Qingzhe Jin

Human Milk Fat Globules from Different Stages of Lactation: A Lipid Composition Analysis and Microstructure Characterization

The physicochemical properties of human milk fat globules (MFG) at different lactation stages from Danish mothers and the microstructure changes of MFG membrane (MFGM) at varied temperatures were investigated, and the relationship between chemical composition and the microstructure of MFGM was elucidated. The fat content in MFG was found to be significantly increased as lactation progressed, and colostrum MFG had the largest mean diameter of 5.75 ± 0.81 μm and the lowest ζ potential of -5.60 ± 0.12 mV. Chemical composition analyses of MFG revealed the following: (i) Colostrum milk fat constituted higher content in PUFAs (ω-6, and long-chain ω-6 and ω-3) than transitional and mature milk fats, with the corresponding lower content of SFA in its sn-2 position. (ii) The content of polar lipids among total lipids varied during lactation course (maximized at transitional stage); however, in terms of subclasses of polar lipids, no significant change of the relative content of sphingomyelin was observed, while the content of phosphatidycholine in mature milk was higher than that in colostrum and transitional milk. (iii) Inspection of fatty acid composition in phospholipids from different lactation milk revealed no remarkable and regular changes could be generalized; and no obvious difference of the morphologies of MFGM at different lactation stages can be visualized. An investigation of the microstructure change of MFGM vs temperature demonstrated that the segregated domains became larger as temperature decreased to 4 °C, while it became smaller when increased to 37 °C. This phenomenon indicated that, in addition to sphingimyelin and cholesterol, phospholipids might also contribute to increasing the segregated domains at lower temperature, while, at elevated temperature, these domains could be diminished, most likely due to a restructuring or distributing of sphingimyelin and cholesterol.

Lipid Composition Analysis of Milk Fats from Different Mammalian Species: Potential for Use as Human Milk Fat Substitutes

The lipid compositions of commercial milks from cow, buffalo, donkey, sheep, and camel were compared with that of human milk fat (HMF) based on total and sn-2 fatty acid, triacylglycerol (TAG), phospholipid, and phospholipid fatty acid compositions and melting and crystallization profiles, and their degrees of similarity were digitized and differentiated by an evaluation model. The results showed that these milk fats had high degrees of similarity to HMF in total fatty acid composition. However, the degrees of similarity in other chemical aspects were low, indicating that these milk fats did not meet the requirements of human milk fat substitutes (HMFSs). However, an economically feasible solution to make these milks useful as raw materials for infant formula production could be to modify these fats, and a possible method is blending of polyunsaturated fatty acids (PUFA) and 1,3-dioleoyl-2-palmitoylglycerol (OPO) enriched fats and minor lipids based on the corresponding chemical compositions of HMF.

Changes in Volatile Compounds of Peanut Oil during the Roasting Process for Production of Aromatic Roasted Peanut Oil

UNLABELLED The changes in volatile compounds composition of peanut oil during the roasting process of aromatic roasted peanut oil (ARPO) production were investigated. The analyses were performed by gas chromatography-mass spectrometry combined with headspace solid phase microextraction (HS-SPME/GC-MS). Among the volatiles identified in ARPO, the N-heterocyclic chemical class possessed the highest relative percentage area (RPA) 61.68%, followed by O-heterocyclic group with an RPA of 24.57%. Twenty pyrazines were considered to be the key contributors to the intense nutty/roasty flavor typical of ARPO. Compounds that increased significantly in concentration during the roasting process were mainly Maillard reaction products, as well as compounds derived from Strecker degradation and lipid peroxidation. The results clearly showed that the roasting process was necessary to obtain the typical nutty/roasty aroma of ARPO. PRACTICAL APPLICATION ARPO is the traditional edible oil in China that possesses a characteristic strong nutty and roasty flavor that distinguishes it from other edible vegetable oils. During the production, the roasting process is the crucial factor for the formation of the typical roasted peanut aroma that plays an important role in sensory quality of peanut oil. In our investigation, not only the volatile changes of peanut oil pressed from relevant peanut seeds roasted at different roasting time were determined, but also the contributions of identified volatiles on the typical nutty/roasty flavor of ARPO were discussed. Our work clearly demonstrated the significant effect of roasting process on the typical flavor formation of ARPO. The results are valuable as scientific guidance for the roasting process that better satisfy demands of the peanut oil industries for better flavor.

Photodegradation kinetics and byproducts identification of the Aflatoxin B1 in aqueous medium by ultra-performance liquid chromatography–quadrupole time-of-flight mass spectrometry

A photodegradation study of Aflatoxin B(1) (AFB(1)) in water solution was performed under UV irradiation at different AFB(1) initial concentrations and UV irradiation intensities. The effect of UV intensity on the AFB(1) photodegradation ratio is dominative, when compared with AFB(1) initial concentration. The photodegradation of AFB(1) was proved to follow first-order reaction kinetics (R(2) > or = 0.99). Three photodegradation products, i.e. P(1) (C(17)H(14)O(7)), P(2) (C(16)H(14)O(6)) and P(3) (C(16)H(12)O(7)), were identified on the basis of low mass error and high matching property by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF MS), and the degradation pathway was proposed. This study first reports the appearance of these photodegradation products and the proposed degradation pathway in aqueous media.

Lipase-catalyzed preparation of human milk fat substitutes from palm stearin in a solvent-free system.

