| It is hard for the cold-pressed oils produced in the industry scale to meet the food oil standard inChina without the treatment of refining. However, the traditional refining technology is based on thechemical refining process with long time and high temperature, which makes high energy consumption,loss of oil and nutrients, and residues of harmful ingredients. The chemical refining is obviouslyunsuitable to the cold-pressed oils. The objective of this paper is to develop a low-temperature refiningtechnology for cold-pressed rapeseed oils (CROs). The present study evaluated the effects of soliddephosphorization agent (SDPA) and cellulose-based deacidfication agent (CDA) on the removal ofphospholipids (PLS) and free fatty acids (FFA) respectively, and also the key characteristics of CROswere investigated. The main results of the paper are as follow.1. SDPA was prepared with calcium montmorillonite and analyzed with electron microscopescanner, X-ray diffraction and thermal gravimetric analyzer. The behavior of PLS adsorption on SDPAwas investigated. The results showed that the PLS adsorption process was a favorable adsorption, and awell fitted Freundlich equation was obtained for the adsorption isotherm. The PLS adsorption kineticscould be well described by the pseudo-second order kinetics model. Moreover, the adsorption was anexothermic and spontaneous process, and PLS could be adsorped on SDPA under a wide temperaturerange. The mechanism of PLS adsorption on SDPA was concluded as follows: the strong Lewis acidreactive sites of SDPA combined with the Lewis base groups of PLS into the Lewis acid-base complexesby forming coordination bonds.2. CDA was prepared with a kind of cellulose-based material. The behavior of FFA adsorption onCDA was majorly analyzed. The results showed that the FFA adsorption process was a favorableadsorption, and the Langmuir equation was suitable for the adsorption isotherm. The FFA adsorptionkinetics could be also well described by the pseudo-second order kinetics model. In addition, theadsorption was an endothermic and spontaneous process, and FFA could be adsorped on CDA under awide range of temperature. The mechanism of FFA adsorption on CDA was concluded as follows: thealkali cellulose and activated hydroxyl of the surface of CDA could adsort FFA and form the lipid salt,which would be attached to the surface of CDA.3. A research of low-temperature refining technology (LRT) was carried out with CROs. The effectsof LRT on the quality of CROs and the economic and technical performance were evaluated. The resultsshowed that the CROs yield of refining was98.05%. Moreover, qualities of CROs meet the nationalNO.3standard of edible rapeseed oils, and the retention rate of total tocoperols, total phytosterals andtotal phenol were90.1%,85.4%and88.8%. LRT improves the refining yield, and also reduces thepower consumption, cost and waste emissions of refining, compared with the traditional refiningtechnology.4. Volatile flavor components (VFC) of CROs were analyzed with head-space solid-phasemicroextraction, gas chromatograph-mass spectrometer and olfactory detection port. The results showedthat VFC were composed of glucosinolate degradation products (GSDP), aldehydes, alcohols, hydrocarbons and furans. The relative content of GSDP was more than60%including1-butene-4-isothiocyanate, methallyl cyanide and2-methyl-3-butenenitrile. Morever, VFC ofmicrowave-pretreatment cold-pressed rapeseed oil of low erucic (M-LCRO) were investigated, whichconsisted of GSDP, aldehydes, alcohols, and pyrazine. GSDP were derived from thermal degradation.Compared with CROs,2,5-dimethyl pyrazine and2-ethyl-3,5-dimethyl pyrazine were generated inM-LCRO. The sensory analysis results showed that flavor of CROs majorly reflected seed-like, woody,astringent and bitter, and the most intense flavor was seed-like. There was no significant effect for LRTon the sensory of CROs (P>0.01). As for M-LCRO, it presented a pleasant nutty and roasted flavor.5. The rheological properties of CROs were investigated. The results showed that CROs behave as anon-Newtonian fluid of shear-thinning. CROs indicated a Newtonian behavior as the shear rates weregreater than5s-1. The chain length of fatty acids of glycerides and temperature were important factors onaffecting viscosities, loss modulus (G''), plastic consistency coefficients (ηp) and yield stress (τo)values of CROs. The viscosities and G'' of CROs were improved with an increase in the erucic acidcontents. Additionally, viscosities, G'' and ηpof CROs decreased with the enhancement of temperature.Minor components could be the contributing factors for differences of viscosities of CROs, and thevalues of ηpof CROs were positively correlated with the level of Minor components. Furthermore,there was no significant effect for LRT on viscosities of CROs(P>0.01).
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