The effect of microwave pre-treatment of rapeseed on the degradation kinetics of lipophilic bioactive compounds of the oil during storage

Degradation kinetics of rutin encapsulated in oil-in-water emulsions: impact of particle size

BACKGROUND

Rutin is a natural bioactive flavonoid that is poor in water solubility and chemical stability. Encapsulation can be used to protect bioactive molecules from chemical or physical decomposition during food processing and storage. Thus, the effect of initial particle size on the ability of oil-in-water emulsions to retain rutin during storage was investigated.

RESULTS

Rutin was encapsulated in oil-in-water emulsions with different mean surface-weighted diameters: d_3,2  = 0.56 μm (small), 0.73 μm (medium), and 2.32 μm (large). As expected, the resistance of the emulsions to coalescence and creaming during storage increased as the particle size decreased due to weakening of the colloidal and gravitational forces acting on the droplets. The concentration of rutin in the emulsions decreased during storage (28 days), which was mainly attributed to photodegradation of the flavonoid. The loss of rutin from the emulsions during storage was fitted using a second-order equation. The rutin degradation rate constant k decreased and the half-life t_1/2 increased with decreasing droplet size, which was attributed to the stronger encapsulation and light scattering by smaller oil droplets reducing the amount of light that can penetrate into the emulsions.

CONCLUSION

This study has important implications for the design of more efficacious emulsion-based delivery systems for incorporating health-promoting nutraceuticals into foods. © 2022 Society of Chemical Industry.

Optimization of Canolol Production from Canola Meal Using Microwave Digestion as a Pre-Treatment Method

Canola meal, the by-product of canola oil refining, is a rich source of phenolic compounds and protein. The meal, however, is primarily utilized as animal feed but represents an invaluable source of nutraceuticals. Of particular interest are the sinapates, sinapine and sinapic acid, with the decarboxylation of the latter to form canolol. Extracting these phenolics has been carried out using a variety of different methods, although there is an urgent need for environmentally safe and sustainable methods. Microwave-assisted solvent extraction (MAE), as a green extraction method, is receiving considerable interest. Its ease of use makes MAE one of the best methods for studying multiple solvents. The formation of canolol, from sinapine and sinapic acid, is primarily dependent on temperature, which favors the decarboxylation reaction. The application of MAE, using the MultiwaveTM 500 microwave system with green extractants, was undertaken to assess its ability to enhance the yield of sinapates and canolol. This study examined the effects of different pre-treatment temperature-time combinations of 140, 150, 160, and 170 °C for 5, 10, 15, 20, and 30 min on the extraction of canolol and other canola endogenous phenolic compounds. Total phenolic content (TPC), total flavonoid content (TFC), as well as metal ion chelation (MIC) and DPPH radical activity of the different extracts were assessed. The results confirmed that extractability of canolol was optimized with methanol at 151 °C and with ethanol at 170 °C with pre-treatment times of 15.43 min and 19.31 min, respectively. Furthermore, there was a strong positive correlation between TPC and TFC (p < 0.05) and a negative correlation between TFC and DPPH radical activity. Interestingly, no significant correlation was observed between MIC and DPPH. These results confirmed the effectiveness of MAE, using the novel MultiwaveTM 500 microwave instrument, to enhance the yield of canolol. This was accompanied by substantial improvements in the antioxidant activity of the different extracts and further established the efficacy of the current MAE method for isolating important natural phenolic derivatives for utilization by the nutraceutical industry.

Front-Face Fluorescence Spectroscopy and Chemometrics for Quality Control of Cold-Pressed Rapeseed Oil During Storage

The aim of this study was to test the usability of fluorescence spectroscopy to evaluate the stability of cold-pressed rapeseed oil during storage. Freshly-pressed rapeseed oil was stored in colorless and green glass bottles exposed to light, and in darkness for a period of 6 months. The quality deterioration of oils was evaluated on the basis of several chemical parameters (peroxide value, acid value, K₂₃₂ and K₂₇₀, polar compounds, tocopherols, carotenoids, pheophytins, oxygen concentration) and fluorescence. Parallel factor analysis (PARAFAC) of oil excitation-emission matrices revealed the presence of four fluorophores that showed different evolution throughout the storage period. The fluorescence study provided direct information about tocopherol and pheophytin degradation and revealed formation of a new fluorescent product. Principal component analysis (PCA) performed on analytical and fluorescence data showed that oxidation was more advanced in samples exposed to light due to the photo-induced processes; only a very minor effect of the bottle color was observed. Multiple linear regression (MLR) and partial least squares regression (PLSR) on the PARAFAC scores revealed a quantitative relationship between fluorescence and some of the chemical parameters.