Cold-pressed and hot-pressed rapeseed oil: The effects of roasting and seed moisture on the antioxi- dant activity, canolol, and tocopherol level

Abstract

Background. The paper looks at the levels of canolol, tocopherols and antioxidant activity in cold-pressed and hot-pressed rapeseed oils produced from seeds of various moisture levels (5%, 7.5%, and 10%). The paper also considers the effects of seed roasting on the levels of these compounds. Material and methods. The material used for the tests was rapeseed cv. Adrianna. The quality of the oils obtained is determined using peroxide and acid values. The levels of canolol and tocopherols are analyzed using HPLC. The DPPH radical-scavenging activity method for oil samples and phenolic extract from oils was used.Results. It has been demonstrated that the oils produced from rapeseeds with a 5% moisture content, and in particular from cold-pressed oils, were characterized by the lowest peroxide values. Cold-pressed oils produced from rapeseeds with a 5% moisture content were characterized by higher levels of tocopherols and plastochromanol-8. In the case of hot-pressed oils, the highest levels of tocopherols were found in oils produced from seeds with a 7.5% moisture content, and the greatest amount of PC-8 (more than 4 mg/100 g) was found in oils produced from seeds with a 10% moisture content. Hot-pressed oils have been shown to have higher levels of these compounds than cold-pressed oils. Both roasting and hot pressing led to an increase in the amount of canolol in the oils investigated. When analysing the antioxidant activity of the oils and phenolic extracts it was shown that phenolic compounds are responsible for approx. 10% of total antioxidant activity. Conclusion. Various levels of biologically active compounds were shown to be present in the rapeseed oil obtained from raw materials of a varying moisture content. The type of pressing process (cold-pressing or hot-pressing) and whether the seeds have undergone roasting has also been shown to affect the resulting oil and the level of native antioxidants it contains.

Degradation of triadimefon and residue levels of metabolite triadimenol: tracing rapeseed from harvesting and storage to household oil processing

“…As shown in Table , the moisture in the rapeseed samples varied between 7.06–7.10%. These moisture levels would not cause differences in antioxidant activity . On the other hand, triadimefon degraded completely and only its metabolite, triadimenol, was detected in rapeseed – not only in the recommended commercial dosage group but also in the threefold and fivefold higher dosage groups.…”

Low concentration short time ozonation of rapeseed seeds reduces the stability of the oil and content of some antioxidant components

“…Rapeseed oil contains from 30 to 120 mg per 100 g oil tocopherols, depending on the method of oil preparation, rapeseed cultivar and the initial quality parameters of seeds (Siger et al ., ; Redondo‐Cuevas et al ., ). The composition of tocopherols in tested oils was typical and characteristic for cold pressed rapeseed oil.…”

“…Cold-pressed rapeseed oil differs significantly from the refined oil by physicochemical parameters and the content of pro-and antioxidant compounds. Coldpressed oils are characterised by a lower oxidative stability and a higher content of primary oxidation products, but lower secondary (Siger et al, 2017). However, they show a higher nutritional value due to the presence of biologically active compounds: carotenoids, sterols, tocopherols and phenolic compounds, which are removed in the refining.…”

Quality evaluation of rapeseed oil in Chinese traditional stir‐frying

“…Among the important components of rapeseed oil, 2,6‐dimethoxy‐4‐vinylphenol (canolol), which is a free polyphenol and a potent radical scavenger, has received considerable attention in the last few years (Rekas, Scibisz, Siger, & Wroniak, ; Shrestha, Stevens, & Meulenaer, ). Several research teams have studied the extraction, formation mechanism, antioxidant activity, and enrichment products of canolol and other free phenolic acids during rapeseed oil processing (Rekas, Wroniak, & Krygier, ; Siger, Czubinski, Dwiecki, Kachlicki, & Nogala‐Kalucka, ; Siger & Józefiak, ; Siger, Józefiak, & Górnaś, ). Canolol content in rapeseed oil can be enhanced via microwaving or roasting (Siger, Gawrysiak‐Witulska, & Bartkowiak‐Broda, ; Wijesundera et al, ).…”