Acid In Milk Samples Research Articles

Eco-friendly fluorescent detection method for Cu2+ ions combined with smartphone-integrated paper strip sensors based on highly fluorescent 2-aminoterephthalic acid in milk samples

The creation of smart, real-time sensing devices is crucial in food monitoring, though it continues to be a major challenge. Here, we report an eco-friendly fluorescent detection method for Cu2+ ions using 2-aminoterephthalic acid (NH2-H2BDC). Fluorescence (FL) quenching occurs at 425 nm under excitation at 330 nm, with detection limits (LOD) as low as 16.25 nM for Cu2+ ions. Additionally, a smartphone can visually and quantitatively detect Cu2+ ions by analyzing the RGB values on test paper. The results show high sensitivity, with a LOD of 11.07 μM. This work not only reveals fluorescent detection methods but also develops a convenient, low-cost, and portable smartphone-integrated paper strip for Cu2+ ion sensing. Two metrics, AGREEprep and BAGI, were employed to assess the method's environmental friendliness. The evaluation confirmed its exceptional eco-friendliness. This method marks a significant advancement for Cu2+ ion monitoring in diverse fields, especially food monitoring.

Comparison of the Effectiveness and Environmental Impact of Selected Methods for the Determination of Fatty Acids in Milk Samples

Determination of the fatty acid profile in milk samples is one of the most important in food analysis. There are many methodologies for FA determination. The conventional procedure for determining the FA composition of milk is isolation of fat or indirect methylation, trans-methylation, extraction of fatty acids, and analysis by gas chromatography. In this study, eight methods based on alkaline methylation were compared for the analysis of fatty acids in cow's milk. The response factors (RF) for GC analysis using FID were calculated. For most acids, RFs were close to 1, with the exception of short-chain fatty acids (C4:0-C8:0). To facilitate the selection of the method for the determination of fatty acids in milk samples, the methods were assessed using the environmental assessment tools of the analytical procedure: the Analytical Eco-Scale, Green Analytical Procedure Index (GAPI), and Analytical Greenness for Sample Preparation (AGREEprep). The method based on direct milk methylation received the highest scores. Omitting the lipid separation step has an impact on reducing the quantity of used toxic chemicals and reagents, and produces a smaller amount of waste, a much higher throughput, and a reduced cost analysis.

Voltammetric determination of lactic acid in milk samples using carbon paste electrode modified with chitosan-based magnetic molecularly imprinted polymer

Voltammetric determination of lactic acid in milk samples using carbon paste electrode modified with chitosan-based magnetic molecularly imprinted polymer

Electrochemical Study of Gold Microelectrodes Modified with PEDOT to Quantify Uric Acid in Milk Samples

AbstractA gold microelectrode (10 μm diameter) with an electropolymerized layer of poly(3,4‐ethylenedioxythiophene) (PEDOT) was used to quantify uric acid and investigate the antioxidant profile of milk and flavored milks. Comparisons were made with a bare gold microelectrode and a PEDOT‐glassy carbon macroelectrode (3 mm diameter). Two different electropolymerization processes were undertaken in an aqueous and an organic solution, and superior polymer growth was observed for PEDOT polymerized in lithium perchlorate/propylene carbonate. In the presence of a ferri/ferrocyanide redox couple, diffusion‐controlled redox peaks were observed with the PEDOT‐gold microelectrode rather than the plateau current typical of a bare microelectrode. Likewise, an anodic peak for uric acid was observed at the high surface‐area PEDOT‐gold microelectrode, with evidence for pre‐adsorption of uric acid at the electrode. The linear concentration range for uric acid standards was from 6 to 200 μM, and the limit of detection, limit of quantification, and sensitivity were determined to be 7 μM, 24 μM, and 397 μAμM−1cm2, respectively. Cyclic voltammograms of chocolate and espresso flavored milks exhibited significant contributions from the phenolic compounds present. Peak separation was more clearly defined using the PEDOT‐microelectrode compared to a PEDOT‐glassy carbon macroelectrode.

