Rapeseed Protein Research Articles

Antihypertensive and free radical scavenging properties of enzymatic rapeseed protein hydrolysates

In this study, rapeseed protein isolate (RPI) was digested with various proteases to produce rapeseed protein hydrolysates (RPHs), which were then separated into different peptide fractions (<1, 1–3, 3–5, and 5–10kDa) by membrane ultrafiltration. Membrane fractionation showed that peptides with sizes <3kDa had significantly (p<0.05) reduced surface hydrophobicity when compared to the RPHs and peptide fractions with sizes >3kDa. In contrast, the <3kDa peptides showed significantly (p<0.05) higher oxygen radical scavenging ability when compared to the >3kDa peptides and RPHs. In vitro inhibition of angiotensin I-converting enzyme (ACE) was significantly (p<0.05) higher for the Thermolysin, Proteinase K and Alcalase RPHs when compared to the pepsin+pancreatin (PP) and Flavourzyme RPHs. The Alcalase RPH had significantly (p<0.05) higher renin inhibition among the RPHs, while with the exception of Thermolysin, the 5–10kDa peptide fraction had the least renin-inhibitory ability when compared to the <5kDa peptide fractions. Oral administration (100mg/kg body weight) of the RPHs and RPI to spontaneously hypertensive rats (SHR) showed the Alcalase RPH to be the most effective in blood pressure (BP) reduction (∼24mmHg) while Proteinase K RPH was the least effective (∼5mmHg) after 8h. However, the PP RPH had the most prolonged effect with BP reduction of ∼20mmHg after 24h of oral administration. We conclude that the strong BP-lowering ability of Alcalase and PP RPHs could be due to high resistance of the peptides to structural degradation coupled with high absorption rate within the gastrointestinal tract.

Blue mussel meal as feed attractant in rapeseed protein-based diets for turbot (Psetta maximaL.)

Antinutritional factors in rapeseed products have been identified to reduce feed palatability and growth performance of turbot. Therefore, we evaluated the potential of blue mussel (Mytilus edulis L.) meal as feed attractant in rapeseed protein-based diets for turbot. Triplicate fish groups received isonitrogenous and isocaloric diets with fish meal (FM) protein replacements of 50% or 75% by rapeseed protein concentrate (RPC 50, RPC 75). These diets were supplemented with 0%, 2%, 4% or 8% of blue mussel meal. In contrast with RPC 50 diets, fish fed with RPC 75/0 showed significantly reduced daily feed intake (DFI) and specific growth rate (SGR). With increasing mussel meal inclusion, RPC 75 diets resulted in increased DFI and SGR, suggesting mussel meal as attractant in rapeseed proteinbased diets for turbot. Feed conversion was unaffected by any treatment. Protein productive value and apparent digestibility coefficients were unaffected by either RPC or mussel meal inclusion. With regard to the whole body composition, no differences in crude protein, crude lipid and ash content could be determined. Haematological characteristics were unaffected among the treatments indicating good nourished and unstressed fish. In conclusion, we demonstrated that the utilization of blue mussel meal improved the palatability of rapeseed protein-based diets for turbot.

Purification and hypotensive activity of rapeseed protein-derived renin and angiotensin converting enzyme inhibitory peptides

Rapeseed protein isolate (RPI) was hydrolyzed with Alcalase followed by reverse-phase high performance liquid chromatography (RP-HPLC) purification of bioactive peptides. The rapeseed protein hydrolysate (RPH) obtained after 4h digestion with Alcalase had a degree of hydrolysis (DH) of ∼11%. Gel permeation chromatography separation showed high contents of low molecular weight peptides in the RPH when compared to the RPI. After preparative and analytical RP-HPLC separations, three peptides (LY, TF and RALP) were purified and amino acid sequence determined by tandem mass spectrometry. LY (IC50, 0.11mM) was the most potent (p<0.05) against ACE activity when compared to TF (IC50, 0.81mM) and RALP (IC50, 0.65mM). However, RALP (IC50, 0.97mM) was the most potent (p<0.05) against renin activity when compared to LY (IC50, 1.87mM) and TF (IC50, 3.1mM). Single oral administration (30mg/kg body weight) to spontaneously hypertensive rats showed LY and RALP to be the more effective hypotensive agents with maximum blood pressure reduction of −26 and 16mmHg, respectively when compared to TF (−12mmHg). The results suggest that the higher number of hydrophobic amino acid residues LY and RALP contributed to their higher in vitro and in vivo activities when compared to TF.

Plant protein interactions studied using AFM force spectroscopy: nanomechanical and adhesion properties

The present work was focused on the nanomechanical and adhesion properties of the napin (2S albumin) and cruciferin (12S globulin) rapeseed (Brassica napus L.) proteins, respectively, a low and high molecular weight seed protein. Using chemically modified AFM tips, force spectroscopy experiments demonstrated notable differences in the tip-protein interaction strength with regard to the nature of the protein and pH of the aqueous environment. The results clearly underline the role of residence time and electrostatic interactions in the protein-protein adhesion force. Although the nanomechanical experiments concerned more than a single molecule, unfolding length and force characteristics of the rapeseed proteins have been statistically found to be sensitive to the structural properties of the protein. This study provides insight into the characterization of rapeseed proteins and then a better knowledge of their interaction and assembling at the nanoscale range.

Molecular cloning and functional expression of a water-soluble chlorophyll-binding protein from Japanese wild radish

Hydrophilic chlorophyll (Chl)-binding proteins have been isolated from various Brassicaceae plants and are categorized into Class II water-soluble Chl-binding proteins (WSCPs). Although the molecular properties of class II WSCPs including Brassica-type (e.g., cauliflower WSCP, Brussels sprouts WSCP and BnD22, a drought- and salinity-stress-induced 22kDa protein of rapeseed), a Lepidium-type, and an Arabidopsis-type WSCPs have been well characterized, those of Raphanus-type WSCPs are poorly understood. To gain insight into the molecular diversity of Class II WSCPs, we cloned a novel cDNA encoding a Raphanus sativus var. raphanistroides (Japanese wild radish called ‘Hamadaikon’) WSCP (RshWSCP). Sequence analysis revealed that the open reading frame of the RshWSCP gene consisted of 666bp encoding 222 aa residues, including 23 residues of a deduced signal peptide. Functional recombinant RshWSCP was expressed in Escherichia coli as a hexa-histidine fusion protein (RshWSCP-His). Although the RshWSCP-His was expressed as a soluble protein in E. coli, the apo-protein was highly unstable and tended to aggregate during a series of purification steps. When the soluble fraction of RshWSCP-His-expressing E. coli was mixed immediately with homogenate of spinach leaves containing thylakoid, RshWSCP-His was able to remove Chl molecules from the thylakoid and formed a stable Chl-WSCP complex with high hydrophilicity. UV–visible absorption spectra of the reconstituted RshWSCP-His revealed that RshWSCP-His is one of the Class IIA WSCP with the highest Chl a/b ratio analyzed thus far. A semi-quantitative reverse transcription-polymerase chain reaction analysis revealed that RshWSCP was transcribed in buds and flowers but not in roots, stems and various leaves.

Nutritional evaluation of rapeseed protein compared to soy protein for quality, plasma amino acids, and nitrogen balance – A randomized cross-over intervention study in humans

Plant proteins such as rapeseed have received little attention for human nutrition due to their high level of antinutritive compounds. Today, newer technologies can eliminate such compounds. The present intervention study aimed to evaluate nutritional and physiological properties of two manufactured canola proteins with special focus on their bioavailability in humans. 28 healthy male subjects (ø 25 years) consumed 30.0 g protein (canola protein isolate--CPI, canola protein hydrolyzate--CPH or soy protein isolate--SPI) in a randomized, double-blind, cross-over study. Blood samples were regularly drawn over the 8-h postprandial period and a 24-h urine sample was collected. True digestibility of the canola proteins determined in a separate rat assay showed 93.3% for CPI and 97.3% for CPH. In humans, consumption of either 30.0 g canola protein or soy protein mixed in a drink led to significant increases in plasma amino acids after 62.3 and 83.6 min, respectively. While the CPH produced an earlier response compared to CPI and SPI, total amino acid response (AUC for 8 h) was comparable between all interventions. The nitrogen balance between the three proteins tested showed no statistical differences. High digestibility of rapeseed protein was found in rats. In humans, this is the first intervention study showing rapeseed protein (both isolate and hydrolyzate) as having a high nutritional quality and can be considered to be as efficient as soy protein for a postprandial amino acid response. This trial was registered at ClinicalTrials.gov Identifier: NCT01481584.

Antioxidant activities of enzymatic rapeseed protein hydrolysates and the membrane ultrafiltration fractions

In this study, rapeseed protein isolate was hydrolyzed with various proteases to obtain hydrolysates that were separated by membrane ultrafiltration into four molecular size fractions (<1, 1–3, 3–5, and 5–10kDa). Alcalase hydrolysis significantly (p<0.05) produced the highest yield of protein hydrolysate while Flavourzyme produced the least. The <1kDa fraction was the most abundant after the membrane ultrafiltration of the protein hydrolysates, which indicates that the proteases were efficient at reducing the native rapeseed proteins into low molecular weight peptides. Antioxidant properties of the resulting hydrolysates and membrane fractions were characterized and results showed the Pepsin+Pancreatin (P+P) protein hydrolysate had significantly highest (p<0.05) scavenging activity against DPPH radical among the unfractionated enzymatic hydrolysates. But the P+P hydrolysate was not as effective as other hydrolysates during long-term inhibition of linoleic acid oxidation. For most of the samples, fractionation into the <1kDa peptides significantly (p<0.05) improved DPPH and superoxide scavenging properties when compared to the unfractionated protein hydrolysates. Only the <1kDa fraction showed ferric reducing antioxidant power and the effect was dose-dependent. Overall, Alcalase and Proteinase K seem to be more efficient proteases to release antioxidant peptides from rapeseed proteins when compared to P+P, Flavourzyme and Thermolysin.

Metabolism of soluble rapeseed meal (Brassica rapa L.) protein during incubations with buffered bovine rumen contents in vitro

Accurate quantitative information on the fate of dietary protein in the rumen is central to modern metabolizable protein systems developed to improve the efficiency of nitrogen utilization in ruminants. An in vitro method was developed to estimate the rate of soluble rapeseed meal (Brassica rapa L.) protein (SRMP) degradation. Unlabeled and 15N-labeled solvent-extracted rapeseed meal were incubated alone or as an equal mixture (125mg of N/L) with buffered rumen contents and a mixture of carbohydrates formulated to provide a constant source of fermentable energy during the course of all incubations. Incubations were made over 0.33, 0.67, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 6.0, 8.0, and 10.0h. Enrichment of 14N and 15N isotopes in total N of ammonia (AN), soluble nonammonia (SNAN), and insoluble (ISN) fractions liberated during incubations with test proteins was determined. A model with 4 pools that accounted for both intracellular and extracellular N transformations was used to estimate the rate of SRMP degradation. Parameter values used in the model were adjusted based on the size of A14N, A15N, SNA14N, SNA15N, IS14N, and IS15N pools, measured at different time points during incubations with buffered rumen fluid. The mean rate of N degradation for SRMP was estimated at 0.126 (SD 0.0499) h−1. No substantive difference in the rate of protein degradation or microbial protein synthesis was observed during incubations of labeled and unlabeled substrates with rumen fluid. In conclusion, combined use of data from incubations of unlabeled and 15N-labeled rapeseed protein with buffered rumen inoculum provided sufficient information to allow for estimation of parameter values in a complex dynamic model of soluble protein degradation. Results indicate the potential of the technique to evaluate the degradability of SNAN of other dietary protein sources and implicate ruminal escape of soluble rapeseed protein as an important source of amino acids in ruminants.

