Abstract
The stability of minor bioactive compounds in olive-pomace oils (OPOs) was evaluated at frying temperature under the conditions of a thermoxidation test. Bioactive compounds analyzed included squalene, tocopherols, sterols, triterpenic acids and alcohols, and aliphatic alcohols. In order to determine the amount of OPO bioactive compounds incorporated into foods after frying, three different kinds of frozen products were selected, i.e., pre-fried potatoes (French fries), pre-fried battered chicken nuggets, and chicken croquettes (breaded patties), and were used in discontinuous frying experiments. Results obtained in both the thermoxidation and frying studies showed high stability of triterpenic alcohols (erythrodiol and uvaol), oleanolic acid, and aliphatic alcohols, naturally present in OPOs. In all fried foods, the content of lipids increased after frying, as expected, although the extent of absorption of OPOs into fried foods and the exchange with food lipids depended on the food characteristics. Overall, frying with OPOs improved the nutritional properties of all products tested by increasing the level of oleic acid and by the incorporation of squalene, triterpenic acids and alcohols, and aliphatic alcohols, in significant quantities.
Highlights
Olive-pomace oil (OPO) is the main by-product of virgin olive oil production
60–80% remained in the OPO after the fourth frying operation, its content in the fried products was relatively high as a result of oil absorption
The results obtained in the present study agreed with those reported by Kalogeropoulos and Andrikopoulos [57] in fried potatoes and those published by de Alzaa et al [22] in nuggets, in both studies using virgin olive oil
Summary
Olive-pomace oil (OPO) is the main by-product of virgin olive oil production. It is obtained mainly by solvent extraction from the olive cake and refined before consumption. When virgin olive oils were used for repeated frying operations, their phenolic contents and, their main antioxidant protection was found to decrease significantly [4,5], while sterols, squalene and triterpenic alcohols (erythrodiol and uvaol), and acids (oleanolic and maslinic acids) showed high stability at frying temperature [6]. With regard to the incorporation of oil bioactive compounds to fried foods, different oils have been used in the studies published so far, as reviewed by Chiou and coworkers [3,21] They showed and discussed the data obtained regarding the retention of tocopherols, phytosterols, polyphenols, squalene, and carotenoids in French fries prepared with a variety of vegetable oils, including virgin and refined olive oils [21]. Analyses of the oils and lipids extracted from the fried foods included characterization and quality determinations and quantification of squalene, sterols, tocopherols, triterpenic acids and alcohols, and aliphatic alcohols
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