A spectrophotometric procedure for sialic acid determination in milk employing a flow-batch analysis system with direct heating

The quantitative determination of sialic acid can indicate the addition of cheese whey to milk. This work describes an automated procedure to determine sialic acid in milk samples using a flow-batch system analysis with direct heating. The sialic acid quantification was based on a reaction between the sialic acid and acid ninhydrin producing a stable compound with maximum absorption at 470 nm. The flow-batch system was designed using heating and spectrophotometric detection in the reaction chamber. Under the optimum experimental conditions, a linear response ranging from 1.0 to 10.0 mg L−1 sialic acid (R = 0.99 and n = 7), a detection (3σ criterion) and quantification (10σ criterion) limit estimated at 0.239 and 0.726 mg L−1, respectively, a relative standard deviation of 1.90% (n = 10) for a reference solution of 4.0 mg L−1 sialic acid and a sampling rate of 7 determinations per hour were achieved. Analysis of eleven milk samples, application of the t-test to the results found, and comparison with the official method provided no significant differences at a 95% confidence level. Compared to the official method, the proposed system reduced reaction time by 50%, temperature of the reaction by 30%, and diminished the consumption of reagents and samples by 90%. Thus, the use of the proposed system is an economically viable and environmentally friendly option for the determination of sialic acid in milk.

Effects of Sodium Bicarbonate on milk preservation

The present investigation was carried out to assess the effect of sodium bicarbonate (NaHCO3) on the keeping quality of raw cow milk. Milk samples were collected from Bangladesh Agricultural University (BAU) Dairy Farm and initial quality were evaluated using physical and chemical tests at Dairy Technology Laboratory of the Department of Dairy Science, BAU. Then, collected samples were preserved at room temperature (28- 30°C) with 0.0 (control), 0.3, 0.4 and 0.5 per cent NaCHO3. The quality of milk samples were measured at every two hours interval up to 6 hours, one hour interval upto 16 hours and thereafter every half an hour interval until spoilage. Initially, colour, flavour and texture of all milk samples were normal (100%), but with progressive storage time colour, flavour and texture of all samples deteriorated gradually, which was more rapid for control samples than that of the NaHCO3 treated samples. Acidity per cent of all samples increased gradually during storage period and the differences in acidity of milk samples in different treatments were significant (p<0.01). Control samples spoiled after 11¼th hours but that of 0.3, 0.4 and 0.5 percent NaHCO3 treated samples spoiled after 16¾th, 17¾th and 18¾th hours,, respectively. It may be concluded that NaHCO3 is the effective chemical neutralizing the acids produced by acid producing bacteria and can be used as a short term preservation of milk under rural condition of Bangladesh where scientific cooling or pasteurization facilities are not available.Res. Agric., Livest. Fish.5(1): 75-85, April 2018

Study of the inhibitory effect of ferulic acid on short-chain fatty acids in milk samples by dispersive liquid–liquid micro-extraction in combination with fluorescence derivatization

ABSTRACTA sensitive high-performance liquid chromatography (HPLC) method was developed to study the influence of ferulic acid on the formation of volatile fatty acids and lactic acid in milk and soybean milk samples. Volatile fatty acids were extracted by liquid–liquid micro-extraction using chloroform and acetonitrile as the extraction and disperser solvents, respectively. The analytes were derivatized with 2-(5-benzoacridine)ethyl-p-toluenesulfonate that showed excellent fluorescence property and made the sensitive HPLC analysis of short-chain fatty acids become possible. The optimized HPLC sensitivity was in the range of 1.1–1.9 µg L−1. Ferulic acid was added in milk and soybean milk samples to study its preservative effect. The results indicated that ferulic acid with concentration of 0.2% (m/v) could effectively reduce the formation of short-chain fatty acids.

