Determination of lead and cadmium in milk by electrothermal atomic absorption spectrophotometry

The concentration of lead and cadmium in different kinds of milk samples (powdered, infant formula, market, buffalo, condensed and human) were determined using electrothermal atomic absorption spectrophotometric technique. Among all the varieties of milk analysed, condensed milk was found to contain much higher amount of lead. Human milk as expected was found to have lowest concentration of these elements. The results were compared with the reported values of other countries. Daily intake of these toxic elements by adults and babies up to the age of six months through the consumption of various types of milk was estimated and compared with the tolerance levels.     

Determination of Danofloxacin and Marbofloxacin in Milk Samples by Micellar Liquid Chromatography with Fluorescence Detection

Abstract

A simple, rapid, and sensitive analytical method has been developed for the determination of two fluoroquinolones, danofloxacin and marbofloxacin, in bovine milk samples. Separation and quantification were performed by micellar liquid chromatography with fluorescence detection (MLC?FD), using sodium dodecyl sulfate (SDS) as a surfactant. The influence of the principal factors, namely, the micelle concentration, the amount of organic modifier, tail‐reducing agents, the pH, and the temperature were studied. The suitable condition was found to be 75 mM SDS?10 mM phosphate buffer–18 mM tetrabutylammonium bromide/3% (v/v) 1‐propanol at pH 3.0 for the separation of marbofloxacin, danofloxacin, and tosufloxacin (internal standard) in about 20 min. The linear concentration range of application was 1.8–30.0 ng · mL^?1 for danofloxacin and 16–120 ng · mL^?1 for marbofloxacin, and the relative standard deviation ranged between 4.9 and 2.7%. The limit of detection found for danofloxacin was 0.5 ng · mL^?1 and 5 ng · mL^?1 for marbofloxacin. These values were lower than the maximum residue limits (MRLs) established by the European Union for these compounds in bovine milk. It was applied to check the eventual existence of these compounds above these limits on commercial milk samples. The validation method was completed with spiked milk samples. Recovery levels obtained were 90.3–108.2%.     

Simple Multiresidue Determination of Fluoroquinolones in Bovine Milk by Liquid Chromatography with Fluorescence Detection

Abstract

A simple and sensitive method for the simultaneous determination of five fluoroquinolones (ciprofloxacin, enrofloxacin, danofloxacin, difloxacin, and sarafloxacin) in bovine milk was developed. Protein precipitation from milk samples was achieved by the addition of acetonitrile and o‐phosphoric acid. Acetonitrile was removed with dichloromethane, leaving the fluoroquinolones in the acid aqueous extract. The aqueous extract was analyzed by liquid chromatography with fluorescence detection (LC–FD). The mobile phase was composed of acetonitrile and 10 mM citrate buffer solution of pH 4.5, with an initial composition of acetonitrile‐water (12∶88, v/v) and using linear gradient elution. Norfloxacin was used as an internal standard. The limits of detection found ranged from 1 to 6 ng · mL^?1 and were below the maximum residue limits (MRLs) established by the European Union. The proposed method was applied to the determination of these compounds in different bovine milk samples. Method validation was carried out by a recovery assay.     

A New First-Derivative Photochemically-Induced Fluorescence Spectrometric Method for the Determination of Sulfapyridine in Milk

Abstract

A new first-derivative photochemically-induced fluorescence (D-PF) method is proposed for the determination of sulfapyridine (SPY) in milk. An 60:40 v/v ethanol-water medium and a 8-min UV irradiation time were selected for D-PF measurements. The method is suitable for SPY concentrations ranging from 0.1 to 0.6 ppm. Limits of detection are comprised between 6 and 21 ppb. Recoveries between 95 and 102% are found. This new D-PF method is remarkably simple, rapid, precise, and it allows one to determine low levels of SPY in milk without prior separation.     

Storage Stability of Antioxidant in Milk Products Fermented with Selected Kefir Grain Microflora

The aim of the study was to assess the antioxidant potential of goat’s milk and whey from goat’s milk fermented with selected bacteria strains from kefir grain (L. plantarum, L. fermentum, L. rhamnosus and L. acidophilus) with regard to fermented cow’s milk with the same bacteria strains. The assessment of antioxidant potential was made by ABTS, DPPH, TPC and FRAP methods. The work also assessed metabolic activity of tested lactic acid bacteria using measurement of electrical impedance changes in the growing medium. The highest values describing the antioxidant potential were found for fermented milk by L. acidophilus. It was also found that the time of cooling storage causes significantly increasing the antioxidant potential of most analyzed samples. Metabolic activity of tested lactic acid bacteria was the highest for cow’s milk. The course of curves for goat’s milk and whey from goat’s milk was similar, which confirms the differences between cow and goat milk.     

