Characterization and demusification of cream emulsion from aqueous extraction of peanut

The Optimization of Demulsification Using Composite Fatty Acids in Aqueous Enzymatic Extraction and the Changes of the Emulsion Stability During Demulsification

Aqueous enzymatic extraction (AEE) can simultaneously separate oil and protein. However, a stable O/W emulsion is present in the AEE process, which is not favorable for extracting oils. This study optimized the use of heptanoic and octanoic acids for demulsification in aqueous enzymatic extraction. The optimal condition for demulsification, including a fatty acid ratio of 1:3 (heptanoic acid to octanoic acid) with 1.00% addition, a reaction time of 40 min, a temperature of 70 °C, and a solid-to-liquid ratio of 1:5, resulted in a demulsification rate of 97.95% ± 0.03%. After demulsification, the particle size of the peanut emulsion increased, while the absolute potential value and conductivity decreased. The type and content of proteins decreased, and the tertiary structure also changed, with tryptophan residues buried within the proteins, shifting the system from a polar to nonpolar environment. The microstructure of the emulsion changed and the emulsion transformed into W/O. To summarize, composite fatty acid had a significant effect on the demulsification of emulsion.

Characteristic and stability changes of peanut oil body emulsion during the process of demulsification using heptanoic acid

In this paper, the changes in oil body emulsion (OBE) during heptanoic acid demulsification (HD) were investigated from the macro and microscopic points of view. Specifically, the OBE particle size increased from 3.04 to 8.41 µm, while the zeta potential absolute decreased to 2.89 mV. The interfacial tension and apparent viscosity of OBE were reduced significantly. Heptanoic acid could contribute to oil droplets aggregation. The findings indicated that high-molecular proteins, including lipoxygenase (97.58 kDa) and arachin (70.28 kDa), detached from the OBs' interface. HD caused alterations in the secondary structure of protein and the environment around proteins changed. The HD mechanism was speculated that the addition of heptanoic acid resulted in the reduction in pH and changes of environment surrounding OBE, which triggered polymerization and the phase transformation of the oil droplets. Overall, this study is vital for solving the problem of demulsification during aqueous enzymatic extraction (AEE).

Effects of the Roasting-Assisted Aqueous Ethanol Extraction of Peanut Oil on the Structure and Functional Properties of Dreg Proteins

The effects of the roasting-assisted aqueous ethanol extraction of peanut oil on the structure and functional properties of dreg proteins were investigated to interpret the high free oil yield and provide a basis for the full utilization of peanut protein resources. The roasting-assisted aqueous ethanol extraction of peanut oil obtained a free oil yield of 97.74% and a protein retention rate of 75.80% in the dreg. The water-holding capacity of dreg proteins increased significantly, and the oil-holding capacity and surface hydrophobicity decreased significantly, reducing the binding ability with oil and thus facilitating the release of oil. Although the relative crystallinity and denaturation enthalpy of the dreg proteins decreased slightly, the denaturation temperatures remained unchanged. Infrared and Raman spectra identified decreases in the C-H stretching vibration, Fermi resonance and α-helix, and increases in random coil, β-sheet and β-turn, showing a slight decrease in the overall ordering of proteins. After the roasting treatment, 62.57-135.33% of the protein functional properties were still preserved. Therefore, the roasting-assisted aqueous ethanol extraction of peanut oil is beneficial for fully utilizing the oil and protein resources in peanuts.

Ultrasonic-ethanol pretreatment assisted aqueous enzymatic extraction of hemp seed oil with low Δ9-THC

In this study, ultrasonic-ethanol pretreatment combined with AEE was developed for oil extraction from hemp seeds. The oil yield reached a maximum of 23.32 % at 200 W ultrasonic power and 30 min ultrasonic time, at this point, the degradation rate of Δ9-THC was 83.11 %. By determining the composition of hemp seed before and after pretreatment, it was shown that ultrasonic-ethanol pretreatment reduced the protein content of the raw material. An enzyme mixture consisting of pectinase and hemicellulase (1/1/1, w/w/w) was experimentally determined to be used, and the AEE extraction conditions were optimized using the Plackett-Burman design and the Box-Behnken. The optimal conditions were determined to be pH 5, total enzyme activity of 37,800 U/g, liquid-solid ratio of 10.4 mL/g, enzyme digestion temperature of 32 °C, enzymatic time of 189 min, and oil recovery of 88.38 %. The results of confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) showed that the emulsion formed during ultrasonic ethanol pretreatment was not uniformly distributed, and the droplets appeared to be aggregated; and the irregular pores of hemp seed increased after pretreatment. The contents of Δ9-THC and CBN in the extracted oil samples were 9.58 mg/kg and 52.45 mg/kg, respectively. Compared with the oil extracted by Soxhlet extraction (SE), the oil extracted by this experimental method was of better quality and similar in fatty acid composition.

