Abstract
Experimental tests were carried out to ascertain the influence of malaxation time of olive paste on extraction yields and qualitative characteristics of virgin olive oils obtained by a centrifugal decanter at water saving. Results show that malaxation time has to be no less than 45 minutes to have a satisfactory oil extraction yield. Furthermore, it was ascertained that the malaxation time, protracted up to 90 minutes, does not have influence upon qualitative and organoleptic characteristics of oils. Only the total phenols content of oils changed significantly when the malaxation time of olive paste increased from 15 to 90 minutes. However, in this research has been demonstrated that in some cases the total phenols content of oils increased during the first 30-45 minutes of malaxation and after it diminished. This is due to the variation of total phenols content of vegetable water that in the first time increased and after diminished very quickly. Because of the partition equilibrium law, the total phenols content of oil changed in the same way. Finally, results show that the composition of volatile substances of head-space of oils did not change increasing the malaxation time of olive paste obtained from good quality olive fruits.
Highlights
Olive processing by mechanical systems needs the malaxation of olive paste to increase the extraction yields
To avoid or cut down the emulsion state, it needs to increase the malaxation time and, in some cases, the malaxation temperature (Solinas et al, 1978). This may cause a negative influence on the qualitative characteristics of virgin olive oil because of the activity of the enzymes, naturally present in the olive paste, which may develop affecting the percentage of free fatty acids content, peroxide value and phenol content of oil
The reduction of natural antioxidants content (Solinas et al, 1978; Di Giovacchino, 1991; Servili et al, 1992; Servili et al, 1994; Montedoro et al, 1994; Amirante et al, 1995; Hermoso et al, 1996; Alloggio et al, 1996; Lercker et al, 1999; Cert et al, 1999) and the variation of the volatile substances composition (Angerosa et al, 1998; Lercker et al, 1999) of oil obtained from olive paste longer mixed, can be dangerous for oil containing less quantity of these substances due to natural causes or to water added during the extraction process with the conventional decanter, called at 3 phases (Di Giovacchino et al, 1994a, c), that requires 50-70 liters of lukeworm water added to 100 kg of olive paste
Summary
Influence of malaxation time of olive paste on oil extraction yields and chemical and organoleptic characteristics of virgin olive oil obtained by a centrifugal decanter at water saving. Experimental tests were carried out to ascertain the influence of malaxation time of olive paste on extraction yields and qualitative characteristics of virgin olive oils obtained by a centrifugal decanter at water saving. The total phenols content of oils changed significantly when the malaxation time of olive paste increased from 15 to 90 minutes. In this research has been demonstrated that in some cases the total phenols content of oils increased during the first 30-45 minutes of malaxation and after it diminished. Results show that the composition of volatile substances of head-space of oils did not change increasing the malaxation time of olive paste obtained from good quality olive fruits. KEY-WORDS: Malaxation of olive paste - Olive processing Virgin olive oil
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