Samson Agboola

Canola Proteins for Human Consumption: Extraction, Profile, and Functional Properties

Canola protein isolate has been suggested as an alternative to other proteins for human food use due to a balanced amino acid profile and potential functional properties such as emulsifying, foaming, and gelling abilities. This is, therefore, a review of the studies on the utilization of canola protein in human food, comprising the extraction processes for protein isolates and fractions, the molecular character of the extracted proteins, as well as their food functional properties. A majority of studies were based on proteins extracted from the meal using alkaline solution, presumably due to its high nitrogen yield, followed by those utilizing salt extraction combined with ultrafiltration. Characteristics of canola and its predecessor rapeseed protein fractions such as nitrogen yield, molecular weight profile, isoelectric point, solubility, and thermal properties have been reported and were found to be largely related to the extraction methods. However, very little research has been carried out on the hydrophobicity and structure profiles of the protein extracts that are highly relevant to a proper understanding of food functional properties. Alkaline extracts were generally not very suitable as functional ingredients and contradictory results about many of the measured properties of canola proteins, especially their emulsification tendencies, have also been documented. Further research into improved extraction methods is recommended, as is a more systematic approach to the measurement of desired food functional properties for valid comparison between studies.

Antioxidant properties of Australian canola meal protein hydrolysates

Antioxidant activities of canola protein hydrolysates (CPHs) and peptide fractions prepared using five proteases and ultrafiltration membranes (1, 3, 5, and 10kDa) were investigated. CPHs had similar and adequate quantities of essential amino acids. The effective concentration that scavenged 50% (EC50) of the ABTS(+) was greatest for the <1kDa pancreatin fraction at 10.1μg/ml. CPHs and peptide fractions scavenged DPPH(+) with most of the EC50 values being <1.0mg/ml. Scavenging of superoxide radical was generally weak, except for the <1kDa pepsin peptide fraction that had a value of 51%. All CPHs inhibited linoleic acid oxidation with greater efficiency observed for pepsin hydrolysates. The oxygen radical absorbance capacity of Alcalase, chymotrypsin and pepsin hydrolysates was found to be better than that of glutathione (GSH) (p<0.05). These results show that CPHs have the potential to be used as bioactive ingredients in the formulation of functional foods against oxidative stress.

Production Technologies for Reduced Alcoholic Wines

The production and sale of alcohol-reduced wines, and the lowering of ethanol concentration in wines with alcohol levels greater than acceptable for a specific wine style, poses a number of technical and marketing challenges. Several engineering solutions and wine production strategies that focus upon pre- or postfermentation technologies have been described and patented for production of wines with lower ethanol concentrations than would naturally arise through normal fermentation and wine production techniques. However, consumer perception and acceptance of the sensory quality of wines manufactured by techniques that utilize thermal distillation for alcohol removal is generally unfavorable. This negative perception from consumers has focused attention on nonthermal production processes and the development or selection of specific yeast strains with downregulated or modified gene expression for alcohol production. The information presented in this review will allow winemakers to assess the relative technical merits of each of the technologies described and make decisions regarding implementation of novel winemaking techniques for reducing ethanol concentration in wine.

Screening of whey protein isolate hydrolysates for their dual functionality: Influence of heat pre-treatment and enzyme specificity

Heat pre-treated and non heat pre-treated whey protein isolate (WPI) were hydrolysed using α-chymotrypsin (chymotrypsin), pepsin and trypsin. The in vitro antioxidant activity, ACE-inhibition activity and surface hydrophobicities of the hydrolysates were measured in order to determine if peptides with dual functionalities were present. Dual functional peptides have both biological (e.g. antioxidant, ACE-inhibition, opioid activities) and technological (e.g. nanoemulsification abilities) functions in food systems. Heat pre-treatment marginally enhanced the hydrolysis of WPI by pepsin and trypsin but had no effect on WPI hydrolysis with chymotrypsin. With the exception of the hydrolysis by trypsin, heat pre-treatment did not affect the peptide profile of the hydrolysates as analysed using size exclusion chromatography, or the antioxidant activity (P>0.05). Heat pre-treatment significantly affected the ACE-inhibition activities and the surface hydrophobicities of the hydrolysates (P<0.05), which was a function of the specificity of the hydrolysing enzyme. Extended hydrolysis (up to 24 h) had no significant effect on the DH and the molecular weight profiles (P>0.05) but in some instances caused a reduction in the antioxidant activity of WPI hydrolysates. The chymotrypsin hydrolysate showed a broad MW size range, and was followed by pepsin and then trypsin. The bioactivities of the hydrolysates generally decreased in the order; chymotrypsin>trypsin>pepsin. This study showed that by manipulating protein conformation with pre-hydrolysis heat treatment, combined with careful enzyme selection, peptides with dual functionalities can be produced from WPI for use as functional ingredients in the manufacture of functional foods.

Purification and characterization of a Kunitz-type trypsin inhibitor from Acacia victoriae Bentham seeds.

An Acacia victoriae trypsin inhibitor (AvTI) was purified from the seeds of prickly wattle (A. victoriae Bentham) by salt precipitation, ion exchange, and gel filtration chromatography and then characterized by electrophoresis and N-terminal amino acid sequencing. AvTI had a specific activity of 138.99 trypsin inhibitor units per milligram (TIU mg(-1)), which was 21-fold higher than that of the salt precipitate. A molecular mass of 13 kDa was estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions, which also indicated that AvTI may consist of two polypeptide chains linked by at least one disulfide bond. Although only a single peak was resolved by ion exchange and reverse phase high-performance liquid chromatography (RP-HPLC), native-PAGE and isoelectric focusing revealed the presence of three isoforms possessing acidic pI values of 5.13, 4.76, and 4.27, respectively. N-Terminal amino acid sequencing analysis of native and reduced AvTI showed two sequences with a high degree of homology with a typical Kunitz-type trypsin inhibitor. All isoforms had considerable trypsin inhibitory activity but showed relatively very low inhibition against alpha-chymotrypsin.