Antioxidant activities of rapeseed peptides produced by solid state fermentation

In this study, rapeseed peptides (RPs) were prepared by solid state fermentation with Bacillus subtilis followed by evaluation of peptide antioxidant activities (scavenging of DPPH, ferric reducing power, ferrous ion-chelation and ability to inhibit linoleic acid autoxidation, in vitro). The content of soluble peptides increased rapidly within the first 2days of fermentation, which suggested high susceptibility of the rapeseed proteins to microbial proteases. After 3days of fermentation, RPs were composed mainly of five peptide fractions within the 180–5500Da size range; however, proportion of peptides with <3000Da size decreased significantly (p<0.05) after 5days of fermentation. Glutamic acid (19.5%), lysine (7.6%) and proline (7.3%) were the most dominant amino acids present in the RPs but serine (1.5%), tryptophan (1.3%) and cysteine (0.5%) were present in least amounts. A concentration-dependent effect on antioxidant activities was present in RPs, which showed high activities of scavenging free radical, reducing power, and inhibition of lipid peroxidation, but low ferrous ion-chelating activity. We concluded that fermentation provided a suitable medium for converting rapeseed meal into antioxidant peptides that may be used to formulate functional foods and nutraceuticals.

Enzyme assisted protein extraction from rapeseed, soybean, and microalgae meals

Oilseed meals that are by-products from oil production are potential resources for protein. The aim of this work is to investigate the use of enzymes in assisting in the extraction of protein from different oilseed meals, namely rapeseed, soybean, and microalgae meals. In addition, microalgae without prior oil removal was also tested. The extraction was performed varying temperature, pH, and type of enzyme. More protein was extracted at alkaline conditions, compared to acidic conditions. At alkaline pH, 80% protein of soybean meal and 15–30% protein of rapeseed and microalgae meals was extracted without enzyme addition. The addition of enzyme under this condition increased protein extraction yield to 90% for soybean meal and 50–80% for rapeseed and microalgae meals. Here, Protex 40XL, Protex P, and Protex 5L that work at alkaline pH assisted protein extraction particularly for rapeseed and microalgae meals. Microalgae without prior oil removal had the lowest protein extraction yield, illustrating that oil removal prior to protein extraction is beneficial for protein recovery. In general, protein extraction was influenced by pH, the type of biomass, and the addition of enzyme, but not by the type of enzyme that was used.

Aqueous Enzymatic Extraction of Rapeseed Oil and Protein from Dehulled Cold-pressed Double-low Rapeseed Cake

Abstract The oil and protein of dehulled cold-pressed double-low rapeseed cake was extracted by an aqueous enzymatic process. The rapeseed cake was treated by the chosen combined enzymes of Viscozyme L and Alcalase 2.4L (VLA,1:1,w/w). Preliminary experiments and Response Surface Methodology (RSM) were used to study the effects of enzyme concentration, incubation time and water-to-cake ratio on the extraction yield of oil and protein. This is how the desirable conditions were obtained. Transmissive electron microscope photo showed that after cold-pressing the cell structure of rapeseed was partly damaged while dehulling had little effect on the cell structure of rapeseed. In RSM experiments water-to-cake ratio showed significant effects on the extraction of oil and protein (P&lt;0.05),while incubation time only showed significant effects on protein yield (P&lt;0.05).The desirable conditions were as follows: 1.0% concentration (w/w) of VLA; water-to-cake ratio(w/w),6:1; 80 min incubation time. Under this condition, the extraction yield of protein and oil were 82.10% and 71.89%, respectively. Through combining both the cold-press and the aqueous enzymatic processes together, the total oil yield reached 91.6%, which is higher than the normal cold-press process or the aqueous enzymatic extraction process alone.

Nutritional evaluation of rapeseed protein isolate as fish meal substitute for juvenile turbot (Psetta maxima L.) — Impact on growth performance, body composition, nutrient digestibility and blood physiology

