Browning is a problem for fruit juices and particularly apple juice. It occurs in the presence of oxygen when the enzyme polyphenol oxidase (PPO) converts phenolic compounds into dark coloured pigments.
“This browning decreases both the acceptability and nutritional quality of the fresh juice; therefore, the use of anti-browning agents is required,” explained Mexican researchers in LWT – Food Science and Technology.
“However, market trends on food preservation are limiting the use of synthetic additives and the search for natural anti-browning products is increasing in correspondence to industrial and consumer demands.”
In keeping with the natural trend, the researchers examined the potential of a range of natural anti-browning agents to inhibit the activity of PPO in an apple juice product.
Four agents were tested: an extract from Palo Fierro honey, caffeic acid phenetyl ester, L-cysteine, and 4-hexylresorcinol. The compounds were used over a range of concentrations.
Results showed that apple juice containing the honey extract, cysteine, and 4-hexylresorcinol showed virtually no browning, while the caffeic acid-containing juice did undergo significant browning.
On the other hand, caffeic acid, in addition to the honey extract and 4-hexylresorcinol showed “high inhibition of apple juice PPO”, said the researchers.
“In view of these results, we suggest that Palo Fierro Honey (as a natural product) or its flavonoid rich extract has great potential in being used as an anti-browning agent for apple juice, since it reduces enzymatic browning, while at the same time provides bioactive ingredients with health-promoting properties,” concluded the researchers.
Source: LWT – Food Science and Technology
Published online ahead of print, doi: 10.1016/j.lwt.2010.05.030
“Mechanism for the Inhibition of Apple Juice Enzymatic Browning by Palo Fierro (Desert ironweed) Honey Extract and other Natural Compounds”
Authors: L.A. de la Rosa, E. Alvarez-Parrilla, E. Moyers-Montoya, M. Villegas-Ochoa, J.F. Ayala-Zavala, J. Hernández, S. Ruiz-Cruz, G.A. González-Aguilar