(31)P NMR phospholipid profiling of soybean emulsion recovered from aqueous extraction

Transesterification of phosphatidylcholine with DHA-rich algal oil using immobilized Candida antarctica lipase B to produce DHA-phosphatidylcholine

Docosahexaenoic acid (DHA) enriched with phospholipids (PLs) (DHA-PLs) is a type of structured PL with good physicochemical and nutritional properties. Compared to PLs and DHA, DHA-PLs has higher bioavailability and structural stability and many nutritional benefits. To improve the enzymatic synthesis of DHA-PLs, this study investigated the preparation of phosphatidylcholine (PC) enriched with DHA (DHA-PC) via enzymatic transesterification of algal oil, which is rich in DHA-triglycerides, using immobilized Candida antarctica lipase B (CALB). The optimized reaction system incorporated 31.2% DHA into the acyl chain of PC and converted 43.6% PC to DHA-PC within 72 h at 50 °C, 1:8 PC: algal oil mass ratio, 25% enzyme load (based on total substrate mass), and 0.02 g/mL molecular sieve concentration. Consequently, the side reactions of PC hydrolysis were effectively suppressed and products with high PC content (74.8%) were produced. Molecular structure analysis showed that exogenous DHA was specifically incorporated into the sn-1 site of the PC by immobilized CALB. Furthermore, the evaluation of reusability with eight cycles showed that the immobilized CALB had good operational stability in the present reaction system. Collectively, this study demonstrated the applicability of immobilized CALB as a biocatalyst for synthesizing DHA-PC and provided an improved enzyme-catalyzed method for future DHA-PL synthesis.

Study on the texture properties and oxidation characteristics of egg yolk powder gel

The gel was prepared by thermal induction of egg yolk powder as raw material in this study. Firstly, the lipid component of egg yolk powder gel and the correlation between the gel strength of egg yolk powder and Texture Profile Analysis were analyzed, and then the changes of oxidation products. The method of principal component analysis (PCA) was used to determine the relationship between secondary oxidation products and fatty acids content. Moreover, Redundancy analysis (RDA) was used to study the relationship between fatty acids, Phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), peroxide value (POV) in Egg Yolk Gel. Result indicated, Lipid content of egg yolk powder gel was lower than egg yolk powder, the gel strength was positively correlated with hardness, adhesion, viscosity and masticatory (p < 0.01), and had a significant negative correlation with recovery (p < 0.01). In the nuclear magnetic map, the signal of primary oxidation product E, E-conjugate form was at 5.70 ppm, the signal of secondary oxidation product n-aldehyde was at 9.75 ppm. Combined with PCA and RDA, the results showed that the changes of fatty acid content were negatively correlated with the changes of peroxide value, while the changes of PC and PE were positively correlated, and the contents of fatty acids, PE, PI and PC were negatively correlated with the changes of POV, of which PE and POV were the most correlated.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13197-021-05027-2.

Extraction Methods of Oils and Phytochemicals from Seeds and Their Environmental and Economic Impacts

Over recent years, the food industry has striven to reduce waste, mostly because of rising awareness of the detrimental environmental impacts of food waste. While the edible oils market (mostly represented by soybean oil) is forecasted to reach 632 million tons by 2022, there is increasing interest to produce non-soybean, plant-based oils including, but not limited to, coconut, flaxseed and hemp seed. Expeller pressing and organic solvent extractions are common methods for oil extraction in the food industry. However, these two methods come with some concerns, such as lower yields for expeller pressing and environmental concerns for organic solvents. Meanwhile, supercritical CO2 and enzyme-assisted extractions are recognized as green alternatives, but their practicality and economic feasibility are questioned. Finding the right balance between oil extraction and phytochemical yields and environmental and economic impacts is challenging. This review explores the advantages and disadvantages of various extraction methods from an economic, environmental and practical standpoint. The novelty of this work is how it emphasizes the valorization of seed by-products, as well as the discussion on life cycle, environmental and techno-economic analyses of oil extraction methods.

