FFA
The efficiency of deodorization is usually quantified by the reduction
of FFA. For most conventional-processed 1st-grade
refined oils, the target residual FFA content is 0.03-0.05%, and the
upper limit for FFA in past national standards for these oils in China
was 0.10%. In order to conform to the development trend of minimal
processing, the national standards for these oils in China have been
revised and updated successively in recent years, and the upper limit
for FFA is currently 0.25%. Fig. 6 shows the comparisons of FFA of four
oils (soybean oil, rapeseed oil, maize oil and sunflower seed oil)
obtained by conventional high-temperature deodorization or DCDT
deodorization. The content of FFA of these deodorized oils are all less
than 0.08%, not only meeting the internal quality standard for the
trial-production (≤0.10%) but also meeting the national standards for
1st-grade refined oils. Since FFA contents of oils
obtained by the DCDT deodorization were all slightly higher than the
conventional ones due to the lower deodorization temperatures, the oil
stability during the shelf life might be a concern and will be discussed
later.