Changes in the Physicochemical and Nutritional Parameters of Picual and Arbequina Olive Oils during Frying

Effect of kesse, koseret, and tosign extract treatments on the oxidative stability of oil during the repeated frying of potato chips

Fried food safety and quality are crucial concerns for consumers and the food industry due to the deterioration of oil quality and the loss of sensory properties during repeated frying. The current study investigated the use of leaf extracts from endemic dietary herbs: kesse (Lippia adoensis var. adoensis), koseret (Lippia adoensis var. koseret), and tosign (Thymus schimperi Ronninger) to enhance oil quality during the repeated frying of potato chips. The analysis of various parameters, including free fatty acids (FFA), iodine value (IV), peroxide value (PV), thiobarbituric acid reactive substances (TBARS), viscosity, and color (L*, a*, and b*), was conducted after every 5th frying cycle to assess oil quality. The results revealed significant (p < 0.05) decreases in deterioration markers for oils treated with herb extracts compared to the control oils. Specifically, after 20 frying cycles, oils treated with the dietary herb extracts exhibited lower percentage of FFA (0.63-1.05), IV (51.7-46.7), PV (6.69-7.68), and TBARS (50.27-56.08) compared to the control. The herb-treated oils also maintained lower FFA, PV, and TBARS values throughout the frying cycles and reduced viscosity, while IV gradually decreased. Furthermore, the L* value decreased gradually, and a* and b* values increased as the number of frying cycles increased. The herb extracts provided better protection against degradation compounds compared to BHT-treated and control oils, which was attributed to their lower FFA and PV. Sensory analysis indicated that potato chips fried in kesse extract-treated oil were the most preferred, followed by those treated with tosign extract. These findings highlight the potential application of herb extracts to increasing oil stability during repeated frying cycles, which add value at the interface between culinary excellence and health perspectives. Natural antioxidants from endemic herbs can maintain oil quality, reduce harmful compounds, and enhance the sensory properties of fried foods, making them a promising alternative to synthetic antioxidants.

Evaluation of the qualitative properties of the oil extracted from the mixture of Helianthus annuus and Nigella sativa seeds during heating

The oil obtained from black cumin (Nigella sativa) seeds has many health-effective properties, which is used in food applications and in traditional medicine. One practical method to extract its oil is mixing with other seeds such as sunflower (Helianthus anuus) seeds before oil extraction by press. The effectiveness of the cold-press oil obtained from the mixture of black cumin seeds (BS) and sunflower seeds (SF) in different proportions 100:0, 95:5, 90:10, 85:15 and 0:100 (w/w) was studied to evaluate their qualitative properties including peroxide value (PV), acid value, p-anisidine value (AnV), pigments (carotenoid and chlorophyll) content, polyphenols, and profile of fatty acids during heating process (30-150 min at 180 °C). The results revealed that the acid and p-anisidine value of the all samples enhanced with the extension of the heating time, and the peroxide value increased at the beginning of the heating and then decreased with the prolongation of the heating time (p < .05). With the increase of temperature and heating time, the peroxide of sunflower oil increased with a higher slope and speed than that of black seed and blends oil. Changes in the PV and AnV were the fastest in sunflower oil. Blending and heating caused considerable changes in the fatty acid composition of oils, especially myristic, palmitic, and stearic acids. Moreover, the levels of certain unsaturated fatty acids, namely linoleic, oleic, and linolenic acids declined after heating. The carotenoids, chlorophyll and total phenol content decreased gradually during heating treatments. Among extracted oils, SF:BS (15%) had the good potential for stability, with total phenol content of 95.92 (Caffeic acid equivalents/100 g), PV of 2.16 (meq O2/kg), AV of 2.59 (mg KOH/g oil), and AnV of 8.08 after the heating. In conclusion, oil extracted from the mixture of SF and BS can be used as salad and cooking oils with a high content of bioactive components and positive nutritional properties.

A Comparison of the Stability of Refined Edible Vegetable Oils under Frying Conditions: Multivariate Fingerprinting Approach

The stability of highly consumed vegetable refined oils after discontinuous frying of potatoes was compared. Both those vegetable oils containing additives and those that did not were considered. Vegetable oil samples were evaluated using refractive index, anisidine and peroxide values, UV absorbance and dielectric constant-based determination of the content of total polar compounds. Chemical changes caused over the frying time were monitored and multivariate modelling of the data was carried out. A new gas chromatographic-mass spectroscopy method was intended to record a fingerprint of both polar and non-polar compound fractions. Multivariate models of chromatographic fingerprints were also developed, and the results obtained from both approaches were verified to be statistically similar. In addition, multivariate modelling also allows to differentiate among vegetable oils according to oxidation performance. Indeed, it was initially observed that olive oils presented the highest natural thermo-oxidative stability compared to other seed oils, although it should be noted that these differences were not significant when regarding olive pomace oils and seed oils containing synthetic additives.

