Olive paste expression behaviour
1994
Rastelli, C. | Peri, C. | Piazza, L. | Bernardi, L. (Milan Univ. (Italy). Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche)
The kinetics and yield of olive paste expression were studied at different values of some process variables (compaction rate, maximum pressure applied and specific outflow surface), by using expression and compaction-relaxation tests. Expression curves include the following two phases: a first phase, carried out at constant outflow rate and increasing pressure, and a second phase, at constant pressure, during which time the kinetics of liquid separation can be described by the empirical exponential equation: (Y00 - Y/Y00=exp(-kt sup(n)). The lower the compaction rate or the higher the specific outflow surface, the higher the extraction yield becomes. At the minimum compaction rate of 1 mm/min, about 93% of the total liquid content of the paste was extracted in the first, constant outflow rate phase. At the highest specific outflow surface of 0.22 mm sup(-1) and at a compaction rate of 2 mm/min, about 90% of the yield was obtained during the first phase. The relationship between the maximum yield Y00 and the pressure applied is: Y00=a [1-exp (-bP sup(c))]. Y00 tends to a constant value for P5MPa. It follows that if the compaction rate and specific outflow surface are not optimized, no advantages are to be expected from larger and larger increases in pressure
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