Effects of Pretreatment on Stability of Peanut Oil Bodies and Functional Characteristics of Proteins Extracted by Aqueous Enzymatic Method

Effects of dry and wet grind on peanut oil and protein yield, oil bodies (OBs) stability, fatty acid composition, protein composition and functional characteristics were systematically analyzed. Results showed that peanut oil and protein yields reached highest at dry grind 90 s (92.56% and 83.05%, respectively), while peanut oil and protein yields were 94.58% and 85.36%, respectively, at wet grind 120 s. Peanut oil and protein yields by wet grind was 2.18% and 2.78% higher than that of dry grind, respectively. Surface protein concentration (Г) and absolute value of zeta potential of OBs extracted by wet grind (WOBs) were 11.53 mg/m 2 and 18.51 mV, respectively, which were higher than OBs extracted by dry grind (DOBs), indicating stability of WOBs was higher than DOBs. Relative contents of oleic acid and linoleic acid in peanut oil, essential and hydrophobic amino acids in protein extracted by wet grind were higher than dry grind. There was little difference in protein composition between wet and dry grind, but thermal denaturation degree of protein obtained by wet grind was lower than dry grind. Solubility, oil retention, emulsion stability, foaming and foam stability of protein obtained by wet grind were better than dry grind. Results from this study provided theoretical basis for grind pretreatment selection of aqueous enzymatic method.

Effects of Roasting Temperatures on Peanut Oil and Protein Yield Extracted via Aqueous Enzymatic Extraction and Stability of the Oil Body Emulsion

Oil body emulsions (OBEs) affect the final oil yield as an intermediate in the concurrent peanut oil and protein extraction process using an aqueous enzyme extraction (AEE) method. Roasting temperature promotes peanut cell structure breakdown, affecting OBE composition and stability and improving peanut oil and protein extraction rates. Therefore, this study aimed to investigate the effects of pretreatment at different roasting temperatures on peanut oil and protein yield extracted through AEE. The results showed that peanut oil and protein extraction rates peaked at 90 °C, 92.21%, and 77.02%, respectively. The roasting temperature did not change OBE composition but affected its stability. The OBE average particle size increased significantly with increasing temperature, while at 90 °C, the zeta potential peaked, and the interfacial protein concentration hit its lowest, indicating OBE stability was the lowest. Optical microscopy and confocal laser scanning microscopy confirmed the average particle size findings. The oil quality obtained after roasting treatment at 90 °C did not differ significantly from that at 50 °C. The protein composition remained unaffected by the roasting temperature. Conclusively, the 90 °C roasting treatment effectively improved the yield of peanut oil extracted using AEE, providing a theoretical basis for choosing a suitable pretreatment roasting temperature.

Demulsification of Emulsion Using Heptanoic Acid during Aqueous Enzymatic Extraction and the Characterization of Peanut Oil and Proteins Extracted

Peanut oil body emulsion occurs during the process of aqueous enzymatic extraction (AEE). The free oil is difficult to release and extract because its structure is stable and not easily destroyed. Demulsification can release free oil in an oil body emulsion, so various fatty acids were selected for the demulsification. Changes in the amount of heptanoic acid added, solid-liquid ratio, reaction temperature, and reaction time were adopted to investigate demulsification, and the technological conditions of demulsification were optimized. While the optimal conditions were the addition of 1.26% of heptanoic acid, solid-liquid ratio of 1:3.25, reaction temperature of 72.7 °C, and reaction time of 55 min, the maximum free oil yield was (95.84 ± 0.19)%. The analysis of the fatty acid composition and physicochemical characterization of peanut oils extracted using four methods were studied during the AEE process. Compared with the amount of oil extracted via other methods, the unsaturated fatty acids of oils extracted from demulsification with heptanoic acid contained 78.81%, which was significantly higher than the other three methods. The results of physicochemical characterization indicated that the oil obtained by demulsification with heptanoic acid had a higher quality. According to the analysis of the amino acid composition, the protein obtained using AEE was similar to that of commercial peanut protein powder (CPPP). However, the essential amino acid content of proteins extracted via AEE was significantly higher than that of CPPP. The capacity of water (oil) holding, emulsifying activity, and foaming properties of protein obtained via AEE were better than those for CPPP. Overall, heptanoic acid demulsification is a potential demulsification method, thus, this work provides a new idea for the industrial application of simultaneous separation of oil and proteins via AEE.

