The Mechanism of Extraction of Peanut Protein and Oil Bodies by Enzymatic Hydrolysis of the Cell Wall.

Degradation of the peanut cell wall is a critical step in the aqueous enzymatic extraction process to extract proteins and oil bodies. Viscozyme® L, a compound cell wall degrading enzyme, has been applied as an alternative to protease in the process of aqueous enzymatic extraction, but the mechanism of cell wall enzymolysis remains unclear. The present study aims to investigate the changes in cellulose, hemicellulose, and pectin content of the peanut cell wall hydrolyzed by Viscozyme® L. The degree to which the main components of the peanut cell wall, such as trans-1, 2-cyclohexanediamine-N,N,N',N'-acetic acid-soluble pectin (CDTA-soluble pectin), Na2CO3-soluble pectin, cellulose, and hemicellulose, are degraded is closely related to the extraction of oil bodies and peanut protein at different solid-liquid ratio of powered peanut seed in distilled water, enzyme concentration, enzyme hydrolysis temperature, and enzyme hydrolysis time. The key sites of Viscozyme® L activity on cell wall polysaccharides were explored by comparing the changes in chemical bonds under different extraction conditions using Fourier-transform infrared spectroscopy (FT-IR) absorption bands and principal component analysis (PCA). Viscozyme® L acted on the C-O stretching, C-C stretching, and CH2 symmetrical bending of cellulose, the C-O stretching and O-C-O asymmetrical bending of hemicellulose, and the C-O stretching and C-C stretching of pectin.

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.

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.

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.

Extraction of Peanut Oil Using Thermosonication: Modeling and Multiobjective Optimization of Process Parameters Using Box-Behnken Design.

The extraction of peanut oil was investigated using the combination of ultrasound and heat application, which is known as a novel technology called thermosonication. The study was set up using the Box-Behnken design and the models based on quadratic equations were established. The effects of extraction time (4-12 min), extraction temperature (40-60°C), solvent-to-solid ratio (SSR) (3:1-9:1)(v/w) and ultrasound power (60-100%) on the extraction yield and the oleic acid concentration of extracted oils were investigated. Results showed that the extraction yield was primarily affected by the extraction temperature and SSR. The average maximum yield of 39.93% was achieved when variables were set to 12 min of time, 50°C of temperature, 9:1(v/w) of SSR and 80% of ultrasound power. Thermosonication did not significantly affect the fatty acid composition. Since it was targeted to determine an optimum point where the maximum extraction yield and oleic acid concentration were obtained, a multiobjective optimization was performed. The optimum thermosonication conditions were determined as 4 min of time, 60°C of temperature, 9:1(v/w) of SSR and 100% of power with a maximum extraction yield of 39.86%. Also, the oleic acid concentration was determined as 63.51% in this optimum condition.

Foodomics Revealed the Effects of Extract Methods on the Composition and Nutrition of Peanut Oil.

Processing technology has a significant effect on the functional quality of vegetable oil, but the exact mechanism is not yet very well known so far. The purpose of this study was to investigate the effects of extract methods on the composition and nutrition of peanut oil. Peanut oil was prepared by cold pressing, hot pressing, and enzyme-assisted aqueous extraction, and their trace components were determined by liquid chromatography-mass spectrometry (LC-MS). Serum and liver samples from Sprague-Dawley (SD) rats fed with different extract oils were profiled by gas chromatography-mass spectrometry (GC-MS) and LC-MS. The component analysis showed that different process technologies cause differentiation of trace active ingredients. Metabolomics analysis revealed that a high-fat diet causes serum and hepatic metabolic disorders, which can be ameliorated by hot-pressed and hydroenzymatic peanut oil, including downregulation of partial amino acids, fatty acids, phospholipids, and carbohydrates in cold-pressed peanut oil as well as the upregulation of palmitic acid, uric acid, and pyrimidine in enzyme-assisted aqueous oils. Canonical correspondence analysis (CCA) uncovered strong associations between specific metabolic alterations and peanut oil trace components. The data obtained in this study offers a new insight on the roles of oil processing.

Effect of Physiochemical Factors and Peanut Varieties on the Charge Stability of Oil Bodies Extracted by Aqueous Method.

In order to explore the scientific basis for the application of oil bodies (OBs) from different peanut varieties in food, the effect of NaCl (0-100 mM), thermal processing (25-45°C, 1 h) and pH (3.0, 7.4, and 9.0) on their zeta potentials was analyzed in this study. The zeta potentials of OB suspensions (in 10 mM phosphate buffer) prepared from five peanut varieties in different salt concentrations (0-100 mM) were positive at pH 3.0, while they remained negative at pH 7.4 and 9.0. The absolute values of zeta potentials were over 20 mV at a lower salt concentration (< 10 mM NaCl) at pH 3.0 and 7.4. Particularly, the values of zeta potentials of Yuhua27 and Yuhua9830 were as high as 40 mV in the absence of NaCl at pH 7.4. The OBs exhibited diverse change trends between the five peanut varieties in the temperatures from 25 to 45°C (0 mM NaCl, pH 7.4). The OBs from Yuhua9830 exhibited the best thermal adaptability at the different temperatures tested than the other four peanut varieties. These outcomes suggested that OBs extracted from different varieties possess diverse properties and may provide a new insight into choosing a suitable peanut variety for the food industry.