The effect of harvest time on rebaudioside A levels

[seetharam annadana]

Poerpoint presentation brief on

The effect of harvest time on rebaudioside A levels in Stevia rebaudiana

F. M. Dickie and L. Ackerman
Paul L. Byrne Memorial A. T. R. C
CSU, Chico

Stevia rebaudiana -- Native to Paraguay
glycoside on leaves
glycoside sweetness from glucose molecules

Rebaudioside A
300 times sweeter than sugar
minimal aftertaste
non-caloric
non-fermentable
extract sells for $100/lb.

Literature review
Day length affects glycoside levels (Metivier and Viana, 1979)

There is an increase in glycoside in LD conditions (Zaidan, Dietrich and Felippe, 1979)

Objectives
Determine the effect of harvest dates on rebaudioside A yields
Assess the value of multiple cuttings in a single growing period

Methods
8 harvest dates
10 plants per harvest date homogenized to obtain single sample from each date
Thin layer chromatography to assess glycoside levels
High-pressure liquid chromatography to obtain quantitative analysis
Regress rebaudioside A levels vs. harvest date
TLC extraction modified from Bieleski and Turner, 1966
TLC according to Metivier and Viana, 1979
HPLC performed by Hawaii Agriculture Research Center, 2000

Implications
P-value does not allow for reliable prediction of harvest date
Trend line indicates varying glycoside levels
Crop value would determine date and number of harvests per season

Acknowledgements
C. Morris, Sweet Aloha Farms
Dr. J Pushnik, Dr. R. Baldy, Dr. W. Patton, and Dr. L. Kirk
Dr. J. Brandle and Dr. B. McGarvey, Agriculture and Agri-Food Canada
Dr. M. Jackson, Hawaii Agriculture Research Center
C. Sellers and K. Berry-Garrett,College of Agriculture Laboratory, CSU, Chico