JPH05273124A - Spectroscopic continusou measuring emthod for acidity in fermented milk and near infrared absorption spectrum detecting terminal - Google Patents

Abstract

PURPOSE:To continuously measure oxygen by radiating near infrared rays with the specific wavelength to obtain the spectral spectrum, content in a specimen by the multi-variate analysis method, and calculating oxygen. CONSTITUTION:Optical fibers 3, 4 connected with the outside 3 to a light source l and connected with the inside 4 to a detector are fitted to a sensor section. Near infrared rays with the wavelength 700-1200nm are radiated to the fermented milk in the fermentation process to obtain the spectral spectrum. The near infrared absorption spectrum is measured on multiple specimens, preferably 30 specimens or more, and the wavelength suitable for the acidity measurement by the multi-variate analysis method and the constituent conversion factor value are obtained by the multiple regression analysis with a computer based on the measured values to generate a calibration curve. After the calibration curve is generated, the near infrared absorption spectrum is measured at the optimum wavelength for obtaining the acidity in the fermented milk by the same method as that for generating the calibration curve, and the measured value is compared with the calibration line to obtain the acidity in the fermented milk.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a spectroscopic continuous measurement method of acidity in fermented milk for nondestructively and rapidly measuring the time-dependent change in acidity of fermented milk in a fermentation process by using near infrared rays. The present invention relates to a near infrared absorption spectrum detection terminal used for it.

[0002]

2. Description of the Related Art Conventionally, in the process control of foods produced by lactic acid fermentation using lactic acid bacteria such as fermented milk, the acidity during the fermentation process is often used as a process index. The acidity was measured with 1% phenolphthalein as an indicator and 0
-Titrated with 1N sodium hydroxide solution, and calculate the percent amount of lactic acid per 100g from the titration amount.
This is based on the so-called titratable acidity measurement method.

[0003]

However, during the fermentation process in which the acidity changes with time, it is necessary to frequently sample from inside the fermentation tank, and the end point of the titration can be judged by the operator's sense. Since it is judged, the titration value tends to vary. In addition, in order to control the fermentation process with pH, a pH electrode is installed inside the fermentation tank to continuously measure the pH.
Electrodes need to be attached, washed, sterilized, etc., and if they are insufficient, there is a problem such as damage or secondary contamination by microorganisms. In order to solve the above problems, there is proposed a method of measuring the electric conductivity during fermentation and knowing the time when the fermentation is finished, as shown in Japanese Patent Publication No. 2-9780. It is necessary to insert the detection end into the fermented milk to bring it into contact with the fermented milk, and there is a problem that the detection end cannot be sufficiently washed. For this reason, complete non-destructive and non-contact remote measurement technology is required, but a method for performing these by an optical method has not been established. In recent years, a method for measuring components rapidly using near-infrared rays and non-destructively measuring is being put to practical use, but it has been reported at all about measuring the acidity continuously in the fermentation process of fermented milk. Absent.

[0004]

Means for Solving the Problems The present inventors have investigated a method for rapidly and continuously measuring the acidity of a fermentation process non-destructively using near infrared rays, and as a result, multivariate analysis was carried out. It was found that the object can be achieved by creating and using a calibration curve by the method, and the present invention has been completed. That is, the fermented milk in the fermentation process has a wavelength of 700 to 1200 n.
A spectral spectrum is obtained by irradiating near-infrared rays up to m, and from the obtained spectral spectrum, a wavelength suitable for estimating the content of a component that correlates with the acidity in the object is obtained by a multivariate analysis method, and the acidity is calculated from the wavelength. Is a spectroscopic continuous measurement method of the acidity of fermented milk using near-infrared rays, characterized in that the apparatus for irradiating the near-infrared rays to the object of the fermentation tank and the inside of the object irradiated with the near-infrared rays Near infrared absorption spectrum detection consisting of a translucent body that is exposed in a fermentation tank that is connected with an optical fiber to a detector that can measure the amount of transmitted light of the It is a terminal.

[0005]

[Operation] Near infrared rays are radiated to the target object through the optical fiber cable and the light-transmitting body covered with the external light-shielding member exposed in the fermentation tank, and the amount of transmitted light inside the target object is measured by the detector to obtain the spectral spectrum. From the obtained spectroscopic spectrum, two or more specific wavelengths suitable for measuring the acidity are calculated by a multivariate analysis method, and the acidity is measured from the wavelengths.

[0006]

EXAMPLES The present invention applies to fermented milk having a wavelength of 700 to 1200 nm.
Irradiate up to certain near infrared rays. As shown in FIGS. 1, 2, and 3, coaxial optical fibers 3 and 4 connected to the light source 1 at the outer side 3 and connected to the detector at the inner side 4 are attached to the sensor portion. Then, the sensor part is covered with a dark box 5 which is an external light blocker so that external light does not enter the optical fibers 3 and 4, and the upper end of the terminal is at least below the upper surface of the fermented milk in the fermentation tank 7. Install it in a safe place. It can be attached to the bottom of the tank, but it is usually recommended to attach it to the side. The near-infrared spectrum is measured with time by irradiating the object in the fermentation process with near-infrared light through the light-transmitting body of the sensor thus installed, that is, the glass 6. 1 shows the translucent body 6 directly attached to the side wall of the tank 7, and FIG. 2 shows the dark box 5 protruding into the tank. FIG. 3 shows the translucent body 6 separated from the side wall of the tank 7. Although it is not necessary to limit the light-transmitting body 6 to glass, glass is used in the embodiment. Quartz glass is preferable as the material of the glass in order to eliminate the influence of impurities on the spectrum, and the thickness of the glass is preferably 5 to 10 mm. Then, at the time of measurement, glass of the same material and the same thickness as those used when the calibration curve was created is used.

