SU1748058A1 - Method for assaying milk for fat and protein - Google Patents

Abstract

Usage: The invention relates to a technique for researching food products, namely to methods for determining the FIBER DETECTION of the holding of fat and protein in milk and dairy products, can be used in the dairy industry and in the agricultural sector. SUMMARY OF THE INVENTION: A controlled sample is irradiated with two continuous highly monochromatic laser streams of various frequencies directed at a given angle to each other, then the radiation from the intersection of the streams is recorded by one photodetector, and the spectrum of the photoelectric signal is analyzed. spectra are selected that correspond to both fractions, determine their shape, width, and amplitude, determine how many particles of fat and protein are involved in the scattering of light. The proposed method for determining fat and protein in milk is highly reproducible and accurate. 2 Il. Yo

Description

The invention relates to a technique for the study of food products, namely to methods for determining the content of fat and protein in milk and dairy products, and can be used in enterprises of the dairy industry and in agriculture.

There is a known method for determining fat and protein in dairy products by irradiating a sample of a controlled product with an electromagnetic flux and registering a scattered flux, measuring the complete scattering indicatrix and optimal glut of scattering for each of the components, determining the content of the latter in the sample according to the radiation intensity flow at optimal angles.

The disadvantages of this method are low accuracy and reliability of measurements of the content of fat and protein in milk, due to the non-monochromatic electromagnetic probe flux.

The closest in technical essence to the present invention is a method for determining the content of fat and protein B milk, including diluting a milk sample with distilled water, homogenizing the test solution, irradiating it with a continuous monochromatic laser stream, photoelectric recording of scattered radiation signals and converting them into percentage readings. content and protein.

The disadvantage of this method is the low accuracy of the determination of fat and

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protein in the original product. The reason for the low accuracy of the method is the lack of control over the actual distribution of fat and protein particles in size, which, at a given angle, makes a real contribution to the dispersion of fat and protein fraction. In measurements, the intensity of the scattered light flux depends not only on the scattering angle, the concentration of scattering particles, the volume of the irradiated sample, but also on the size of the particles.

The low reproducibility and the accuracy associated with it in this method is based on the fact that milk, being a rather complex organic product, in each specific case shows a number of individual features that determine the physicochemical structure and size of protein particles. Therefore, the calibration indicatrix scattered for one milk does not reflect the actual fat and protein content in a controlled sample of another.

The purpose of the invention is to improve accuracy.

The goal is achieved by those. that when implementing the method of determining the content of fat and protein in milk, which involves diluting a milk sample with water, homogenizing, irradiating a sample with a monochromatic light flux, photoelectric recording of scattered light radiation, irradiation of milk production occurs with two laser streams of different frequencies directed at a static angle to one another , the scattered radiation is recorded by a single photodetector, and the percentage of fat and protein is determined from the analysis of the photoelectric Si spectrum drove by detecting the spectra of the fat and protein components and measuring the height and width of the spectral distribution of each of the components.

The photoelectric signal is scattered by spectral analysis, which makes it possible to determine the presence or absence of motion of scattering particles, as well as to distinguish between protein and fatty particles that make Brownian motion in the spectrum; by the broadening of individual spectra, control the average size of protein and fatty particles; follow the process of conglomeration of fat in the solution associated with the random adhesion of small fat particles: due to the artificial frequency of the frequency, a high signal-to-noise ratio is achieved due to the exclusion of statics; the second partition on the cuvette windows.

optical elements, dust, etc., as well as various kinds of quasistatic interference (electrical, mechanical, thermal, etc.) in the zero frequency range. As a result

in comparison with the known method, the accuracy of determining the content of fat and protein in milk is significantly improved.

Figure 1 is a diagram of the device for implementing the method for determining

the fat and protein content of the milk; Fig. 2 shows the spectra of the signal scattered in a sample of milk and its fractions.

The method is carried out as follows.

