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.