Development of Respiration Rate Measurement System for Agricultural Products (Case study: Lettuce)

In the recent years, agricultural products packaging was faced with some challenges. One of these challenges is measuring the oxygen and carbon dioxide amount during the respiration of stored products. Due to the high cost of the sensors and measuring devices of oxygen and carbon dioxide, the researchers have been looking for alternative methods for those measuring. The major aims of this study is to find a mathematical measurement method based on temperature, humidity ratio, and absolute and differential pressure during the respiration of lettuce storage. The present study was conducted at three temperature levels (5, 15, and 25 °C) and three storage time levels (24, 48 and 72 h). Based on the results of the mathematical model, the accuracy of prediction at the storage temperature of 5, 15, and 25°C for oxygen measurement were 96%, 98% and 97% and for carbon dioxide measurement were 95%, 99% and 98%, respectively. The statistical analysis of the variation parameters of carbon dioxide, humidity ratio and absolute and differential pressure with the variation of temperature and storage time of lettuce was significant at 1% levels.