Effect of Vitamin C Source on Its Stability during Storage and the Properties of Milk Fermented by Lactobacillus rhamnosus

The enrichment of commonly consumed foods with bioactive components might be helpful in promoting health and reducing the risk of disease, so the enrichment of probiotic fermented milk with vitamin C can be considered appropriate. The effect of vitamin C addition depends on the source of origin (rosehip, acerola and ascorbic acid in powder form) on the growth and survival of Lactobacillus rhamnosus and the quality of fermented milk on the 1st and 21st day of storage was analyzed. The pH, total acidity, vitamin C, syneresis, color, texture profile and numbers of bacterial cells in fermented milk were determined. The organoleptic evaluation was also performed. The degradation of vitamin C in milk was shown to depend on its source. The lowest reduction of vitamin C was determined in milk with rosehip. The least stable was vitamin C naturally found in control milk. The addition of rosehip and acerola decreased syneresis and lightness of milk color, increasing the yellow and red color proportion. In contrast, milk with ascorbic acid was the lightest during the whole experimental period and was characterized by a very soft gel. The growth of Lactobacillus rhamnosus during fermentation was most positively affected by the addition of rosehip. However, the best survival of Lactobacillus rhamnosus was demonstrated in milk with acerola. On the 21st day of storage, the number of L. rhamnosus cells in the control milk and the milk with vitamin C was >8 log cfu g⁻¹, so these milks met the criterion of therapeutic minimum. According to the assessors, the taste and odor contributed by the addition of rosehip was the most intense of all the vitamin C sources used in the study.     

Presence of pesticides in breast milk and infants’ formulae in Himachal Pradesh,India

This study documents the levels of pesticide residues in milk samples of mothers from Himachal Pradesh, India, and time trend comparison of pesticide load based on various studies conducted around the world. The regional difference in xenobiotic levels of breast milk varied with demographic characteristics of mothers and altitudinal variations. The single or multiple pesticides contamination of p,p′-DDE, p,p′-DDT and chlorpyrifos was revealed in 27.45% mothers’ milk samples. Among these p,p′-DDE was the major contaminant found in 26.79% samples followed by p,p′-DDT (1.31%) and chlorpyrifos (0.65%). However, residues of other 26 pesticides comprising organochlorines, organophosphorus and synthetic pyrethroids included in this study were below detectable limit (BDL). The determination of a low DDT/DDE ratio (0.050) indicated past exposure of mothers to DDT from the environment. The pesticide residues level in samples drawn from 14 branded infant formulae was BDL. The calculated infants’ daily intake (DI) of DDT was 0.0015 mg kg^?1 body weight per day compared with a decade-old study (0.021 mg kg^?1 body weight per day) suggesting a sharp decline in the residue levels of these pesticides in the Himalayan region. The trend comparison with past studies conducted around the world indicate a decline in the levels of organochlorine pesticide residues in mothers’ milk and further drop of DI in infants. However, such comparisons confer very limited utilisation of data generated on pesticide load in mothers’ milk and simultaneous infants’ DI due to lack of proper research protocol.     

Synthetic Potential of Fucosyltransferase III for the Synthesis of Fluorescent‐labeled Milk Oligosaccharides

Various fundamental biologic roles of milk oligosaccharides have been recognized; however, their structure‐affinity relationship is still not fully revealed. Herein, we describe the synthesis of the fluorescent‐labeled milk oligosaccharides 3‐(5‐dimethylaminonaphthalene‐1‐sulfonylamino)propyl β‐D‐galactopyranosyl‐(1→3)‐[α‐L‐fucopyranosyl‐(1→4)]‐2‐acetamido‐2‐deoxy‐β‐D‐glucopyranoside (1) and 3‐(5‐dimethylamino‐naphthalene‐1‐sulfonylamino)propyl β‐D‐galactopyranosyl‐(1→3)‐[α‐L‐fucopyranosyl‐(1→4)]‐β‐D-glucopyranoside (2) as useful tools for synthetic, analytic, and biologic applications. For the fucosylation of lactose and lacto‐N‐biose, the chemical and the enzymatic syntheses using fucosyltransferase III were compared.     

