Effects of microwave treatment on the oxidative stability of peanut (Arachis hypogaea) oils and the molecular species of their triacylglycerols

Abstract

Effects of microwave treatment on the oxidative stability of peanut (Arachis hypogaea) oils and the molecular species of their triacylglycerolsPeanut seeds (Arachis hypogaea) were roasted for 6, 12, 20, or 30 min at a frequency of 2450 MHz using a microwave oven. The quality characteristics and the compositions of the oils, i.e. their tocopherol distributions and the molecular species of the triacylglycerols (TAGs) were investigated. These results were compared with those of an unroasted oil sample. Only minor increases (p <0.05) in chemical and physical properties of the oils, such as the carbonyl value, the p-anisidine value and the color development occurred after a prolonged roasting period. Compared to the original level, more than 92 wt-% tocopherols remained after 30 min of roasting. A modified thin-layer chromatography argentation procedure provided 12 different groups of TAGs, based on both the degrees of unsaturation and the total fatty acid chain-length. Although significant increases (p <0.05) generated in these chemical and physical changes of the oils after 20 min of roasting, no significant loss (p >0.05) was observed in the molecular species of the TAGs during microwave roasting. These results indicate that phospholipids may be attributed to the quality characteristics of peanut oils during microwave roasting.

Assessment of the Hazelnuts Roasting Process by Pressure Differential Scanning Calorimetry and MID-FT-IR Spectroscopy

“…Similar results were obtained previously for hazelnuts (Amaral et al 2006), peanuts (Yoshida et al 2003) and sunflower seeds (Yoshida et al 2002), with at least 90, 85 and 90 % of tocols recovery after roasting process, respectively.…”

Microwave roasting effects on the physico‐chemical composition and oxidative stability of sunflower seed oil

“…In the present analysis, the loss in weight of sunflower oilseeds was found to be greater as compared with those reported by Yoshida et al (2), which might be attributable to variations in the genetic makeup and the original moisture contents of the varieties of sunflower oil seeds investigated. Yoshida and Kojimoto (9) and Yoshida et al (3,5) reported that after roasting for different times, changes in the weight of peanut and sesame seeds may be due to the presence of moisture and volatile components. In contrast to these, Yoshida et al (12) reported no significant differences in the weight loss among different cultivars of soybeans at different roasting times.…”

“…Although there is sufficient information available on the consequences of microwave heating on the composition and nutritional quality of food, there has been speculation on the ease of free radical formation when fatty foods are exposed to microwave energy (5). The differential heating behavior of food components can result in severely uneven heating of certain foods rich in fats and proteins (6).…”

Chemical and Structural Changes in White Sauces Thawed by Microwave or Conventional Oven

“…The effects of microwave heating on the food components can differ from those produced by conventional heating. The main studies relating the effects of microwave to changes on food components have been found on oils (Albi et al 1997;Yoshida et al 2003;Malheiro et al 2009). It has been speculated that free radicals can be formed by exposure to microwave energy (Albi et al 1997) and it was found that the rate of oxidation, depends on the polyunsaturated fatty acid content (Hassanein et al 2003).…”