Study on the Stability Mechanism of Peanut OBs Extracted with the Aqueous Enzymatic Method

In this study, the internal relationships among oil bodies (OBs), the protein-phospholipid interactions in aqueous phase, oil-water interface behavior, and the stability of reconstituted OBs were analyzed from the bulk phase, interface, and macro perspectives, and the stability mechanism of OBs was discussed. OB proteins and phospholipids were combined through hydrophobic and electrostatic interactions, resulting in the stretching of protein conformation. OB proteins and phospholipids act synergistically to increase interface pressure and the rate of increase in interface pressure with relatively stable elastic behavior, which is beneficial to the formation and stability of interfacial films. When OBs were reconstituted by an OB protein-phospholipid complex system, phospholipids bound to OB proteins through hydrophobic and electrostatic interactions. OB proteins and phospholipids uniformly covered the oil droplet surface of reconstituted OBs to form a stable interfacial film, which maintained the stability of OBs. The addition of phospholipids significantly reduced the particle size of OBs prepared by OB proteins in a dose-dependent manner, and particle size decreased with the increase in phospholipid content (p < 0.05). Phospholipids increased the net surface charge, enhanced electrostatic repulsion, and improved the physicochemical stability of reconstituted OBs. The stability mechanism elucidated in this study provides a theoretical basis for the demulsification of peanut OBs.

Investigation on the emulsification mechanism in aqueous enzymatic extraction of edible oil from Schizochytrium sp

BACKGROUND

The interaction between emulsified substances and lipids generates an emulsification system during the extraction of microalgae edible oil by aqueous enzymatic method. This study aimed to resolve the dynamics of interfacial protein adsorption during the extraction of microalgae oil at different enzymatic times and the effect on the stability of the interfacial membrane formed by the proteins based on interfacial effects.

RESULTS

At 1.5 h of enzymatic hydrolysis, the molecular weights of the proteins/peptides were all below 35 kD. In addition, the protein-peptide structure was loose, with the lowest number of disulfide bonds, peak surface hydrophobicity, the highest number of residues, and disordered lipid acyl arrangement. At the same time, the physical stability of the emulsion was the lowest, and the interfacial membrane rupture was distinct. On excessive enzymatic hydrolysis (at 3.0 h), a more uniform interfacial membrane was re-formed on the lipid surface.

CONCLUSION

Protein is the main emulsifying substance in the emulsification system. The addition of protease affects the stability of the interfacial membrane formed by proteins. In addition, sufficient enzymatic hydrolysis (1.5 h) inhibited emulsification, while excessive enzymatic hydrolysis (3.0 h) promoted emulsification. © 2023 Society of Chemical Industry.

Polyphenolic compounds from rapeseeds (Brassica napus L.): The major types, biofunctional roles, bioavailability, and the influences of rapeseed oil processing technologies on the content

The rapeseed (Brassica napus L.) are the important oil bearing material worldwide, which contain wide variety of bioactive components with polyphenolic compounds considered the most typical. The rapeseed polyphenols encompass different structural variants, and have been considered to have many bioactive functions, which are beneficial for the human health. Whereas, the rapeseed oil processing technologies affect their content and the biofunctional activities. The present review of the literature highlighted the major types of the rapeseed polyphenols, and summarized their biofunctional roles. The influences of rapeseed oil processing technologies on these polyphenols were also elucidated. Furthermore, the directions of the future studies for producing nutritional rapeseed oils preserved higher level of polyphenols were prospected. The rapeseed polyphenols are divided into the phenolic acids and polyphenolic tannins, both of which contained different subtypes. They are reported to have multiple biofunctional roles, thus showing outstanding health improvement effects. The rapeseed oil processing technologies have significant effects on both of the polyphenol content and activity. Some novel processing technologies, such as aqueous enzymatic extraction (AEE), subcritical or supercritical extraction showed advantages for producing rapeseed oil with higher level of polyphenols. The oil refining process involved heat or strong acid and alkali conditions affected their stability and activity, leading to the loss of polyphenols of the final products. Future efforts are encouraged to provide more clinic evidence for the practical applications of the rapeseed polyphenols, as well as optimizing the processing technologies for the green manufacturing of rapeseed oils.