Synthesis of Molecularly Imprinted Polymer for Sensitive Penicillin Determination in Milk

Abstract

Penicillin G (PG) in milk is unsafe for human and is a big problem for the foods industry. Hence, the better analytical and eliminative techniques are demanded. We investigated a PG molecular imprinted polymer (MIP), which can sensitively detect and extract the PG from milk and other samples. The MIP synthesis involved a β-lactam antibiotics PG, methacrylic acid (MAA) and dimethyl formamide (DMF). Its properties were analyzed with Scatchard plot, which showed that there were two affinity sites of the PG polymer. The first equilibrium dissociation constant of the high-affinity binding sites Kd₁ was 1.14 × 10^?4 mol/L and the binding capacity Q_max1 was 46.01 µmol/g; the second equilibrium dissociation constant of the low-affinity binding sites Kd₂ was 1.35 × 10^?3 mol/L and the binding capacity Q_max2 was 72.55 µmol/g. Furthermore, two PG determination methods using the polymer were developed. The first was carried out quantitatively with a spectrophotometer and the detection limit was 1 ppm. The other one was the combination of the MIP particles with milk fermentation for PG analysis and the sensitivity was 10 ppb.     

Analysis of Free Amino Acids and Protein Contents of Mature Human Milk from Turkish Mothers

Abstract

This study was designed to evaluate free amino acid (FAA) composition and total protein in mature human milk from Turkish mothers. Free amino acid concentrations in mature human milk were determined in all subjects using a high‐performance liquid chromatography (HPLC) with postcolumn derivatization system, with a fluorescence detector. Total protein content was determined by the classical biuret method. Total protein concentration was found to be 1.3±0.4 mg/dl. Glutamic asid plus glutamine is the most abundant amino acid (1275 µmol/L), followed by taurine (353 µmol/L) and alanine (261 µmol/L). Glutamic acid plus glutamine accounts for the most free amino acids in mature human milk and their sum represents 40% of total FAA. On the other hand, some amino acid derivatives such as citrulline, ethanolamine, ammonium, ornithine, ortophosphoserine, and phosphoethanolamine, not usually a part of protein, are determined and this fraction represented ～21% of the total FAA in mature human milk in the present study.     

Etude Des Teneurs En Cuivre,Zinc, Et Arsenic Dans La Poudre De Lait Par Activation Neutronique

Abstract

Copper, zinc and arsenic have been determined in dehydrated milk powder by neutron activation analysis. Irradiation 13 of ashed milk powder in a flux of 10¹³ thermal neutrons per second per sq. cm. was followed by: elution through an anion exchange resin; solvent extraction of copper with dithizone into a chloroform phase; precipitation and subsequent redissolution of arsenic as As₂, S₃ and as a polysulfide, respectively. The determinative step involved gamma ray spectroscopy of the isotopes Zn⁶⁷, Zn⁶⁵, Cu⁶⁴ and As⁷⁶.     

Detection of bacterial contaminated milk by means of a quartz crystal microbalance based electronic nose

Headspace analysis by means of sensor arrays has been successfully applied to a wide range of qualitative applications. In this study, a six element array of coated Quartz Crystal Microbalance (QCM) sensors was used for the headspace analysis of milk volatiles. The sensors were exposed to uncontaminated samples of milk and samples contaminated with Pseudomonas fragi (Ps. fragi) or Escherichia coli (E. coli). Principal component analysis (PCA) was used to analyse the sensor array responses. No discrimination between uncontaminated milk samples and those contaminated with Ps. fragi was observed. This can be explained by Ps. fragi being a poor fermenter of milk. However, encouraging results were found for the discrimination between the milk samples and those contaminated with E. coli.This revised version was published online in November 2005 with corrections to the Cover Date.     

Isolation of Lipophilic Persistent Organic Pollutants From Human Breast Milk

Background: Lipid removal from biological samples can be achieved by addition of concentrated sulfuric acid. However, certain persistent organic pollutants (POPs) such as chlorophenols are decomposed by sulfuric acid treatment and, thus, a more gentle lipid reduction method is needed for extraction of many environmental contaminants from biological samples. Membrane dialysis extraction (MDE) is a non-disruptive method to extract POPs from biological matrices.

Methods: Human breast milk samples were spiked with radiolabelled p,p′-dichlorodiphenyl trichloroethane ([C-14]-DDT) as a POP proxy and extracted using solid phase extraction (SPE). The extracts obtained were dialyzed by MDE in low-density polyethylene tubings containing a mixture of n-hexane and dichloromethane for 24 h, 48 h, or 72 h.

