RU2345358C1 - Method of determination of early damage of dairy and fermented milk products - Google Patents

Abstract

FIELD: physics, measuring.

SUBSTANCE: invention concerns analytical chemistry of foodstuff and can be used for an establishment of early damage of dairy and sour-milk yields. According to the method the test prepared for the analysis place in a weighing bottle with a polyurethane membrane on a cover, maintain 10 minutes, then use a syringe to extract 1 cm³ of an equilibrium gas phase, which inject in the case of the static "piezoelectronic nose". Last consists from 2 piezoquartz resonators with the electrodes are modified by drawing on their surface of a film of polar chromotographic sorbents in mass of 15 mkg. Further fix an oscillation frequency of piezoquartz resonators with films with an interval 5 seconds during 15 seconds and shape the net signal in the form of the kinetic "weight aromogram" and count its area. Bacterial damage of the product is determined on acidity, using the diagramme of dependence of the "weight aromogram" area from acidity.

EFFECT: provision of accuracy, simplicity and rapidity of determination.

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Description

The invention relates to analytical chemistry of food products and can be used to establish early spoilage of dairy and sour-milk products (milk, yogurt, fermented baked milk, kefir, cocktails, yogurt and its analogues, cottage cheese, curd masses, cheese, ice cream, etc.), including for children's, medical and gerontological nutrition caused by violations of manufacturing technology, formulations, non-compliance with storage conditions.

The closest in technical essence and the achieved effect is the titrimetric method for determining total acidity (GOST R 30648.4-99), indicating spoilage (souring) of dairy products, with fixing the end point of the reaction by changing the color of the indicators or other properties of the system (instrumental method).

The disadvantage of this method is the duration of the experiment, the need for a large number of reagents (titrant, standard solution, indicator solution or device), the presence of special expensive measuring and other utensils (burette, pipette, titration flask, tripod, beaker). With potentiometric titration (instrumental method), a potentiometer, indicator and auxiliary electrodes are additionally required. Also, preliminary sample preparation is necessary when determining the total acidity of all products except milk - extraction of acids with water from a certain volume or a sample of the analyzed sample (yogurt, fermented baked milk, kefir, cocktails, yogurt and its analogues, cottage cheese, curds, cheese, ice cream, etc. P.).

The technical task of the invention is to develop a method for establishing early spoilage of dairy and sour-milk products due to violations of manufacturing technology, formulations and storage conditions using a static "piezoelectronic nose" (detection cell with a set of piezoelectric quartz resonators with sensitive films, a certain algorithm for recording and processing measurement results ), providing high sensitivity, low detection limit, correctness, accuracy, simplicity and expressness defined and I.

The technical problem is achieved in that in a method for establishing early spoilage of dairy and sour-milk products, including sampling, preparing a sample for analysis, establishing bacterial spoilage of the product, it is new that a sample of milk or sour-milk product heated to a temperature of 20 ± 2 ° C is taken 2 ml for liquid and weighing 2 g for viscous products, placed in a 20 cm ³ bottle with a polyurethane membrane on the lid, stand for 10 minutes, then a 1 cm ³ equilibrium gas phase is taken through a polyurethane membrane with a syringe A probe injected into the body of a static “piezoelectronic nose” consisting of 2 piezoelectric quartz resonators, the electrodes of which were previously modified by applying a film of polar chromatographic sorbents with a mass of 15 μg, then the oscillation frequency of the piezoelectric quartz resonators with films with an interval of 5 s in for 15 s and form the total signal in the form of a kinetic "weight aromatogram", calculate its area, and the bacterial spoilage of the product is determined by acidity, using the schedule the dependence of the area of the "weight aromatogram" from acidity (K, ° T).

The technical result of the invention is to increase the rapidity of determination, measurement accuracy and reliability of the results; Simplicity of processing results and making decisions.

Figure 1 - kinetic "weight aromatograms" of fresh baked milk (standard 1) and baby fluorinated pasteurized milk (standard 2) (example).

Figure 2 - dependence of the area (units ² ) of kinetic "weight aromatograms" of baked milk (a) and baby fluorinated pasteurized milk (b) on the acidity of the product (K, ° T):

1 - sample 1 (storage);

2 - sample 2 (storage);

3 - sample 3 (spoilage);

4 - sample 4 (spoilage).

The method of establishing early spoilage of dairy and dairy products is implemented as follows.

Sample preparation of samples of dairy and sour-milk products consists in heating them to a temperature of 20 ± 2 ° C, taking 2 ml for liquid and 2 g for viscous products and placing them in a 20 cm ³ bottle, which is tightly closed with a cover with a polyurethane membrane. The sample in the bottle is kept for 10 minutes. Then, through a polyurethane membrane, a 1 cm ^{3 of the} equilibrium gas phase is taken with a syringe, which is injected into the body of the static "piezoelectronic nose", consisting of 2 piezoelectric quartz resonators, the electrodes of which are previously modified by applying a film of polar chromatographic sorbents weighing 15 μg, then fix the oscillation frequency of piezoelectric quartz resonators with films with an interval of 5 s for 15 s and form the total signal in the form of a kinetic "weighted aromatogram", calculate its area b, and bacterial spoilage of the product is determined by the acidity from the graph of area "aromatogram weight" on the acidity of (K, ° T).

The method is illustrated by the following example.

Example.

