Phenol and polyphenol compounds are common to all olives. Some of these phenol compounds contribute to the color of the olive. Others have antimicrobial activity against a wide variety of microorganisms (including lactic acid bacteria).The phenol fraction of olives (and olive oil) also may have positive dietary and nutritional benefits, due to their antioxi-dant activities (Box 7-5). The most important and abundant phenol is oleuropein (part of a class of compounds called secoiridoids).
Structurally, oleuropein is a glucoside ester of 3,4-dihydroxytyrosol and elenic acid (Figure
7-6). Glucosidic phenols, and oleuropein in particular, are important in olives owing to the pronounced bitter flavor they impart. Some olive varieties can contain as much as 14% oleuropein (on a dry basis) during the early stages of growth, although most contain no more than 3% to 6%.As the olives mature, the oleuropein concentration decreases, and at maturation, about 1 mg to 2 mg per g of pulp is present. Still, between the remaining oleu-ropein and related derivatives, the olives are too bitter to consume. Thus, manufacturing processes for most olives, including some fermented varieties, include sodium hydroxide-treatment steps to remove the bitter oleu-ropein fractions.
Olives, of course contain a significant amount of oil (12% to 30%, depending on cultivar).The fermentable carbohydrate concentration of ripe olives generally ranges from 2% to 5%; most of this carbohydrate is glucose. However, when the olives are washed or treated to remove the bitter components, sugars are also lost.
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