Composition and Rheological Properties of Peanut Oil Bodies from Aqueous Enzymatic Extraction

In this study, the relationship between the composition and rheological properties of peanut oil bodies from aqueous enzymatic extraction was evaluated. Aqueous enzymatic extraction using a combination of cellulase and pectinase at a 1:1 ratio effectively destroyed the structure of the cell wall and resulted in the maximum oil body yield of 90.7%. The microstructure and interfacial membrane composition of the peanut oil bodies were observed by confocal laser scanning microscopy. The oil bodies contained three inherent proteins (oleosin, caleosin, and steroleosin) along with two adsorbed foreign proteins (arachin and lipoxygenase). Five phospholipids were detected using ³¹P nuclear magnetic resonance spectroscopy. Among them, phosphatidylcholine, which plays a major role in the stability of oil bodies, was the most abundant. The measured rheological properties indicated that the oil bodies were a typical elastic system. Elevated temperature and high-speed shear destroyed the binding between proteins and phospholipids, reducing the oil body stability. The findings will facilitate the commercial application of peanut oil bodies by improving the extraction rate of peanut oil bodies and clarifying their stabilization mechanism.Practical Application: This paper studies the enzymatic extraction, composition and rheological properties of peanut oil bodies. It provides a theoretical basis for the large-scale application of peanut oil bodies in the food and cosmetic industries. It is beneficial to improve the application value of peanut resources.

A Thermolabile Phospholipase B from Talaromyces marneffei GD-0079: Biochemical Characterization and Structure Dynamics Study

Phospholipase B (EC 3.1.1.5) are a distinctive group of enzymes that catalyzes the hydrolysis of fatty acids esterified at the sn-1 and sn-2 positions forming free fatty acids and lysophospholipids. The structural information and catalytic mechanism of phospholipase B are still not clear. Herein, we reported a putative phospholipase B (TmPLB1) from Talaromyces marneffei GD-0079 synthesized by genome mining library. The gene (TmPlb1) was expressed and the TmPLB1 was purified using E. coli shuffle T7 expression system. The putative TmPLB1 was purified by affinity chromatography with a yield of 13.5%. The TmPLB1 showed optimum activity at 35 °C and pH 7.0. The TmPLB1 showed enzymatic activity using Lecithin (soybean > 98% pure), and the hydrolysis of TmPLB1 by ³¹P NMR showed phosphatidylcholine (PC) as a major phospholipid along with lyso-phospholipids (1-LPC and 2-LPC) and some minor phospholipids. The molecular modeling studies indicate that its active site pocket contains Ser125, Asp183 and His215 as the catalytic triad. The structure dynamics and simulations results explained the conformational changes associated with different environmental conditions. This is the first report on biochemical characterization and structure dynamics of TmPLB1 enzyme. The present study could be helpful to utilize TmPLB1 in food industry for the determination of food components containing phosphorus. Additionally, such enzyme could also be useful in Industry for the modifications of phospholipids.

Phospholipid Composition and Fat Globule Structure I: Comparison of Human Milk Fat from Different Gestational Ages, Lactation Stages, and Infant Formulas

We compared phospholipids (PLs), PL fatty acid (FA) composition, and milk fat globule size and structure in human milk (n = 120) from mothers of full-term and preterm infants during lactation (colostrum, transition, 1 mo, 2 mo, and 3 mo) and 8 brands of infant formulas. The absolute quantification of PLs was analyzed using ³¹P NMR spectroscopy. Sphingomyelin was the dominant PLs (35.01 ± 3.31%) in human milk, whereas phosphatidylcholine and phosphatidylethanolamine were the dominant PLs in infant formulas. The PL content in preterm milk increased during lactation, whereas that in term milk remained stable. Saturated FAs (mainly 16:0 and 18:0) were the most abundant (>60%) PL FA in both preterm and term milk and increased throughout lactation. The mean diameter of milk fat globules in infant formulas was much smaller than that found in human milk (200 nm vs 5.63 μm). Significant differences were observed between human milk and infant formulas with regard to PLs, suggesting that more research is needed to mimic the PL profile in infant formulas.

