Vacuum oven

This is one of the recommended drying methods for moisture in animal feed (Padmore, 1990, p. 69). About 2 g animal feed is dried to constant weight at 95-100°C under a pressure of ^100 mmHg for about 5 h. A high molasses content requires ^50 mmHg at ^70°C. Vacuum ovens are ideal for drying

Table 2.1. Some drying times for various feeds.

Reference Sample Drying Temperature

Table 2.1. Some drying times for various feeds.

Reference Sample Drying Temperature

time (h)

(°C)

MAFF/ADAS, 1986, p.

4

Herbage, hay (silage dry matter)

18

100±2

MAFF/ADAS, 1986, p.

4

Brassicas

18

100±2

MAFF/ADAS, 1986, p.

4

Root crops (carrots, swedes, etc.

) 48

60

MAFF/ADAS, 1986, p.

4

Potatoes, artichokes

24

60

plus 18

100±2

MAFF/ADAS, 1986, p.

4

Cereal grains

40

100±2

Wallinga et al., 1995

Herbage

24

70

Isaac, 1990, p. 41

Herbage

24

80

Byrne, 1979

Herbage

16

95

products that are heat labile at low temperatures. For dietary fibre analysis, drying at 100-105°C may cause Maillard reaction products which analyse as lignin. It is recommended that a vacuum oven at 60°C or freeze-drying is used (Southgate, 1995, p. 46).

Makers of vacuum ovens include Gallenkamp (from Fisher), Heraeus GmbH & Co. KG, Jouan, and Townson and Mercer (see http://www. sanyogallenkamp.com; http://www.heraeus.com; http://www.jouaninc.com; http:// www.townson-mercer.co.uk).

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