Simultaneous Recovery of High Quality Black Sesame Oil and Defatted Meal by a New Aqueous Method: Optimization and Comparison with Other Methods

A method able to simultaneously obtain oil and defatted meal (rich in proteins) with high quality is preferable to others for processing black sesame seeds, which should also be green, healthy, highly efficient and sustainable. Methods including solvent extraction and hot-pressing currently available for the commercial production of oils are not able to meet all criteria just mentioned above. Therefore, development of new aqueous method of extracting black sesame oil has been promoted. In our study, we developed a new aqueous method using 1.95:10 aqueous salt solution-to-ground black sesame seed ratio which simultaneously recovered 96.54% black sesame oils and defatted meal with only 3.89% residual oils and 50.1% proteins (on dry weight basis). The oil produced had low acid value at 0.43 mgKOH/kg and peroxide value 3.37 mmol/kg and good other quality indexes. We found that proper amount of water added was essential for efficiently recover black sesame oils while other factors including temperature and time of baking raw materials to deactivate lipase activity, pore size of the sieve for ground black sesame seeds to pass through, addition of salt as well as temperature and time of agitating significantly affected the recovery efficiency. As compared with other methods, the new aqueous method had higher oil recovery rate or quality and was more environmentally friendly. No waste water was discharged during separation of oils. The experimental data can be applied to guide the design and manufacture of production line of black sesame oilseeds on a pilot or commercial scale.

Biodiesel from oil produced in vegetative tissues of biomass - A review

Biodiesel is a green, renewable alternative to petroleum-derived diesel. However, using vegetable oil for biodiesel production significantly challenges the food security. Progress in metabolic engineering, understanding of lipid biosynthesis and storage have enabled engineering of vegetative tissues of plants such as sugarcane, sorghum, and tobacco for lipid production. Such sources could be cultivated on land resources, which are currently not suitable for row crops. Besides achieving significant lipid accumulation, it is imperative to maintain the fatty acid and lipid profile ideal for biodiesel production and engine performance. In this study, genetic modifications used to induce lipid accumulation in transgenic crops and the proposed strategies for efficient recovery of oil from these crops have been presented. This paper highlights that lipids sourced from vegetative biomass in their native form would pose significant challenges in biodiesel production. Therefore, different strategies have been presented for improving feedstock quality to achieve high-quality biodiesel production.

Fate of phospholipids during aqueous extraction processing of peanut and effect of demulsification treatments on oil-phosphorus-content

PC (phosphatidylcholine), PE (phosphatidylethanolamine), PI (phosphatidylinositol), and PA (phosphatidic acid) in 9 peanut matrices obtained during the AEP (aqueous extraction processing) of peanut were quantified employing HPLC-ELSD analysis in this study. Phosphorus contents of crude oils obtained from different demulsification treatments were also investigated. Decantation had a larger effect than grinding in terms of phospholipids loss due to alkaline-hydrolysis, indicating this processing step was vital for the manipulation of phospholipids levels remained in oil. Over 80% of initial phospholipids were lost during AEP and only 19.8% of initial phospholipids ended up in cream, skim and sediment phase. 52.55% of the remained phospholipids trapped in cream phase. Just 22.16-32.61 mg/kg phosphorus content could be detected in crude oils, which indicated the separation of phospholipids from the cream phase into aqueous medium. Degumming was not essential in AEP of peanut and the waste generated after demulsification could be a source of phospholipids.

Effects of Pretreatment on the Yield of Peanut Oil and Protein Extracted by Aqueous Enzymatic Extraction and the Characteristics of the Emulsion

