Characterization of critical physical and mechanical properties of freeze-dried grape powder for development of a clinical patient delivery system

Abstract

Grapes are hypothesized to be a “food medicine.” Freeze-dried grape powder (FDGP) is being used to test clinical activity for a variety of applications and a reproducible and reliable delivery system was required. The FDGP was characterized using traditional physico-chemical methods to generate the data needed to identify its primary liability, i.e. moisture sorption. Above a threshold level of moisture content (~25% w/w, at RT), the material becomes both difficult to handle and exhibits significant degradation of several potentially clinically important chemical components (catechin, epicatechin, resveratrol). A moisture sorption isotherm was then used to tie the threshold to the exposure relative humidity above which this occurs. Kinetic uptake studies were used to estimate the maximum safe exposure time at a given humidity (a square root time dependence of moisture uptake was observed). Armed with this knowledge, a FDGP compact coated with a compression coat [100% bees wax or combinations of carnauba wax (70%) with HPC (30%) or Avicel^® PH 102 (30%) or lactose monohydrate (30%)] was developed that will insure the shelf life of the material without the need for special handling for approximately more than 3 months.

Keywords::

• Freeze-dried grape powder
• grape for clinical trials
• physico-chemical characterization
• compression coating
• shelf life

Acknowledgments

We are also thankful to Prof. Richard B. Van Breeman, UIC, Illinois, USA for LC/MS/MS analysis for FDGP. Additionally, the support and advice of Prof. John Pezzeuto, Dean of COP, UHH, Hilo, USA is highly appreciated.

Declaration of interest

The authors gratefully acknowledge the financial support provided by the California Table Grape Commission, Fresno, CA, USA for this work.