The potential of a highly concentrated rapeseed protein isolate (RPI) as partial or total fish meal (FM) alternative in diets for turbot (Psetta maxima L.) was evaluated. In a feeding trial 12 experimental tanks of a saltwater recirculation system were stocked with 15 fish each. Fish were organized in triplicate groups and received isonitrogenous and isoenergetic experimental diets with 0, 33, 66, or 100% (designated as control, RPI 33, RPI 66, RPI 100) of FM protein replaced with RPI. Fish were fed over a period of 56days until apparent satiation.Feed intake, feed conversion ratio and growth performance did not significantly vary between fish fed the RPI 33 (129g RPIkg−1 diet) and the control diet. The RPI 66 (258g RPIkg−1 diet) and the RPI 100 (391g RPIkg−1 diet) diets caused reduced feed ingestion and feed efficiencies, resulting in lower growth performance. Apparent digestibility coefficient (ADC) of dry matter and protein calculated on the basis of stripped feces revealed significantly reduced values for fish fed with RPI 66 diet compared to control diet, whereas ADC in the RPI 100 group recovered to control value. Protein retention decreased with increasing FM substitution levels. Body composition of fish showed a significant reduction in dry matter and crude protein values of the RPI 66 and RPI 100 group compared to control group. Gross energy content varied between the RPI 33 and RPI 100 group, while crude lipid and ash content were unaffected among the treatment groups, suggesting no limitations in dietary mineral or phosphorus availability. Blood parameters including hematocrit, glucose, triglycerides and cortisol were similar between the treatment groups. Histopathology of liver tissue revealed a slight hypertrophy of hepatocytes in the control group and a severe hypertrophy in fish fed with RPI 33 diet. In line with a reduced condition factor and hepatosomatic index a slight hypotrophy of hepatocytes was observed in fish fed with the RPI 100 diet. Neither inflammatory nor degenerative changes of the mid gut were observed among dietary treatments.In conclusion, 66% (314gkg−1) of dietary FM could be replaced by RPI (258gkg−1) without affecting physiological parameters of turbot in terms of animal welfare, but growth performance decreased using FM protein replacement levels above 33% (corresponding to 157gkg−1).

Hydrophilic properties as a new contribution for computer-aided identification of short peptides in complex mixtures

A new method to predict elementary amino acid (AA) composition of peptides (molar mass <1,000 g/mol) is described. This procedure is based on a computer-aided method using three combined analyses-reversed phase liquid chromatography (RPLC), hydrophilic interaction chromatography (HILIC) and capillary electrophoresis coupled with mass spectrometry-and using a software calculating all possible amino acid combinations from the mass of any given peptide. The complementarity between HILIC and RPLC was demonstrated. Peptide retention prediction in HILIC was successfully modelled, and the achieved prediction accuracy was as high as r²=0.97. This mathematical model, based on amino acid retention contributions and peptide length, provided the information about peptide hydrophilicity that was not redundant with its hydrophobicity. Correlations between respectively the hydrophobicity coefficients and RPLC retention time, hydrophilicity and HILIC retention time, and electrophoretic mobility and migration time were used for ranking all potential AA combinations corresponding to the given mass. The essential contribution of HILIC in this identification strategy and the need to combine the three models to significantly increase identification capabilities were both shown. Applied to an 18-standard peptide mixture, the identification procedure enabled the actual AA combination determination of the 14 di- to pentapeptides, in addition to an over 98 % reduction of possible combination numbers for the four hexapeptides. This procedure was then applied to the identification of 24 unknown peptides in a rapeseed protein hydrolysate. The effective AA composition was found for ten peptides, whereas for the 14 other peptides, the number of possible combinations was reduced by over 95 % thanks to the association of the three analyses. Finally, as a result of the information provided by the analytical techniques about peptides present in the mixture, the proposed method could become a highly valuable tool to recover bioactive peptides from undefined protein hydrolysates.

Albumin and globulin rapeseed protein fractions as fish meal alternative in diets fed to rainbow trout (Oncorhynchus mykiss W.)

The potential of two rapeseed protein concentrates partitioned in albumin and globulin fractions as fish meal alternative was evaluated. In a digestibility experiment with juvenile rainbow trout apparent digestibility coefficients (ADCs) were determined by indirect marker method with feces collected by continuous sieving. ADCs of protein from fish meal (89.2±1.1%) and globulin concentrate (88.8±0.6%) were significantly higher than ADCs from albumin concentrate (77.7±1.4%). ADCs of dietary dry matter were similar between the control diet (62.5±4.7%) and the globulin concentrate diet (62.3±0.5%), but significantly lower in the albumin concentrate diet (56.2±1.5%). In a subsequent growth trial, each of 21 experimental tanks of a freshwater flow-through system was stocked with ten rainbow trout (initial average weight 31.5±0.5g). Fish were organized in triplicate groups and received experimental diets with 0, 50, 75, or 100% of fish meal replaced with albumin (A50–100) or globulin (G50–100) concentrate on the basis of digestible protein. At the end of a 70day feeding period feed conversion ratio in the albumin treatment groups was not significantly affected at all substitution levels. But due to lowered feed intake at higher inclusion levels growth performance decreased at A 75 and A 100. Dietary globulin inclusion influenced growth performance by reduced feed intake and utilization in all groups negatively due to higher levels of glucosinolates and sinapinic acid. Significant lower fish survival rates were observed when fish received diets A75, A100, G50, G75, or G100 compared to the control diet or diet A50. For the whole body composition, the crude protein content was significantly lower in fish fed diet G75 or G100 compared to the control diet, while fish fed on diet A50, A75, or A100 were lower in body fat content than fish fed on the control diet. Thus, we demonstrated that the used albumin concentrate can effectively replace 50% of dietary fish meal in rainbow trout diets, whereas the application of the globulin concentrate negatively influenced diet palatability, thereby reducing diet intake and subsequently fish growth.

