Rodney J. Mailer

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.

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.

Comparison of olive oil (Olea europaea) quality extracted by stonemill and hammermill

Abstract This study compared two olive oil extraction processes used in New Zealand to assess the influence of processing on oil quality. The extraction systems included an Enorossi stonemill and an Oliomio 50 hammermill, malaxing basin, and centrifuge. Olives (Olea europaea) from individual harvests were found to show significantly higher polyphenol and chlorophyll content from the hammermill process. Slightly higher free fatty acids resulted from the hammermill. Fatty acid profiles did not show significant differences between the methods of extraction. Storage over 17 months resulted in increased peroxide values for both oils but no change in chlorophyll, free fatty acids, or polyphenols.

Effects of canola proteins and hydrolysates on adipogenic differentiation of C3H10T/2 mesenchymal stem cells

This study assessed the ability of canola protein isolate (CPI) and enzymatic hydrolysates (CPHs) to inhibit adipogenic differentiation of C3H10T1/2 murine mesenchymal stem cells in vitro. Cell viability was maintained at concentrations of 60 μg/ml of sample. Cells treated with Alcalase hydrolysate demonstrated a higher reduction in anti-adipogenic differentiation through quantitation by oil-red O staining. qPCR analysis showed that CPI and CPH-treated cells significantly inhibited PPARγ expression, a key transcription factor involved in adipocyte differentiation, as evident in an ∼ 60-80% fold reduction of PPARγ mRNA. Immunofluorescence staining for PPARγ protein also showed a reduced expression in some treated cells when compared to differentiated untreated cells. The 50% inhibition concentration (IC50) of CPI, CPHs and their membrane ultrafiltration fractions on pancreatic lipase (PL) activity ranged between 0.75 and 2.5 mg/ml, (p < 0.05) for the hydrolysed and unhydrolysed samples. These findings demonstrate that CPI and CPHs contain bioactive components which can modulate in vitro adipocyte differentiation.

Oil content and fruit quality of nine olive (Olea europaea L.) varieties affected by irrigation and harvest times

Abstract A field experiment was conducted on nine olive varieties with the objective of determining the effect of regulated deficit irrigation on olive oil content and physical quality parameters of fruits. Three irrigation levels were applied as a percentage of crop evapotranspiration (ETc) during the pit-hardening period: rainfed, R (0% ETc); deficit, D (50% ETc); and irrigated, I (100% ETc). Rainfall and ETc during the pit-hardening period were 78 mm and 164 mm, respectively. Olives were sampled four times during the normal crop harvest period. Withholding irrigation during the pit-hardening period (R treatment) reduced the fruit size of three of the varieties, but had no effect on oil contents, while saving 35% irrigation water compared with the I treatment. The D treatment resulted in 17.5% water saving with minor effects on fruit size, timing of maturity and oil content. The olive cultivars responded differently to irrigation treatments in terms of most of the parameters considered. This necessitates cultivar-specific irrigation management.

Influence of enzymatic hydrolysis, pH and storage temperature on the emulsifying properties of canola protein isolate and hydrolysates

1 Graham Centre for Agricultural Innovation, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia 2 School of Agricultural and Wine Sciences, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia 3 Department of Food and Human Nutritional Sciences and the Richardson Center for Functional Foods and Nutraceuticals, University of Manitoba, Winnipeg, R3T 2N2 MB, Canada 4 School of Biomedical Sciences, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia