Submitted to: Food Quality Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 7, 1995
Publication Date: N/A
Interpretive Summary: Freshly-squeezed orange juice is usually heated to pasteurize it before it is sold. This heating process changes the flavor, so that it no longer tastes like the fresh-squeezed products. We pasteurized orange juice under normal conditions and also under more severe conditions involving a longer heating time. A sensory panel found the flavor of the more severely heated djuice to be different from that of the fresh juice but found no difference between fresh and normally pasteurized juices. Chemical analysis of fresh and severely heated juice showed only one volatile flavoring substance to increase slightly in the pasteurized juice sample. Distillation of both fresh and severely heated juices to remove volatile flavorings and most of the water left residues whose aromas were different. This suggests that the less-aromatic portion of heated juice was responsible for the flavor change in heated juice. Chemical analysis of the residues failed to show a ameaningful difference in the two samples. However, these results support earlier findings that severe pasteurization conditions are needed to cause a detectable flavor change in orange juice, and any chemical changes caused by the heat treatment are minor, and difficult to determine.
Technical Abstract: Freshly extracted Florida Valencia orange juice was pasteurized at 98 degrees C for 11 sec to produce lightly pasteurized juice, and for 37 sec to produce heavily pasteurized juice. Sensory panels detected a flavor difference between the fresh, unpasteurized juice and the heavily pasteurized juice. Analyses of these two juice samples by headspace gas chromatography (GC) showed no significant qualitative or quantitative differences. GC analyses of methylene chloride extracts of juices and of residues from distillation of the juices showed only one meaningful difference in each case. Extracts of the whole juices showed one GC peak, which was significantly larger in the heavily pasteurized juice, identified as the potential off flavor compound, octanoic acid. Extracts of the high-boiling distillation residue showed one unidentified late-eluting GC peak which appeared only in the heavily pasteurized juice. These findings supplement previous reports that more severe pasteurization conditions tha required for juice processing cause detectable flavor changes in heated juice.