DESIGN AND PERFORMANCE EVALUATION OF A LOW-TEMPERATURE SPIN-DRYING SYSTEM FOR REDUCING BROWNING IN FRESH-CUT ORGANIC GREEN COS LETTUCE
Keywords:
Low-temperature spin-drying system, Browning, Organic green cos lettuce, Postharvest handling, Cooling systemAbstract
Maintaining the quality of fresh-cut, ready-to-eat vegetables, particularly organic green cos lettuce (Lactuca sativa L. var. longifolia), remains a major challenge in postharvest handling because browning directly affects visual quality and consumer acceptance. This study aimed to design and evaluate the engineering performance of a temperature-controlled spin dryer for fresh-cut organic green cos lettuce and to investigate the effect of low-temperature control during spin drying on browning development. The prototype was designed by integrating a refrigeration system into the spin-drying process. After trimming and washing, the lettuce samples were randomly divided into 1-kg batches. The refrigeration system was operated for 5 min before spin drying. The samples were then spin-dried at a constant rotational speed of 180 rpm for 15 min under low-temperature conditions, with supply- and return-air temperatures of 18.0 and 22.3 °C, respectively. Control samples were spin-dried under ambient conditions without operating the refrigeration system. Following spin drying, the samples from each treatment were divided into 20 experimental units of 20 g each, individually packaged in polyethylene bags, and stored at 4 °C for 10 days. Browning development was monitored using image analysis based on the hue–saturation–intensity (HSI) color model, with hue angles ranging from 35° to 50° used to identify browned areas. The engineering performance evaluation showed that the prototype had a cooling capacity of 0.066 TR, an airflow rate of 2.97 m³/min, and an energy efficiency ratio (EER) of 0.73 BTU/h/W. Image analysis revealed that the samples subjected to low-temperature spin drying exhibited less than 2.5% browned area, whereas the control samples exhibited more than 3.6%. The difference between the treatments was statistically significant (p < 0.05). These findings demonstrate that spin drying under controlled low-temperature conditions can reduce browning and help maintain the visual quality of fresh-cut organic green cos lettuce during refrigerated storage.
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