Effects of comminution on peanut particle size and yield of peanut oil and protein were analyzed. Additionally, the emulsion properties (surface protein concentration, particle size, and ξ-potential) were compared. Moreover, different demulsification methods were used to investigate the emulsion stability. Results showed that the yield of peanut oil and protein was highest (87.23% and 82.05%, respectively) after dry comminution for 72 s. Upon wet comminution for 120 s, the yields of peanut oil and protein were 89.91% and 84.70%, respectively, which were both significantly higher than that obtained after dry comminution (p < 0.05). The surface protein concentration and ξ-potential of emulsion made by dry comminution (DCE) were 7.02 mg/m² and 12.08 mV, respectively, and those of emulsion made by wet comminution (WCE) were 10.71 mg/m² and 15.25 mV, respectively, which were significantly higher than that of DCE (p < 0.05). The volume average particle size of DCE was 3.41 µm, which was significantly higher than that of WCE (3.18 µm, p < 0.05). Collectively, these results indicated that WCE was more stable than DCE. Further, the demulsification rate of DCE was significantly higher than that of WCE when treated by freeze-thawing, pH, papain, and phospholipase A2 (p < 0.05). Demulsification effect of Alcalase 2.4L was the best among these five demulsification methods treated, and the demulsification rate of DCE reached 92.77%, which was slightly higher than that of WCE (92.67%), further illustrating the higher stability of WCE.

Characterization and Demulsification of the Oil-Rich Emulsion from the Aqueous Extraction Process of Almond Flour

The aqueous extraction process (AEP) allows the concurrent extraction of oil and protein from almond flour without the use of harsh solvents. However, the majority of the oil extracted in the AEP is present in an emulsion that needs to be demulsified for subsequent industrial utilization. The effects of scaling-up the AEP of almond flour from 0.7 to 7 L and the efficiency of enzymatic and chemical approaches to demulsify the cream were evaluated. The AEP was carried out at pH 9.0, solids-to-liquid ratio of 1:10, and constant stirring of 120 rpm at 50 °C. Oil extraction yields of 61.9% and protein extraction yields of 66.6% were achieved. At optimum conditions, enzymatic and chemical demulsification strategies led to a sevenfold increase (from 8 to 66%) in the oil recovery compared with the control. However, enzymatic demulsification resulted in significant changes in the physicochemical properties of the cream protein and faster demulsification (29% reduction in the incubation time and a small reduction in the demulsification temperature from 55 to 50 °C) compared with the chemical approach. Reduced cream stability after enzymatic demulsification could be attributed to the hydrolysis of the amandin α-unit and reduced protein hydrophobicity. Moreover, the fatty acid composition of the AEP oil obtained from both demulsification strategies was similar to the hexane extracted oil.

Pseudosciaena crocea roe protein-stabilized emulsions for oral delivery systems: In vitro digestion and in situ intestinal perfusion study

Benzyl isothiocyanate (BITC) was encapsulated in oil-in-water emulsions stabilized by Pseudosciaena crocea roe protein isolate (PRPI). The stability, lipid digestion, BITC bioavailability, and retention rate of the emulsions were characterized using a simulated gastrointestinal tract model. Tween-corn and PRPI-medium-chain triglycerides (MCT) emulsions were used as controls. The membrane permeability and BITC absorption from these emulsions were investigated by in situ single-pass intestinal perfusion. The results showed that the PRPI-stabilized emulsions were stable under nonacidic environment conditions. Moreover, the PRPI-corn emulsion had more obvious protective effects than PRPI-MCT and Tween-corn emulsions. Atomic force and confocal laser scanning microscopy images showed that the protein hydrolyzed and oil droplets aggregated during simulated gastric phase digestion. Following the exposure of oil droplets in the small intestine phase, the PRPI-corn emulsion had a high rate of free fatty acid release (99.13 ± 2.49%), and the retention rate and bioavailability of BITC from the PRPI-corn emulsion were 75.93 ± 7.17% and 77.32 ± 5.36%, respectively, which were significantly higher than those measured for the other emulsions (P < 0.05). Moreover, the K_a and P_eff of the PRPI-corn emulsion reached the maximum value at 45 min and then decreased slowly. These results suggest that the PRPI-corn emulsion delivery system is effective in encapsulating, delivering, and protecting BITC. PRACTICAL APPLICATION: This study provides some useful information for the food industry to develop a Pseudosciaena crocea roe protein isolate (PRPI) emulsion that could be successfully used to construct a BITC delivery system and improve benzyl isothiocyanate (BITC) bioavailability. The protective effect on BITC assessed in vitro simulated gastrointestinal tract and in situ single-pass intestinal perfusion are discussed.

