Use of oyster mushrooms (Pleurotus ostreatus) for increased circularity and valorization of rapeseed residues.

In Europe, rapeseed is a common oilseed crop, resulting in the production of 20 million tons of rapeseed press cake yearly. This press cake can be further upcycled and a protein fraction can be extracted for food purposes, leaving de-proteinized fiber-rich residues. This study examined the use of these residues in the production of oyster mushrooms (Pleurotus ostreatus) and of the spent substrate as feed, since mushroom cultivation may improve the feed properties of substrate. In terms of mushroom production, the addition of rapeseed press residues was beneficial, giving significantly higher biological efficiency (BE = 93.1 ± 11.0%) compared with the control, sugar beet pulp substrate (70.0 ± 6.6%). This increase in productivity can most likely be explained by higher energy content in the substrate supplemented with lipid-rich rapeseed residues. Despite differences in BE between the substrates, high similarity was observed in lipid composition of the fruiting bodies (lipid profile dominated by linoleic acid (18:2), palmitic acid (16:0), and oleic acid (18:1)), and in protein and moisture content. After mushroom harvest, approximately 70% of the initial dry weight of both substrates remained as a possible feed source. Both substrates had significantly lower levels of carbohydrates and unchanged neutral detergent fiber content after mushroom harvest, and both gave lower in vitro digestibility, total gas production, and methane production. However, protein concentration differed between the substrates, with the highest concentration (15.8% of dry weight) found in spent substrate containing rapeseed press residues. The result of the present study suggests that the de-proteinized rapeseed press residue is a resource well-suited for use in the production of mushrooms and feed.

The Effect of Precipitation pH on Protein Recovery Yield and Emulsifying Properties in the Extraction of Protein from Cold-Pressed Rapeseed Press Cake.

Rapeseed is the second most cultivated oilseed after soybean and is mainly used to produce vegetable oil. The by-product rapeseed press cake is rich in high-quality proteins, thus having the possibility of becoming a new plant protein food source. This study aimed to investigate how the precipitation pH affects the protein yield, protein content, and emulsifying properties when industrially cold-pressed rapeseed press cake is used as the starting material. Proteins were extracted under alkaline conditions (pH 10.5) with an extraction coefficient of 52 ± 2% followed by precipitation at various pH (3.0-6.5). The most preferred condition in terms of process efficiency was pH 4.0, which is reflected in the zeta potential results, where the proteins' net charge was 0 at pH 4.2. pH 4.0 also exhibited the highest protein recovery yield (33 ± 0%) and the highest protein concentration (64 ± 1%, dry basis). Proteins precipitated at pH 6.0-6.5 stabilized emulsions with the smallest initial droplet size, although emulsions stabilized by rapeseed protein precipitated at pH 5.0-6.0 showed the highest emulsion stability at 37 °C for 21 days, with a limited layer of free oil. Overall, emulsion stabilized by protein precipitated at pH 5.0 was the most stable formulation, with no layer of free oil after 21 days of incubation.

High-Pressure Pasteurization of Soy Okara.

Okara is a by-product from the production of soy beverages, which has a high content of protein and fiber. Even though it has a high nutritional value, it is generally discarded or used as animal feed or compost. The problem is its short shelf life due to its high water content and high water activity. The aim of this study was to investigate the effect of high-pressure pasteurization at 200 MPa, 400 MPa, and 600 MPa on the shelf life of soy okara. Microbiological growth, as well as thermal properties, viscosity, water holding capacity, and oil holding capacity, was evaluated after the pressure treatments. Treatment at 600 MPa significantly reduced (p < 0.05) the growth of total aerobic count, yeast and mold, and lactic acid bacteria for up to four weeks of storage at 4 °C. The pasting properties were increased while the water and oil holding capacities of the soy okara did not significantly change (p > 0.05) after high-pressure pasteurization at 400 MPa and 600 MPa. High-pressure pasteurization is therefore a potential application technique for soy okara to produce a microbiologically safe product with maintained functional properties. However, more research is needed to optimize the process and to further investigate the microbiological species present in untreated soy okara to exclude any potential food safety risks.

High-Pressure Pasteurization of Oat Okara.

The issue of the short microbiological shelf life of residues from the plant-based beverage industry creates a large food waste problem. Today, the oat beverage residue, in this study referred to as oat okara, is generally converted to energy or used as animal feed. High-pressure pasteurization (200 MPa, 400 MPa, and 600 MPa) was applied to oat okara to investigate the effect on shelf life and microbiological activity. A 4-week microbiological storage study was performed and thermal properties, viscosity, and water and oil holding capacities were analyzed. The total aerobic count, including yeast and mold, was significantly reduced (p < 0.05) by 600 MPa after four weeks of storage at 4 °C. The content of lactic acid bacteria after four weeks of storage was low for untreated oat okara (3.2 log CFU/g) but, for 600 MPa, the content remained at the detection limit (2.3 log CFU/g). Conversely, the treatments of 200 MPa and 400 MPa increased the microbial content of the total aerobic count significantly (p < 0.05) after two weeks in comparison to untreated oat okara. The thermal properties of untreated and high-pressure-treated oat okara demonstrated an increase in protein denaturation of the 12S globulin, avenalin, when higher pressure was applied (400-600 MPa). This was also confirmed in the viscosity measurements where a viscosity peak for avenalin was only present for untreated and 200 MPa treated oat okara. The water holding capacity did not change as a function of high-pressure treatment (3.5-3.8 mL/g) except for the treatment at 200 MPa, which was reduced (2.7 mL/g). The oil holding capacity was constant (1.2-1.3 mL/g) after all treatments. High-pressure pasteurization of 600 MPa reduced the microbial content in oat okara resulting in a shelf life of 2-4 weeks. However, more research is required to identify the microorganisms in oat okara to achieve a microbiologically safe product that can be used for food applications.