Aqueous and Enzymatic Extraction of Oil and Protein from Almond Cake: A Comparative Study

The almond cake is a protein- and oil-rich by-product of the mechanical expression of almond oil that has the potential to be used as a source of valuable proteins and lipids for food applications. The objectives of this study were to evaluate the individual and combined effects of solids-to-liquid ratio (SLR), reaction time, and enzyme use on oil and protein extraction yields from almond cake. A central composite rotatable design was employed to maximize the overall extractability and distribution of extracted components among the fractions generated by the aqueous (AEP) and enzyme-assisted aqueous extraction process (EAEP). Simultaneous extraction of oil and protein by the AEP was favored by the use of low SLR (1:12.82) and longer reaction times (2 h), where extraction yields of 48.2% and 70% were achieved, respectively. Increased use of enzyme (0.85%) in the EAEP resulted in higher oil (50%) and protein (75%) extraction yields in a shorter reaction time (1 h), compared with the AEP at the same reaction time (41.6% oil and 70% protein extraction). Overall, extraction conditions that favored oil and protein extraction also favored oil yield in the cream and protein yield in the skim. However, increased oil yield in the skim was observed at conditions where higher oil extraction was achieved. In addition to improving oil and protein extractability, the use of enzyme during the extraction resulted in the production of skim fractions with smaller and more soluble peptides at low pH (5.0), highlighting possible uses of the EAEP skim in food applications involving acidic pH. The implications of the use of enzyme during the extraction regarding the de-emulsification of the EAEP cream warrant further investigation.

Natural phospholipids: Occurrence, biosynthesis, separation, identification, and beneficial health aspects

During the last years, phospholipids (PLs) have attracted great attention because of their crucial roles in providing nutritional values, technological and medical applications. There are considerable proofs that PLs have unique nutritional benefits on human health, such as reducing cholesterol absorption, improving liver functions, and decreasing the risk of cardiovascular diseases. PLs are the main structural lipid components of cell and organelle membranes in all living organisms, and therefore, they occur in all organisms and the derived food products. PLs are distinguished by the presence of a hydrophilic head and a hydrophobic tail, consequently they possess amphiphilic features. Due to their unique characteristics, the extraction, separation, and identification of PLs are critical issues to be concerned. This review is focused on the content of PLs classes in several sources (including milk, vegetable oils, egg yolk, and mitochondria). As well, it highlights PLs biosynthesis, and the methodologies applied for PLs extraction and separation, such as solvent extraction and solid-phase extraction. In addition, the determination and quantification of PLs classes by using thin layer chromatography, high-performance liquid chromatography coupled with different detectors, and nuclear magnetic resonance spectroscopy techniques.

Applications of nuclear magnetic resonance in lipid analyses: An emerging powerful tool for lipidomics studies

The role of lipids in cell, tissue, and organ physiology is crucial; as many diseases, including cancer, diabetes, neurodegenerative, and infectious diseases, are closely related to absorption and metabolism of lipids. Mass spectrometry (MS) based methods are the most developed powerful tools to study the synthetic pathways and metabolic networks of cellular lipids in biological systems; leading to the birth of an emerging subject lipidomics, which has been extensively reviewed. Nuclear magnetic resonance (NMR), another powerful analytical tool, which allows the visualization of single atoms and molecules, is receiving increasing attention in lipidomics analyses. However, very little work focusing on lipidomic studies using NMR has been critically reviewed. This paper presents a first comprehensive summary of application of ¹H, ¹³C &³¹P NMR in lipids and lipidomics analyses. The scientific basis, principles and characteristic diagnostic peaks assigned to specific atoms/molecular structures of lipids are presented. Applications of 2D NMR in mapping and monitoring of the components and their changes in complex lipids systems, as well as alteration of lipid profiling over disease development are also reviewed. The applications of NMR lipidomics in diseases diagnosis and food adulteration are exemplified.

