Talc is a widely used additive in the milling process throughout the world. While many neophytes to the business balk at the use of talc, it is an accepted industry practice, just not a very heavily publicized one. Talc helps increase yields when used with high quality fruit and also facilitates the milling of difficult fruit such as overwatered and/or over-ripe fruit.
Difficult fruit manifests itself in several different ways and, in some batches, two or more of the symptoms may be encountered simultaneously.
- In some cases, oil is retained within the cell walls of the olive paste rather than being released during the crushing and malaxing process. Talc will absorb the droplets of oil retained in the cell walls, forming larger drops, thereby facilitating the extraction of this oil.
- In other cases, oil and water get entrapped in agglomerating microgels. Talc helps to break up these micro gels and release the oil. Additionally, both olive paste and talc have lipophilic characteristics, that is they tend to combine with or retain the oil. The talc helps counteract the paste further releasing oil into an extractable form.
- Perhaps the most common problem caused by difficult fruit is that it creates an emulsion during the milling process. Oil droplets are emulsified with water creating an emulsion that cannot be separated and thus oil is lost. Talc helps prevent the formation of emulsions, and also breaks up emulsions previously formed, allowing the oil to be extracted.
What are the advantages of using talc during the milling process?As talc is a chemically inert mineral, it does not affect the paste or resulting oil. Typically acidity and peroxide levels are unaffected by the use of talc and, according to some studies, levels can sometimes be improved. Using talc reduces the need for oil degrading measures to increase yield such as heating the paste or adding water and therefore often ends up improving the quality of the oil. It reduces the amount of fruit solids left in the oil that can cause cloudiness and higher levels of sediment. Informal organoleptic analyses show no negative impact with the use of talc.
The amount of talc used ranges from 0.3% to 1% of the weight of the olives being milled. Recently finer configurations of talc have been put on the market claiming to require the use of lower quantities of talc for the same or better results.