Effects of Concentration and Type of Lipids on the Droplet Size, Encapsulation, Colour and Viscosity in the Oil-in-Water Emulsions Stabilised by Rapeseed Protein.

The objective of this study was to extract the rapeseed protein from by-products and further examine the effect of lab-made rapeseed protein on the droplet size, microstructure, colour, encapsulation and apparent viscosity of emulsions. Rapeseed protein-stabilised emulsions with an increasing gradient of milk fat or rapeseed oil (10, 20, 30, 40 and 50%, v/v) were fabricated using a high shear rate homogenisation. All emulsions showed 100% oil encapsulation for 30 days of storage, irrespective of lipid type and the concentration used. Rapeseed oil emulsions were stable against coalescence, whereas the milk fat emulsion showed a partial micro-coalescence. The apparent viscosity of emulsions raised with increased lipid concentrations. Each of the emulsions showed a shear thinning behaviour, a typical behaviour of non-Newtonian fluids. The average droplet size was raised in milk fat and rapeseed oil emulsions when the concentration of lipids increased. A simple approach to manufacturing stable emulsions offers a feasible hint to convert protein-rich by-products into a valuable carrier of saturated or unsaturated lipids for the design of foods with a targeted lipid profile.

Protein extraction from cold-pressed hempseed press cake: From laboratory to pilot scale.

During the production of industrial hempseed oil, a press cake is formed as a byproduct, which is often used as animal feed although it contains a high amount of protein that could be used for human consumption. Extracting this valuable protein would reduce food waste and increase the availability of plant-based protein. A protein extraction process based on the pH-shift method was adapted to improve the protein extraction yield from industrial hempseed press cake (HPC). Parameters such as alkali extraction pH, time, and temperature, as well as isoelectric precipitation pH, were investigated in laboratory scale and were thereafter carried out in a pilot trial to explore the suitability for future scale up. The phytic acid content of the extracted protein isolate was also analyzed to investigate any potential inhibitory effect on mineral absorption. A final protein yield of 60.6%, with a precipitated protein content of 90.3% (dw), was obtained using a constant alkali extraction pH of 10.5 for 1 h at room temperature, followed by precipitation at pH 5.5. The pilot trial showed promising results for the future production of industrial hemp protein precipitate on a larger scale, showing a protein yield of 57.0% and protein content of 90.8% (dw). The amount of phytic acid in the protein isolate produced in the optimal laboratory experiment and in the pilot trial was 0.595 and 0.557 g phytic acid/100 g dw, respectively, which is 83%-88% less than in the HPC. This is in the range of other plant-based protein sources (tofu, kidney beans, peas, etc.). PRACTICAL APPLICATION: Industrial hempseed press cake is a byproduct in the production of industrial hempseed oil, which is mostly used as animal feed, but has the potential to become an additional source of plant-based protein for human consumption with a suitable protein extraction method. The extracted hemp protein could be used to develop new plant-based dairy or meat analog products.

The Effect of pH and Storage Temperature on the Stability of Emulsions Stabilized by Rapeseed Proteins.

Rapeseed press cake (RPC), the by-product of rapeseed oil production, contains proteins with emulsifying properties, which can be used in food applications. Proteins from industrially produced RPC were extracted at pH 10.5 and precipitated at pH 3 (RPP3) and 6.5 (RPP6.5). Emulsions were formulated at three different pHs (pH 3, 4.5, and 6) with soy lecithin as control, and were stored for six months at either 4 °C or 30 °C. Zeta potential and droplet size distribution were analyzed prior to incubation, and emulsion stability was assessed over time by a Turbiscan instrument. Soy lecithin had significantly larger zeta potential (-49 mV to 66 mV) than rapeseed protein (-19 mV to 20 mV). Rapeseed protein stabilized emulsions with smaller droplets at pH close to neutral, whereas soy lecithin was more efficient at lower pHs. Emulsions stabilized by rapeseed protein had higher stability during storage compared to emulsions prepared by soy lecithin. Precipitation pH during the protein extraction process had a strong impact on the emulsion stability. RPP3 stabilized emulsions with higher stability in pHs close to neutral, whereas the opposite was found for RPP6.5, which stabilized more stable emulsions in acidic conditions. Rapeseed proteins recovered from cold-pressed RPC could be a suitable natural emulsifier and precipitation pH can be used to monitor the stability in emulsions with different pHs.