Samples of baked milk (sample 1, sample 3) and fluorinated pasteurized baby milk (sample 2, sample 4) were selected as the analyzed ones.

Selected as an example to demonstrate the capabilities of the proposed method, samples of fresh baked milk and baby fluorinated pasteurized milk are placed in flasks, heated to a temperature of 20 ± 2 ° C, thoroughly mixed with glass rods and 2 ml of samples are taken. Samples are placed in 20 cm ³ containers, tightly closed with covers with a polyurethane membrane. Samples in bucks are kept for 10 minutes to saturate the gas phase with volatile compounds of products, then through a polyurethane membrane a 1 cm ^{3 of the} equilibrium gas phase is taken with a syringe, which is injected into the body of the static "piezoelectronic nose", consisting of 2 piezoelectric quartz resonators, the electrodes of which are previously modified by applying onto their surface films of polar chromatographic sorbents (for example, polyethylene glycol-2000, polyethylene glycol adipate or α (+) ramnose, 12-Crown-4, etc.) weighing 15 m d, then the oscillation frequency of the piezoelectric crystal resonators with films with an interval of 5 s for 15 s is fixed and the total signal is formed in the form of a kinetic “weighted aromatogram” (Fig. 1), its area is calculated, and the bacterial spoilage of the product is determined by acidity using the dependence graph the area of "weight aromatogram" from acidity (K, ° T) (figure 2).

It was established that samples 1 and 3 of baked milk differ in the area of the "weight aromatogram" and are 210 units ² and 245 units ^2, respectively. The increase in area by 35 units ² is due to the fact that as a result of bacteriological spoilage of the product, volatile carbonyl compounds accumulate, which affect the intensity of the aroma of the product (sample 3). A similar relationship has been established for pediatric fluorinated pasteurized milk. The area of sample 2 is 205 units ² , sample 4 - 230 units ² . It was found that the analyzed sample 1 of baked milk and sample 2 of baby fluorinated pasteurized milk meet the norm according to the acidity criterion, while sample 3 of baked milk and sample 4 of baby fluorinated pasteurized milk do not.

The duration of the analysis, taking into account sample preparation, is 15 minutes, the measurement and processing time is 2 minutes, the number of measurements without updating the piezoelectric crystal resonators with films is 100. The duration of the re-deposition of films on the electrodes of the piezoelectric crystal does not exceed 20 minutes.

The method is feasible. It is possible to establish early spoilage of dairy and sour-milk products, including for baby and medical nutrition, due to a violation of manufacturing technology, formulations and storage conditions (changing the area of "weight aromatograms" of the equilibrium gas phases of the samples compared to the standards).

Comparative characteristics of the methods for establishing early spoilage of dairy and sour-milk products for baby and medical nutrition according to the prototype and the claimed method are presented in the table.

As follows from the example, figure 1, 2 and the table, the proposed method using a static "piezoelectric nose" with two piezoelectric crystals, the electrodes of which are previously modified by applying a film of polar chromatographic sorbents (for example, polyethylene glycol-2000, polyethylene glycol adipate or α (+) ramnose, 12-Crown-4, etc.) weighing 15 μg, early signs of spoilage of dairy and sour-milk products with high sensitivity for the determination of volatile carbonyl soybeans are possible İnönü.

Changing the mass of films on the electrodes of piezoelectric crystals, the nature of the sorbents and replacing them with medium-polar, non-polar, mixed or combined algorithms for processing the responses of piezoelectric crystals with films leads to an increase in the error of analysis, a small difference in the "weight aromatograms" of standards and analyzed samples, worsens the metrological characteristics of the method , does not allow to establish early spoilage of dairy and dairy products.

The proposed method for establishing early spoilage of dairy and sour-milk products allows to provide a low detection limit, correctness, accuracy, simplicity and expressness of determination.

Table Comparative characteristics of the prototype and the proposed method for establishing early spoilage of dairy and sour-milk products Characteristic Prototype The inventive method Sample preparation - sample weighing and temperature control + + - extraction with warm water (15-20 min) + - - filtration (10 min) + - - obtaining the equilibrium gas phase (10 min) - + Analytical Signal Measurement 2-5 min 15 s Preparing the system for repeated measurements 1-3 min 10 s Time saving 0 35-50 min Error 25% 10-15% The cost of one analysis 100-150 r 30-50 r

Claims (1)

A method for determining early spoilage of dairy and sour-milk products, including sampling, preparing a sample for analysis, determining bacterial spoilage of a product, characterized in that a sample of a dairy or sour-milk product with a volume of 2 ml is taken for liquid and weighing 2 g viscous product, placed in a 20 cm ³ bottle with a polyurethane membrane on the lid, stand for 10 minutes, then 1 cm ^{3 of the} equilibrium gas phase is taken through a polyurethane membrane with a syringe, which is injected into the static of a zoelectronic nose ”, consisting of 2 piezoelectric crystals, the electrodes of which were previously modified by applying a film of polar chromatographic sorbents with a mass of 15 μg to their surface, then the oscillation frequency of the piezoelectric crystals with films with an interval of 5 s for 15 seconds is fixed and a total signal is generated in the form of a kinetic “Weight aromatogram”, calculate its area, and bacterial spoilage of the product is determined by acidity, using a graph of the dependence of the area of “weight aromatogram” from acid NOSTA (K, ° T).

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