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The objective of this study was to determine the β-CN phenotypes in cow milk collected from HF and cross-bred HF dairy cattle in Phu Dong, Vietnam. In total, 85 samples of raw milk were collected from 85 individual cows. Beta-casein (β-CN) phenotypes in cow milk were determined using ultra-high performance liquid chromatography coupled to high resolution mass spectrometry (UHPLC-HRMS). The results showed that three β-CN variants A1, A2 and I were detected and identified in the milk samples. Five β-CN phenotypes A1A1, A1A2, A1I, A2A2 and A2I were found with percentages of 0.035, 0.400, 0.059, 0.482 and 0.024, respectively. The higher proportion of β-CN phenotype A2A2 compared to other phenotypes was expected because of changes in dairy cow breeding in Phu Dong, Vietnam.

Beta-casomorphin peptides including beta-casomorphin 5 (β-CM5) and beta-casomorphin 7 (β-CM7) in raw cow milk were analyzed using a liquid chromatography-tandem mass spectrometry (LC-MS/MS). Milk samples were acidified with HCl followed by centrifuged and cleaned-up using solid-phase extraction (SPE). The eluents were evaporated to dryness and subsequently reconstituted with methanol. Limits of detection (LOD) were 0.32 ng/g for β-CM5 and 0.24 ng/g for β-CM7 and limits of quantification (LOQ) were 1.06 ng/g and 0.69 ng/g for β-CM5 and β-CM7, respectively. Recoveries ranged from 89.7% to 99.4% for β-CM5 and from 96.3% to 98.9% for β-CM7. Intra-day precision was ranged between 7.3% and 22.7% for β-CM5; and 4.5% and 7.3% for β-CM7, meanwhile inter-day precision resulted 7.3%–16.5% for β-CM5 and 9.3%–12.8% for β-CM7. The concentration of β-CM5/7 was analyzed in different milk samples. β-CM7 was detected in 21 out of 30 samples and ranged from 0.76 to 8.41 ng/g milk, while β-CM5 was unequivocally identified in 3 samples, its concentration was 0.4–0.64 ng/g. This is the first report to describe the natural occurrence of β-CM5/7 in raw milk using LC-MS/MS. The present study provides evidence of β-CMs, especially β-CM7 that can be released in raw milk from different breeds.

Cilj ove doktorske disertacije je bio razvoj brzih i pouzdanih voltametrijskih metoda zasnovanih na primeni jednostavnih i savremenih elektroda/senzora na bazi ugljeničnih materijala (ugljenične paste napravljene od grafitnog praha i parafinskog ulja i štampanih ugljeničnih elektroda) za određivanje H 2O2 u odabranim složenim model i realnim uzorcima. U tu svrhu, ispitana je primenljivost različitih radnih elektroda. Amperometrijska metoda zasnovana na elektrodi od ugljenične paste (CPE) zapreminski modifikovane sa 5% (m:m) MnO2 je, pri optimizovanim uslovima i pri radnom potencijalu od 0,40 V u odnosu na zasićenu kalomelovu elektrodu (ZKE) u fosfatnom puferu pH 7,50 kao pomoćnom elektrolitu, omogućila kvantifikaciju H 2O2 u opsegu koncentracija od 1,4 do 65 µg mL -1 sa relativnom standardnom devijacijom (RSD) manjom od 10%. Ova metoda je primenjena za određivanje sadržaja H 2O2 u uzorcima podzemne vode iz centralnog Banata (Pokrajina Vojvodina, Srbija) tretirane Fentonovim (Fe 2+ i H 2O2 ) i Fentonu-sličnim (Fe 3+ i H 2O2 ) reagensima u cilju uklanjanja prirodnih organskih materija (POM) pri čemu su korišćene različite početne koncentracije gvožđa i različiti odnosi molarnih koncentracija gvožđa i H 2O2 . Utvrđeno je da oksidaciono stanje gvožđe (Fe 2+ ili Fe 3+) i molarni odnos jona Fe i H 2O2 utiču na stepen potrošnje/razgradnje H 2O2 u podzemnoj vodi sa visokim sadržajem POM. Takođe, u slučaju Fentonu-sličnog procesa, za sve početne koncentracije Fe 3+ i H 2O2 , signifikantna količina H 2O2 ostaje neiskorišćena, što ukazuje na nižu efikasnost ovakvog sistema u poređenju sa Fentonovim procesom.Štampana ugljenična elektroda (SPCE) zapreminski modifikovana sa MnO 2 kao medijatorom je primenjena za određivanje sadržaja H 2O2 u toku Fentonovog (Fe 2+ , H2O2 ) i vidljivom svetlošću potpomognuto, The aim of this doctoral dissertation was the development of fast and reliable voltammetric methods based on the application of simple and contemporary electrodes/sensors based on carbonaceous materials (carbon paste made of graphite powder and paraffin oil and screen printed carbon electrodes) for the determination of H 2 O2 in the selected complex model and real samples.For this purpose, applicability of different working electrodes was investigated.The amperometric method based on carbon paste electrode (CPE) bulk- modified with 5% (m:m) MnO 2 , under optimized conditions, with a working potential of 0.40 V vs. the saturated calomel elect rode (SCE) and a phosphate buffer solution (pH 7.50) as supporting electrolyte, enabled the quantitation of H 2 O2in the concentration interval from 1.4 to 65 µg mL −1 with a relative standard deviation (RSD) of less than 10%. This meth od was applied for the determination of the H 2 O2 consumption in samples of groundwater fro m the Central Banat region (Province of Vojvodina, Serbia) treated by the Fenton (Fe 2+ and H 2O2 ) and Fenton- like (Fe 3+and H 2O2 ) reagents to remove natural organic matter (NOM) at differentinitial concentrations of iron species, and of their molar ratios to the initial concentration of H2O2 . It was found that the form of Fe (Fe 2+ or Fe 3+ )and the molar ratio to H 2O2influenced the degree of the H 2O2 decomposition in the groundwater with high NOM content. Besides, in the case of the Fenton-like process, for all initial doses of Fe 3+ and H 2 O2, a sign ificant amount of H 2 O2 remained unused, whi ch also indicates a lower efficiency of such system compared to the Fenton process. Screen printed carbon electrode (SPCE) bulk-modified with MnO 2 as a mediator was applied for amperometric determination of the H 2 O2 content during the Fenton (Fe 2+ , H 2 O2 ) and visible light-assisted , photo-Fenton (Fe 2+ , H 2 O2

A DNA oligonucleotide array for duplex pathogen detection on a DVD platform is developed. The assay involves hybridization of PCR products and optical detection using compact disc technology. Different DNA array constructions for attachment of synthetic oligonucleotides on to DVD surface are evaluated, finding that streptavidin-biotin coupling method yielded the highest sensitivity in combination with enzymatic signal amplification. Issues of importance for the DNA array construction such immobilized probes design, PCR product labeling strategy and composition of the hybridization buffer were addressed. The methodology was proved scoring single nucleotide polymorphisms with high selectivity. The assay capability was also demonstrated by the identification of two pathogenic microorganisms in powder milk samples. In fifty minutes, the DVD-array system identifies Salmonella spp. and Cronobacter spp. (previously named Enterobacter sakazakii) precise and simultaneously with a sensitivity of 100 and 102 cfu/mL, respectively, in infant milk. Results were in good agreement with those obtained by quantitative real-time PCR. © 2012 Elsevier B.V. All rights reserved.