Total fish meal replacement with rapeseed protein concentrate in diets fed to rainbow trout (Oncorhynchus mykiss Walbaum)

The potential of rapeseed protein concentrate as fish meal alternative in diets for rainbow trout (initial average weight 37.8 ± 1.4 g) was evaluated. Nine experimental tanks of a freshwater flow-through system were stocked with 12 fish each. Triplicate groups of fish received isonitrogenous (47.9 ± 0.5% CP) and isoenergetic (22.4 ± 0.2 kJ g−1) experimental diets with 0, 66 and 100% of fish meal substituted with rapeseed protein concentrate (71.2% CP), thereby providing 0, 29 and 43% of dietary protein. As the amino acid profile of rapeseed protein concentrate was comparable to fish meal, there was no need to supplement experimental diets with synthetic amino acids. At the end of the 84 days of feeding period, fish growth performance, feed intake and feed efficiencies were not compromised, when 100% of fish meal in the control diet was replaced with rapeseed protein concentrate, revealing a SGR of 1.19 or 1.10, a FCR of 1.09 or 1.18 and a feed intake of 78.5 or 74.7 g in fish fed on the control diet or fed the diet devoid of fish meal, respectively. Intestinal morphology did not reveal any histological abnormalities in all dietary groups. Blood parameters including haematocrit and haemoglobin as well as glucose, triglycerides and total protein in the plasma were not different between treatment groups. Thus, the rapeseed protein concentrate tested here has great potential as an alternative to fish meal in rainbow trout diets.

Rapeseed and milk protein exhibit a similar overall nutritional value but marked difference in postprandial regional nitrogen utilization in rats

BackgroundRapeseed is an emerging and promising source of dietary protein for human nutrition and health. We previously found that rapeseed protein displayed atypical nutritional properties in humans, characterized by low bioavailability and a high postprandial biological value. The objective of the present study was to investigate the metabolic fate of rapeseed protein isolate (RPI) and its effect on protein fractional synthesis rates (FSR) in various tissues when compared to a milk protein isolate (MPI).MethodsRats (n = 48) were given a RPI or MPI meal, either for the first time or after 2-week adaptation to a MPI or RPI-based diet. They were divided in two groups for measuring the fed-state tissue FSR 2 h after the meal (using a flooding dose of 13C-valine) and the dietary N postprandial distribution at 5 h (using 15N-labeled meals).ResultsRPI and MPI led to similar FSR and dietary nitrogen (N) losses (ileal and deamination losses of 4% and 12% of the meal, respectively). By contrast, the dietary N incorporation was significantly higher in the intestinal mucosa and liver (+36% and +16%, respectively) and lower in skin (-24%) after RPI than MPI.ConclusionsAlthough RPI and MPI led to the same overall level of postprandial dietary N retention in rats (in line with our findings in humans), this global response conceals marked qualitative differences at the tissue level regarding dietary N accretion. The fact that FSR did not however differed between groups suggest a differential modulation of proteolysis after RPI or MPI ingestion, or other mechanisms that warrant further study.

Replacement of fish meal with rapeseed protein concentrate in diets fed to wels catfish (Silurus glanis L.)