Optimization of normal phase chromatographic conditions for lipid analysis and comparison of associated detection techniques

One important challenge in lipid class analysis is to develop a method suitable or, at least adaptable, for a vast diversity of samples. In the current study, an improved normal-phase liquid chromatography (NPLC) method allowed analyzing the lipid classes present in mammalian, vegetable as well as microorganism (yeast and bacteria) lipid samples. The method effectively separated 30 lipid classes or subclasses with a special focus on medium polarity lipids. The separation was carried out with bare silica stationary phase and was coupled to evaporative light scattering detection (ELSD), charged aerosol detection (Corona-CAD®) and mass spectrometry. Solutions are provided to circumvent technical issues (such as pumping solvents of low viscosity, solvent purity, rinsing step). The influence of mobile phase composition and addition of ionic modifiers on the chromatographic behavior of particular lipid classes is documented. A comparison between ELSD and Corona-CAD® confirmed the interest of this later detector for samples with a wide range of concentration of different lipids. Three common atmospheric pressure ionization interfaces were used for coupling the NPLC separation to a LTQ Velos Pro® mass spectrometer. The comparison of the chromatographic profiles showed that atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) are both suitable to detect the different lipid classes whereas APPI allows a better sensitivity for lipids at low-concentration.

The structure of a calcium-dependent phosphoinositide-specific phospholipase C fromPseudomonassp. 62186, the first from a Gram-negative bacterium

Bacterial phosphoinositide-specific phospholipases C (PI-PLCs) are the smallest members of the PI-PLC family, which includes much larger mammalian enzymes responsible for signal transduction as well as enzymes from protozoan parasites, yeast and plants. Eukaryotic PI-PLCs have calcium in the active site, but this is absent in the known structures of Gram-positive bacteria, where its role is instead played by arginine. In addition to their use in a number of industrial applications, the bacterial enzymes attract special interest because they can serve as convenient models of the catalytic domains of eukaryotic enzymes forin vitroactivity studies. Here, the structure of a PI-PLC fromPseudomonassp. 62186 is reported, the first from a Gram-negative bacterium and the first of a native bacterial PI-PLC with calcium present in the active site. Solution of the structure posed particular problems owing to the low sequence identity of available homologous structures. Its dependence on calcium for catalysis makes this enzyme a better model for studies of the mammalian PI-PLCs than the previously used calcium-independent bacterial PI-PLCs.

Supplementation of laying-hen feed with annatto tocotrienols and impact of α-tocopherol on tocotrienol transfer to egg yolk

Hens can efficiently transfer nutrients from their feed to the eggs. Tocotrienols (T3s) have various health benefits including lowering cholesterol. Annatto is the only known source of T3s without the presence of α-tocopherol; hence it can be used to study T3 transfer without the interference of α-tocopherol. In this study, hens were fed diets for 7 weeks containing annatto at 100, 500, or 2000 ppm (by weight) and also 2000 ppm annatto with 200, 600, or 1000 ppm of added α-tocopherol to study the effect of α-tocopherol on transfer of T3s. No significant differences were found in egg production or properties. Significant differences (p < 0.05) were found in transfer efficiencies of tocopherol and T3s to the yolks. α-Tocopherol was transferred more efficiently (21.19-49.17%) than γ-T3 (0.50-0.96%) or δ-T3 (0.74-0.93%). Addition of 1000 ppm of α-tocopherol decreased the amount of γ-T3 but did not impact the transfer of δ-T3 to the egg. These feeding treatments did not impact the cholesterol content of the eggs.

Total Phospholipids in Edible Oils by In-Vial Solvent Extraction Coupled with FTIR Analysis

A simple procedure for the determination of total phospholipids (TPL) in edible oils was developed by combining a single-step, in situ methanol/acetonitrile (MeOH/ACN) extraction of the oil sample followed by Fourier transform infrared (FTIR) spectroscopic analysis of the extract. Spectral analysis of extracts in a 25 μm CaF₂ cell obtained using 1:1 MeOH/ACN added to oil in a 2:1 ratio indicated that measurements made using only the asymmetric phosphate diester PO₂^- stretching band at 1243 cm^-1 in second-derivative spectra were sufficient for the accurate measurement of TPL with minimal coextracted triglyceride interferences being encountered. FTIR calibration spectra were devised using only phosphatidylcholine (PC) as a representative phospholipid standard, covering a range of 0-50000 μg/g TPL and spiked into 1:1 MeOH/ACN, capable of tracking the added PC with an SD of <200 μg/g. The FTIR method was initially validated using model PC-spiked degummed canola oil and subsequently with commercial crude and refined soy and rapeseed oils as well as a lecithin tablet with the FTIR TPL predictions compared to those of the AOCS Ca 12-55 molybdenate method. The FTIR method tracked the AOCS results well, being somewhat more reproducible than the reference method (±3.2 vs ±4.9%), which limited its accuracy relative to the AOCS reference procedure (±2.2%). The simple in-vial solvent extraction procedure, followed by FTIR analysis of the extract, is a simple, efficient, and rapid procedure that is also amenable to automation using an autosampler-equipped FTIR if multiple samples are to be analyzed.