Characterisation of phenolic components present in raw and roasted wattle (Acacia victoriae Bentham) seeds.

The effect of roasting on the phenolic components of Australian wattle (Acacia victoriae Bentham) seed was investigated. Wattle seeds were roasted at 200°C for 5-30min and ground to flour, which were then extracted with 70% acetone. The total phenolic and flavonoid contents of the extracts were determined, and the phenolic components were analysed by reverse phase-high performance liquid chromatography (RP-HPLC) coupled with an on-line post-column reaction system to determine the active antioxidant peaks. The major peaks were then purified by preparative HPLC and identified by gas chromatography-mass spectrometry (GC-MS) analysis. Roasting of wattle seeds resulted in significant increases in its soluble phenolic content. The concentration of total phenolics and flavonoids in the seeds roasted for 30min was more than nine and four times higher, respectively, than that in the raw seeds. The major phenolic acids present in wattle seeds were found to be succinic and gallic acids, the concentration of which increased by up to 10-fold as a result of roasting.

Biophenols and antioxidant properties of Australian canola meal.

During the extraction of canola oil, large quantities of meal are produced. Extracting biophenols from Australian canola meal (ACM) adds value to an otherwise low-value agro-industrial byproduct. This study examined the biophenol content and the antioxidant activity of ACM, the impact of extraction conditions, and varietal differences. Sinapine was the principal biophenol in ACM. In crude and hydrolyzed extracts, 31 compounds were identified: 2 dihexosides, 2 organic acids, 4 glucosinolates, 17 sinapic acid derivatives, 2 cyclic spermidine alkaloids, caffeic acid and its dihexoside, kaempferol, and its C-glucoside. ACM showed significant free radical scavenging activity in DPPH(•) and ABTS(•+) assays. Sinapine was the chief contributor to ACM antioxidant activity, whereas kaempferol sinapoyl triglucoside isomer was the most potent antioxidant. Biophenol content ranged between 12.8 and 15.4 mg GAE/g DW. Differences among studied cultivars were generally quantitative. The Tarcoola cultivar showed the highest biophenol content and antioxidant activity.

Technological and Bioactive Functionalities of Canola Meal Proteins and Hydrolysates

Canola meal proteins have been credited with some technological food functional abilities, including foaming, water absorption, solubility, gelling, emulsifying, and foaming properties, despite the presence of other nonprotein moieties in the preparations studied to date. Unfortunately, these proteins have found limited practical use in food processing, presumably due to their poor solubility in aqueous systems at neutral pH. Consequently, canola meal proteins are undervalued as food ingredients. There is, however, high potential to improve the value of canola meal proteins via modification, especially by enzymatic hydrolysis to improve their solubility, and, hence, many of these functional properties. Enzymatic hydrolysis can also be employed to generate nutritionally functional hydrolysates and bioactive peptides. The most studied bioactive properties of canola protein hydrolysates was found to be the angiotensin-converting enzyme (ACE) inhibitor and antioxidant activities, whereas others such as the antimicrobial and anticancer properties have been less investigated. Therefore, this review looks into some of the studies carried out on canola proteins and gives an insight to the future research needs.

Effects of Roasting on the Characteristics of Australian Wattle (Acacia victoriae Bentham) Seed and Extracts

The effects of roasting at 200°C for up to 30 min on the color, chemical composition, and trypsin inhibitor activity of wattle seed (Acacia victoriae Bentham) and its extracts were studied. Results showed that roasting induced significant (p < 0.05) changes in color difference index (ΔE*ab) of flours compared to seeds. Furthermore, chemical analysis showed that protein solubility decreased as a result of roasting. Polyacrylamide gel electrophoresis and reverse phase high performance liquid chromatography of soluble proteins showed that large molecular weight polypeptides were rapidly broken down, with resultant formation of smaller, more hydrophilic fragments. Both total and soluble carbohydrates decreased during roasting, most likely due to Maillard-type reactions and caramelization, and polyacrylamide gel electrophoresis and spectrophotometric assays confirmed the essential elimination of trypsin inhibitor activity after 20 min of roasting.

Glycosylation, amino acid analysis and kinetic properties of a major Kunitz-type trypsin inhibitor from Acacia victoriae Bentham seeds

An Acacia victoriae trypsin inhibitor (AvTI) was purified from the seeds of prickly wattle (A. victoriae Bentham) by salt precipitation, ion-exchange and gel filtration chromatography, and its degree of glycosylation, amino acid composition, and kinetic properties were determined. Gel electrophoresis revealed at least four glycoprotein bands in the crude extract, salt-precipitated and ion-exchange protein fractions, while the purified AvTI showed only one band and a degree of glycosylation of 2.06%. Glutamate (13.3%), aspartate (10.3%), leucine (7.62%) and lysine (7.01%) were the major amino acids in AvTI while the contents of sulphur-containing amino acids, cysteine (1.38%) and methionine (0.75%), as well as of tryptophan (1.17%) were low. Its dissociation constant (Ki) for the inhibition of bovine trypsin was found to be 1.06×10(-8)M, indicating a high affinity between AvTI and this enzyme, and its role as a competitive inhibitor was confirmed by a double reciprocal plot. These results complement our earlier studies which indicated the presence of three isoforms of this Kunitz-type trypsin inhibitor in prickly wattle seed.