Two probing high-monochromatic streams 1 and 2, having different frequencies Pcs, 0) 2 and directed at an angle a to each other, are irradiated to a cuvette 3 with a breakdown of milk, previously

diluted with distilled water and subjected to homogenization. Radiation 4, scattered by Brownian particles of the solution from the intersection of the probing light fluxes: recorded

photodetector 5. The electrical signal from photodetectors is examined using a spectrum analyzer 6. According to the measured characteristics of the spectrum, the content of fat and protein in milk is determined

fractions. The artificial frequency shift QD (& i W1 in the proposed method allows the separation of the recorded spectral signal from low-frequency noise with high efficiency

whose frequency range overlaps and distorts it. this way is difficult to analyze. This is especially important for recording narrow spectra, the frequency range of which is very small (a few hertz), and low-frequency noise due to vibroacoustics, electric pickups, plasma discharge fluctuations in an active laser element, competition of laser modes, etc. are significant.

By irradiating the sample with two light monochromatic fluxes, the method is differentiated as

shows a theoretical calculation of the spectrum of the photoelectric power of the signal scattered on particles of fat and protein, making Brownian motion in the region of intersection of the irradiating flows, describes a simple Formula containing the sum of deux Lorentz contours:

ROT-U.Y.M ,,, HB (GB) MB ii 12

GB / I

(0)

where 11 and 12 are the intensities of the light fluxes, respectively, with the frequencies al and al so that 0) 2 - on Q: Mf, Ne is the number of fat and protein particles involved in scattering; perishing (GJ) and UB (PZ) - the effectiveness of scattering, respectively, on fat and protein particles; ГЖ and Гб - half-widths, respectively, of the fat and protein lines of the scattering, each of which is determined by the Brownian motion of the particles of the corresponding fraction:

ГЖ

where is j

Jd2; GB CT

- Dbchg iDb

CT

BLT / GZ w

diffusion factors of particles, considered fat and protein fractions, a q

q Ki - K2 Ksin a / 2 2l / I sin a / 2. - the magnitude of the difference wave vector determined by the wavelength of the laser radiation and the angle between the light probing fluxes, preferably between 20 and 60 °, to ensure on the one hand a sufficiently large contribution to the total dispersion of the protein fraction, on the other, the broadening of the narrow fat spectral a component that can be used for spectroanalyzer measurements with low spectral resolution. The half width of the scattered line for each kind of particles does not depend on the direction and angular aperture of the reception of scattered radiation and is determined only by the difference wave vector. This property of the differentiation of the proposed method is essential since the analysis of milk samples and calibration measurements are carried out with a fixed scattering geometry.

Due to the fact that the average size of fat particles after homogenization is 0.5

Distribution height

- coefficient Percentage of fat content in milk Og / Og / lzh / 0zh ...

o

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with a high absolute accuracy of 0.05%, determine the percentage of Au (Hw, and Ob (GB, We) in the sample, using calibration data on their dependencies on the half-width Gh. GB and heights of the corresponding spectral distributions Wx, We.

Provided gzh. GB 0.03 I - 0.02 µm (Ach 0.63 µm) The scattering of light on milk particles is described by Mie theory, when the intensity of the scattering is proportional to the geometric cross section of an individual particle, a g with a proportionality coefficient in general, depending on the radius g For homogeneous fat particles, the size of which is forcibly calibrated during sample preparation, the corresponding spectral dispersion density (spectrum of the fat component) is as follows;

Rzh (Dz) Azh-IZh-GZh-l

(A (af

(3)

where Mzh is the number of fat particles per unit volume, Ash Q-Oz Al is the empirical coefficient of proportionality, which is constant for a given particle radius. At the maximum of the distribution, i.e. when we have

MW Ј

MF Rzh (0) Already

Gzh

And ... 4lg s

Azh GOzh -kg Gzh d. m % / o J Alzhi,

S. S jyKTq

Since OC N-VX100% is a percentage, and MJ is the height of the spectral distribution of the fat fraction, expression (4), which reflects a directly proportional relationship between them

R w / Aux Nj const, allows to obtain calibration table data

wi, / wi / wS / w2

e Ex / Ex / Ex ...

/ Wj / qx

um by an order of magnitude greater than the average size of the protein particles of pi 0.05 um, the separation and control of the contributions of both fractions to the total scattering using spectral analysis of the scattered flux is greatly simplified. The dependence of the spectrum (1) on the frequency within 0 Q 2GJ with a relative accuracy of 0.5% is determined mainly by the narrow spectral component of fat. those. the first member of the sum (1). This makes it possible to separate the contributions of life in the signals of the scattering. In spite of the fact that the protein fraction is not subjected to homogenization and the average size of its particles can fluctuate quite strongly during the transition from one milk to another, the spectrum of the protein part has a similar appearance.