Simultaneous Determination of Different Anions in Milk Samples Using Ion Chromatography with Conductivity Detection

The description of a simple method for simultaneous determination of chloride, nitrate, sulfate, iodide, phosphate, thiocyanate, perchlorate, and orotic acid in milk samples was outlined. The method involves the use of dialysis cassettes for matrix elimination, followed by ion chromatography on a high capacity anion exchange column with suppressed conductivity detection. The novelty of dialysis process was that it did not need any chemical and organic solvent for elimination of macromolecules such as fat, carbohydrates and proteins from milk samples. External standard calibration curves for these analytes were linear with great correlation coefficients. The relative standard deviations of analyte concentrations were acceptable both inter-day and intra-day evaluations. Under optimized conditions, the limit of detection (Signal-to-Noise ratio = 3) for chloride, phosphate, thiocyanate, perchlorate, iodide, nitrate, sulfate, and orotate was found to be 0.012, 0.112, 0.140, 0.280, 0.312, 0.516, 0.520, and 0.840 mg L −1 , respectively. Significant results were obtained for various spiked milk samples with % recovery in the range of 93.88 - 109.75 %. The proposed method was successfully applied to milk samples collected from Istanbul markets. The advantages of the method described herein are reagent-free, simple, and reliable.

Molecularly imprinted polymer cartridges coupled to liquid chromatography for simple and selective analysis of penicilloic acid and penilloic acid in milk by matrix solid-phase dispersion

A simple, fast and sensitive method for determination of the degradation products of penicillin (penicilloic acid and penilloic acid) in milk samples has been developed by combining selective surface molecularly imprinted matrix solid-phase dispersion and high performance liquid chromatography (SMIPs-MSPD-HPLC). The selected dispersant SMIPs had high affinity for penicilloic acid and penilloic acid in milk matrix and the obtained extract was sufficiently clean for direct injection for HPLC analysis without any interference from the matrix. The proposed SMIPs-MSPD-HPLC method was validated for linearity, precision, accuracy, limit of detection and limit of quantitation. Linearity ranged from 0.04 to 4 μg g−1 (correlation coefficient r2 > 0.999). Recoveries of penicilloic acid from milk samples at different spiked levels were between 79.8 and 90.3%, with RSD values within 5.2–7.4%, and the limit of detection and limit of quantitation values were 0.04 and 0.13 μg g−1, respectively. Recoveries of penilloic acid from milk samples at different spiked levels were between 77.4 and 86.2%, with RSD values within 3.1–6.4%, and the limit of detection and limit of quantitation values were 0.05 and 0.17 μg g−1, respectively. The developed SMIPs-MSPD-HPLC method was successfully applied to direct determination of penicilloic acid and penilloic acid in milk samples.

Fatty acid composition and fat content in milk from cows grazing in the Alpine region

The variation in the fat profile of pooled milk from cows grazing in pastures in June and July at 400–700 m and at 1400–2250 m of altitude was evaluated by gas chromatography and compared with that from cows stalled in barns and fed with a diet without fresh grass. The ratios unsaturated/saturated fatty acid in milk samples were 1.33, 1.71 and 1.69 in June and 1.21, 1.69 and 1.84 in July for cows fed with prepared diet, grazing at 400–700 m or grazing at 1400–2250 m, respectively. Analogously, the ratios (oleic plus stearic acid)/palmitic acid were, for the same group of cows, 0.59, 0.72 and 0.78 in June and 0.56, 0.73 and 0.81 in July. In milk from pastured cows, the percentage of oleic, vaccenic, rumenic and α-linolenic acids increased as a function of the altitude; instead, that of linoleic acid and of cis-12-octadecenoic acid decreased. The yield of fat was always highest in milk from 1400 to 2250 m of altitude (up to 3.6 g per 100 mL). For the milk collected in July at 1400–2250 m of altitude, it was observed a decrease in the percentage of decanoic (capric) and dodecanoic acids and an increase in pentadecanoic, stearic, arachidic and docosanoic (behenic) acids. Possible reasons for the differences observed in the milk samples were discussed.

