Automated Headspace Ammonia Analysis of Shrimp

Determination of shrimp odor by sensory evaluation is subjective, difficult to quantify, or depends on complex and time consuming chemical analyses. Ammonia (NH3) is the main off-odor of shrimp. This study developed a methodology for repeatable, objective and rapid headspace NH3 analysis of shrimp. An electrode was connected to a computer to quantify NH3 in the headspace of intact shrimp kept in an air-tight box. The only sample preparation was to spray NaOH on shrimp. Less than two minutes were needed to obtain results. Ammonia levels measured by this method were comparable to that of wet chemical methods. A sensory panel determined that the rejection level of NH3 in shrimp was 230 ppm. This procedure could be used as a fast, simple and objective method to evaluate shrimp odor quality.