Infrared Drying Characteristics and Quality Variations of Lily Bulbs Under Blanching Pretreatment

Abstract

Infrared drying characteristics and quality variations (color change, hardness, contents of polyphenol and flavonoid) of lily bulbs under blanching pretreatment are investigated. Influences of parameters such as pretreatment temperature and time and infrared drying temperature are discussed. Effective moisture diffusivity coefficient, activation energy, and energy consumption were calculated. Results showed that drying time was reduced by 62.5%, 56.3%, and 61.5% at 90 °C compared to 60 °C when blanching time was 4, 5, and 6 min, respectively. A blanching time of 5 min and drying temperature of 70 °C were ideal for pretreatment and drying to maintain good color quality. Hardness value of lily bulb decreased as drying temperature and blanching time increased. Seventy to eighty degree celcius was ideal drying condition to maintain good hardness quality. Blanching time and drying temperature differently affected contents of flavonoids and polyphenols of lily bulbs. Basically, when blanching time was relatively long and drying temperature was relatively high, the content of polyphenols was high.