Development of a high-performance liquid chromatography method for simultaneously analyzing Guanosine 5’-monophosphate (GMP) and Inosine 5’-monophosphate (IMP) in food

This study aimed to develop a HPLC method to simultaneously analyze guanosine 5’-monophosphat (GMP) and inosine 5’-monophosphat (IMP) in food products. Sample preparation procedure was simple, fast. A C18 column (250 mm × 4.6 mm, 5 µm) was used as stationary phase, and a mixture of 10 mM potassium dihydrogen phosphate and 5 mM sodium heptanesulfonate was applied as mobile phase, and PDA detector at 250 nm. The method validation followed AOAC criteria. Selectivity, linearity (R2 > 0.999), recovery (IMP: 90.5 % - 102.8 %, GMP: 91.5 % - 103.9 %), repeatability (RSDR of IMP: 3.07 % and GMP: 2.83 %) were acceptable to determination GMP and IMP in food matrix under AOAC guidelines. LOD of GMP and IMP were of 2.32 and 2.77 mg/kg, respectively. This method was used to determination GMP, IMP in food products collected in Hanoi markets.

Study on the production of Reference Material (RM) for Vitamin B1, B2, B6 in health supplements

Vitamins are essential nutrients commonly found in food products in general and health supplements in particular. In order to accurately evaluate product quality, laboratories need to use reference material in analysis, proficiency assessment, method validation and ensure the validity of the results. The use of reference materials plays an important role in the quality control of test results and is a mandatory requirement for laboratories wishing to demonstrate appropriate competence as required by ISO/IEC 17025:2017. The need to provide reference materials for laboratories is huge. However, at present, there are very few domestic organizations that can produce reference materials, while the cost of buying reference materials from reputable firms in the world is expensive. In this study, we introduced the procedure and production reference materials for the analysis of B-group vitamins (B1, B2, B6). These reference materials were evaluated for homogeneity and stability in 322 days. The certified values are consistent with the concentrations of substances present in normal samples in practice. The measurement uncertainty ranges from 14.5 - 23.3 %. The reference materials can be used for internal quality control for domestic laboratories and is also a premise for further research on standard samples with different matrix and analytical criteria.

Analysis of ethylene glycol in animal feed using liquid chromatography electrospray ionization tandem mass spectrometry

A determination method of ethylene glycol in animal feed by liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) was developed. The analysis was performed with a C18 column (150 mm × 4.6 mm, 3.5 µm), and a gradient mobile phase of 0.1 % formic acid solution and acetonitrile. Ethylene glycol and surrogate standard (propylene glycol) were extracted by water at room temperature, derivatized with benzoyl chloride in alkaline medium, and analyzed by LC-ESI-MS/MS. The method has high specificity and selectivity with a detection limit of 0.1 mg/kg, linearity range of 1 - 20 µg/mL, repeatability of 3.08 - 4.41 %, and recovery of  91.1 - 102.0 %, which meet AOAC requirements. This method has been applied to analyze some marketed animal feed samples.

A report on characterization of submerged fermentation of Phellinus linteus in Vietnam

Phellinus linteus strain GC was cultured for harvesting biomass by submerged fermentation method in 100 L fermenter which produced in Vietnam. The process of cultivation of this fungus was performed in aerobic conditions with aeration at 1 vvm, stirred at 150 rpm, temperature from 27oC to 29oC. The observation of cultivation was performed to evaluate the optimum time of growth which produce highest biomass of the mycelium for application purpose of using as functional food. The pH of medium was slightly changed with decrease then increase again, and reached about 6.0 when cultivation process ends. The biomass of mycelium was gradually increased until about 11 days of cultivation with about 30 g/L of dried biomass and the content of of sugar reduced in medium decreased from 40 g/L to 6 g/L.

Determination of morpholine residues in apples by liquid chromatography tandem mass spectrophotometry (LC-MS/MS)

Morpholine is an emulsifier that is normally used as a protective wax coating on the surfaces of fruit and vegetable. In order to keep fruits fresh, extend their shelf-life, against insect and fungal contamination for a long time, morpholine has been widely applied despite of the reported carcinogenic potential in previous studies and export prohibition in many countries. A highly sensitive method has been developed for the determination of this food additive in fruits using ultra-performance liquid chromatography tandem mass spectrophotometry. By using 1 % acetic acid in methanol for extraction and analyzing with binary ammonium formate 20 mM and acetonitrile, the method has been applied successfully to determine morpholine residues in apple samples collected at local markets in Hanoi, Vietnam. The good coefficient correlation was achieved in the linear range of 5 - 300 µg/L (R2 = 0.9998). The low limit of detection (LOD) and limit of quantification (LOQ) were 2 µg/kg and 5 µg/kg, respectively. The recoveries of morpholine were 83 – 108 % over three spike levels 20 - 60 μg/L for apple, peel and pulp matrices. The repeatability (RSDr %) was 1.1 % for apple matrix, 2.36 % for peel and 3.67 % for pulp. The reproducibility values (RSDR %) were 1.49, 3.50 and 4.08 % for apple, peel and pulp, respectively. This method could be further performed in different type of fruit and vegetable comiditities to determine the morpholine content.

