*119956*

Agriculture / 4. Technologies of storage and processing of agricultural products

PhD Romanenko O.V.

PhD Donchevska R.S.

PhD Romanenko R.P.

Kyiv National University of Trade and Economics, Ukraine

Determination of jellied fish products optical properties

Sensory methods are the most common for optical properties of jellied products evaluation. However, these are based on the primary subjective perception of smell, taste, sight, touch sensations. Therefore, to improve the objectivity and to provide the possibility of not only finished products but also semi-prepared foods evaluation we need to use semi-optical methods.

Transparency or turbidity indicator of jellied food products can be determined according to its environment ability to disperse and reduce light flux rate, this process is aimed to evaluate quality rate and the possibility of jellied food products storage. In linear optics this indicator is called environment transparency.

Colloidal solutions, emulsions, suspensions transparency can be identified in transmitted light, it means that the sample should be contained between light source and receiver. Transparency is usually determined using monochromatic light sources or light rays with a wide range of frequencies, the most accurate results can be obtained using the monochromatic source. With emission frequency decreasing (increasing wavelength) transparency increases, therefore determination of this indicator is recommended to be held using light with the larges visible wavelength – red spectrum light.

As we know the basic quantitative methods of turbidity determination are described in DSTU ISO 7027:2003 (State standard of Ukraine ISO) “National Standard of Ukraine: water quality. Determination of turbidity”. The indicator of turbidity can also be determined by turbidimeter. Scope of this method is wider, but the factors of peculiarities associated with turbidimeter calibration features, where the reflection / absorption coefficient of cuvette optical glass is engaged and adjustment for heterogeneity geometrical dimensions of the sample are absent makes determination of jellied fish products turbidity impossible.

Developed method allows to determine gelatinous structures turbidity due to taking into account the heterogeneity of the samples geometrical dimensions and the reflection coefficient of jellied product by itself, not the glass reflection / absorption coefficient. Jellied product transparency determining unit (figure 1) is much simpler than the others equipment for the determination of optical parameters of the products.

Figure 1. Diagram of jellied product transparency determining unit

"Universal guage ITM" that consists of electronic units, a set of sensors and software to interface with the Windows OS is used in this device for high-frequency fixation of luxmeter values. Laboratory monochrome gas discharge laser emitter ESPE-11 with a 660 nm wavelength is used as a source of radiation.

In Figure 2 the photos of the cuvette with tested sample during the laser ray without the diffraction grating (one beam) passing through are represented. The photos of samples were took in dark without using the flash.

Figure 2. Photos of cuvette with the studied samples during the laser beam passing through. Left image is inverted.

Advantages of suggested method are connected with the fact that, firstly, possibility to determine the turbidity of broth at a certain depth appears, secondly, coherent monochromatic waves with length 660 nm which extend the boundaries of turbidity measuring are applied.

Basic in the claimed invention is the goal to improve methods of gelatinous food products, particular structure-based food broths, quality assessment.

In the case when the radius of the base of the cone scattering laser beam is smaller than the Illuminometers sensor (luxmeters) radius, light flow intensity can be defined by the next formula:

(1)

where: I – is light flow intensity, Lm; J – is the level of Illuminometers sensor (luxmeters) lightning, LH; R - radius of the base of the scattering laser beam cone, mm; r - Illuminometers sensor radius, mm.

Light flow extinction coefficient can be defined by the next formula:

; (2)

where: k – is extinction coefficient, mm^-1; I₀ - intensity of the light flow in the chamber without turned on laser, Lm; I₁ – is turned on lasers light flow intensity, Lm; I_sample – the intensity of light flow after passing the sample, Lm; l_sample - samples thickness, mm.

Jellied food products turbidity is determined by the formula:

(3)

Where: S - jellied food products turbidity; k_sample– is the conversion coefficient, which is equal to FNU (formazine Nephelometric Unit) - 162,43 FNU, mm.

The proposed method of determining the transparency of jellied fish products contributes to the improvement of methods of a comprehensive assessment of the quality and storage period of jellied food products and its semi-manufactures in correlation depending on the intensity of the light flow, the functional and technological properties of the product.