Results: The lipid content was reduced by 86.2% after one dialysis cycle of 24 h using MDE, and 87.1% recovery of the [C-14]-DDT standard was obtained. The DDT recovery could be further increased up to 96.3% and 98.1% by repeating the dialyses for one or two more cycles, respectively. However, the increased [C-14]-DDT recovery includes a concomitant increase in lipid carryover from 13.8% with one dialysis cycle to 22.1% with three cycles.

Conclusion: An SPE procedure for extracting POPs from breast milk and dialytic conditions for isolation of the extracted POP with minimal lipid carryover was established. The method is nondestructive and acceptable recoveries can be obtained within a single solvent shift as demonstrated by spiking standards. The lipid carryover was minimized, and the method may be considered for lipid removal before HPLC or GC analysis of environmental contaminants.     

Determination of organochlorine pesticides (OCPs) in breast milk from Rio Grande do Sul,Brazil, using a modified QuEChERS method and gas chromatography-negative chemical ionisation-mass spectrometry

ABSTRACT

The food chain is the main source of exposure to humans by organochlorine pesticides (OCPs) due to the bioaccumulation. Breast milk can accumulate OCPs, so this matrix is often used as an environmental bioindicator. The currently available methods for the determination of several OCPs and metabolites in breast milk involve, in general, multi-step sample preparation and quantification techniques with low selectivity, high cost and much time and labour. Thus, a fast and efficient method based on sample preparation using the quick, easy, cheap, effective, rugged and safe (QuEChERS) method combined with gas chromatography coupled to mass spectrometry with negative chemical ionisation (GC-NCI-MS) was developed, validated and applied for determination of 16 OCPs and metabolites in breast milk samples. The extract was cleaned by dispersive solid-phase extraction (d-SPE) using MgSO₄ and C18, evaporated in a Turbovap® system, redissolved and analysed by GC-NCI-MS. The method was validated showing acceptable recoveries (72–118%) and precision (RSD <19%). Method limits of detection (LODs) and quantification (LOQs) ranged from 0.75 to 7.5 ng g^?1 and from 2.5 to 25 ng g^?1 lipid, respectively. The method was successfully applied to 20 samples of breast milk from different regions of the Rio Grande do Sul state, Brazil, of which 75% contained residues below the LOQs.     

The Influence of Bacteria Causing Subclinical Mastitis on the Structure of the Cow’s Milk Microbiome

Mastitis is the most expensive disease of dairy cattle across the world and is the main reason for the use of antibiotics in animal husbandry. The aim of this study was to analyze the microbiome of raw milk obtained from a semi-subsistence farm located in the Kuyavian–Pomeranian Voivodeship in Poland. Milk from healthy cows and from cows with subclinical mastitis was analyzed. The following pathogenic bacteria were found in milk from individuals with subclinical mastitis: Escherichia coli or Streptococcus agalactiae. The composition of drinking milk was assessed on the basis of 16S rRNA gene sequencing using the Ion Torrent platform. Based on the conducted research, significant changes in the composition of the milk microbiome were found depending on the physiological state of the cows. The microbiome of milk from healthy cows differed significantly from the milk from cows with subclinical mastitis. Two phyla dominated in the milk from healthy cows: Firmicutes and Proteobacteria, in equal amounts. On the contrary, in the milk from cows with diagnosed subclinical mastitis, one of the types dominated: either Firmicutes or Proteobacteria, and was largely predominant. Moreover, the milk microflora from the ill animals were characterized by lower values of the determined biodiversity indicators than the milk from healthy cows. The presence of pathogenic bacteria in the milk resulted in a significant reduction in the share of lactic acid bacteria in the structure of the population of microorganisms, which are of great importance in the production technology of regional products.     

Comparison of Phosphonic and Pyrophosphonic Acids as Collectors for the Cassiterite Flotation

Abstract

Styryl phosphonic acid (SPA) is a collector used in the industrial flotation of cassiterite, During its production from styrene and PCl₅ by-products are formed in different amounts. One of these is condensed SPA caused by uncomplete hydrolysis of the intermediary phosphonic acid chloride. Attempts were made to synthesize definite forms of condensed SPA in order to study their influence on the results of flotation. Conventional methods-partial hydrolysis of phosphonic acid chlorides or reaction of acid chlorides with the free acid-did not lead to the desired result. Diammonium salt of the pyro-SPA was obtained by the method of (1) using dehydration of phosphonic acid by heating with urea. A series of analogous aromatic pyro-phosphonic acids was synthesized. The hydrophobization effect on Sn0₂ surfaces was studied by microflotation tests in a modified Hallimond tube. Pyrophosphonic acids are more hydrophobic than the corresponding phosphonic acids. The results of the microflotation experiments were confirmed by batch flotation tests with a natural tin ore in a 2–1 cell. The Sn recovery was higher with the pyro compounds.     

