Thesis
ESTUDIO DEL EFECTO DEL CAMPO ELÉCTRICO SOBRE LA ISOMERÍA DE LOS ÁCIDOS GRASOS DEL AGUACATE
Autor
M. T. A. ARIZA ORTEGA, JOSÉ ALBERTO
Institución
Resumen
Avocado and avocado products are having increased demand over the last decades, however
avocado has a very short shelf life and new technologies are under current research. The main
challenge is decrease the activity of the polyphenoxidase (PPO) enzyme, which causes brown color in
the avocado pulp. In the present work the effect of a electric field (EF) on the fatty acids of the
avocado-oil was evaluated, when the EF is applied to diminish the activity of the PPO.
It is well known that the avocado oil contain an important amount of functional fatty acids which
can be affected by the use of the EF. Some related articles indicate that the extraction method of the
oil could be a factor that increases the trans fatty acids, (TFA). The idea behind this work was to
evaluate the possible TFA formation after three different extraction methods and application of
different conditions of a EF. Previously it was stated that the PPO enzyme is inactivated at 9 kV/cm,
720 Hz and 3 min. In this work the following conditions were applied: voltages of 3 and 9 kV/cm, 60
and 720 Hz, and 10 and 180 s, using a factorial design 23.
For this study two strategies were utilized, first the oil was extracted and then treated with the
EF, (Oil 1), second the pulp was first treated with the EF and the oil was extracted, (Oil 2). The TFA
were analyzed by infrared spectroscopy, (FTIR 400-4000 cm-1) and gas chromatography, (GC). The
FTIR results show that all the oils studied had very light amounts of TFA, evidenced by the 968 cm-1
band compared with the very high peaks at 725 cm-1, corresponding to the cis form of the C-H bond. It
was also observed that the best method of oil extraction was the centrifugation, (15,557 g at 40 ºC
during 10 min) reaching <0.5 g TFA /100g oil, although the yield was very poor, this amount is within
the limits of several regulations. In practice, the centrifugated and EF treated avocado oil is safe to the
consumer.
The traditional extraction method using dissolvent with or without heat had a light increase in
the amount of TFA, with 6.1% and 0.7% respectively, compared with centrifugated and EF treated oil.
On the chemical indexes of the oils, the oil extracted with dissolvent and heat had a major
deterioration. Besides that, when the paste was treated with higher voltage and time of EF the yield of
the oil was lightly superior, (6%), however, under these conditions the oils had more TFA.
With all these results it is proposed that the EF technology can be used to treat avocado pulp
in order to extend their shelf life without apparent losses of the fatty acids and other valuable
compounds.