Yunping Yao

Comparison and analysis of fatty acids, sterols, and tocopherols in eight vegetable oils.

The similarities and differences of eight vegetable oils produced in China were investigated in terms of their fatty acid, sterol, and tocopherol compositions and subsequent data processing by hierarchical clustering analysis and principal component analysis. The lipid profiles, acquired by analytical techniques tailored to each lipid class, revealed great similarities among the fatty acid profiles of corn and sesame oil as well as few differences in their sterol profiles. It turns out that not only was there great similarity between the fatty acid profiles of corn oil and sesame oil but also there were not too many differences for the sterol profiles. Sunflower and tea-seed oil showed similar sterol compositions, while the tea-seed oil tocopherol was very similar to palm oil. The results demonstrated that the use of only one of these profiles was unreliable for indentifying oil origin and authenticity. In contrast, the use of the sterol or tocopherol profile together with the fatty acid profile more accurately discriminates these oils.

Identification of phospholipids classes and molecular species in different types of egg yolk by using UPLC-Q-TOF-MS

Egg phospholipids (PLs) are currently the products of greatest commercial interest with major area of importance in various fields. Therefore, in this study, duck, hen and quail egg yolk PLs were isolated by solvent extraction with chilled acetone precipitation, and subsequently separated and identified by using ultra-performance liquid chromatography with quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS). Egg PLs were separated on hydrophilic interaction liquid chromatography (HILIC) with ethylene bridged hybrid (BEH) column by gradient elution using acetonitrile/ammonium formate as a mobile phase, and detected by mass spectrometry (MS) under electrospray ionization in positive and negative ion mode. Structural characterizations of 57 molecular species of egg yolk PLs were identified based on MS/MS fragment ion information and elemental composition in MassLynx 4.1 software. The obtained results showed that phosphatidylcholine (16:0-18:1), phosphatidylethanolamine (18:0-20:4), phosphatidylinositol (18:0-18:2), phosphatidylserine (18:0-18:2), sphingomyelin (d18:1/16:0) and lysophosphatidylcholine (16:0) were the predominant species among the different classes of egg yolk phospholipids.

Microstructural and lipid composition changes in milk fat globules during milk powder manufacture

The purpose of this study was to investigate the effects of milk powder processing conditions (pasteurisation, homogenisation and spray-drying) on the microstructure and composition of fat globules in cow milk. In general, the process of pasteurisation results in fewer changes in the microstructure and lipid composition than do other processing methods. The phospholipid, sterol, and the fatty acid composition of the phospholipids, with the exception of the fatty acids of total lipids, underwent significant changes under different processing conditions compared with the untreated milk fat globules. The contents and distribution of the phospholipids in pasteurised milk indicated a high level of stability, but the amounts of phosphatidylethanolamine, phosphatidylserine, and sphingomyelin were significantly affected by homogenisation. A reduction in the cholesterol content was observed after pasteurisation and homogenisation. The results indicate that processing had a significant effect on the composition and structure of the membrane of the phospholipids in milk fat globules.

Combined urea-thin layer chromatography and silver nitrate-thin layer chromatography for micro separation and determination of hard-to-detect branched chain fatty acids in natural lipids

A simple, fast and efficient procedure was developed for micro separation and enrichment of branched chain fatty acids (BCFA) from natural products using successive thin layer chromatography (TLC) technique coupling novel urea-TLC with AgNO3-TLC, which rely on the formation of urea adduction and AgNO3 bonding in methanol. These natural lipids contain a significant amount of straight chain fatty acids (FA). Fresh and fast urea-TLC and AgNO3-TLC plate making techniques were developed with more even coating and less coating material contamination before being utilized for separation. Goat milk fat was used as a model. Various experimental parameters that affect urea-TLC and AgNO3-TLC separation of BCFA were investigated and optimized, including coating of urea, concentration of original oil sample, mobile phase and sample application format. High efficiency of removal of straight chain FA was achieved with a low amount of sample in an easy and fast way. A total BCFA mix with much higher purity than previous studies was successfully achieved. The developed method has also been applied for the concentration and analysis of BCFA in cow milk fat and Anchovy oil.

Gene regulation in Aspergillus oryzae promotes hyphal growth and flavor formation in soy sauce koji

Aspergillus oryzae 100-8 and the parental strain A. oryzae 3.042 are used in soy sauce fermentation in China. The growth rate of A. oryzae 100-8 is faster than A. oryzae 3.042, and the soy sauce flavors obtained with A. oryzae 100-8 fermentation are better than those obtained with A. oryzae 3.042. In this study, comparisons were made through biomass, reactive oxygen species (ROS) and gas chromatography-mass spectrometry (GC-MS) measurements, and the reasons for these differences were investigated through transcriptome and qRT-PCR analysis. The analysis indicated that several unique genes are closely associated with hyphal growth and flavor formation, as demonstrated by changes in the expression levels of these genes. These unique genes regulate hyphal growth and flavor formation in soy sauce koji fermentation.

Effects of freeze drying and spray drying on the microstructure and composition of milk fat globules

Freeze drying and spray drying are conventional methods for converting milk into powder in the dairy industry. The purpose of this study was to investigate the effects of these drying methods on the physical, chemical and structural features of milk fat globules (MFGs). The globule sizes increased after freeze drying and spray drying, but the integrity of their microstructures was still maintained. Compared with that in untreated MFGs, the composition of the fatty acids underwent fewer changes under the two different drying conditions. The main phospholipids showed some differences between the freeze-dried milk and spray-dried milk, and the saturation of the fatty acids of phospholipids was increased after the drying treatments. A reduction in the cholesterol content was observed after the freeze-drying and spray-drying processes. The level of unsaturation decreased as the diameter of the globules increased. The results indicated that freeze drying had a significant effect on the liquid-ordered domains in the MFG membrane, which was formed by sphingolipids and cholesterol. However, spray drying influenced the liquid-disordered domains, which were formed by glycerophospholipids. Thus, the drying method appears to affect the physical, chemical and microstructure characteristics of MFGs, which may affect the stability of the globules in milk and the way the milk is digested.

Specificity of acyl-CoA binding protein to acyl-CoAs: influence on the lipid metabolism in Aspergillus oryzae

Acyl-CoA binding protein (ACBP) is involved in lipid metabolism and regulation of gene expression in eukaryotic cells, however, the specific functional roles of this important class of proteins remain to be elucidated. We have cloned and expressed a recombinant Aspergillus oryzae ACBP (AoACBP) that has a preference for binding relatively long chain acyl-CoAs such as palmitoyl (C16:0)-CoA (Kd = 82 nM) and stearoyl (C18:0)-CoA (Kd = 59 nM) by microscale thermophoresis binding assay. The high affinities for binding C16:0-CoA and C18:0-CoA were also conformed to the composition of fatty acids in A. oryzae 3.042. Moreover, the increased AoACBP levels were analyzed by Western blot procedure. And the expression levels and distribution patterns of AoACBP in this fungal life cycle were also investigated by RT-PCR and immunofluorescence. The accumulation of AoACBP have an effect on lipid metabolism, and it was significantly increased from 24 to 48 h suggest that AoACBP plays an important role in the later growth stage of A. oryzae 3.042 for fatty acid synthesis.