Fresh horticultural commodities are fundamental components in a balanced healthy diet, providing vitamins, minerals and phytochemicals. Harvested horticultural products remain as living tissues subject to continuous metabolism. Before harvesting, when horticultural commodities are attached to the parent plant, losses of substrates and moisture due to respiration and transpiration are replaced. After harvest, however losses are not replaced and quality declines, limiting horticultural commodities shelf life.
Moisture loss by transpiration in fresh products is associated with mass and quality losses and it is assumed to be a major cause of post-harvest loss in some commodities such as leafy vegetables or citrus fruits. The low levels of O2 and the high levels of CO2 in modified atmospheres can potentially reduce respiration rate, ethylene sensitivity and production, decay and physiological changes, namely oxidation, with the resultant benefit of extending the storage life of the fresh produce.
In mushrooms, post-harvest biological changes are particularly fast. Mushrooms have high respiration rate, tends to lose moisture rapidly and gets dis-coloured at a very fast rate. Mushroom quality and consumer acceptability of fresh mushrooms is strongly influenced by colour texture and appearance. Mushrooms have high respiration rates, which is high when compared with other horticultural produce. Differences in physiological activities as well as morphological characteristics of the mushroom cap may be important with regard to the maintenance of postharvest quality of particular specie.
Placing mushrooms under controlled humidity atmosphere improve their quality and increases store ability. Mushrooms shelf life can end up due to: high rate of respiration; high rate of dehydration; browning and texture changes. Post harvest losses of water by transpiration are significant in mushroom fruit body.
Predicting the kinetics of respiration and transpiration rate of oyster mushrooms (Pleurotus ostreatus), as influenced by temperature, relative humidity and storage time, is important in order to overcome the lack of information regarding the effect of storage conditions on oyster mushroom quality. Colour changes are also a factor known to affect postharvest quality of mushrooms and severe browning or discoloration may occur due to enzymatic and/or microbial activities.
The lack of packaging films with suitable permeability to O2, CO2 and moisture cause diverse problems related with the accumulation of phytotoxic CO2 levels and/or the appearance of condensation within mushroom packages.
Storage temperature had a significant effect in mushrooms quality. A gradual yellowness and high mass losses were also found throughout storage life, with an increase rate as storage temperature increases. Under the conditions tested, storage of fresh oyster mushrooms at 2 °C has the potential to increase shelf life.
Lower respiration rate was found when mushroom was stored under 2 % O2 and 20 % CO2 (v/v), under this levels may have potential in increasing oyster mushroom shelf life.
Post harvest transpiration is also an important physiological process affecting storage life and overall quality. Both humidity and temperature had a significant effect on oyster mushroom transpiration rate. Low temperatures and high humidity decreases mass losses over storage time and therefore transpiration rate.