The hand-held spectrophotometer is used to improve the quality evaluation index of product color and improve the quality evaluation method of products. The hand-held spectrophotometer is helpful to classify products and improve the competitiveness of products. Let's take a look at the application of handheld spectrophotometer in the detection of shrimp products.

Shrimp has high economic and nutritional value and has been loved by people all the time. With the increasing demand for shrimp products at home and abroad in recent years, the shrimp breeding industry has developed rapidly, the breeding area has been expanding, and the output has increased year by year. In the domestic market, the price difference of shrimp with different freshness per kilogram is about 10 yuan, while the price difference of export products is greater. The overall price of Chinese shrimp export is low, which is plagued by anti-dumping. The main reason is that the quality of Chinese shrimp products is not hard, the lack of quality evaluation indicators and perfect quality evaluation methods, and the mixed loading and sales of shrimp products of different quality, resulting in the poor connection between the price and quality of shrimp products.

The appearance in the quality grading elements and quality grading of shrimp products can directly reflect the external quality of products. In particular, luster and color not only affect people's preferences, but also reflect the quality of products to a certain extent. For example, the change of shrimp color is related to the quality difference. The fresh shrimp body is complete and shiny, the body surface texture is clear, and the shell is cyan gray and translucent; The body color of the stale shrimp gradually deepens from translucency, and the shell turns red or black. Sensory evaluation method can directly reflect product characteristics, but the evaluation results are inevitably subjective. It is a fuzzy evaluation of quality and can not be accurately quantified.

A Fisheries Research Institute studies the shrimp quality evaluation system based on computer vision, hoping to develop a shrimp packaging and grading system, which uses computer vision to grade and package shrimp instead of manual operation. The purpose is to provide reference for promoting the standardization and rationalization of the quality evaluation and grading system of aquatic products in China. CS-660 handheld spectrophotometer of CHNSpec technology was used in the experiment.

CS-660 spectrophotometer

During the storage of aquatic products, the apparent color changes in brightness, brightness and purity. This change trend has a good correlation with the sensory changes of products. In the quality inspection of aquatic products in Europe, CIELAB system is often used to measure the color difference of samples, which is described by the three-dimensional coordinate system of light − dark, yellow − blue and red − green attributes. The researchers used CIELAB system to measure the color of cooked shrimp, selected the central position of the first section of shrimp chest, measured it with CHNSpec CS-660 handheld spectrophotometer, and evaluated its color with L value (lightness index). Similarly, the handheld spectrophotometer of CIELAB system is used to measure the color changes of frozen shrimp shell and meat under different storage conditions. The experimental results are as follows:

表一 虾肉色泽特性分析

Note: there is significant statistical difference between values with different letters in the same line (P < 0.05) n=10;  x ±SD

The experimental results show that the change of B value (yellow and blue chromaticity index) has a good correlation with sensory evaluation. The analysis of shrimp samples with different culture modes showed that l was in good agreement with sensory evaluation, and a (red and green color index) and B played a reference role in quality evaluation.

The classification elements shall select the product characteristic elements closely related to quality, and can be accurately and uniformly measured, explained and identified. In the future research on shrimp grading system, based on sensory evaluation, detection and analysis technologies such as color difference instrument and handheld spectrophotometer can be introduced to quantitatively analyze the product quality. This can make up for the lack of strong subjectivity of sensory evaluation methods to a certain extent, and provide a reference basis for the comprehensive evaluation of the quality of aquatic products.