The effect of enzyme systems and processing on the hydrolysis of peanut (Arachis hypogaea L.) protein

In vitro protein digestion studies were carried out on raw and roasted peanut flour as the starting material in the production of peanut protein hydrolysate. Peanut flour was hydrolyzed with alcalase and alternately in a sequential digestion with pepsin-pancreatin, both for up to 24 h. The degree of hydrolysis (DH) at different times of hydrolysis was determined using the trinitrobenzenesulfonic acid (TNBS) method. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to indicate destruction of native protein units in the enzymatic digests.Hydrolysis with alcalase was very rapid for the first 6 h after which a plateau was reached, whereas that with pepsin–pancreatin was more gradual reaching a plateau after 12 h of hydrolysis. Raw peanut hydrolyzed with alcalase and pepsin–pancreatin had 23% and 21% DH after 24 h respectively, whilst roasted peanut hydrolyzed with alcalase had 21% DH, with the pepsin–pancreatin hydrolysate recording the highest value of 25% after 24 h of hydrolysis.SDS-PAGE results showed that raw peanut samples behaved differently from the roasted samples; increasing hydrolysis time reduced larger peanut protein subunits, with only peptides of <20 kDa visible after hydrolysis for raw peanut, and virtually no distinct visible bands for the roasted peanut after 3 h of hydrolysis.     

Development and characterization of dehydrated peanut–cowpea milk powder for use as a dairy milk substitute in chocolate manufacture

This study explored the feasibility of producing peanut–cowpea milk for use in vegetable milk chocolates. Development of the vegetable milk followed a 3 × 2 factorial design, with peanut–cowpea ratio (1:1, 1:2 and 1:3), and treatment with enzyme (i.e. enzyme hydrolyzed and non-hydrolyzed milk) as the factors. The milk was dehydrated and then milled using a hammer mill (mesh size 40). It was then used in recipes to produce chocolates and evaluated sensorially based on ranking for preference. Skimmed milk powder was used to produce the control chocolate. The ratio of cowpea to peanut affected the chemical and functional characteristics of the vegetable milk. Vegetable milk made from 1:2 ratios of peanuts:cowpea produced the most preferred chocolates. The successful application of this by industry will improve the utilization of the legume crops and enhance their market value.     

Effect of SiO2 and Al2O3 on the setting and hardening of high calcium fly ash-based geopolymer systems

This study investigates the effect of silica and alumina contents on setting, phase development, and physical properties of high calcium fly ash (ASTM Class C) geopolymers. The characteristic rapid setting properties and, hence, limited workability range of high calcium fly ash geopolymers has restricted both development and potential application of these binder systems compared to conventional geopolymer binders derived from bituminous coal, i.e., (ASTM Class F) sources or from calcined kaolin feedstocks. For this study, control of setting and hardening properties were investigated by adjusting SiO₂/Al₂O₃ ratio of the starting mix, via series of mixes formulated with varying SiO₂ or Al₂O₃ contents to achieve SiO₂/Al₂O₃ in the range 2.87–4.79. Foremost is the observation that the effect of varying silica and alumina in high calcium fly ash systems on setting and hardening properties is markedly different from that observed for traditional Class F geopolymer systems. Overall, increases in either silica or alumina content appear to shorten the setting time of high calcium-based systems unlike conventional geopolymer systems where increasing Al₂O₃ accelerates setting. The setting process was associated primarily with CSH or CASH formation. Furthermore, there appears to be a prevailing SiO₂/Al₂O₃ ratio that prolongs setting, rather than Ca²⁺ ion content itself, while NASH primarily contributes to strength development. SiO₂/Al₂O₃ ratios in the range of 3.20–3.70 resulted in products with highest strengths and longest setting times. These results suggest that initial predominance of Ca²⁺ ions and its reactions effectively help maintaining a SiO₂/Al₂O₃ ratio at which amorphous geopolymer phase is stable to influence setting and initial strength development.     

Angiotensin converting enzyme inhibitory activity of proteolytic digests of peanut (Arachis hypogaea L.) flour

Defatted raw and roasted peanut flour were hydrolyzed with alcalase or sequentially with pepsin and pancreatin, and then the hydrolyzates were fractionated by RP-HPLC and tested for hypotensive potential. This research revealed that proteolytic peanut digests have an inhibitory effect on the activity of angiotensin converting enzyme (ACE). Three fractions from the hydrophobic end of the chromatogram of each hydrolyzate were the most potent for inhibiting ACE activity in comparison to seven other fractions. These potentially potent fractions were then assayed for IC₅₀. Fractions from the alcalase digestion of raw peanut exhibited IC₅₀ values of 8.7-122 μg/ml, and those from roasted flour exhibited values of 12-235 μg/ml. IC₅₀ values of 7.9-65.9 μg/ml, and 11-36 μg/ml for raw and roasted peanut, respectively, from the pepsin-pancreatin system were observed. These values compare to the IC₅₀ value of 0.36 μg/ml of a known commercial ACE inhibitor (pGlu-Trp-Pro-Arg-Pro-Gln-Ile-Pro-Pro).     

Relationships between composition,structure and strength of inorganic polymers

This article is the second in a two-part series and discusses inorganic polymers derived from fly ash. Part 1 [1] concerns inorganic polymers derived from a metakaolin precursor. For this study, 15 fly ash-derived inorganic polymers were produced with various compositions. The effect of the concentration of each of the four component oxides (Na₂O, SiO₂, Al₂O₃ and H₂O) and two alkali cations (Na and K) on the microstructure and compressive strengths were assessed. Similar to metakaolin-derived inorganic polymers, it was observed that high-strength fly ash inorganic polymers were related to low porosity and a dense, fine-grained microstructure. Such structures were characteristic of formulations with high silica mole fractions (SiO₂/Al₂O₃ ∼ 3.9) and low water contents, as well as those with high alkali and low alumina contents. For the latter, not only was a characteristic slower strength development with increasing alkali content observed, but there was also a limit of alkali concentration (Na₂O/Al₂O₃ ∼1) beyond which the strength deteriorated. Furthermore, SEM micrographs disclose that the fly ash precursor dissolves more readily in the sodium-based system compared to the potassium equivalent. The interrelation between microstructures of the respective formulations and their strength development are discussed. It is observed that the charge-balancing role of the alkali cations in the fly ash formulations may be dominant compared to initial alkali dissolution reaction of the aluminosilicate fly ash particles, which is partly responsible for initial strength development.     

Reduction of aflatoxins in peanut meal by extrusion cooking in the presence of nucleophiles

This study explored the feasibility of degrading aflatoxins in contaminated peanut meal by extruding in the presence of calcium chloride with lysine and methylamine. A 2 × 2 × 3 experiment (moisture, pH and nucleophile) was designed to screen for a nucleophile to use in a study of extrusion conditions to degrade aflatoxins in peanut meal. The nucleophile was mixed with peanut meal at 2 g/100 g protein level and the samples “spiked” with aflatoxin standards. They were extruded using a single screw extruder, and aflatoxins quantified by HPLC.The presence of calcium chloride impeded the degradation of aflatoxins by extrusion. However, methylamine and lysine showed comparable efficacies to mediate aflatoxin reduction. There were significant (p ≤ 0.05) interactions between moisture and pH, as well as moisture and temperature. Contour plots from regression models (R² = 0.85) showed a bimodal effect of moisture on aflatoxin degradation. Extrusion cooking reduced aflatoxins from an initial 417.72 μg/kg to 66.87 μg/kg (i.e. 84% reduction) in the peanut meal.