Water content, critical micelle concentration of phospholipids and formation of association colloids as factors influencing autoxidation of rapeseed oil.

BACKGROUND: The exact mechanism of lipid autoxidation in vegetable oils, taking into account physical aspects of this phenomenon, including the role of association colloids, is still not fully understood. The purpose of this study was to consider changes in moisture content and DOPC phospholipid (1,2-dioleoyl-sn-glycero-3-phosphocholine) critical micelle concentration (CMC) in rapeseed oil during autoxidation as well as to find the relationship between these parameters and the accumulation of primary and secondary lipid oxidation products. RESULTS: The experiments were performed at initial oil humidity 220 ppm and 700 ppm, with DOPC below and above CMC. The increase in water concentration was favored by the presence of phospholipids above CMC and, at the same time, high initial water level, which favored oxidation processes and the creation of amphiphilic autoxidation products. At relatively high water level and low amphiphilic DOPC concentration, the growth of water content does not affect the concentration of oxidation products. CONCLUSION: Amphiphilic substances play a significant role in increasing the water content of oil. Autoxidation products may reduce CMC of DOPC, but water is able to compensate for the CMC-reducing effect of oxidation products. The presence of association colloids and initial water content play a crucial role in the oxidation process of rapeseed oil. The increase in water concentration does not cause a sufficiently large increase in the number of micelles or sufficiently significant changes in their structure to effect an increase in the level of oxidation products. The formation of micelles requires an appropriate content of both water and amphiphilic substances derived from seeds (phospholipids). © 2021 Society of Chemical Industry.

The quality of cold-pressed rapeseed oil obtained from seeds of Brassica napus L. with increased moisture content.

BACKGROUND: The basic parameter influencing the quality of cold-pressed oil is the quality of seeds used  for pressing. Adverse moisture content and storage temperature of rape seeds may affect the quality of oil obtained from them. This paper presents the effects of increased rapeseed moisture content on the quality of the oil pressed. METHODS: The material used for the tests was rapeseed (canola) cv. PR 46 W14. The moisture content of the seeds was adjusted to 10%, 12% and 20%, and the seeds were stored at room temperature for 14 days. The samples were then dried to a seed moisture equal to 7% and oil was pressed from them. Acid and peroxide values, as well as the content of water, tocopherols and phenolic acids, were determined. In addition, a sensory analysis of the oil samples was carried out, and structural changes in the association colloids in the oil were determined using a fluorescent probe. RESULTS: With the increase in seed moisture, the increase in peroxide and acid values of the analyzed oils was recorded. A slight decrease in tocopherol content and a significant increase in phenolic acid concentration, depending on the seed moisture content, was observed. Sensory analysis showed odor sensory profile changes that probably indicate microflora development. CONCLUSIONS: The rapeseed moisture content has a crucial influence on the quality of oil obtained from them. Along with an increase in seed moisture, the possibility of developing undesirable microflora grows, which results in a deterioration in the quality of the obtained oil.

Physicochemical characteristics of the cold-pressed oil obtained from seeds of Fagus sylvatica L.

A physicochemical characteristic of the cold-pressed oil obtained from seeds of common beech (Fagus sylvatica L.) has been presented. This plant may be considered as unconventional oilseeds crops because of relatively high content of fat (27.25%). The analyzed beech seeds oil has been classified as oleic-linoleic acids oil with more than 76% percentage share of those species. Beech seeds oil contains 4.2% of gamma-linolenic acid (GLA). Unique characteristic is the high content of γ-tocopherol (75.4mg/100g) and δ-tocopherol (34.05mg/100g). γ-Tocopherol is effective scavengers of reactive nitrogen species and prevents DNA bases nitration, what makes beech seeds oil interesting raw material in the production of cosmetics. Additionally the content of carotenoids, very effective photooxidation inhibitors, is at high level in comparison with other cold-pressed oils. It was demonstrated that PCA analysis may help to determine the authenticity of oil obtained from beech seeds.

The Interactions Between Rapeseed Lipoxygenase and Native Polyphenolic Compounds in a Model System.

The focus of the present research was to study inhibition of lipoxygenase activity by rapeseed native polyphenols and the interactions between those compounds and the enzyme. The enzyme and polyphenolic compounds (polyphenols, phenolic acids) were extracted from rapeseed (Brassica napus) varieties Aviso and PR45DO3. The total phenolic compounds concentration in tested rapeseed was 1,485-1,691 mg/100 g d.m. (dry matter) and the free phenolic acids content in both rapeseed varieties was about 76 µg/100 g d.m. The isolated proteins showed lipoxygenase activity. Prooxidant properties of phenolic compounds in the presence of lipoxygenase and linoleic acid were observed rather in the case of extracts containing a relatively high concentration of miscellaneous polyphenols. Antioxidant properties were recorded in the case of phenolic acid extracts which contain only 1.4-1.9% of phenolics present in raw phenolic extracts. We propose that the prooxidant effect of phenolic compounds comes from quinone and oxidized polyphenols formation. The observed antioxidant activity of phenolic acid extracts is probably due to their ability to scavenge free radicals formed from linoleic acid. However, reduction of lipoxygenase ferric to ferrous ions, which prevent the activation of the enzyme and inhibited its activity, was also observed.