A novel system for rapidly predicting produce water loss and measuring respiration rate

Abstract

Water loss through transpiration after harvest can significantly decrease fruit and vegetable quality and profitability. Preharvest factors, such as cultivar, produce size, field sprays, fertilizer application, and irrigation, can all affect water loss after harvest. Postharvest treatments, such as coatings, packaging, and storage conditions also influence water loss. This paper describes a low-cost system for rapid transpiration measurement (i.e. the rate of water leaving a product) and water loss prediction (i.e. the total amount of water lost over a predetermined storage period) in produce. Transpiration rates were measured using readings from a temperature, relative humidity, and pressure sensor to calculate the change in water vapor in a sealed container over 30 s. Transpiration measurements were validated in 21 different combinations of products, packaging, and storage temperatures using changes in product weight as a comparison method. Initial transpiration rates using the described system were well correlated to changes in product weight measured at the end of storage. However, total water loss over the storage life was overpredicted using the initial transpiration rate for many products due to changes in the product weight loss rate over time. The change in weight loss rate over time was negatively correlated with the initial weight loss rate. Based on this relationship, a novel water loss prediction model was developed incorporating the initial weight and transpiration rate. Use of this model greatly improved the agreement between predicted and measured weight loss, and the systemic overprediction of weight loss was eliminated. Incorporation of a CO2 sensor into the sealed chamber allowed for respiration measurements in 10 min per sample with good agreement when compared to a standard gas analysis method. This system could be used for comparing varieties and evaluating the impact of pre and postharvest practices.