Effects of vitamin D(3) -enriched diet on egg yolk vitamin D(3) content and yolk quality

A 40-wk experiment was conducted using Hy-Line W-36 laying hens (19-wk old) to investigate the impact of feeding cholecalciferol-enriched diets on egg yolk quality. Feeds were enriched with 4 cholecalciferol levels, 9700 (diet 2), 17200 (diet 3), 24700 (diet 4), and 102200 (diet 5) IU/kg feed. The control (diet 1) contained 2200 IU cholecalciferol/kg feed. Eggs from each replicate group of enriched diets were collected daily and the yolks were pooled into 2-d period during the first 2 wk. During weeks 3, 4, 6, 8, 12, 16, 20, 24, 28, 32, 36, and 40, pooled samples were generated by daily collection of 3 consecutive days of egg production. The cholecalciferol content of egg yolk from the enriched diets increased rapidly during the first 3 wk. The peak cholecalciferol concentrations in egg yolk that occurred at week 3 were 865, 1641, 2411, and 34815 IU/100 g egg yolk (wet basis) from diet 2 to 5. The average cholecalciferol concentration in yolk during weeks 3 to 40 and the deposition rate of cholecalciferol during the first 3 wk were both linearly increased with the dietary cholecalciferol level when the feed contained no more than 24700 IU/kg cholecalciferol. Egg yolk lipid profile (total lipid content, fatty acid composition, phospholipid composition, and unsaponifiables), physical and functional properties (yolk viscosity and emulsifying property), and sensory quality of hard-boiled egg yolk were not affected by the cholecalciferol enrichment in the feed.

PRACTICAL APPLICATION

A linear dose-response relationship between dietary vitamin D(3) level and egg yolk vitamin D(3) content was established at relatively low enrichment levels. Such relationship can be used to formulate feed to achieve a target egg vitamin D level. High vitamin D yolk showed no difference from the conventional yolk in other compositional, functional, and sensory properties.

Chemistry of phospholipid oxidation

The oxidation of lipids has long been a topic of interest in biological and food sciences, and the fundamental principles of non-enzymatic free radical attack on phospholipids are well established, although questions about detail of the mechanisms remain. The number of end products that are formed following the initiation of phospholipid peroxidation is large, and is continually growing as new structures of oxidized phospholipids are elucidated. Common products are phospholipids with esterified isoprostane-like structures and chain-shortened products containing hydroxy, carbonyl or carboxylic acid groups; the carbonyl-containing compounds are reactive and readily form adducts with proteins and other biomolecules. Phospholipids can also be attacked by reactive nitrogen and chlorine species, further expanding the range of products to nitrated and chlorinated phospholipids. Key to understanding the mechanisms of oxidation is the development of advanced and sensitive technologies that enable structural elucidation. Tandem mass spectrometry has proved invaluable in this respect and is generally the method of choice for structural work. A number of studies have investigated whether individual oxidized phospholipid products occur in vivo, and mass spectrometry techniques have been instrumental in detecting a variety of oxidation products in biological samples such as atherosclerotic plaque material, brain tissue, intestinal tissue and plasma, although relatively few have achieved an absolute quantitative analysis. The levels of oxidized phospholipids in vivo is a critical question, as there is now substantial evidence that many of these compounds are bioactive and could contribute to pathology. The challenges for the future will be to adopt lipidomic approaches to map the profile of oxidized phospholipid formation in different biological conditions, and relate this to their effects in vivo. This article is part of a Special Issue entitled: Oxidized phospholipids-their properties and interactions with proteins.