Abbreviations
LCD, Liquid crystal display; TBHQ, Tertiary butylhydroquinone; AV, Acid
value; PV, Peroxide value; FFA, Free fatty acid; HPLC, High performance
liquid chromatography; GC, Gas chromatography; GC–O, Gas
chromatography-olfactometry; SD, Standard deviation; ANOVA, Analysis of
variance.
Practical
applications: Experiments were carried out to study the possibility of
improving the oxidation stability of peanut and soybean oils at
industrial and market level. According to the preliminary results, it
should be interesting to better explore the suitability of storing
peanut and soybean oils in underground tanks.
Introduction
Soybean and peanut are the first and second most important sources of
vegetable oils in the world and the major edible oil produced and
consumed in China. The conservation of vegetable oils is a very complex
operation, because, to maintain the quality level over time, it is
necessary to take precautions to avoid increased acidity and the onset
of rancidity caused by oxidation. The oxidation rate depends on a number
of factors including the availability of oxygen, light and temperature
[1].
To retard or prevent oxidative deterioration of vegetable oils,
synthetic antioxidants, such as butylated hydroxyanisole (BHA),
butylated hydroxytoluene (BHT) and tert-butyl hydroquinone (TBHQ) have
widespread use as oil additives in many countries [2], a maximum
amount of 200 mg/kg oil is allowed [3]. However, the safety of
synthetic antioxidants and their decomposition products has been
re-recognized and evaluated in recent years [4,5]. Recent reports
reveal that these compounds may be implicated in many health risks
[6,7]. Therefore, many countries banned their utilization. Until
now, many experimental studies have been carried out to verify that
nitrogen can improve the stability and the shelf life of oil, and slow
down its oxidative changes. The use of nitrogen atmosphere and the
reduction of the oxygen in the headspace volume can appreciably control
quality changes of vegetable oil during storage time [8-12].
Moreover, the most significant factor affecting the vegetable oil
quality is storage temperature [13-15]. Under high temperature
conditions, even with nitrogen as the conditioning gas, this condition
favors the increase in AV and the K270 value of
vegetable oil [16]. The current vegetable oil storage technology is
to prevent the main factors (oxygen, light, temperature). It is
difficult to find a balance between oil quality and storage costs. There
is a tendency to find new ways to replace existing storage technologies.
In the other hand the new cultivars of high oleic peanuts (75-82% of
oleic acid) were assayed for oxidation stability with a better results
than conventional peanuts (43-50% oleic acid) because the mayor
proportion of oleic acid [17]. As very few studies were focused on
the use of underground condition, where is a dark, low-temperature
storage environment.
The goal of this work is to investigate the change in peanut and soybean
oils quality, based on the analysis of such parameters as AV, PV, fatty
acids, tocopherols, phytosterols and the volatile flavor compounds
during different storage conditions (added TBHQ storage, nitrogen
storage, underground storage) of stainless steel tanks. This work is to
develop a preservation method that can maintain the high quality of
peanut and soybean oils as long as possible, increasing its shelf life.