Abstract
Frying performance of olive-pomace oils (OPOs) as compared to sunflower oils (SOs) and high-oleic sunflower oils (HOSOs) was studied in discontinuous frying (DF) and continuous frying (CF) for the first time. DF is used in household, restaurants and frying outlets, while CF is used in the food industry. Oil alteration during frying was determined by measurements of polar compounds (PC) and polymers. Fried potatoes were analyzed for oil absorption and alteration, color, and evaluated in an acceptability test. Results for DF showed that all SOs reached 25% PC at the 9th frying operation (FO), whereas HOSOs did between the 17–18th FO and variable results were found for OPOs since initial levels of diacylglycerols were different. Rates of formation of PC or polymers were the lowest for OPOs, thus showing the best performance in DF. Specifically for PC, relative rates of formation were 1.00–1.11, 2.46–2.71 and 1.37–1.41 for OPOs, SOs and HOSOs respectively. In CF, OPOs and HOSOs behaved similarly and better than SOs, although none reached 25% PC after 40 FO. The good performance of OPOs can be attributed to the high monounsaturated-to-polyunsaturated ratio, in common with HOSOs, and the additional positive effect of minor compounds, especially β-sitosterol and squalene.
Highlights
Oils obtained from olives, including virgin olive oils, olive oils and olive-pomace oils, are key components of the Mediterranean diet and stand out for their high content of oleic acid and low amount of polyunsaturated fatty acids thereby presenting great stability and suitability for frying [1]
The total content of minor components was higher for olive-pomace oil (OPO), and their composition was different compared to sunflower oil (SO) and high-oleic sunflower oils (HOSOs), especially due to the occurrence of squalene, triterpenic and aliphatic alcohols, and residual amounts of phenolic compounds and triterpenic acids
Hydrolytic compounds remained practically at the same levels as those found in the fresh oils (Table 3) and, among the groups of oxidation compounds, the greatest increments were found for triacylglycerol polymers, which were significantly higher for SOs and HOSOs than for OPOs
Summary
Oils obtained from olives, including virgin olive oils, olive oils and olive-pomace oils, are key components of the Mediterranean diet and stand out for their high content of oleic acid and low amount of polyunsaturated fatty acids thereby presenting great stability and suitability for frying [1]. As to aliphatic fatty alcohols, characteristic of OPOs, studies have shown anti-inflammatory activity [10] and improvement of lipoprotein profile [11] For all these reasons olive-pomace oil can be an excellent alternative oil for frying. Giuffrè and coworkers [16] evaluated variations in chemical parameters of vegetable oils during heating at 180 and 220 ◦C They reported data that suggested better performance of extra virgin olive oil and palm oil than olive-pomace oil, but neither polar compounds nor polymers, the most recommended measurements of frying oil alteration, adopted in countries where the level of alteration is regulated and limited for human consumption, were determined [17]. The fried potatoes were analyzed for oil absorption, color and evaluated in a preliminary acceptability test
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