Microwave drying of hides under vacuum

Several important attributes of microwave drying under vacuum render it feasible and attractive. Unlike during other forms of drying, during microwave drying the moisture content is the same throughout the hide, especially if the hides are uniformly exposed to microwave energy by tumbling inside mixers. This permits drying of unhaired, delimed and wrung hides to a uniform moisture content at which they can be accurately split without delay. By carrying out the drying operation under vacuum (about 36 torr absolute pressure), denaturation of collagen is prevented. Furthermore, unlike warm air drying, microwave drying is quick enough to limit microbial contamination of the product. Costing $14.60 per hide, the drying process is expensive; yet it is economical because the flesh split is clean and can be sold as edible-grade collagen. If splitting is conducted at a moisture content below 38% on a moisture free basis, growth of bacteria is insignificant. At 21% moisture content on a moisture free basis all microbial growth ceases. By marketing the products at the latter moisture content wrapped in plastic to prevent rehydration, their storage life is expected to be very long.