Effect of Papain on the Demulsification of Peanut Oil Body Emulsion and the Corresponding Mechanism

This study investigated the effect of papain on the demulsification of peanut oil body emulsion extracted using an aqueous enzymatic method and the associated mechanism. The highest free oil yield using papain (92.39%) was obtained under the following conditions: an enzymatic hydrolysis temperature of 55°C, sample-to-water ratio of 1:3, enzyme concentration of 1400 U/g, and an enzymatic hydrolysis time of 3 h. Papain degraded the peanut oil body protein to small-molecular-weight peptides (≤ 14.4 kDa). Compared to the emulsion before enzymatic hydrolysis, the amino acid content in the aqueous phase was higher after enzymatic hydrolysis, the viscosity of the oil body emulsion was lower, and the particle diameter of the emulsion was significantly larger. The following demulsification mechanism was derived. Papain degrades the protein on the peanut oil body and dissolves it in water. The outer side of the oil body loses the protection of electrostatic repulsion and steric hindrance provided by the membrane protein. This causes the viscosity of the emulsion system and the molecular steric hindrance to decrease. As a result, the oil droplets gather and eventually demulsify. The results of this study provide the theoretical basis for the instability in oil body emulsions and are expected to promote the application of enzymatic demulsification in industry.

Combination of Alcalase 2.4 L and CaCl2 for aqueous extraction of peanut oil

The combined application of CaCl₂ and Alcalase 2.4 L to the aqueous extraction process of peanuts was evaluated as a method to destabilize the oil body (OB) emulsion and improve the oil yield. After adding 5 mM CaCl₂ , the oil yield was reached to 92.0% which was similar with that obtained using Alcalase 2.4 L alone, and the required enzyme loading was decreased by approximately 60 times. In addition, the demulsification mechanism during aqueous extraction process was also investigated. Particle size and zeta-potential measurements indicated that the stability of the peanut OB emulsion dramatically decreased when CaCl₂ was added. Under these conditions, the demulsification of Alcalase 2.4 L performed was more efficiently. SDS-PAGE results showed that adding CaCl₂ changed the subunit structure of the peanut OB interface proteins and promoted the cross-linking among the arachin Ara h3 isoforms, resulting in unstable emulsions.

Study on Extraction of Peanut Protein and Oil Bodies by Aqueous Enzymatic Extraction and Characterization of Protein

Cell wall degrading enzymes break down the cell wall by degrading the main cell wall components and destroying structure of the cell wall without influencing the protein. Effects of various enzymes (Viscozyme® L, cellulase, hemicellulase, and pectinase) on the molecular weight distribution of peanut protein and yield of peanut protein and oil bodies during an aqueous enzymatic extraction process were investigated in this study. The molecular weight distribution of peanut protein was not changed, and Viscozyme® L was selected to assist peanut protein and oil bodies extraction by the aqueous extraction process. The aqueous enzymatic extraction process was optimized by a signal factor experiment and response surface methodology, and the optimal condition was enzyme hydrolysis temperature of 52°C, solid-liquid ratio of 1 : 4, enzyme concentration of 1.35%, and enzyme hydrolysis time of 90 min. A peanut protein yield of 78.60% and oil bodies yield of 48.44% were achieved under the optimal condition. Compared with commercial peanut protein powder (CPPP), the solubility and foaming properties of peanut protein powder obtained by aqueous enzymatic extraction (AEEPPP) were a little lower. However, the functional properties of foam stability, emulsifying activity, emulsifying stability, water holding capacity, and oil holding capacity of AEEPPP were better than that of CPPP.

Critical functional properties of defatted peanut meal produced by aqueous extraction and conventional methods

The functional properties of the defatted peanut meal produced by aqueous extraction, solvent extraction and cold screw pressing followed by solvent extraction were studied. Good gelling property, color and nitrogen dispersibility as well as the high protein content of the defatted peanut meals produced by these methods were verified to be the critical functional properties for their high value of application to the food industry (e.g. production of ham sausages or hotdog sausages) though they are not suggested to be applied to the foods needing good oil binding capacity, emulsifying activity or stability and foaming capacity or stability. These results should provide valuable reference data for the application of defatted peanut meal to the food industry, the correct selection of processing method of peanut kernels which should be pursued by manufacturers and the determination of research direction that peanut processing technologists should be interested in.

