DEVELOPMENT AND TESTING OF AN AUTOMATED QUALITY EVALUATION DEVICE FOR SHRIMP
Shrimp is one of the most important seafood products in the United States. Its safety and quality depends on good manufacturing, handling and storage practices, as well as a reliable inspection and quality control. Current inspection of shrimp quality, either by producers, industry or regulatory agencies, relies on subjective sensory evaluation. Trained inspectors evaluate the shrimp for different visual, odor and texture attributes. This procedure is subjective, prone to error, time consuming, difficult to relate with other inspector's results, and difficult to quantify. This study developed the hardware and software for an automated quality evaluation device to provide repeatable and objective information on some of the quality attributes of shrimp. Three main areas were analyzed by the automated device:
Visual: a video camera connected to a computer evaluated the shrimp for its count, uniformity ratio, color, melanosis and foreign objects. Shrimp view area was used to accurately estimate the weight, count and uniformity ratio of shrimp. The system quantified color change of white shrimp during iced storage. Some colors in a spectrum of 64 colors could be used as estimators of white shrimp quality. Melanosis increased during storage time. It was quantified by the system, and correlated with the grading of a human expert.
Odor: an ammonia electrode, connected to a computer through an analog-to-digital (A/D) converter, quantified ammonia in the headspace of intact shrimp kept in an air-tight box. A method was developed for an automated headspace ammonia analysis of shrimp, which obtained results comparable to that of wet chemical methods. No sample preparation was required except for NaOH to be sprayed on the shrimp. Less than 2 minutes were needed to obtain reliable results. Ammonia levels in shrimp were correlated with a sensory panel, who determined that the level of ammonia at which the shrimp should be rejected is 230 ppm.
Texture: an automated force-deformation device was built with a stepper motor and a load cell. The device was connected to a computer which gathered force-deformation data. The effects of shrimp size, crosshead speed, sample temperature and deformation levels on the elasticity of shrimp were studied. The elasticity measurement from the automated device showed no significant differences when compared with that of the Instron Machine. Elasticity and Texture Profile Analysis of white shrimp was measured during iced storage. Measured elasticity and springiness decreased with storage time, while adhesiveness increased.
The automated system could perform the total evaluation of quality attributes of a shrimp sample in less than 4 minutes. This device can minimize the subjectivity of quality evaluation, increase efficiency and be a decision-making tool for producers, purchasers and processors of shrimp, and for regulatory agencies.