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Related Concept Videos

Adaptations that Reduce Water Loss01:57

Adaptations that Reduce Water Loss

Though evaporation from plant leaves drives transpiration, it also results in loss of water. Because water is critical for photosynthetic reactions and other cellular processes, evolutionary pressures on plants in different environments have driven the acquisition of adaptations that reduce water loss.
Constant Pressure Calorimetry03:02

Constant Pressure Calorimetry

Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a substance. The heat is exchanged with a calibrated and insulated device called the calorimeter. Calorimetry experiments are based on the assumption that there is no heat exchange between the insulated calorimeter and the external environment. The well-insulated calorimeters prevent the transfer of heat between the calorimeter and its external...
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Concrete members with a small surface-to-volume ratio are cured by oiling and moistening the forms before casting the concrete member. These forms can be left in place for a prolonged period to prevent moisture loss, and can be wetted if made of a material suitable for wetting. If the forms are removed early, the concrete member is moistened and covered with polythene sheets to maintain moisture. For large horizontal concrete surfaces exposed to dry weather, a temporary covering is suspended...
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Related Experiment Video

Updated: Jul 15, 2026

Diffuse Reflectance Infrared Spectroscopic Identification of Dispersant/Particle Bonding Mechanisms in Functional Inks
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Drying strategies of spent coffee grounds using refractance window method.

Alberto Claudio Miano1, Meliza Lindsay Rojas1

  • 1Centro de Investigación Avanzada en Agroingeniería, Universidad Privada del Norte (UPN), Peru.

Food Research International (Ottawa, Ont.)
|February 3, 2024
PubMed
Summary

Refractive window (RW) drying of spent coffee grounds is up to 50% faster than convective air drying. Ethanol pretreatment and ultrasound significantly accelerated RW drying, best preserving bioactive compounds.

Keywords:
By-products dryingDrying kineticsMarangoni effectSpent coffee groundsUltrasound

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Area of Science:

  • Food Science and Technology
  • Chemical Engineering
  • Biotechnology

Background:

  • Spent coffee grounds (SCG) are a rich source of bioactive compounds.
  • Efficient drying methods are crucial for SCG valorization.
  • Traditional convective air (AC) drying can degrade sensitive compounds.

Purpose of the Study:

  • To evaluate ethanol pretreatment and ultrasound-assisted refractive window (RW) drying of SCG.
  • To compare RW drying with conventional AC drying.
  • To assess the impact on drying kinetics, phenolic content, and antioxidant capacity.

Main Methods:

  • SCG samples were dried using AC (80°C, 0.8 m/s) and RW methods.
  • RW drying was tested with and without ethanol pretreatment and ultrasound.
  • Drying kinetics were modeled using Fick and Page models.
  • Total phenolic content and antioxidant capacity were quantified.

Main Results:

  • RW drying was up to 50% faster than AC drying, showing higher effective diffusivity and kinetic parameters.
  • Ethanol pretreatment and ultrasound significantly accelerated RW drying kinetics.
  • AC drying kinetics were not significantly affected by treatments.
  • Ethanol pretreatment with RW drying best preserved phenolic compounds and antioxidant capacity.

Conclusions:

  • RW drying, especially with ethanol pretreatment and ultrasound, offers a faster and more effective method for SCG drying.
  • These strategies enhance drying efficiency while preserving valuable bioactive compounds.
  • Optimized RW drying of SCG facilitates subsequent utilization in various applications.