The physico-chemical characteristics of the seeds and seed oils of four citrus species, Mitha (Citrus limetta), Grapefruit (Citrus paradisi), Mussami (Citrus sinensis), and Kinnow (Citrus reticulata) were investigated. The hexane-extracted oil content of citrus seeds ranged from 27.0 to 36.5%. The protein, fiber and ash contents were found to be 3.9-9.6%, 5.0-8.5%, and 4.6-5.6%, respectively. The extracted oils exhibited an iodine value of 99.9-110.0; refractive index (40°C), 1.4639-1.4670; density (24°C), 0.920-0.941 mg/mL; saponification value, 180.9-198.9; unsaponifiable matter, 0.3-0.5%; acid value (mg KOH/g of oil), 0.5-2.2 and color (1-in. cell) 1.4-3.0R + 15.0-30.0Y. The oils revealed a good oxidative stability as indicated by the determinations of specific extinctions at 232 and 270 nm (2.3-4.4 and 0.6-0.9, respectively), p-anisidine value (2.2-3.2) and peroxide value (1.6-2.4 mequiv/kg of oil). The citrus seed oils mainly consisted of linoleic acid (36.1-39.8%). Other prominent fatty acids were palmitic acid (25.8-32.2%), oleic acid (21.9-24.1%), linolenic acid (3.4-4.4%), and stearic acid (2.8-4.4%). The contents of tocopherols (a, c, and d) in the oil were 26.4-557.8, 27.7-84.1, and 9.1-20.0 mg/kg, respectively. The results of the present study demonstrated that the seeds of citrus species investigated are a potential source of valuable oil which might be utilized for edible and other industrial applications.

The changes in regular canola oil as affected by frying temperature were studied. French fries were fried intermittently in canola oil that was heated for 7 h daily over seven consecutive days. Thermo-oxidative alterations of the oil heated at 185 ± 5 or 215 ± 5°C were measured by total polar components (TPC), anisidine value (AV), color components formation, and changes in fatty acid composition and tocopherols. Results showed that TPC, AV, color and trans fatty acid content increased significantly (P \ 0.05) as a function of frying temperature and time. The oil polyunsaturated fatty acids (PUFA) decreased in direct proportion to frying temperature and time. After 7 days of frying, the amount of PUFA was reduced by half and the trans isomers contribution increased 2.5 times during frying at 215°C. Of the parameters assessed, total polar component and color had the highest correlation, with correlation coefficients of 0.9650 and 0.9302 for frying at 215 and 185°C, respectively. TPC formation correlated inversely with the reduction of tocopherols.

Refined olive, corn, soybean, and sunflower oils were used as cooking oils for deep-frying at two different temperatures, 160 and 190 °C, and for pan-frying of potatoes at 180 °C for 10 successive sessions under the usual domestic practice. Several chemical parameters were assayed during frying operations to evaluate the status of the frying oils. Refined olive oil, as frying oil, was found to be more stable than the refined seed oils. In fact, this oil has proven the greatest resistance to oxidative deterioration, and its trans-fatty acid contents and percentages of total polar compounds were found to be lower at 160 °C during deep-frying. Finally, chemometric analysis has demonstrated that the lowest deterioration of the quality of all refined oils occurred in the refined olive oil during deep-frying at 160 °C and the highest deterioration occurred in the refined sunflower oil during pan-frying at 180 °C.

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The frying performance of rapeseed, soybean, and sunflower oils with modified fatty acid composition, and palm olein (PALMO) was compared during a rotational frying operation. The frying was conducted at 185 ± 5°C for 6 days where French fries, battered chicken, and fish sticks were fried in succession. At the end of the frying period, high‐oleic rapeseed and sunflower oils exhibited a significantly higher frying stability than PALMO and other modified oils, based on total polar components (TPC), polymers, and non‐volatile carbonyl compounds formation (anisidine value (AV)). The rate of TPC formation was 2.9, 2.9, 3.2, 3.2, and 3.4% per frying day for high‐oleic low‐linolenic rapeseed (HOLLRAP), high‐oleic sunflower (HOSUN), mid‐oleic sunflower (MOSUN), low‐linolenic soybean (LLSOY), and PALMO, respectively. Although the contents of free fatty acids (FFA) in the used oils were significantly below the regulatory discard level, in PALMO formation of these compounds was 1.7 times higher compared to the modified oils. Color component formation and tocopherol degradation were also observed to be the highest in palm olein. A 15‐member consumer panel awarded HOLLRAP and HOSUN the highest overall sensory acceptance scores, while for LLSOY and PALMO the lowest. Practical applications: Although several frying oils are available in today's market, only a few of them can deliver satisfactory performance during extended frying operation. Thus, the search for the ideal frying oils/fats is an ongoing task. The present study assessed frying performance in the quest for the appropriate frying oils/fats in order to deliver healthy fried products with optimized nutritional qualities.

Fourteen cyclolinopeptides (CLPs) from flaxseed oil and meal were separated, identified and quantified by HPLC coupled to an Orbitrap MS. The oxidative stability of the cyclolinopeptides was assessed during storage of flaxseed oil and meal. A significant decrease in the amounts of the methionine containing CLPs, namely CLP‐B, CLP‐J and CLP‐M, and a concurrent increase in the amounts of methionine sulfoxide containing CLPs, such as CLP‐C, CLP‐E and CLP‐G were observed. The cyclolinopeptides with two methionine units, CLP‐L and CLP‐M, exhibited the greatest decrease, followed by CLP‐J, the major flaxseed oil bitter taste precursor, and CLP‐B, a biologically active cyclolinopeptide. At the end of the storage period, the amount of the bitter CLP‐E increased fourfold in the oil while the immunosuppressive cyclolinopeptides A remained unchanged. No significant changes in the amount of each of the CLPs were observed in the stored flaxseed meals. A fast and reliable procedure has been developed for quantitative analysis of cyclolinopeptides. Due to the high predisposition of methionine containing cyclolinopeptides to oxidation and the easiness of CLPs’ quantification with the proposed method, it is possible to reliably assess the extent of flaxseed meal and oil oxidation.

The effect of carbon dioxide blanketing (CDB) and vacuum frying (VF) on the frying performance of regular canola oil was evaluated. For 7 h daily and for 7 days French fries were fried in regular canola oil at 185 6 5 7C without and with CDB and in a vacuum fryer. The extent of changes in the oil was assessed by analysis of total polar compounds (TPC), anisidine value (AV), color component formation and changes in composition of fatty acids and tocopherols. Frying under CDB reduced the amount of TPC by 54%, while 76% reduction was observed during VF compared to standard frying conditions (SFC). Similarly, lower oxidative degradation was observed when measured by AV. At the end of the frying period, the reduction in unsaturated fatty acid content was 3.8, 1.9 and 12.7% when frying under CDB, vacuum and SFC, respectively. The rate of tocopherol degradation was three and twelve times slower in VF when compared to CDB and SFC, respectively.