Human milk fat substitutes (HMFSs) were synthesized by lipozyme RM IM-catalyzed acidolysis of chemically interesterified palm stearin (mp = 58 °C) with mixed FAs from rapeseed oil, sunflower oil, palm kernel oil, stearic acid, and myristic acid in a solvent-free system. Response surface methodology (RSM) was used to model and optimize the reactions, and the factors chosen were reaction time, temperature, substrate molar ratio, and enzyme load. The optimal conditions generated from the models were as follows: reaction time, 3.4 h; temperature, 57 °C; substrate molar ratio, 14.6 mol/mol; and enzyme load, 10.7 wt % (by the weight of total substrates). Under these conditions, the contents of palmitic acid (PA) and PA at sn-2 position (sn-2 PA) were 29.7 and 62.8%, respectively, and other observed FAs were all within the range of FAs of HMF. The product was evaluated by the cited model, and a high score (85.8) was obtained, which indicated a high degree of similarity of the product to HMF.

A strategy for the highly efficient production of docosahexaenoic acid by Aurantiochytrium limacinum SR21 using glucose and glycerol as the mixed carbon sources.

Glucose and glycerol are useful carbon sources for the cultivation of Aurantiochytrium limacinum SR21. Glucose facilitates rapid growth and lipid synthesis, and glycerol promotes the accumulation of docosahexaenoic acid (DHA) in A. limacinum SR21. To improve the DHA productivity of A. limacinum SR21, shake flask and fed-batch cultures were performed using glucose and glycerol as mixed carbon sources (MCSs). Along with optimization of the MCSs, the best DHA yield and productivity (32.36 g/L and 337.1 mg/L/h) were obtained via fed-batch fermentation with maintenance of a constant air supply. The DHA productivity was 15.24% higher than that obtained using glucose as single carbon source (SCS). This study presents a highly efficient and economic strategy for the production of DHA by A. limacinum SR21.

Model for Human Milk Fat Substitute Evaluation Based on Triacylglycerol Composition Profile

Being the dominant components in human milk fat (HMF), triacylglycerol (TAG) composition might be the best approximation index to represent the composing characteristics of HMF. In this study, TAG composition of HMF from different lactation stages was analyzed by RP-HPLC-APCI-MS, and the establishment of a model for the precise evaluation of human milk fat substitutes (HMFSs) based on TAG composition was indirectly realized by employment of fatty acid composition and distribution and polyunsaturated fatty acid (PUFA) and TAG compositions. The model was verified by the selected fats and oils with specific chemical compositions, and the results revealed the degrees of similarity of these fats and oils in different evaluation aspects reflected their differences in corresponding chemical composition with HMF. The newly established evaluation model with TAG composition as a comparison base could provide a more accurate method to evaluate HMFSs and might have some inspirations for HMFS production in the future.

In vitro toxicity of aflatoxin B1 and its photodegradation products in HepG2 cells

The effects of aflatoxin B1 (AFB1) were studied using the HepG2 cell line. Cytotoxicity, apoptosis and p53 expression were assessed after exposure to different concentrations of AFB1 (0–100 μm) and its two types of degradation products, namely the mixtures of photodegradation products in water (Pw) and the mixtures of photodegradation products in peanut oil (Po) for different time periods (0, 24, and 48 h). After exposure of the HepG2 cells to these compounds for different times and concentrations, the cytotoxicity of Pw and Po decreased approximately 40 and 100% compared with AFB1, respectively. The expression of p53 protein decreased significantly in AFB1‐exposed cells, decreased slightly in Pw‐treated cells and did not decrease compared to the untreated cells. The results of the in vitro cytotoxicity assay indicate that Pw is less toxic than AFB1, and Po has almost no toxicity, which can be explained by the differences in the chemical nature of the various kinds of the test compounds. Copyright

Enhanced arachidonic acid production from Mortierella alpina combining atmospheric and room temperature plasma (ARTP) and diethyl sulfate treatments

To obtain mutant strains with higher arachidonic acid (ARA) yields, the oleaginous fungus Mortierella alpina was mutated using atmospheric and room temperature plasma (ARTP) coupled with diethyl sulfate (DES). A visual compound filter operation was used in which a screening medium was supplemented with cerulenin, an inhibitor of fatty acid synthase (FAS), and triphenyltetrazolium chloride (TTC). The mutant strain D20 with an ARA production of 5.09 g/L, a 40.61% increase over the original strain (3.62 g/L), was isolated. The relative ARA content increased from 38.99% to 45.64% of total fatty acids. After optimizing fermentation conditions, the maximum ARA yield (6.82 g/L) for strain D20 was obtained in shake flasks. This work provides an appropriate strategy for obtaining high ARA-yield strains by conventional random mutation methods with an efficient screening assay.

Efficient production of arachidonic acid by Mortierella alpina through integrating fed-batch culture with a two-stage pH control strategy.

Arachidonic acid (ARA) yield and productivity of Mortierella alpina mutant D20 were enhanced by integrating a fed-batch culture combined with a two-stage pH control strategy. Following a kinetic analysis of the whole fermentation process, a two-stage pH control strategy was developed in which the pH was maintained at 5.5 for the first 48 h and then shifted to 6.5 till the end of fermentation. Using this strategy, a maximum ARA production of 8.12 g/L was achieved. On the basis of pH control, the effects of fed-batch cultures on ARA productivity were further investigated. A maximum ARA productivity of 1.40 g/L/d was obtained with a two-stage constant-speed glucose feeding strategy, starting with a glucose concentration of 50 g/L. This strategy was simple and economical to operate, and it may be possible to apply this approach for large-scale industrial production of ARA.