The potential of rapeseed protein concentrate as fish meal alternative in diets for wels catfish (initial average weight 86.5 ± 1.9 g) was evaluated. Sixteen fish were stocked into each of 12 experimental tanks being part of a freshwater recirculation system. Fish were organized in triplicate groups and received isonitrogenous (603 ± 3 g CP kg−1) and isocaloric (23.0 ± 0.3 kJ g−1) experimental diets with 0%, 25%, 50% and 75% of fish meal replaced with rapeseed protein concentrate (710 g CP kg−1). At the end of the 63-day feeding period, weight gain, standard growth rate, feed intake, feed conversion ratio and protein efficiency showed no significant difference between control group and fish fed on diets with 25% reduced fish meal content by inclusion of rapeseed protein concentrate. Higher dietary fish meal replacement negatively affected diet quality and palatability resulting in reduced feed intake, feed efficiencies and fish performance. However, blood serum values of triglycerides, glucose and protein were not significantly different between treatment groups, still indicating a favourable nutrient supply from all experimental diets.

Some characteristics and functional properties of rapeseed protein prepared by ultrasonication, ultrafiltration and isoelectric precipitation

The presence of complex protein constituents and difficulties in extracting protein from rapeseed meal limit the application of rapeseed protein in food processing. However, double-low rapeseed (low erucic acid, low glucosinolate) protein is a type of complete protein that is of potential use in the food industry. In this study the characteristics and functional properties of rapeseed protein prepared by ultrasonic-assisted extraction, ultrafiltration and isoelectric precipitation were analysed and compared with those of soybean protein. The extraction efficiency with the ultrasonic-assisted method was significantly higher than that obtained with the traditional method. Ultrafiltration and isoelectric precipitation yielded three different proteins: ultrafiltered protein RPs and precipitated proteins RP5.8 and RP3.6. Chromatographic separation of RPs resulted in four fractions: RPsI, RPsII, RPsIII and RPsIV. The distribution of the isoelectric point of rapeseed protein was investigated by two-dimensional electrophoresis. The amino acid composition of RPs renders it suitable for human consumption. The hydrophobic/hydrophilic amino acid ratio of rapeseed protein was higher than that of soybean protein. The functional properties (oil adsorption ability, emulsifying capacity, foaming capacity and foam stability) of RPs, RP5.8 and RP3.6 were found to be better than those of soybean protein. Ultrasonication and ultrafiltration were significantly better than the traditional method of rapeseed protein extraction. The ultrafiltered rapeseed protein RPs had superior functional properties. The results of this study provide useful indicators for rapeseed protein as a potential replacement for other proteins.

Preparation and Mechanical Properties of Edible Rapeseed Protein Films

Edible films were manufactured from rapeseed oil extraction residues. To prepare rapeseed protein (RP) films, various concentrations of plasticizers and emulsifiers were incorporated into the preparation of a film-forming solution. The optimal conditions for the preparation of the RP film were 2% sorbitol/0.5% sucrose as plasticizer and 1.5% polysorbate 20 as an emulsifier. In addition, RP blend films were prepared. Gelidium corneum or gelatin was added to improve the physical properties of the RP film, and the highest tensile strength value of the films was 53.45 MPa for the 3% RP/4% gelatin film. Our results suggest that the RP-gelatin blend film is suitable for applications in food packaging. Edible RP films prepared in the present investigation can be applied in food packaging.

Effect of rapeseed protein–gelatin film containing grapefruit seed extract on ‘Maehyang’ strawberry quality

SummaryTo develop a packaging film for ‘Maehyang’ strawberries, an edible film containing antimicrobial grapefruit seed extract (GSE) was manufactured. Addition of GSE to the rapeseed protein–gelatin (RG) film inhibited the growth of pathogenic bacteria such as Escherichia coli O157:H7 and Listeria monocytogenes. Packaging of ‘Maehyang’ strawberries with the RG film containing 1.0% GSE decreased the populations of total aerobic bacteria and of yeast and moulds in the strawberries by 1.03 and 1.34 log CFU g−1, respectively, after 14 days of storage, compared to that of the control. Sensory evaluation of the GSE‐RG film‐packaged strawberries produced better sensory scores than did the control. These results suggest that RG film containing GSE can be used to package strawberries and to extend shelf life.