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Microfluidization is a technique commonly used to disrupt and homogenize dispersions such as oil-in-water emulsions or cellular suspensions. In this study, we investigated its ability to alter the physicochemical properties of plant-derived insoluble protein aggregates such as those found in pea protein extracts. Insoluble pea protein dispersions (5% w/w, pH 7) were homogenized at 25–150 MPa for 1–5 cycles. Increasing the homogenization pressure and cycles decreased the particle size (d43) of the unhomogenized insoluble pea proteins from 180 ± 40 μm to 0.2 ± 0.0 μm (at ≥ 125 MPa), leading to more transparent dispersions. Furthermore, the solubility of the insoluble pea proteins increased from 23 ± 1% to 86 ± 4%. Treatments with chaotropic agents, dithiothreitol and urea, revealed that insoluble pea protein aggregates were stabilized not only by disulphide bonds but also by hydrogen bonds and hydrophobic interactions. These molecular interactions were disrupted by microfluidization. The study provides insights into the disruption mechanism of insoluble pea proteins by applying microfluidization and offers a mean to improve their technofunctional properties to facilitate further use in food manufacture.

Nine multiparous Holstein-Friesian cows (initially 97 d in milk), were used in a. 3 x 3 lattice square design experiment with 4-wk periods. All cows received 4 kg/d concentrates and dietary treatments were based on silages offered ad libitum: perennial ryegrass (PRO); timothy (TIM); tall fescue (TF); red clover (RC); red clover/corn silage mixture [40/60 on a dry matter (DM) basis; RCC]; red clover/whole-crop oat silage mixture (40/60 on a DM basis; RCO); or red clover/whole-crop oat silage mixture (25/75 on a DM basis; ORC). The remaining treatments were based on RCO with feed intake restricted to the level of PRG (RCOr) or with a low protein concentrate (50/50 mixture of barley and molassed sugar beet pulp; RCO1p). Experiment objectives were to evaluate diet effects on N partitioning and N isotopic fractionation. Yields of milk and milk protein were consistently high for diets RC, RCC, and RCO and low for the diets based on poorly ensiled grass silages. Restriction of intake (RCOr) and inclusion of a higher proportion of whole-crop oat silage (ORC) and the low-protein concentrate (RCO1p) led to some loss of production. Diet had little effect on milk fat, protein, and lactose concentrations: low concentrations of milk protein and lactose reflect, the restricted energy intakes for all treatments. The highest diet digestibilities were measured for RC and PRO, whereas increasing inclusion of the whole-crop oat silage (0, 60, and 75% of forage DM) led to a marked decrease in diet digestibility (0.717, 0.624, and 0.574 g/g, respectively). Urinary excretion of purine derivatives, an indicator for rumen microbial protein synthesis, was significantly higher for RCC than for TIM and TF. Nitrogen intake ranged between 359 and 626 g/d (treatment means). Partitioning of N intake to feces and urine was closely related to N intake, although urinary N losses were less than predicted from N intake for the 60/40 mixtures of cereal silage and red clover silage. The N-15 content of milk, urine, and feces were all influenced by diet N-15 content. Isotopic fractionation meant that feces and milk were enriched and urine was depleted in N-15 relative to the diet. Significant relationships were observed between the extent of enrichment of urine, feces, and milk, suggesting some commonality in fractionation pathways. The trend for the lowest N-15 enrichment in milk protein occurring in diets with low N-use efficiency (milk N/feed N) was contrary to expectations, possibly because of endogenous contributions to milk protein or fractionation when dietary ammonia was incorporated into microbial protein.

This study provides an overview of the development and environmental effects of protein crop production in Europe. Nine policy options for supporting protein crops are presented: six inside the CAP, and three outside. We recommend an integrated policy approach combining the inclusion of protein crops into greening measures, investment in research and constraints on the use of synthetic nitrogen fertiliser. We conclude that increasing the production of protein crops would be an important contribution to the sustainable development of European agricultural and food systems.