Abstract
In this study, flaxseed was pretreated by steam explosion technology and subsequently pressed to prepare flaxseed oil. GC, UPLC, HPLC, and GC‐MS techniques were used to analyze the quality characteristics of the prepared flaxseed oil. These included the food safety risk indices, micronutrient components, and oxidative stability. The effects of different steam explosion pressures on the quality characteristics and relative volatile components of flaxseed oil were also investigated. The results revealed that steam explosion pretreatment technology could significantly increase the oil yield, improve micronutrient content, and strengthen the oxidation stability of the product. Moreover, the food safety risk indices (e.g., benzopyrene) were controlled within a reasonable range, while the fatty acid content remained almost unchanged. Notably, the relative pyrazine content in the total volatile components of flaxseed oil was 68.25% when the steam explosion pressure reached 1.2 MPa. This was considered as the main factor that contributed to the unique concentrated fragrance of the produced flaxseed oil. To prove the superiority of the steam explosion pretreatment, we compared this technique with traditional high‐temperature roasting and popular microwave pretreatment techniques. The results revealed that flaxseed oil prepared by steam explosion pretreatment displayed the best quality characteristics and most concentrated fragrance. Thus, steam explosion technology shows great potential for application to produce high‐quality concentrated fragrance flaxseed oil. This study provides significant reference and guidance for the preparation process of flaxseed oil.
Highlights
Flaxseed oil, which is rich in α-linolenic acid, provides the correct balance of essential fatty acids in the human diet and is gaining increasing popularity as a cooking vegetable oil (Chirino-Galindo, Barrera-Argüelles, Trejo-González, Mejía-Zepeda, & PalomarMorales, 2017; Jiajie & Ma, 2014; Morshedzadeh et al, 2019)
According to a previously reported method (Yang et al, 2013), 10 g of the oil sample was weighed, and volatile components were adequately extracted with headspace solid-phase micro-extraction (HS-SPME) instrument (2 cm, 50/30 μm DVB/ Carboxen/PDMS, Agilent Technologies) for 10 hr at room temperature and analyzed by using GC-MS system (Agilent Technologies) installed with a HP-5MS capillary column (0. 25 μm × 0.25 mm, 30 μm)
This study investigated three flaxseed oil pretreatment methods, namely traditional high-temperature roasting, popular microwave, and steam explosion of flaxseed
Summary
Flaxseed oil, which is rich in α-linolenic acid, provides the correct balance of essential fatty acids in the human diet and is gaining increasing popularity as a cooking vegetable oil (Chirino-Galindo, Barrera-Argüelles, Trejo-González, Mejía-Zepeda, & PalomarMorales, 2017; Jiajie & Ma, 2014; Morshedzadeh et al, 2019). Yu, Shi, Hong, Huang, and Zhou (2019) pretreated flaxseed at different roasting temperatures with subsequent pressing and analyzed the quality characteristics of the produced flaxseed oils. The results indicated that proper roasting temperature (180–195°C) could provide oils with better flavor and increase oxidation stability. The results revealed a rapid drop in the relative alcohol contents of the volatile compounds in the hotpressed flaxseed oil, and the characteristic volatile compounds mainly comprised pyrazines, pyrroles, and pyridines, which endowed hot-pressed flaxseed oil with a unique toasting flavor. Ren, Zhang, Sun, Duan, and Zhang (2015) studied the effect of microwave pretreatment on the extraction of flaxseed oil and determined the quality characteristics of the flaxseed oils extracted using different radiation intensities and extraction times. The transmission electron microscopy (TEM) results revealed that the microstructures of the pretreated samples were modified after microwave pretreatment, while the fatty acid compositions were not affected by different microwave radiation conditions
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