Shelf life stability
Although the initial value of quality parameters (FFA and COLOR) of zero-TFA deodorized oils were a modestly higher than conventional deodorized oils, there were no significant differences in the shelf life stability between the oils processed by these two technologies. Soybean oil is shown as an example in Fig.9. Changes during the 18-month shelf life of important quality parameters (AV, PV, COLOR) for conventional refined oils and “zero TFA” oils are illustrated. The AV of both soybean oils increased slightly during the whole shelf life and well met the national standard for 1st-grade soybean oil (≤0.5 mgKOH/g), which means that there was no significant difference in AV change trends between the different processed oils. The PV is an important indicator for the degree of primary oxidation of fats and oils. Hydroperoxides can be decomposed to volatile and non-volatile lower molecular weight components such as aldehyde and ketone at temperatures above 100°C (Tsiadi et al., 2001) used during the deodorization and therefore the PV value of freshly finished oils were all zero. During the whole shelf life, it was found that both soybean oils had a rising trend in PV, and most of the time conventional rerfined soybean oil showed higher PV than zero-TFA soybean oil. The color (R-value) of these two soybean oils both rose to a certain extent (Fig.9), but at end of the 18-month-shelf live there was no differences between the two oils. Besides, the flavor of them did not show significant differences in changes during the shelf-life either (data not shown). Not only soybean oil, but also rapeseed oil, maize oil and sunflower seed oil showed similar trends in these quality parameters during the shelf-life test obtained by the two different deodorization methods (data not shown). In conclusion, DCDT and conventional deodorization of several kind of oils had similar overall shelf-life stability without significant differences, which is critically important for industrial vegetable oil production and sales.