TITLE:
Study to Solve the Problem of Color Reversion in Refined Soybean Oil
AUTHORS:
Nahed M. M. Atta, Mohamed Fawzy Al-Okaby
KEYWORDS:
Soybean Oil, Color Reversion, Refining Process, Citric Acid
JOURNAL NAME:
Food and Nutrition Sciences,
Vol.13 No.3,
March
15,
2022
ABSTRACT: This study carried out on the soybean oil samples taken from the processing
lines during refining process (degumming, neutralization, bleaching and deodorization
process) for crude soybean oil as well as on color reversed oil after
deodorization step during storage for several hours to study the physical and
chemical properties (color, refractive index (RI), free fatty acid (FFA), peroxide
value (PV), p-Anisidine value (p-AV), total oxidative (TOTOX) value, oxidative
stability (OS), saponification value (SV), iodine value (IV), unsaponifiable
matter (unsap. %), soap content, minerals, waxes, total phenols content, K232 and k270 nm),
the fatty acids composition, sterol compound, total tocopherols and their
components (α, β, γ and δ tocopherol)
and tocored compound for these oils and to find out the reason for the color
reversion after a short period from storage for the deodorized
soybean oil. Citric acid has been added (0.2%) to each color reversed and
neutralized soybean oils, then procedure of bleaching and deodorization process
on them, and studied its effect on the physical and chemical properties for
them specially the color units (red and yellow), tocopherols
contents and tocored compound. The
results showed that refining process for soybean oil caused to a gradual
decrease in values of AV, oxidative stability, IV, wax, % Unsapo.,
K232 and K270 nm, total polyphenols, minerals (P, Ca and
Mg), total tocopherols and their compounds (α, β, γ and δ tocopherol) and also caused decrease in all sterol components, but they
showed a few differences in percentages of fatty acids as result refining process. Color
values (red and yellow unites) recorded gradually decreased during
refining process, but these values were increased in deodorized soybean oil
after storage (color reversed soybean oil). Reduction of α, β, γ and δ tocopherol contents was found
to be linearly with the increase of red and yellow color units (color darking).
The tocored is responsible for the color reversion phenomenon, where as maximum
amount of tocored was in crude soybean oil 169.2 ppm, which gradually decreased
during refining process 120.35, 99.82, 20.25, and 8.46 ppm, respectively, but
it was found to be 46.5 ppm in color reversed soybean oil. Addition of citric
acid (0.2%) related to the removal of tocored from soybean oil during the
bleaching and deodorization process of soybean oil before and after color
reversion in parallel with the significant decrease in the color values.