A method has been developed for the separation of anthocyanins and anthocyanidins with high performance liquid chromatography (HPLC). Experimental designs were applied for multivariate optimization of the HPLC experimental conditions with using response surface methodology (RSM). Three independent factors, namely formic acid concentration, initial ratio of acetonitrile in gradient program and flow rate, were used to design mathematical models. The responses were resolutions of four peak couples which were the most difficult to separate including: pelargonidin-3-glucoside and delphinidin, delphinidin and peonidin-3-glucoside, peonidin-3-glucoside and malvidin-3-glucoside, peonidin and malvidin. Variance analysis proved a chosen model was highly fit and the RSM method yielded good results in improving separation of anthocyanins and anthocyanidins. The optimized HPLC parameters were as follows: C18 column (250 mm × 4.6 mm × 5 µm), mobile phase is FA 10 % and ACN used as a gradient; flow rate 0.8 mL.min-1. Using these optimum conditions, separation of compounds with good resolutions and a run time of less than 30 min were archived. The results for method validation satisfied the requirement of AOAC, linearity range from 0.2-10 ppm with R 2 ≥ 0.9955, LOD from 0.05-0.1 mg/kg, RSD from 4.79-6.45 % and the recovery is from 85.4-109.6 %. The method was applied to determone anthocyanins and anthocyanidins in some fruits and vegetables samples with the content of anthocyanidins being from 5.74-218.27 mg/100g. Anthocyanins primarily concentrate in peel of fruits and vegetables, black bean peel contains most anthocyanins.

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A risk assessment study of 6 types of food additives (including benzoates, sorbates, cyclamate, saccharin, tartrazine, and sunset yellow) in Vietnamese diets was conducted based on the food consumption research and food additives concentration followed by the guideline of World Health Organization. Surveys on food consumption and food sampling were conducted in 6 provinces including Ha Noi, Ho Chi Minh, Thua Thien Hue, Nam Dinh, Tay Ninh and Quang Tri. The survey results have determined the amount of food consumed for each different food product groups on different age groups. Test results of 6 food additives including benzoates, sorbates, saccharins, cyclamates, tartrazine and sunset yellow FCF using HPLC method show that benzoates and sorbates are the two most discovered groups of substances in the tested samples. The highest concentrations of these compounds were on jelly, soft drinks, ground meat, chilli sauce … Types of food additives used as sweeteners are common in dried fruits, jam; the cyclamate content was very high in these two product groups. The colouring agents content were at a much lower level, mainly found in chili sauce. Risk assessment results show that total intake of sorbate and benzoate in the group of children under 5 years old were the highest value, which was 38 % of ADI. For all other age groups, the risk ranged from 10.6 to 34.0 % ADI for benzoates and from 0.56 to 1.8 % ADI for sorbates. For the remaining 4 food additives, total consumption was much lower than their ADIs. With the assumption that people used all types of food, 0.8 % of the population had the intake of benzoate exceed its ADI.

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Contamination of antibiotic-resistant bacterial pathogens in raw food is becoming an increased health risk in numerous countries, including Vietnam where raw herbs and vegetables are used daily in many dishes as a flavor enhancer and a source of vitamin and nutrients. However, raw vegetables can also be a reservoir of various foodborne pathogens such as Pseudomonas spp. and Enterobacteriaceae. In this study, we evaluated the extent of Pseudomonas spp. contamination in 180 ready-to-eat (RTE) vegetables samples from restaurants in Hanoi, examined their antibiotic susceptibility profiles and determined the ability to produce β-lactamase enzymes of Pseudomonas spp. strains. Our results showed that 21.67 % (n = 39) of ready-to-eat vegetables samples in Hanoi were contaminated with Pseudomonas spp.. Of those, sixteen samples were determined to be β-lactamase producing strains including Pseudomonas putida, P. mendocina and P. aeruginosa. Further analysis revealed six strains (37.50 %) producing extended spectrum β-lactamase (ESBL) enzyme, five strains (31.25 %) producing ampC β-lactamase enzyme and five strain (31.25 %) producing both ESBL and ampC β-lactamases. It can be concluded that ready-to-eat vegetables in Hanoi would be a source of contamination of β-lactamase producing Pseudomonas spp. that could pose a threat to public health in the community.