Fluorescence characteristics of several whey samples subjected to different treatments and conditions

Pulgarı́n, José A. Murillo; Molina, Aurelia Alañón; Pardo, M.T Alañón

doi:10.1016/j.aca.2004.12.087

Cited by 14 publications

(6 citation statements)

References 12 publications

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“…The applications and analyses of these molecular spectroscopies, empirical or quantitative, on highly mixed and "dirty" systems such as whey proteins have not been published to our best knowledge. Recent attempts have been made, however, to apply these spectroscopic techniques to study qualitatively milk and dairy products with a particular focus on the detection of heat treatment (Birlouez-Aragon et al, 1998;Chen et al, 2005;Murillo Pulgarín et al, 2005;Schamberger and Labuza, 2006). Highly controlled experiments (e.g., keeping total protein concentration constant) combined with self-consistent and comparative analyses from these complementary techniques could yield more detailed information on the structural changes and thermal stability of whey proteins, assuming complex interactions among various whey protein components are absent.…”

Section: Introductionmentioning

confidence: 99%

Effect of homogenization and pasteurization on the structure and stability of whey protein in milk

Ren

Xiao

et al. 2015

Journal of Dairy Science

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The effect of homogenization alone or in combination with high-temperature, short-time (HTST) pasteurization or UHT processing on the whey fraction of milk was investigated using highly sensitive spectroscopic techniques. In pilot plant trials, 1-L quantities of whole milk were homogenized in a 2-stage homogenizer at 35°C (6.9 MPa/10.3 MPa) and, along with skim milk, were subjected to HTST pasteurization (72°C for 15 s) or UHT processing (135°C for 2 s). Other whole milk samples were processed using homogenization followed by either HTST pasteurization or UHT processing. The processed skim and whole milk samples were centrifuged further to remove fat and then acidified to pH 4.6 to isolate the corresponding whey fractions, and centrifuged again. The whey fractions were then purified using dialysis and investigated using the circular dichroism, Fourier transform infrared, and Trp intrinsic fluorescence spectroscopic techniques. Results demonstrated that homogenization combined with UHT processing of milk caused not only changes in protein composition but also significant secondary structural loss, particularly in the amounts of apparent antiparallel β-sheet and α-helix, as well as diminished tertiary structural contact. In both cases of homogenization alone and followed by HTST treatments, neither caused appreciable chemical changes, nor remarkable secondary structural reduction. But disruption was evident in the tertiary structural environment of the whey proteins due to homogenization of whole milk as shown by both the near-UV circular dichroism and Trp intrinsic fluorescence. In-depth structural stability analyses revealed that even though processing of milk imposed little impairment on the secondary structural stability, the tertiary structural stability of whey protein was altered significantly. The following order was derived based on these studies: raw whole>HTST, homogenized, homogenized and pasteurized>skimmed and pasteurized, and skimmed UHT>homogenized UHT. The methodology demonstrated in this study can be used to gain insight into the behavior of milk proteins when processed and provides a new empirical and comparative approach for analyzing and assessing the effect of processing schemes on the nutrition and quality of milk and dairy product without the need for extended separation and purification, which can be both time-consuming and disruptive to protein structures.

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Section: Introductionmentioning

confidence: 99%

Effect of homogenization and pasteurization on the structure and stability of whey protein in milk

Ren

Xiao

et al. 2015

Journal of Dairy Science

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“…A previous work demonstrated the constant shape of fluorescent spectra for the same wheys corresponding to different milk obtained from different mammals and subjected to several treatments and conditions (a necessary condition for application of this new synchronous technique). The different whey samples exhibited the same time of fluorescence, with a slight variation on the position of the former band depending on the nature of the milk.…”

Section: Resultsmentioning

confidence: 94%

Determination of Ciprofloxacin, the Major Metabolite of Enrofloxacin, in Milk by Isopotential Fluorimetry