Vitamin E in foodstuff: Nutritional, analytical, and food technology aspects

Vitamin E is a group of isoprenoid chromanols with different biological activities. It comprises eight oil-soluble compounds: four tocopherols, namely, α-, β-, γ-, and δ-tocopherols; and four tocotrienols, namely, α-, β-, γ, and δ-tocotrienols. Vitamin E isomers are well-known for their antioxidant activity, gene-regulation effects, and anti-inflammatory and nephroprotective properties. Considering that vitamin E is exclusively synthesized by photosynthetic organisms, animals can only acquire it through their diet. Plant-based food is the primary source of vitamin E; hence, oils, nuts, fruits, and vegetables with high contents of vitamin E are mostly consumed after processing, including industrial processes and home-cooking, which involve vitamin E profile and content alteration during their preparation. Accordingly, it is essential to identify the vitamin E content and profile in foodstuff to match daily intake requirements. This review summarizes recent advances in vitamin E chemistry, metabolism and metabolites, current knowledge on their contents and profiles in raw and processed plant foods, and finally, their modern developments in analytical methods.

Performance of Olive-Pomace Oils in Discontinuous and Continuous Frying. Comparative Behavior with Sunflower Oils and High-Oleic Sunflower Oils

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.

Impact of potatoes deep-frying on common monounsaturated-rich vegetable oils: a comparative study

Aiming to distinguish the nutritional and safety impacts on consumer's health of prolonged frying with vegetable oils rich in monounsaturated fatty acids (MUFA), namely peanut oil (PO), canola oil (CO) and extra virgin olive oil (EVOO), a domestic deep-frying assay using fresh potatoes was implemented (175 °C, 8 h per day, up to 28 h). Based on a total polar compounds (TPC) degradation limit of 25%, PO and CO enabled 18-20 h of frying, while EVOO allowed significantly higher frying hours (> 28 h). Despite the non-significant variations in oxidized triglycerides contents observed through time, and loss of all major antioxidants during the first 8 to 12 h of frying, PO showed statistically higher amounts of conjugated dienes (27 at 20 h; against 19 in CO and 17 in EVOO) and CO of anisidine value (252 at 20 h; against 209 in PO and 100 in EVOO), indicative of different oxidation patters. This was corroborated with the analysis of major volatiles, with PO and CO being statistically richer in alkenals and alkadienals, respectively. Therefore, despite the MUFA predominance, differences in their unsaturation profile impact on the type and amount of degradations products formed under prolonged frying and consequently on consumer's health. As to EVOO use for prolonged frying, despite its increased resistance to oxidation and lower risk of formation of unhealthy volatiles, it loses its pool of natural bioactive compounds in the first hours of frying.

Physicochemical properties and oxidative stability of frying oils during repeated frying of potato chips

Physicochemical properties and oxidative stability of refined coconut oil (RCO), refined soybean oil (SBO), pure olive oil (POO), and vegetable shortening (VST) during repeated frying of potato chips were determined. Polyunsaturated fatty acids of all the oils significantly decreased after frying. Tocopherols in SBO, POO and VST, and DPPH radical scavenging activities of POO and VST significantly decreased after frying. L* values of the oils significantly decreased, and a* and b* values significantly increased after 80 times repeated frying. Conjugated dienes and p-anisidine value of SBO after 80 times repeated frying were 21.8 mmol/L and 47.7, respectively, the highest among the oils. Levels of total polar compounds of all the oils after 80 times repeated frying were between 8.1 and 9.5%, not exceeding rejection limit after frying. Compositions and contents of alkanals, 2-alkenals, and 2,4-alkadienals in the oils during frying were largely affected by their fatty acid compositions.

Virgin Olive Oil as Frying Oil

Frying is one of the oldest cooking procedures and is still among the most popular ones for food preparation. Due to their unique sensory characteristics, fried foods are consumed often and with pleasure. During frying, part of the oil is absorbed by the food, thereby becoming part of our diet; most interestingly, in the Mediterranean area approximately 50% of total fat intake is provided by cooking fats. Olive oil is the key lipid component of the Mediterranean diet, the health-promoting effects of which have been largely attributed to olive oil intake. Olive oil is unique among vegetable oils due to its desirable lipid profile and some of its minor components. Scientific evidence now indicates that during frying olive oil behavior is usually equal or superior to that of refined vegetable oils. Herein, an overview of virgin olive oil performance under frying is given, with special reference to the fate of olive oil microconstituents. The compositional changes of foods fried in olive oil are also reviewed and discussed in detail.