|17.1 Characteristics and fitness for container transport|
|Hygroscopic foodstuffs are goods with a low water content (WC > 1.5 - < 30%) of water content class 2 (WCC 2), from which water has been removed by natural or artificial drying, thereby increasing their storage life and thus fitness for container transport. They interact with the water vapor content of the ambient air, i.e. they release water vapor or absorb water vapor until they are at equilibrium with the water vapor content of the ambient air (see Section 10.2.2). They include the majority of foodstuffs and semiluxury items, such as cereals, oil-bearing seeds/fruits, dried fruit, spices, coffee, cocoa, tobacco and tea. Animal raw materials and natural fibers also belong to this group, however. Their adsorption isotherms form a continuous, generally S-shaped, curve.
Hygroscopic goods do, however, also include goods which have low water contents (WC > 0 to < 1.5%) i.e. which belong to water content class 1 (WCC 1). They are of crystalline or pulverulent structure, e.g. sugar, salts or citrus powder. Their adsorption isotherms are characterized by discontinuities (see Fig. 5 in Section 10.2.7).
Some hygroscopic foodstuffs are goods displaying 2nd order biotic activity (BA 2), i.e. living organs which continue to respire but which lack any supply of new nutrients due to separation from the parent plant, e.g. cereals, oil-bearing seeds. Some are goods displaying 3rd order biotic activity (BA 3), such as dried fruit.
Crystalline and pulverulent foodstuffs are goods displaying 3rd order biotic activity (BA 3), in which respiration is suspended but in which biochemical, microbial and other decomposition processes still proceed.
Hygroscopic foodstuffs require particular temperature, humidity/moisture and possibly ventilation conditions (SC VI) (storage climate conditions). Undesirable changes occur as a function of relative humidity and temperature, in particular due to dampening (mold, rot, mildew stains, fermentation, deliquescence, self-heating, loss of crispness, mustiness, loss of aroma, syrup formation) or to desiccation (solidification, jamming/caking, fragmentation, drying-out). The critical water content is the most significant value, being that which, when exceeded, results in changes in quality. The foodstuffs in this group do not have any particular requirements as to ventilation conditions, if they are container dry.
In order correctly to set the necessary parameters, such as temperature and relative humidity, as a function of route, duration of voyage, season and period of time the goods spend in the container, ventilation may be necessary, i.e. the decision has to be made as to whether to use a standard container or a ventilated container. Most hygroscopic foodstuffs may be transported in standard containers, provided certain restrictions are taken into account.
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