To determine effects of expeller oil pressing and decreased linolenic acid, intermittent batch frying tests were conducted with tortilla chips using soybean oil (SBO), expeller pressed SBO (EPSBO), expeller pressed low linolenic SBO (EPLLSBO), high oleic sunflower oil, corn oil and hydrogenated SBO for up to 35 h of frying. Chips were aged at 25C and trained, experienced analytical sensory panelists evaluated their flavor. Oxidative stability of the chips was determined by hexanal analyses and oil fry life was measured by total polar compounds. The stability of tortilla chips fried in EPLLSBO was significantly better than chips fried in SBO or EPSBO as judged by rancid flavor intensity and hexanal formation after storage. This effect may be due, in part, to less linolenic acid in EPLLSBO and better tocopherol retention compared to EPSBO. The combination of expeller pressing and low linolenic acid (EPLLSBO) produced a significantly more stable fried product than expeller pressing (EPSBO) alone.
Food manufacturers are interested in oils that can be used for frying as alternatives to trans fat-containing hydrogenated fats. Since polyunsaturated vegetable oils are not sufficiently oxidatively stable for frying, alternatives such as modified fatty acid composition oils, additives and oil processing techniques could be used individually or in combination to increase fry life of the oil and shelf life of foods. Although expeller pressing of SBO or reducing linolenic acid of SBO alone have not given SBO the stability equivalent to HSBO, we found that combining decreased linolenic acid and expeller pressing of SBO produced frying oil and fried tortilla chips with the stability similar to that of hydrogenated fat in early stages of frying.
Drupe characteristics, phenolic content and antioxidant capacity of olive fruits were studied for 12 Italian oil cultivars grown in two areas (Cerignola and Torremaggiore) of Daunia district. The effects of plantation place were higher than those exerted by cultivars on drupe characteristics such as weight, pulp/stone ratio, oil content and maturation index. Olive fruits from Cerignola, which is located at a lower altitude than Torremaggiore, showed the highest phenolic content. The highest phenolic content (14 g gallic acid/kg dry olive) was detected on Peranzana and Cellina di Nardò grown in Cerignola groves. The lowest values were registered for FS17 and Cima di Melfi (about 7 g/kg). 1-Acetoxypinoresinol, 3,4-dihydroxyphenylethyl 4-formyl-3-formylmethyl-4-hexenoate, the dialdehydic form of decarboxymethyl elenolic acid linked to hydroxytyrosol (3,4-DHPEA-EDA), hydroxytyrosol and luteolin, were the phenolic compounds detected in a greater amount and in most of the cultivars. Independently on the assay applied, the highest antioxidant activity was detected for Cellina di Nardò (Cerignola). The lowest antioxidant activity values were different depending on the method applied. According to the 2,2′-azino-bis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) assay, the lowest value was detected for Moraiolo from Torremaggiore, whereas Nociara showed the lowest contribution to the inhibition of lipid oxidation (β-carotene beaching assay). A strong positive linear correlation (R = 0.82) existed between total phenolic content and antioxidant activity measured according to the ABTS method, whereas a low linear correlation coefficient (R = 0.36) was obtained when the β-carotene bleaching assay was used.
The experimental results obtained with this research could help farmers to increase their knowledge of the minor components of some major and minor Italian olive cultivars. In fact, there are very few works on the characterization of olive fruits destined for oil production. The analytical findings of this study can also provide useful information to the oil industries interested in processing olives having high phenolic content and high antioxidant capacity. Furthermore, the diffusion of these results could help consumers to choose, among monovarietal extra virgin oils available in the market, those derived from the cultivars rich in antioxidant compounds.
Differential scanning calorimetry (DSC) was employed to detect high oleic sunflower oil (HOSo) as an adulterant in extra-virgin olive oil (EVOo) by means of cooling and heating thermograms. Addition of HOSo did not significantly alter cooling profiles of EVOo except for onset temperature of crystallization, which was significantly shifted toward lower temperature at 40% of adulterant addition. At the same percentage of adulteration, the heating profile of EVOo was significantly changed as the major endotherm broadened and the minor event became smaller and less evident. Cooling thermograms of pure oils and their admixtures were deconvoluted into three constituent exothermic peaks in an attempt to detect addition of HOSo at levels lower than 40%. Thermal properties of the two lower-temperature exotherms (area percentage, offset temperature and range of transition) were significantly changed at≥20% of HOSo substitution, suggesting that DSC can be employed to detect this oil as an EVOo adulterant.
Adulteration of extra-virgin olive oil (EVOo) with cheaper oils from other vegetable sources or seeds, as well as with lower quality olive oils, is a serious concern for oil suppliers and consumers and requires the use of new analytical techniques for their detection. Differential scanning calorimetry (DSC) exhibits some advantages over the classical analytical methods as it does not require sample preparation and use of solvents, thus resulting in a reduced environmental impact. Results suggested that its application to the detection of EVOo adulteration with high oleic sunflower oil, a vegetable oil largely employed for this type of fraud, is promising with the support of the deconvolution analysis of cooling thermograms.
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