Pulgarı́n

Molina

Fernández

2008

J. Agric. Food Chem.

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A new method for the determination of ciprofloxacin, the major metabolite of enrofloxacin, for concentrations between 20 and 200 ng/mL by means of matrix isopotential synchronous fluorescence spectrometry and derivative techniques is proposed. This new method is useful for the determination of compounds in samples with unknown background fluorescence, such as ciprofloxacin in whey, without the need of tedious preseparation. The determination was performed in an ethanol/water medium (20% v/v) at pH 4.8, provided by adding a sodium acetate/acetic acid buffer solution. Since enrofloxacin is widely used as an antibacterial agent in veterinary medicine, the method was successfully applied to the determination of its main metabolite in milk. An exhaustive statistical analysis has been developed to all calibration graphs. This treatment includes robust regression such as least median of squares, which also detects outliers and leverage points. The overall least-squares regression has been applied to find the more exact straight line that fits the experimental data. The error propagation has been considered to calculate the detection limit and the repeatability of the method.

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“…Milk has intrinsic fluorescent components such as vitamin A, aromatic amino acids, NADH and some advanced Maillard compounds [43]. Whey proteins such as β-lactoglobulin and α-lactalbumin have at least one amino-acid tryptophan residue, responsible for whey proteins' intrinsic fluorescence [44]. Tryptophan fluorescence depends on the environment, and thus on milk characteristics [10].…”

Section: Fluorescence Spectroscopymentioning

confidence: 99%

“…Murillo et al [44] evaluated total fluorescence spectra (bandpasses of 4 nm for both excitation and emission with 3.2 increments and 0.4 nm step size) of whey obtained from milk samples subjected to different treatments (raw, pasteurized and UHT). In the UV region, two fluorescent bands were obtained.…”

Section: B Fluorescence Spectroscopymentioning

confidence: 99%

“…Hence, it was proven that the FAST index allows for the estimation of the intensity of heat treatment in milk by quantifying protein denaturation through changes in fluorescence intensity. Murillo et al [44] evaluated total fluorescence spectra (bandpasses of 4 nm for both excitation and emission with 3.2 increments and 0.4 nm step size) of whey obtained from milk samples subjected to different treatments (raw, pasteurized and UHT). In the UV region, two fluorescent bands were obtained.…”

Section: B Fluorescence Spectroscopymentioning

confidence: 99%

See 1 more Smart Citation

Thermal Denaturation of Milk Whey Proteins: A Comprehensive Review on Rapid Quantification Methods Being Studied, Developed and Implemented

Freire

Zambrano

Zamora

et al. 2022

Dairy

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Heat treatment of milk signifies a certain degree of protein denaturation, which modifies the functional properties of dairy products. Traditional methods for detecting and quantifying the denaturation of whey proteins are slow, complex and require sample preparation and qualified staff. The world’s current trend is to develop rapid, real-time analytical methods that do not destroy the sample and can be applied on/in-line during processing. This review presents the rapid methods that are being studied, developed and/or applied to determine and quantify the thermal denaturation of whey proteins, including spectroscopic, electrochemical and miniaturized methods. The selected methods save a significant amount of time and money compared to the traditional ones. In addition, the review emphasizes the methods being applied directly to milk and/or that have potential for on/in/at-line application. There are interesting options to quantify thermal denaturation of whey proteins such as biosensors, nanosensors and microchips, which have fast responses and could be automated. In addition, electrochemical sensors are simple to use and portable, while spectroscopy alternatives are suitable for on/in/at-line process.

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Fluorescence characteristics of several whey samples subjected to different treatments and conditions

Cited by 14 publications

References 12 publications

Effect of homogenization and pasteurization on the structure and stability of whey protein in milk

Effect of homogenization and pasteurization on the structure and stability of whey protein in milk

Determination of Ciprofloxacin, the Major Metabolite of Enrofloxacin, in Milk by Isopotential Fluorimetry

Thermal Denaturation of Milk Whey Proteins: A Comprehensive Review on Rapid Quantification Methods Being Studied, Developed and Implemented

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