ABSTRACT
Although steam is commercially employed to sterilize and blanch food products, there is a lack of readily available data that can be used with confidence to simulate packed bed heating of diced vegetables by steam injection. Basic parameters and properties required are the food product thermal diffusivity at temperatures over 100
C and the convective surface heat transfer coefficient (h value) for steam. Data on h values for food processing applications range from 400 (Zhang and Cavalieri, 1991) to 12,000 W/m
C (Tung et al., 1990). An h value of about 5000 W/m
C is commonly employed (Skjöldebrand and Ohlsson, 1993) for steam heating, but for a 12-mm food cube this provides a Biot number (Bi) of about 50, indicating infinite resistance to surface heat transfer. This may not be so in light of data presented by Rumsey et al. (1980), Pannu et al. (1990) and Zhang and Cavalieri (1991), which show that 0.1
≤
Bi
≤
40. Also, very little work has been documented in the area of packed bed processing of moist food solids with steam.