In the present invention, first, the near-infrared absorption spectrum of a plurality of samples, preferably 30 or more samples, is measured by the above method, and the obtained measured value is used to measure the acidity by a multivariate analysis method using a computer. The wavelength and component conversion coefficient values suitable for are obtained by multiple regression analysis, and a calibration curve is created. For example, the calibration curve of acidity (C%) in milk can be approximated by the following formula. C% = K ₀ + K ₁ λ ₁ + K ₂ λ ₂ + ... + Kn λn (1) where λ _{1 and} λ ₂ are absorption strengths at specific wavelengths correlated with acidity, It is a value determined for each sample and each component. K is a component conversion coefficient value, which is a proportional constant determined for each sample and each component. Here, the value of K is determined using a multivariate analysis method so that the correlation coefficient between the acidity and the value estimated by the equation (1) by the titratable acidity measurement method described above becomes the highest. After creating the calibration curve, measure the near-infrared absorption spectrum at the optimum wavelength to determine the acidity in fermented milk by the same method as when creating the calibration curve, and compare the obtained measurement value with the calibration curve to fermented milk. You just have to find the acidity in it. The present invention will be described below with reference to specific examples.

12% reduced skim milk is sterilized at 98 ° C for 30 minutes and then cooled to 42 ° C. St.the as starter after cooling
1.5% each of rmophilus and L. bulgaricus was added, and the cells were cultured at 42 ° C. Immediately after the starter was added, it was set as 0 minute, and culture was performed for 6 hours while measuring the near infrared absorption spectrum every 15 minutes. The near-infrared absorption spectrum was measured, and at the same time, titrated acidity was determined by titrating with 0.1N sodium hydroxide solution using 1% phenolphthalein as an indicator. A wavelength suitable for estimating the acidity was determined from the measured near-infrared absorption spectrum by multiple regression analysis, and a calibration curve was prepared. If a calibration curve is created for each cultivar in which the components such as the total solid content and fat content of the target fermented milk are almost constant, more accurate measurement can be performed. Therefore, when measuring all varieties with significantly different fermented milk components, perform a calibration with a large number of samples to include all components such as total solid content and fat content that give fluctuations. Can be solved with. In this case, it is advisable to perform calibration with 100 or more samples, for example. Table 1 shows the selected wavelengths and the measurement accuracy when the acidity is estimated using the wavelengths. Further, FIG. 4 shows the time-dependent changes in titratable acidity during fermentation and acidity determined by near-infrared radiation.
The calculated approximate expression is Y = 3.190-93.992.
It is [902] +192.292 [870]. Y = lactic acid degree (%) [λ]: absorbance at λ nm Then, using a calibration curve prepared using the wavelengths shown in Table 1, the near-infrared absorption spectrum in the fermented milk of the newly prepared fermented milk was measured with time, and the acidity was determined from the measured value. The accuracy of measurement of the actual acidity (titrated acidity) at this time and the result of acidity obtained by near-infrared rays is shown in Table 2, and the measured values over time at that time are shown in FIG. Table 3 shows a comparison of the calculation time per sample for determining the lactic acid acidity obtained by this method and the conventional method. From the above results, it was proved that the present invention is effective.

[0009]

EFFECTS OF THE INVENTION According to the present invention, the change in acidity with time during fermentation of fermented milk can be measured rapidly and without any pretreatment such as chemical treatment, and continuously without destruction. You can In addition, since the sensor does not come into contact with the target object, it does not require cleaning or sterilization of the sensor, and prevents microbiological contamination of the production line of fermented milk that requires a high degree of sterility in terms of microorganisms. can do.

[Brief description of drawings]

FIG. 1 is an explanatory view of a translucent body forming a near-infrared absorption spectrum detection terminal of fermented milk on a side wall of a tank.

FIG. 2 is an explanatory view of the translucent body of the above in a tank.

FIG. 3 is an explanatory view of the above-mentioned translucent body outside the tank.

FIG. 4 is a view showing a change with time of acidity in fermented milk.

FIG. 5 is a time-dependent change diagram of acidity in fermented milk obtained using a prepared calibration curve.

[Explanation of symbols]

 1 Light source 2 Detector 3 Optical fiber 4 Optical fiber 5 External light blocking body 6 Light transmitting body 7 Tank

Claims (2)

[Claims] 1. Fermented milk in the fermentation step has a wavelength of 700-
A spectral spectrum is obtained by irradiating near infrared rays up to 1200 nm, and a wavelength suitable for estimating the content of a component that correlates with the acidity in the object is obtained from the obtained spectral spectrum by the multivariate analysis method, and the acidity is calculated from the wavelength. A method for continuous spectroscopic measurement of acidity of fermented milk using near-infrared rays, characterized by calculating. 2. An optical fiber is connected to a device for irradiating an object in a fermentation tank with near infrared light and a detection device for measuring the amount of light transmission inside the object irradiated with the near infrared light and obtaining a spectral spectrum. Near-infrared absorption spectrum detection terminal consisting of a translucent body exposed in the fermentation tank and covered with an external light blocker