45C-12 |
Effects of antioxidants on the stability of (E, Z)-2,6-nonadienal and (E)-2-nonenal in fresh cucumber homogenates |
M. J. CHO and R. W. Buescher. Department of Food Science, University of Arkansas, 2650 N. Young Avenue, Fayetteville, AR 72704 (E, Z)-2,6-nonadienal (NDE) and (E)-2-nonenal (NE) are naturally formed in response to physical disruption of cucumber tissues, however these two flavor volatiles are very unstable. Therefore, investigations were conducted to determine the cause and possible control from the loss in order to advance the stabilities of natural NDE and NE. The objectives were to determine effects of chelators (EDTA, o-phenanthroline, and citric acid) and antioxidants (ascorbic acid, BHA, BHT, and propyl gallate) on the stability and degradation products of NDE and NE. Fresh cucumbers were blended and filtered through micracloth. Aliquots were sampled and held at 30oC in sealed vials during 30 min. Headspace volatiles were adsorbed by Carboxen-PDMS SPME and analyzed at 1 h interval by GC-MS. Volatiles were desorbed onto CP-Sil8CB-MS column for 2 min at 270oC. Changes in volatiles with or without treatments were quantitated by an internal standard. Over 95% of NDE and NE disappeared after several hours holding at 30oC. Alcohols, (E, Z)-2,6-nonadienol, nonanol, (Z)-3-hexenol, and ethanol, increased while the aldehydes in cucumber homogenates declined during holding. Additions of BHA, BHT, citric acid, o-phenanthroline, and propyl gallate delayed the degradation of NDE and NE. EDTA of 20 and 100 ppm did not improve the stability of NDE and NE. Antioxidants were combined to take advantage of their different properties. Combination of BHA, BHT, and citric acid improved NDE stability by almost 19-fold at 35 h holding. Propyl gallate provided the greatest protection of NDE degradation. When propyl gallate and citric acid were combined, the stabilizing property was mainly provided by propyl gallate. The o-phenanthroline reduced unsaturated aldehydes reduction to alcohols. Formation of (Z)-heptenal and increase in acetaldehyde indicated that Retro-Aldo reduction was partially involved in NDE degradation. The formation alcohols by enzymatic reduction of NDE and NE was the first step of the loss, whereby enzymatic degradation were greater than non-enzymatic. NDE was continuously degraded by Retro-Aldo reduction even though it was very low amount.
Session 45C, Food Chemistry: Flavor and aroma chemistry
|