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Sterols are important minor constituents of the unsaponifiable fraction of virgin olive oil. They have critical roles in determining the authenticity of the oil and they are known to be affected by process conditions and maturity. Here, optimization of the malaxation temperatures at between 21 and 49 degrees C and times at between 24 and 66 min by response surface methodology is aimed in terms of oil yield, and contents of individual sterols and triterpene dialcohols of oils from olives at three maturity stages (spotted, purple, black). Results show that the amount of sterols is varied in different extents depending on the malaxation conditions as well as maturity stages. Mathematical models display high prediction performance to explain the variation in the studied responses of apparent beta-sitosterol, total sterol, beta-sitosterol, campesterol, and stigmasterol for all maturity stages. The optimum conditions of malaxation temperature and time are 31 degrees C/44 min, 36 degrees C/26 min, and 37 degrees C/24 min from spotted, purple, and black fruits, respectively. In end, this study proves transition to the highest desired sterols with oil yield, and the lowest undesired sterols and triterpene dialcohols from fruits to oil by malaxating at moderate temperatures, not cold and hot pressing. Practical applications: Sterols and triterpene dialcohols make up a large part of the minor components of olive oil. This group has gained high importance, especially after their significant impacts on the authenticity of olive oil. Sterolic content and triterpene dialcohols of olive oil depend especially on the fruit's maturity and processing methods. Malaxation temperature and time were optimized to achieve the transferability of the highest desired sterols and the lowest undesired sterols and triterpene dialcohols according to limits of the Commission Regulation (EEC). The current study was also evaluated by the change of total sterol content and individual sterol and triterpene diols profile of oils obtained from olives at different maturity stages. The optimized malaxation conditions are successful to achieve goals. Overall, it can be stated that olive oils with high desired sterols and low triterpene diols and undesired sterols in terms of EEC limits are economically precious. |
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