. RB (LS) LB.M5-Ya1 | - G

and the percentage of protein will also be proportional to the height of the corresponding spectral distribution. However, the proportionality coefficient

H & (G,) - Ro / O is not in this case constant as for fat, but has a number of values nb - uniquely associated with calibration measurements with a number of average values of the radius of protein particles rfe, determined by the widths of the protein spectral GB components

Example. A homogenized sample of m & Loka with a fat and protein content in the range of 2–7%, with a volume of 1 ml, is diluted with distilled water at a ratio of 1:20 and placed in a stationary cuvette with a volume of 1 ml {3 mm thick). The analyzed sample is illuminated with two parallel beams (A 0.63 µm L / 1 mW) of different frequencies (& J2 -) / 2 L 1 MHz) focused in the cell with the help of the forming objective TZK, that the angle at which the light fluxes intersect in the cuvette is 30 °. The scattered flux within a solid angle of 0.5 sterad is collected using a receiving lens at the photoelectric probe of the PMT-79 receiver. Using a mixer, the frequency of the beating of an electric signal from the 1 MHz region is shifted to the field of view of the spectrum analyzer, at the output of which with a resolution of 0.1 Hz, the spectrum is recorded on a recorder at a single recording time of 10-20 minutes. The resulting spectrum is divided into spectral components corresponding to fat. and squirrel. Then, the height and width of each of the spectral distributions resulting from the separation are measured, and. use of pre-calibration tabular data,

the fat and protein content of the milk is divided.

Fig. 2a shows the typical spectrum of the scattered signal in an analyzed milk sample with a fat content of 1.4% and a protein of 6.8%, and fig.2b and 2c show the result of its separation into fractional spectra: fat and protein, respectively, fig.2b. at. The radius of the protein particles was GB 0.042 μm and fat, respectively, GJ 0.44 μm. Thanks to that narrow

3

„J

1 C, I

0

(upper) part of the spectrum (Fig. 2a) is almost completely determined by scattering on fat particles the total spectrum is easily divided into components with half widths G

4.1 Hz and Gb 31.3 Hz. Comparison of the experimental data obtained on different samples showed that the size of the protein particles from milk to milk varies greatly within

0 0.03 GB 0.07 microns. This circumstance is not taken into account in the prototype, which significantly reduces the accuracy of determining the fat and protein in milk.

Thus, the use of the proposed method for determining the fat and protein in milk in comparison with the prototype makes it possible to increase the reliability, reproducibility and, thus, the accuracy of determining their percentage in milk and dairy products. The proposed method has an accuracy exceeding also the accuracy of the chemical method (0.1%) widely used in industry. In addition, the proposed method makes it easy to automate the measurement process.

Ph o r u m a l i z o b r i u Method of determining the content of fat and protein in milk, which involves diluting a milk sample with water, homogenizing it, irradiating the sample with a monochromatic light flux, and photoelectric recording of the scattered light radiation, characterized by that, in order to increase accuracy, the irradiation of a milk sample is effected by two laser streams of different frequencies, directed at a static angle to each other, register the scattered radiation by one photodetector, analyze the spectrum of the photoelectric signal, reveal the spectra of the fat and protein components, determine the height and width of the spectral

5 of the distribution of each of the components, the percentage of fat and protein is determined depending on the measured values of the height and width of the spectral distribution of the respective components.

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FIG. 2

Claims (1)

Claim A method for determining the content of fat and protein in milk, involving the dilution of a milk sample with water, homogenization. irradiation of the sample with monochromatic light flux; photoelectric registration of scattered light radiation. characterized in that. that, in order to increase accuracy, the milk sample is irradiated with two laser streams of different frequencies directed at a static angle to one another, 40 scattered radiation is recorded by one photodetector, the spectrum of the photoelectric signal is analyzed, the spectra of the fat and protein components are detected, the height and width of the spectral distribution are determined of each component, determine the percentage of fat and protein depending on the measured values of the height and width of the spectral distribution corresponding to mponent.