample pretreatment method combined with ultra performance liquid chromatography-quadrupole/orbitrap mass spectrometry (UPLC-Q/Orbitrap MS). Chromatographic conditions, mass spectrometric parameters and pretreatment conditions were optimized. Samples were extracted with acetonitrile in the presence of anhydrous sodium sulfate, purified using a mixture of primary secondary amine (PSA) and C18, separated on an Accucore RP-MS column (100 mm × 2.1 mm, 2.7 μm), and detected by UPLC-Q/Orbitrap MS. Good linearity was observed for all the analytes in the investigated concentration ranges with correlation coefficients (r2) of greater than 0.99. The limit of quantification (LOQ) of the proposed method was 0.5 μg/kg. The average recoveries at spiked concentration levels of 0.5, 2.0 and 10.0 μg/kg were 67.2%–110.2% with relative standard deviations (RSDs) of 3.6%–17.4% (n = 6). The method is simple and sensitive, and suitable for simultaneous detection of the 21 veterinary drugs in cow and goat milk and milk powder.

Comparative Analysis of Frozen Concentrated Milk and Whole Milk Powder: A Nutritional Perspective

WEN Hongrui, LI Nan, LI Fengying, LIU Yunjun

2024, 47(2):  30-41.  DOI: 10.7506/rykxyjs1671-5187-20240401-016

Asbtract ( )   HTML ( )   PDF (7455KB) ( )  

Related Articles | Metrics

To compare the differences in nutritional composition and functional properties between frozen concentrated milk and whole milk powder, this study measured changes in immunoglobulins (Igs), lactoferrin, B vitamins, and metabolomics. It was found that the frozen concentrated milk had significantly higher levels of IgA and IgG, lactoferrin, B vitamins, vitamin A, vitamin D, and vitamin C compared to whole milk powder. Non-targeted metabolomics analysis revealed that the main differential metabolites between frozen concentrated milk and whole milk powder were annotated to multiple key pathways involved in amino acid and peptide (isoleucine, levodopa, phenylalanine-tyrosine, creatine, D-proline, L-glutamate, L-arginine, asymmetric dimethylarginine, L-pipecolic acid, L-histidine, and N-methyl-L-glutamate) metabolism, and carbohydrate (maltotetraose, trehalose, D-maltose, and isomaltose) metabolism. These metabolites showed significantly higher relative expression levels in frozen concentrated milk compared to whole milk powder (P < 0.05). The results indicate that frozen concentrated milk is significantly superior to whole milk powder in terms of nutritional composition.

Verification and Application of Biochip for Detection of Veterinary Drug Residues in Raw Milk

QI Bing, CHEN Rouhan, YANG Xiaojun, JIANG Chunling, MA Yingqing, DENG Bo

2024, 47(2):  42-48.  DOI: 10.7506/rykxyjs1671-5187-20240415-022

Asbtract ( )   HTML ( )   PDF (2050KB) ( )  

Related Articles | Metrics

In order to verify the efficacy of biochip technology in the detection of veterinary drug residues in raw milk and to promote its application, 80 common veterinary drugs in raw milk were detected by biochip and confirmed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results showed that the limit of detection (LOD) of the biochip method met the requirements of the national standard, and the LOD for some veterinary drugs was below the national standard limits. The linear range of the method was wide, with correlation coefficient (r) greater than 0.99. Recoveries for negative samples spiked at 2 × and 4 × LOD concentrations were 70%–130%, with coefficient of variation (CV) of 5%–10%. This method has the advantages of simple pretreatment, short detection period and high sensitivity and is suitable for rapid screening of large quantities of samples. Using the proposed method, 10 of 100 batches of raw milk collected from Shanghai during 2022–2023 were tested positive for veterinary drug residues. Streptomyci was detected in 4 batches at concentration levels of 5.86–10.26 μg/kg, sulfapyridine in 3 batches at 1.09–1.42 μg/kg, sulfamonomethoxine in 2 batches at 1.38–1.46 μg/kg, and avermectin in 1 batch at 1.75 μg/kg. These concentration levels were far lower than the maximum residue limits set by international organizations, an announcement of the Ministry of Agriculture and Rural Affairs, and the national standard. Compared with traditional HPLC-MS/MS, the biochip method has the advantages of high sensitivity, wide linear range and fast detection rate. It can be used as a supplementary means for rapid detection of veterinary drug residues in raw milk, and has high application value.

Optimization of a Method for the Detection of 1,2-Propanediol in Infant Formula

LIU Yuxuan, MENG Genhua, LIN Tingjuan, GUO Ruifang

2024, 47(2):  49-55.  DOI: 10.7506/rykxyjs1671-5187-20240116-002

Asbtract ( )   HTML ( )   PDF (3005KB) ( )  

Related Articles | Metrics

According to the first method for the determination of 1,2-propanediol in foods specified by the national food safety standard GB 5009.251-2016, 1,2-propanediol was extracted from milk powder using acetonitrile and was detected using a gas chromatograph (GC). Extraction solvent and standing time were investigated by one-factor-at-a-time method. Furthermore, response surface methodology (RSM) was employed to optimize oscillation time and standing time based on 1,2-propanediol recovery. The optimum extraction conditions were determined as acetonitrile, 4 ℃, 94–102 s and 1.2–1.4 h for extraction solvent, standing temperature, oscillation time and standing time, respectively. Under these conditions, the spiked recovery range of 1,2-propanediol was 95.2%–99.8%. The coefficient of variation for repeatability of the method was 1.62%, and it had good selectivity. The optimized method is suitable for the determination of 1,2-propanediol in milk powder.

Reviews

Research Progress on the Functionality of Probiotic Fermented Dairy Products

ZHANG Yuxin, LI Zhengyu, RAO Fulin, TIAN Qiquan, LI Aoqiang, LI Jiaxin

2024, 47(2):  56-60.  DOI: 10.7506/rykxyjs1671-5187-20240422-027

Asbtract ( )   HTML ( )   PDF (1749KB) ( )  

Related Articles | Metrics

Probiotic fermented dairy products are rich in beneficial microorganisms such as lactic acid bacteria as well as a variety of bioactive substances, conferring multiple health benefits to consumers. This paper reviews the latest research developments in probiotic fermented dairy products, including the types and functions of probiotics and their roles in treating inflammatory bowel disease, improving obesity, enhancing cognitive function, alleviating allergic symptoms, maintaining bone health, combating constipation, lowering cholesterol, and managing diabetes. The paper concludes with a summary and outlook on the future development directions of probiotic fermented dairy products, highlighting the importance of the development, clinical testing and market exploitation of personalized products. It is hoped that this review will lay a theoretical foundation for further research into probiotic fermented dairy products.