This study was executed in order to enrich the transcriptome information of flaxseeds and explore the reasons for the difference in the aroma of flaxseed oils from different cultivars at the molecular level. Two specialty flaxseed cultivars (Yiya-3 and Tianya-6) in Xinjiang were selected to perform transcriptome sequencing analysis using the Illumina high-throughput sequencing platform and a variety of bioinformatic methods. The results showed that a total of 61995756 high-quality clean reads were obtained. Further, a total of 33218 unigenes were obtained after de novo assembling of the sequence data. Non-Redundant Protein (NR) database annotations revealed that the flaxseed transcriptome had the highest sequence similarity to Jatropha curcas, and 17269 unigenes were annotated in the Cluster of Orthologous Group (COG) database, which were divided into 22 branches in three categories, including cellular processes and signals, information storage and processing, and metabolism. There were 1658 significant differentially expressed genes (DEGs) identified between the two cultivars. Compared to Tianya-6, 825 genes were up-regulated and 833 genes were down-regulated in Yiya-3. The annotation of the DEGs in the Gene Ontology (GO) database showed that they were distributed in three categories: biological processes, cellular components and molecular functions. The 380 DEGs annotated in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database were mainly enriched in fatty acid metabolism and other metabolic pathways, and 17 DEGs could be annotated in the fatty acid metabolism pathway, with eight being annotated in the unsaturated fatty acid metabolism pathway. This study provides a theoretical basis and technical support for the analysis of the difference in the aroma of flaxseed oils from different cultivars in Xinjiang.

This study aimed to investigate the effects of four different preparation processes, namely, cold pressing, hot pressing, solvent extraction, and ultrasonic-assisted extraction, on physicochemical properties, fatty acid composition, and the contents of beneficial lipid concomitants and volatile components in tomato seed oil. The results showed that the contents of fatty acid, tocopherol and phytosterol in tomato seed oils obtained by different methods differed significantly (P < 0.05), with the highest total phenol content (88.43 mg/kg) being in the hot-pressed oil and the highest contents of tocopherol (707.26 mg/kg) and sterol (2442.66 mg/kg) being in that obtained by ultrasound-assisted extraction. The results of gas chromatography (GC) and Fourier transform infrared spectroscopy (FTIR) showed that extraction was more favorable for the retention of unsaturated fatty acids than pressing, and hot pressing was more likely to induce the production of secondary oxidation products such as aldehydes and ketones; by headspace-gas chromatography-mass spectrometry (HS-GC-MS), 38, 42, 32 and 32 volatile components were identified in the oil samples obtained by cold pressing, hot pressing, solvent extraction, and ultrasonic-assisted extraction, respectively, with the major ones being aldehydes (7.47–18.09 μg/g). By principal component analysis (PCA) and cluster heatmap analysis, the four samples were clearly distinguished from each other. The conclusion of this study can provide a theoretical basis for the quality control of tomato seed oil.

The effects of different preparation techniques (aqueous enzymatic extraction, aqueous extraction, cold pressing, hot pressing and organic solvent extraction) on the physical and chemical properties, nutritional components and oxidation stability of tiger nut oil from the cultivar ‘Zhongyousha 1’ grown in Xinjiang were investigated. The results showed that organic solvent extraction gave the highest extraction rate (88.31%), and there were significant differences in the physicochemical properties of tiger nut oils prepared by different processes (P < 0.05). Oleic acid accounted for 76.04% of the total fatty acids in the oil prepared by aqueous extraction, which was 1.72-2.34 percentage points higher than that obtained with other preparation processes (P < 0.05). Different preparation techniques had significant effects on the lipid concomitant content and oxidation stability of tiger nut oil (P < 0.05). The oil obtained by organic solvent extraction had the highest contents of tocopherol (370.67 mg/kg), total phenol (168.59 mg/100 g) and phytosterol (271.26 mg/100 g), while the content of squalene was highest (162.04 mg/kg) in the oil obtained by aqueous extraction. The cold pressed oil had the highest oxidation stability index (24.15 h) indicating good oxidation stability. Correlation analysis indicated that the oxidation stability of tiger nut oil was positively correlated with unsaturated fatty acid and oleic acid (r = 0.72, r = 0.48), and the antioxidant capacity (1,1-diphenyl-2-picrylhydrazyl and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) free radical scavenging rate) of polar components was significantly positively correlated with total phenol content (r = 0.91, r = 0.96, P < 0.05). The results of principal component analysis (PCA) revealed that the cold pressed oil was similar to the oil obtained aqueous enzymatic extraction, while the oils prepared by organic solvent extraction, hot pressing and aqueous extraction were differentiated well. These results can provide a theoretical basis for the development of high-quality tiger nut oil.

An ω-3 and ω-6 fatty acid balanced pumpkin-flaxseed oil was prepared by mixing the seeds of seed purpose pumpkin in Xinjiang as raw material and flaxseed, a specialty oilseed crop in Xinjiang, as auxiliary material and then pressing them or the reverse sequence as a control and was refined. Changes in the physicochemical properties, nutritional composition, fatty acid composition, and oxidative stability of the two blended oils were studied before and after refining. The results showed that the physicochemical properties of the refined oils were significantly improved when compared with those of the crude oils (P < 0.05), and all quality indexes met the requirements of the national standards for edible oil. There were no differences in physicochemical indexes between the crude oils and between the refined oils (P > 0.05). The composition and content of fatty acids did not significantly change before and after refining (P > 0.05), while the contents of total tocopherol and total phenol and oxidative stability significantly decreased (P < 0.05). Compared with the control, the crude and refined oils prepared by mixing and then pressing had higher contents of total tocopherols and total phenols and better oxidative stability (P < 0.05), thus being more advantageous. The results of this study provide a theoretical basis for the market development of pumpkin seed oil.