Development and Characterization of Extrudates Based on Rapeseed and Pea Protein Blends Using High-Moisture Extrusion Cooking.

Rapeseed protein is not currently utilized for food applications, although it has excellent physicochemical, functional, and nutritional properties similar to soy protein. Thus, the goal of this study was to create new plant-based extrudates for application as high-moisture meat analogs from a 50:50 blend of rapeseed protein concentrate (RPC) and yellow pea isolate (YPI) using high-moisture-extrusion (HME) cooking with a twin-screw extruder to gain a better understanding of the properties of the protein powders and resulting extrudates. The effects of extrusion processing parameters such as moisture content (60%, 63%, 65%, 70%), screw speed (500, 700, and 900 rpm), and a barrel temperature profile of 40-80-130-150 °C on the extrudates' characteristics were studied. When compared to the effect of varying screw speeds, targeted moisture content had a larger impact on textural characteristics. The extrudates had a greater hardness at the same moisture content when the screw speed was reduced. The specific mechanical energy (SME) increased as the screw speed increased, while increased moisture content resulted in a small reduction in SME. The lightness (L*) of most samples was found to increase as the target moisture content increased from 60% to 70%. The RPC:YPI blend was equivalent to proteins produced from other sources and comparable to the FAO/WHO standard requirements.

High-Moisture Meat Analogues Produced from Yellow Pea and Faba Bean Protein Isolates/Concentrate: Effect of Raw Material Composition and Extrusion Parameters on Texture Properties.

Yellow pea and faba bean are potential candidates to replace soybean-based ingredients due to their suitability for cultivation in the northern hemisphere, non-genetically modified organisms cultivation practice and low risk of allergenicity. This study examined the functionality of local yellow pea and faba bean protein isolates/concentrate as meat analogue products. The most critical factors affecting the texture properties of meat analogue were also determined. Extrusion was used to produce high-moisture meat analogues (HMMAs) from yellow pea and faba bean protein isolates/concentrates and HMMAs with fibrous layered structures was successfully produced from both imported commercial and local sources. The texture properties of the HMMA produced were mainly affected by the ash, fiber and protein content and water-holding capacity of the source protein. Three extrusion process parameters (target moisture content, extrusion temperature, screw speed), also significantly affected HMMA texture. In conclusion, functional HMMA can be produced using protein isolates derived from locally grown pulses.

Emulsifying and Anti-Oxidative Properties of Proteins Extracted from Industrially Cold-Pressed Rapeseed Press-Cake.

One of the functional proteins in rapeseed-the amphiphilic protein oleosin-could be used to stabilize emulsions. The objectives of this study were to extract oleosins from cold-pressed rapeseed press-cake, optimize the extraction process, and investigate their emulsifying and anti-oxidative capacity. The proteins were recovered from industrially cold-pressed rapeseed press-cake at different alkali pHs. Emulsifying properties and oxidation rates were assessed. Oleosin extracted at pH 9 stabilized smaller emulsion droplets than oleosin extracted at pH 12, although the protein yield was higher at pH 12. Emulsions were formulated from flaxseed oil and corn oil and were stabilized by oleosin, bovine serum albumin, de-oiled lecithin and Tween 20,h and the emulsions were stored in accelerated conditions (30 °C) for 12 days. Oleosin stabilized emulsions to the same extent as commercial food-grade emulsifiers. Flaxseed oil emulsions stabilized by oleosin had a significantly lower concentration of malondialdehyde (MDA) which indicates a lower oxidation rate compared to BSA, de-oiled lecithin and Tween 20. For corn oil emulsions, oleosin and BSA had a similar capacity to delay oxidation and were significantly more efficient compared to de-oiled lecithin and Tween 20. Rapeseed oleosin recovered from cold-pressed rapeseed press-cake could be a suitable natural emulsifier with anti-oxidation properties.

Development of High-Moisture Meat Analogues with Hemp and Soy Protein Using Extrusion Cooking.

The interest in plant-based products is growing in Western countries, mostly due to health and environmental issues that arise from the consumption and production of animal-based food products. Many vegan products today are made from soy, but drawbacks include the challenges of cultivating soy in colder climates such as northern Europe. Therefore, the present study investigates whether industrial hemp (Cannabis sativa) could substitute soy in the production of high moisture meat analogues (HMMA). A twin screw co-rotating extruder was used to investigate to what extent hemp protein concentrate (HPC) could replace soy protein isolate (SPI) in HMMAs. The substitution levels of HPC were 20 wt%, 40 wt% and 60 wt%. Pasting properties and melting temperature of the protein powders were characterized by Rapid Visco Analyzer (RVA) and Differential Scanning Calorimeter (DSC), respectively and the produced HMMA was analysed by determining the texture and colour attributes. The results showed that it is possible to extrude a mixture with up to 60% HPC. HPC absorbed less water and needed a higher denaturing temperature compared to SPI. Increasing the moisture content by 5% would have resulted in a reduction of hardness and chewiness. The lightness (L* value) was found to be significantly higher in SPI product and decreased in the mixture with higher HPC (p < 0.05).