39B-14

S. M. SON¹, K. D. Moon², and C. Y. Lee¹. (1) Dept. Food Sci. & Tech., Cornell University, Geneva, NY 14456, (2) Dept. Food Sci. & Tech., Kyungpook Natl. University, Daegu, South Korea

Justification: To meet consumersŐ demand for non-chemical additives in our foods, it is necessary to search for effective antibrowning agents from the natural products.

Objective: To determine and establish the efficacy of rhubarb juice as a potent antibrowning agent on fresh-cut apple slices.

Methods: Fresh rhubarb obtained from a local grower was washed and cut into small pieces and pressed using a screw extruder with approximately 80 % (w/w) yield. Liberty apple slices were dipped into the various concentrations of rhubarb juice (100%, 80%, 60%, 40%, 20%, 10%, and 5%) and the degree of browning at room temperature was measured by a Hunter Colorimeter.

Results: Antibrowning activities of diluted rhubarb juice solutions (100%, 80%, 60%, 40%, 20%, 10%, and 5%) on fresh-cut apple slices varied greatly. Apple slices treated with 5-10% rhubarb juice solutions showed browning activity with the dL values of 2.3-2.5 at two hours. However, the higher concentrations of rhubarb juice solution above 20% inhibited apple browning effectively with no change in the L value. The lowest concentration of rhubarb juice for an effective antibrowning activity was 20%. The potency was very comparable to those of kojic acid and cysteine. Oxalic acid was found to be one of the major organic acids at a concentration of 334 mg/100g juice and this acid appeared to be the major source of antibrowning activity as observed in our previous study (Son et al., 1999).

Significance: Rhubarb juice is a very potent natural antibrowning agent. It has a strong potential for commercial use because rhubarb is easily obtainable, inexpensive, safe, natural and free of regulatory constraints.