Direct Determination of Mn in Breast Milk by GF AAS After Multivariate Optimization

Abstract

The procedure proposed in this work includes a 50% v/v dilution of breast milk with TRIS (hidroximetilaminometano 80% v/v) or MEA (monoetanolamina 20% v/v) solutions and the introduction of 20 µL samples or analytical solutions in a graphite furnace. The optimization of the instrumental conditions was made using multivariate tools (fractional factorial and central composite design planning). The accuracy was tested with certified reference material (Infant Formulat NIST® 1846) using the optimized conditions for each diluent. The accuracy has only been acceptable when TRIS was used. The method used to determine Mn in breast milk with a limit of detection of 0.28 µg L^?1 and a characteristic mass of 1.9 pg.     

Determination of total selenium and selenium distribution in the milk phases in commercial cow’s milk by HG-AAS

A procedure has been developed for determining the selenium in cows milk using hydride generation–atomic absorption spectrometry (HG-AAS) following microwave-assisted acid digestion. The selenium distributions in milk whey, fat and micellar casein phases were studied after separating the different phases by ultracentrifugation and determining the selenium in all of them. The detection limits obtained by HG-AAS for the whole milk, milk whey and micellar casein were 0.074, 0.065 and 0.075 g l^–1, respectively. The accuracy for the whole milk was checked by using a Certified Reference Material CRM 8435 whole milk powder from NIST, and the analytical recoveries for the milk whey and casein micelles were 100.9 and 96.9%, respectively. A mass balance study of the determination of selenium in the different milk phases was carried out, obtaining values of 95.5–100.8%. The total content of selenium was determined in 37 milk samples from 15 different manufacturers, 19 whole milk samples and 18 skimmed milk samples. The selenium levels found were within the 8.5–21 g l^–1 range. The selenium distributions in the different milk phases were studied in 14 whole milk samples, and the highest selenium levels were found in milk whey (47.2–73.6%), while the lowest level was found for the fat phase (4.8–16.2%). A strong correlation was found between the selenium levels in whole milk and the selenium levels in the milk components.     

Camel's Milk and Shubat from the Aral Region

Proteins of camel's milk and shubat were studied by electrophoresis. Their microelement compositions were determined. Electrophoresis showed two bands in camel's milk and several in shubat. It was found that Fe and Zn occur in greater quantities in both camel's milk and shubat than in cow's milk.     

The Raw Milk Microbiota from Semi-Subsistence Farms Characteristics by NGS Analysis Method

The aim of this study was to analyze the microbiome of raw milk obtained from three semi-subsistence farms (A, B, and C) located in the Kuyavian-Pomeranian Voivodeship in Poland. The composition of drinking milk was assessed on the basis of 16S rRNA gene sequencing using the Ion Torrent platform. Based on the conducted research, significant changes in the composition of the milk microbiome were found depending on its place of origin. Bacteria belonging to the Bacillus (17.0%), Corynebacterium (12.0%) and Escherichia-Shigella (11.0%) genera were dominant in the milk collected from farm A. In the case of the milk from farm B, the dominant bacteria belonged to the Acinetobacter genus (21.0%), whereas in the sample from farm C, Escherichia-Shigella (24.8%) and Bacillus (10.3%) dominated the microbiome. An analysis was performed using the PICRUSt tool (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) in order to generate a profile of genes responsible for bacterial metabolism. The conducted analysis confirmed the diversity of the profile of genes responsible for bacterial metabolism in all the tested samples. On the other hand, simultaneous analysis of six KEGG Orthologs (KO), which participated in beta-lactam resistance responsible for antibiotic resistance of bacteria, demonstrated that there is no significant relationship between the predicted occurrence of these orthologs and the place of existence of microorganisms. Therefore, it can be supposed that bacterial resistance to beta-lactam antibiotics occurs regardless of the environmental niche, and that the antibiotic resistance maintained in the population is a factor that shapes the functional structure of the microbial consortia.