High‐temperature pre‐conditioning of rapeseed: A polyphenol‐enriched oil and the effect of refining

Abstract

In this work, a pretreatment process for rapeseeds, which involves the use of high-temperature steam, is presented. This method, besides accomplishing the beneficial effects of the conventional industrial thermal treatment, leads to an enrichment of some important minor compounds (polyphenols and phosphatides) in the resulting oil. Rapeseeds were pretreated at different operative conditions. Then, the seeds were pressed and the press-cake was solvent extracted. The obtained oils were then refined by both chemical and physical refining techniques, and the influence of each refining step on the content of minor compounds was evaluated. The results show that the amounts of polyphenols and phospholipids present in the oil coming from pretreated seeds increase and that their concentrations depend on the conditioning time. The polyphenols present in the oil correspond mostly to 2,6-dimethoxy-4-vinylphenol (vinylsyringol). The content of polyphenols was only slightly reduced during degumming. Neutralization resulted in a complete removal of these minor compounds. For the physical refining process, the type and amount of bleaching clay used had a significant influence on the content of polyphenols. After deodorization, oil samples with a considerable amount of polyphenols were obtained. These samples show a higher oxidative stability than chemically refined oils.

Optimizing refining temperatures to reduce the loss of essential fatty acids and bioactive compounds in tea seed oil

“…For quality indices not (Table 6). Refining has much effect on the composition and final quality of refined sunflower oil (Ortega-García et al, 2006), rapeseed oil (Zacchi and Eggers, 2008), olive oil (Essid et al, 2006), soybean oil and canola oil (Farhoosh et al, 2009). For example, reduce deodorization temperature to 150 • C can significantly increase the composition quality of the refined soybean oil or canola oil because of the lower temperature (Wang et al, 2002;Ghazani et al, 2013), which is consistent with our results.…”

Effects of refining process on sunflower oil minor components: a review

“…Several studies have been done to reduce the loss of micronutriments and preserve final oil quality and nutritional characteristics, D207, page 7 of 10 Dossier A. Ayerdi Gotor and L. Rhazi: OCL 2016, 23(2) D207 for example by using pre heating with microwave (Veldsink et al, 1999;Zacchi and Eggers, 2008) which increases the final tocopherol and polyphenols content; or, modifying the temperatures during the deodorization step (Martinčič et al, 2008) that reduces the losses of phytosterols and tocopherols. However losses persist, but the residual products of this refining process are partially recovered to be used in other industries like cosmetic industry (tocopherols and phytosterols), gums in the form of lecithin is included in several food products instead of soybean lecithin.…”

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

“…It is probable that the variety of rape is of great significance for this phenomenon. Canolol is lost during the production of refined oil, but because of its lipophilic nature, it can be added back to the oil after being isolated from the pressing (Wakamatsu et al, 2005;Zacchi and Eggers, 2008).…”