Peppermint is one of the most important aromatic plants because it has wide range of industrial uses and
is widely accepted by the public for its flavoring and pharmaceutical properties. Hot air or natural drying
of medicinal and aromatic plants, including peppermint, is a common postharvest operation. Drying the
product reduces biochemical and microbiological degradation. However, many studies in the literature
report the results of drying only a small amount of plant material (less than 1 kg) and do not consider the
performances of industrial scale dryers in terms of their effect on product quality, energy consumption
and throughput. A rotary drum dryer was used to dry 15 kg of fresh chopped peppermint plant. The rotary
drum dryer was programmed to operate under two different drying schemes: constant air temperature
drying and rectangular wave-shaped drying air temperature profiles. The drying durations were 15–18 h
and 12–15 h for constant temperature profile and rectangular wave-shaped temperature profiles, respectively.
Hot air drying caused considerable darkening of the dried peppermint leaves. Essential oil contents
of peppermint samples dried by the two different drying procedures were relatively unaffected by drying
scheme (2.08–2.7 mL 100 g dry matter−1). The menthol content of the leaves increased from 32.52%
(fresh) up to 44.52% (dried), their menthone content decreased from 24.85% (fresh) down to 9.07% (dried).
However, the variations within replications were relatively high in terms of the menthol (25.39–44.52%)
and menthone (9.07–18.49%) contents of the dried leaves. These variations might have been caused by
the uncontrolled morphological and physiological changes of the fresh peppermint materials associated
with their maturity. These variations are the main obstacle to obtaining reproducible results and therefore
dried peppermint products with consistent quality. The specific energy consumption values ranged
from 7.88 to 15.08 MJ (kg water removed)−1. Daily fluctuations in ambient air conditions directly affected
the specific energy consumption of rotary drum dryer
Peppermint is one of the most important aromatic plants because it has wide range of industrial uses andis widely accepted by the public for its flavoring and pharmaceutical properties. Hot air or natural dryingof medicinal and aromatic plants, including peppermint, is a common postharvest operation. Drying theproduct reduces biochemical and microbiological degradation. However, many studies in the literaturereport the results of drying only a small amount of plant material (less than 1 kg) and do not consider theperformances of industrial scale dryers in terms of their effect on product quality, energy consumptionand throughput. A rotary drum dryer was used to dry 15 kg of fresh chopped peppermint plant. The rotarydrum dryer was programmed to operate under two different drying schemes: constant air temperaturedrying and rectangular wave-shaped drying air temperature profiles. The drying durations were 15–18 hand 12–15 h for constant temperature profile and rectangular wave-shaped temperature profiles, respectively.Hot air drying caused considerable darkening of the dried peppermint leaves. Essential oil contentsof peppermint samples dried by the two different drying procedures were relatively unaffected by dryingscheme (2.08–2.7 mL 100 g dry matter−1). The menthol content of the leaves increased from 32.52%(fresh) up to 44.52% (dried), their menthone content decreased from 24.85% (fresh) down to 9.07% (dried).However, the variations within replications were relatively high in terms of the menthol (25.39–44.52%)
and menthone (9.07–18.49%) contents of the dried leaves. These variations might have been caused by
the uncontrolled morphological and physiological changes of the fresh peppermint materials associated
with their maturity. These variations are the main obstacle to obtaining reproducible results and therefore
dried peppermint products with consistent quality. The specific energy consumption values ranged
from 7.88 to 15.08 MJ (kg water removed)−1. Daily fluctuations in ambient air conditions directly affected
the specific energy consumption of rotary drum dryer
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