Fabrication and Physicochemical Characterization of Pseudosciaena crocea Roe Protein-Stabilized Emulsions as a Nutrient Delivery System

The aim of this study was to develop a protein emulsifier that can be used to construct a nutrient delivery system. Pseudosciaena crocea roe protein isolate (PRPI) was prepared and tested for its emulsifying properties. Benzyl isothiocyanate (BITC) was used as a model delivery nutrient in the constructed emulsions. The average particle size, zeta potential, and BITC retention rate of the emulsions were used as the main evaluation indexes, and confocal laser scanning microscopy was used to test the storage stability of the emulsions (composition: 5 mg/mL protein, 5% oil, 0 to 5 mg/mL BITC, pH 8). After storing at 20 °C for 7 days, the largest particle size of the emulsion at pH 8 increased from 274.27 to 280.82 nm. Storing at higher temperatures had a negative impact on the particle size and BITC retention rate. On the seventh day, the average particle size at 20 and 4 °C was 289.63 nm and 275.67 nm, respectively, and the BITC retention rate at 20 °C (83.30%) was found to be 15.50% lower than that at 4 °C (98.58%). These results demonstrate that the PRPI-based emulsion system is effective in protecting nutrients and has excellent stability at 4 °C. PRACTICAL APPLICATION: This study provides some useful information for the food industry to develop a nutrient delivery system emulsified with fish roe protein isolate. The properties of the isolated protein and its protective effect on nutrients are discussed.

Combination of thermal pretreatment and alcohol-assisted aqueous processing for rapeseed oil extraction

BACKGROUND

The alcohol-assisted aqueous extraction processing (AAEP) of oil has many advantages such as no need for demulsification and relative low cost compared with enzymatic aqueous extraction processing (EAEP). Three kinds of thermal pretreatments including dry-heating, wet-heating and soak-heating followed by the AAEP of rapeseed oil were investigated.

RESULTS

Both soak-heating and wet-heating had a higher contribution rate to oil yield than dry-heating due to the enhancement of heat transfer rate owing to the high moisture content in the rapeseed cells. However, oil from soak-heated rapeseeds showed a much lower level on peroxide value (0.41 mmol kg^-1 ) than that of wet-heated rapeseeds (5.23 mmol kg^-1 ). In addition, transmission electron microscopy images illustrated that promoting effects of soak-heating and wet-heating on oil release were attributed to the coalescence of oil bodies. A relative low concentration of alcohol solution as an extraction medium, the highest oil recovery of 92.77% was achieved when ground rapeseeds (mean particle size: 21.23 µm) were treated with 45% (v/v) alcohol for 2 h at 70 °C and pH 9.0. Both the acid value and the peroxide value are lower than the commercial oil produced by extrusion and hexane extraction. Furthermore, the oil produced from AAEP also had higher content of tocopherols and lower content of trans-fatty acids than the commercial oil.

CONCLUSION

AAEP of oil from soak-heated rapeseeds is a promising alternative to conventional oil extraction methods. © 2019 Society of Chemical Industry.

Establishment of an aqueous method for extracting soybean oils assisted by adding free oil

Concern for the environment, safety and costs has promoted the development of the method for extracting soybean oil by an aqueous process. An advanced aqueous extraction of soybean oil assisted by adding free oil was established in this study, which recovered 81% of the oil from soybeans with 20.73% crude oil content and produced a de-oiled residue with 4.7% residual oil. The acid or peroxide value of the recovered oil met the Chinese national standard for first class refined oil, which was lower than that produced by solvent extraction or high temperature pressing. No wastewater was produced during the aqueous extraction of oil. The removal of the oil by the addition of oil and a small amount of water generated a residue (solids) containing all the protein, which represents 2/3 of the revenue in the soybean process. The protein-rich residue can be further processed to produce a protein isolate with high purity (e.g. > 90%) by using a higher amount of water. It can also be used as a nutritious ingredient or raw material for the production of many food products, among other applications.

3D confocal Raman imaging of oil-rich emulsion from enzyme-assisted aqueous extraction of extruded soybean powder

The understanding of the structure morphology of oil-rich emulsion from enzyme-assisted extraction processing (EAEP) was a critical step to break the oil-rich emulsion structure in order to recover oil. Albeit EAEP method has been applied as an alternative way to conventional solvent extraction method, the structure morphology of oil-rich emulsion was still unclear. The current study aimed to investigate the structure morphology of oil-rich emulsion from EAEP using 3D confocal Raman imaging technique. With increasing the enzymatic hydrolysis duration from 1 to 3 h, the stability of oil-rich emulsion was decreased as visualized in the 3D confocal Raman images that the protein and oil were mixed together. The subsequent Raman spectrum analysis further revealed that the decreased stability of oil-rich emulsion was due to the protein aggregations via SS bonds or protein-lipid interactions. The conformational transfer in protein indicated the formation of a compact structure.