Effect of blanching and drying temperatures on the browningrelated enzymes and physicochemical properties of lily bulb flours

摘要

The effects of blanching methods and different drying temperatures on the polyphenol oxidase (PPO), peroxidase (POD), and physicochemical properties of lily flours were investigated. PPO, POD, and color results showed that blanching with steam for 1 min effectively inhibited the enzymatic browning of the lily bulbs. L* of the samples blanched with steam combined with 50 degrees C of air drying was higher than that of the rest air-dried samples. Blanching, especially employing steam, could significantly lower the loss of total phenolic contents and antioxidant activities of the samples dried at the same temperature. The starch granules of the air-dried samples with blanching were completely gelatinized, whereas the ones directly dried at 50 degrees C or 70 degrees C were partially gelatinized. Blanching and drying caused a significant increase in particle size. The protein and total starch contents of the samples decreased as drying temperature increased with or without blanching. Practical applications Fresh lily bulbs contain high moisture, high PPO and POD activities, and hence extremely susceptible to turn brown and perishable. The actual applications of this research are to evaluate the physicochemical properties of lily bulbs that underwent different blanching and drying methods. Blanching is an effective and commonly used pretreatment to control enzymatic browning, while over-blanching could cause undesired loss of nutrients, such as protein, phenolics, and starch. In addition, blanching and drying unit can affect the gelatinization of starch-based materials and consequently influence its functional behavior. Thus, this study aimed to find an efficient method and suitable parameters for inactivating endogenous browning enzymes, and also evaluate the effects of blanching and drying temperature on the physicochemical properties of lily bulbs. These findings might be used as a basis for modifying the properties of lily flours as food ingredients in other products, such as noodles, baked products, and mixed porridge.