Capillary electrophoresis with capacitively coupled contactless conductivity detection: Recent applications in food control

Food quality control has become much more important during the last decade and demanded the development of robust, efficient, sensitive, and cost-effective analytical techniques. Capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) is a powerful separation method based on the different migration time rate of components in the background electrolyte solution, and it is suitable for all charged ions. There is a large number of compound groups in food that can be determined by the CE-C4D method, such as amino acids, biogenic amines, fatty acids, food additives, sweeteners, and nutrients. This paper provides an overview of recent applications of the CE-C4D in food analysis over the last decade. General conclusions and future prospects of applicability of the CE-C4D method in food analysis are presented.

Knowledge, practices of food safety of establishment owners, food processors, and customers to prevent the Covid-19 pandemic at foodservice businesses in Son La city in 2020

Ensuring food safety for foodservice businesses is extremely necessary during the current complicated situation of the Covid-19 pandemic. This study has evaluated the knowledge and practices on food safety of establishment owners, food processors, and customers to prevent the Covid-19 pandemic at foodservice businesses in Son La city in 2020. The results show that over 75 % of establishment owners knew regulations to ensure food safety in the prevention of the Covid-19 pandemic, and 100 % of establishment owners were trained in disseminating and guiding pandemic prevention documents. Food processors who have good knowledge and practices of regulations of the Ministry of Health on ensuring food safety to prevent Covid-19, such as wearing masks when working, keeping contact distance with food, washing hands, disinfecting correctly, and do not gather in large numbers in production facilities have reached a high rate of over 90 %. All customers know about the 5K regulations. It is necessary to strengthen the propaganda to ensure food safety to prevent the Covid-19 pandemic so that the subjects can better understand the regulations of the Government, the Ministry of Health, Departments on ensuring food safety and prevention of the Covid-19 pandemic, and good practices of the above regulations.

Determination of myo-inositol content in milk by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD)

A method to determine inositol content in milk using high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was developed and validated. Samples were hydrolyzed with 10 mL HCl in a vacuum oven at 120oC, prolonging 6 h. Hydrolyzed samples were neutralized to a pH from 6 to 7.5 before analysing in an HPAEC-PAD system. The analytical program used Dionex CarboPacTM MA1 column (4 × 250 mm) with a mobile phase of a gradient program including NaOH 50 mM and NaOH 1M. The method was validated following AOAC guidelines: selectivity, linear range from 0,01 to 20 mg/L with a coefficient (R) 0.9998, the recoveries in the range of 99 - 102%, and repeatability with RSD under 1.8%. The limit of detection (LOD) and the limit of quantification (LOQ) of inositol were 0.047 µg/g and 0.155 µg/g, respectively. The method has been applied to determine of inositol content in milk samples with content ranging from 22.5 mg/100g to 64.7 mg/100g.

Developing an electrochemical aptasensor using a specific aptamer to detect neomycin antibiotic in milk

Milk and dairy products, often considered healthy and nutritionally balanced natural foods, include essential nutrients for all ages and are an important part of the daily diet. However, the indiscriminate use of antibiotics, more than the allowable dose, and improper purposes makes food and animal products in general and dairy at risk of harming human health. Sensitive consumers may experience allergies or even more severe health problems. Antibiotics are left over for a long time, and it will lead to antibiotic resistance, making it difficult for people to control diseases and causing many consequences in the future. There are many modern methods proposed to detect antibiotics in food. One of the main methods is the electrochemical method. In this study, we used aptamer Neo6 and gold nanochip to fabricate an electrochemical aptasensor capable of determining neomycin residues in milk with a linear range of 10 - 3,000 ng/mL as determining the accuracy of the neomycin residues in milk. The sensitivity and specificity of the aptasensor are quite high. In addition, we initially compared over 20 milk samples supplemented with antibiotics, showing similar results with those analyzed by LC-MS/MS method.

Determination of antioxidant capacity in some foods by oxygen radical absorbance capacity (ORAC)

Oxygen radical absorbance capacity (ORAC) assay has been applied to determine the Hydrophilic – ORAC index in food. The method measures antioxidant scavenging activity against peroxyl radical induced by 2,2′-azobis(2-amidino-propane) dihydrochloride (AAPH) at 37ºC, used fluororescein as the fluorescent probe. The antioxidant capacity is measured by assemssing the fluorescence decay curve (AUC) of the sample as compared to that of the blank in which no antioxidant is present. Results expressed in ORAC units, equivalent to micromole Trolox per 100 grams sample (Trolox equivalent). The method was shown with high selectivity, a wide linear range, from 5 to 50µM Trolox with linear coefficient R2 = 0.9987. The recovery from 93.2% to 104.4% and repeatability (RSD) was less than 6.60%. The limits of detection and quantitation were 5 and 10µM Trolox, respectively. The method has been applied to determine of H-ORAC index in 65 samples including vegetables, fruits, vegetable products and health supplements with content ranging from 720 µM TE/100g to 310878 µM TE/100g.