The influence of metal ions on the dielectric enhancement and radical generation of rice starch during microwave processing.

In this study, the effect of the enrichment of rice starch with metal ions on its capability to generate free radicals during microwave processing was investigated. The underlying mechanism was explored from two aspects: dielectric and thermal properties. Rice starch was modified with ions of iron, copper, manganese and calcium. The modified starches were analyzed in terms of dielectric properties, activation energy (Ea) and thermodynamic characteristics of gelatinization. The quantity and character of the free radicals were analyzed using electron paramagnetic resonance (EPR). The results showed that the metal ions could change the dielectric property and inter structure of rice starch, thus influencing the ability of rice starch to generate radicals under microwave irradiation.

Study of the optimisation of puffing characteristics of potato cubes by spouted bed drying enhanced with microwave.

BACKGROUND: In commercial deep-fat frying of potato chips, the oil content of the final products ranges from 35 to 45 g 100 g(-1) (wet basis). High-temperature frying may cause the formation of acrylamide, making the products unhealthy to the consumer. The aim of this research was to explore a new method, spouted bed microwave drying, to produce healthier puffed snack potato cubes as possible alternatives to oil-fried potato chips. The influence of drying conditions of the spouted bed microwave drying on puffing characteristics of potato cubes were studied and compared with the direct microwave and hot air drying method. RESULTS: Tandem combination drying of microwave-enhanced spouted bed drying (MWSB) could achieve a good expansion ratio, breaking force and rehydration ratio. The puffing characteristics of potato cubes were significantly affected (P < 0.05) by moisture content before starting microwave power in spouted bed microwave drying, by microwave (MW) power, and by the original size of potato cubes. CONCLUSION: The optimum processing parameters were the moisture content at the start of microwave power (60%), the size of potato cubes (10-12 mm), and microwave power (2-2.5 W g(-1))