English

The present study was conducted to evaluate the quality of milk from Rawalakot and its surroundings. Milk samples were collected from house hold animal, milkman and restaurant milk in order to assess the hygienic status of raw milk, which was collected from three different parts of the city, Rawalakot Azad Jammu and Kashmir. It was observed that the milk samples which were collected from house hold milk showed better quality compared to the other two sources. For the assessment of adulterants, clot-on-boiling (COB), alcohol perception and methyleneblue tests were conducted. In COB test, the result was 29% positive in house hold animal milk, 38% in milkman and 38% in restaurant milk; whereas, in COB test, results of milkman and restaurant milk were similar. The results of alcohol tests showed variation among the three sources of milk: in household animal milk (APT) it was 34%; 44% in milkman and 34% in restaurant milk. Methyleneblue test results show variation among the three sources; the mean values of A+, B+, C+ and D+ for HH were 29, 44, 17, 11 and 14%; 62, 11, 14% were recorded for MM; whereas 14, 33, 33 and 11%, in RM, respectively. The quality of milk was different in all three sources. Milk composition was assessed by specific gravity, fat % and acidity test. The result of Gerber test (fat% age) shows slight variation among the three sources of milk (7.00%, 6.31% and 5.55), respectively. The results of specific gravity were 0.128 g/ml for house hold, 1.027 g/ml for milkman and 0.125 g/ml for restaurant milk, respectively. All three sources showed low specific gravity than standards. The result of acidity test shows slight difference in all three sources of milk. The acidity of milk samples was recorded as 0.18 in house hold milk, 0.21 for milkman milk and 0.19 in restaurant milk. The acidity was higher than the standard values in both milkman and restaurant milk. In organoleptic test, the result was based on sensory evaluation and scoring system. The lowest value was 5.5 and highest value was 7.4. As the results show the HH animal milk was graded as good compared to the other two sources of milk. Key words: Organoleptic, adulterants, milk, acidity.

Validation of an Improved Method for Detection of Mycoplasma bovis in Milk

M. bovis and several other Mycoplasma spp cause intramammary, respiratory and joint infections that have serious economic consequences for the dairy industry (Gonzalez RN et al, 1994). Mycoplasma mastitis is resistant to treatment, therefore control of mycoplasma mastitis relies primarily on early detection and culling of infected animals to reduce transmission and herd prevalence. The current method of detection with culture is less than ideal because this group of fastidious organisms requires special enrichment media, CO2 supplemented incubation chambers with a positive or negative determination requiring an average of 10 days. Previously published molecular methods for the detection of Mycoplasma spp nucleic acids in milk samples have been demonstrated to have similar sensitivity to conventional culture methodology (Cai et al, 2005; Bashiruddin et al, 2005; McAuliffe et al, 2005). Such assays present several challenges beginning with the extraction of DNA from milk samples to the DNA amplification procedures which are technically complex. The goal of our research was to develop and validate a simple, efficient extraction process and couple it with a sensitive real-time PCR assay to detect M. bovis in bulk tank samples.

