May 19, 2016 BrockManwill

An In-Depth Study of Water Retention in Frying Oil Filtration

The following study was conducted by Monoj Gupta, a frying oil filtration expert from MG Edibile Oil Consulting Int’l Inc. Its goal was to determine water retention and water absorption rates by SuperSorb® Carbon Pads.


The objective of the study was to determine if the SuperSorb® filter pad absorbs any water from the fryer oil.

Experimental Procedure

The experiment was conducted by using the following steps of procedure:

  1. The moisture content of the SuperSorb® filter pad was determined
  2. Moisture content of the restaurant fryer oil was determined
  3. Moisture from the unused and the used pad were determined
  4. The moisture retained by the filter pad was calculated
  5. Material balance calculations were used to determine the moisture removed by filter pad

Benefit of Reduced Moisture – My Hypothesis

Fresh oil contains less than 0.05% of moisture. The moisture content of the fryer oil increases with frying. More degraded oil may contain up to 0.5% moisture (Equilibrium Moisture). In this case the moisture content was 0.38%. The filtration through SuperSorb® pad reduced it by 20 percent. As next frying starts, some fresh oil is also added for make up. This will reduce the moisture in the fryer oil further at start. This could help reduce the rate of soap formation according to the following hypothesis.

  • In the chemical reaction process, the reaction progresses forward if the products of reaction are removed from the reaction site as they are formed.
  • In the frying process, the soap is generated from the reaction between the alkali metal ions and the FFA as well as triglycerides.
  • If the concentration of the product of the reaction is high in the reaction medium the reaction begins to slow down somewhat.
  • In this case, if the soap produced in the reaction cannot find enough water around the reaction site for the formation of soap, it may slow down the soap formation.

In case of filtration of fryer oil through the active filter like SuperSorb® pad, there is also a significant amount of soap adsorbed in the pad.

When the oil is filtered through SuperSorb® pad and the fryer is restarted, the fryer oil has presumably 20% or so lower amount of moisture compared to the time when the fryer was shut down. Therefore after the restart, the soap formation will be expected to be somewhat slower as there is less water. There will also be less hydrolytic reaction from the soap present in the oil. This will change as the moisture content of the oil increases.

Therefore partial removal of the moisture from the oil may offer the advantage of reduction in the soap content by reducing its formation during subsequent frying operation. This may not be the same when a simple passive filter is used because there will be no reduction of soap in filtration. This is because the passive filter will not reduce soap in the oil and the equilibrium moisture in the used fryer oil, which is typically 0.45-0.5%, may remain in the oil. The higher soap in the water phase in the fryer oil will catalyze more hydrolytic reaction and form more soap.

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