Assessment of benzoic acid levels in milk in China

Benzoic acid is the most commonly used preservative in foodstuffs. Although benzoic acid is generally recognized as safe (GRAS), adverse effects such as asthma, urticaria, metabolic acidosis and convulsions were observed at low doses in sensitive persons. Some weak clastogenic activity was noted in in vitro assays. The aim of our study was to determine the levels of benzoic acid in milk samples consumed in the city of Guangzhou, China. In this study, 142 samples of pasteurized milk (24), ultra high temperature milk (UHT, n = 45), milk powder ( n = 31) and infant formula ( n = 42) were analyzed by high performance liquid chromatograph (HPLC) with diode array detector (DAD) from October 2006 to January 2007. Benzoic acid was detected in 109 (76.8%) samples, ranging from 0.51 to 111 mg/kg. The LOD for benzoic acid was, respectively, 0.2 mg/kg in pasteurized and UHT milk, 2 mg/kg in milk powder and infant formula. The mean recoveries of spiked samples at 4 levels were 99.5 ± 3.1% in liquid milk, and 98.5 ± 4.3% in milk powder, respectively. The results show that benzoic acid widely occurs in milk and milk products in China at the low levels. The levels found are not high, and should not affect the general public; however, it may affect the infants and/or sensitive persons. Therefore, it is important to assess the levels of benzoic acid in milk in China. Meanwhile, it should be noted that the lowest percentage of positive samples in pasteurized milk probably results from the difference in the quality of raw milk, processing technical and storage condition of milk products.

LC-ion trap electrospray MS-MS for the determination of cyclopiazonic acid in milk samples.

An LC-ESI-MS (negative ions) method was developed for the determination of cyclopiazonic acid (CPA), a mycotoxin produced by many Aspergillus and Penicillium genuses, in milk samples. First, the acquisition parameters of the ESI mass spectrometer were optimised for deprotonated CPA and MS-MS measurements were performed, giving a fragmentation pattern. After this stage, LC separation was applied to milk extracts (with or without CPA spikes) by means of an aminic column, using the selective reaction monitoring (SRM) acquisition mode for MS detection. The CPA response was linear over three decades of concentration and an LOD of 5 ng mL(-1) was estimated; moreover, the extraction procedure produced almost quantitative recoveries of CPA from milk. Twenty different milk samples were analysed and three of them were found to be contaminated with CPA to various extents.

Flow injection spectrophotometric determination of lactic acid in skimmed milk based on a photochemical reaction

A spectrophotometric method for the determination of lactic acid in milk samples based on the use of a photochemical reaction carried out in a Flow Injection System is proposed. Determination is based on the reaction between lactic acid and Fe(III), which is reduced to Fe(II) in the presence of UV light, being the latter made to react with o-phenanthroline. The complex formed between Fe(II) and o-phenanthroline, Fe( o-phen) 3 2+ (ferroin) is a coloured compound and it can be spectrophotometrically monitored at 512 nm. The method shows a linear range between 0.5 and 50 μg ml −1 with a limit of detection of 0.16 μg ml −1. The precision was ±2.15 expressed as relative standard deviation ( n=11) and the sample throughput of 30 samples h −1. Also non-linear adjustments have been made and validated by ANOVA. The proposed method has been applied to the determination of lactic acid in both synthetic and milk samples.

Microbial biosensor for free fatty acids using an oxygen electrode based on thick film technology

A microbial biosensor based on thick film technology was developed. The microorganisms, Arthrobacter nicotianae, were immobilized in Ca-alginate directly on the electrode surface. For the stability of the calcium alginate gel the addition of 0·5 mM CaCl 2 to the assay buffer was necessary. The respiratory activity of the microorganisms was monitored by oxygen consumption at −600 mV vs. Ag/AgCl reference electrode. The sensor was used in a batch system and was applied to the determination of free fatty acids in milk. Shortchain fatty acids (C 4:0–C 12:0) were the preferential substrates, with butyric acid being the main substrate. Consequently, the concentration of free short-chain fatty acids was represented as the butyric acid equivalent. The sensor showed linearity over the concentration range 9·5–165·5 μM (correlation coefficient, r = 0·99920). The response time of the sensor was approximately 3 min. No additional dialysis membrane was necessary, which led to a high sensitivity of the sensor and fast response times. Recovery rates of 98–113% were found for butyric acid in milk samples using the sensor without any additional membrane and a sample dilution of 200 by the assay. Two widespread disadvantages of microbial sensors, long response times and long times to return to the baseline signal after use, could be overcome.

Note on boric acid in milk samples

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