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Aqueous two-phase systems (ATPS) stand out as an alternative technique for recovering and concentrating proteins. However, the study of ATPS to recover Arthrospira platensis protein is still poorly reported. This research used a sequential strategy of experimental design to evaluate the protein recovery from A. platensis protein extract using ATPS composed of polyethylene glycol (PEG: 1500, 4000, 6000, and 8000 Da) and saline solution (potassium phosphate and sodium citrate). The maximized conditions for A. platensis protein recovery were established by using 16% sodium citrate and 18% PEG 1500 Da, reaching 1.02 of purification factor and 75% protein recovery. Electrophoresis analysis showed protein bands between 5 and 15 kDa, characteristic size of phycobiliproteins. PEG and sodium citrate ATPS are a simple and low-cost alternative to the recovery A. platensis protein and show potential for industrial application.

Arthrospira platensis has stood out, especially due to its high protein content and its potential for food application. However, the exploration of protein concentration techniques of this microalgae still presents a great challenge. Thus, the objective of this study was to evaluate the purification of A. platensis proteins by applying two different aqueous two-phase systems (ATS) composed of potassium phosphate and ethanol, and sodium citrate and ethanol, in addition to the association with membrane separation process (MSP), and the characterization of the fractions obtained. ATS under the optimised conditions (19% potassium phosphate and 30% ethanol, and 19.5% sodium citrate and 29% ethanol) resulted in 1.27 and 1.31 purity, and 77.45% and 78% recovery, respectively. The sodium citrate and ethanol ATS showed significantly greater purity; thus, the upper phase was submitted to MSP. The association of ATS and MSP increased the recovery (~ 87%) and the purity (1.5). The top phase of ATS showed higher protein content (61%) than the bottom (5.9%), confirming the protein preference to the top. When the MSP was evaluated, the protein was increased about 8.0%, and antioxidant activity was kept (42 and 40% to top phase and ATS/MSP concentrate, respectively). Emulsions formed by ATS top phase showed a lower droplet size (33.69 µm D4.3 and 6.02 µm D3.2), and a significantly lower degree of overall destabilization (0.04 × 10–6 s−1 kh and 3.54 × 10–3 s−1 ks) than those stabilized with bottom phase and MSP/ATS concentrate. ATS associated with membrane process showed efficiency in the concentration A. platensis protein, being able to be an alternative to be used in industrial systems.

The high protein content of Arthrospira platensis makes this cyanobacterium a great component of food. Thus, the protein obtained should guarantee the nutrient characteristic, in this case, as bioactivity and techno-functional properties. Membrane separation processes (MSPs) have been highlighted by their capacity to separate proteins and keep their properties. Therefore, MSP was used to concentrate and separate the proteins from A. platensis, which were characterized by their physicochemical and techno-functional properties. Different ultrafiltration (UF) membranes and operational conditions (10- and 50-kDa pore size, conventional and tangential flow, hollow fiber type and pressures of 1.0, 1.5, and 2.0 bar) were tested and associated with diafiltration (DF). The maximized condition of UF/DF (hollow fiber, 50 kDa, tangential flow at 1.5 bar, associated with one DF) was up scaled (pilot scale) and allowed concentrate and permeate fractions with 81.75% and 61.20% of protein, respectively, to be obtained. A protein concentrate with 142 mg L−1 of phycocyanin, 90% of antioxidant activity, with proteins more soluble at high pH (50% soluble protein at pH 7.0) and molecular weight among 5–15 and 100 kDa, was obtained. Protein thermal and emulsifying properties were maintained by the MSP, and the concentrate fraction presented results similar as A. platensis biomass, which confirms the advantage of this method in guaranteeing the protein quality.

The aim of this study was to concentrate whey protein by ultrafiltration process, evaluating the pressure at 1–3 bar and temperature of 10–20℃. In the conditions that show the more protein concentration were evaluated the interfacial and emulsifying properties at pH 5.7 and 7.0. The whey concentrate at 10℃ and 1.5 bar showed the higher protein value 36% (w/w), with soluble protein of 33.82% (solubility of 93.94%) for pH 5.7 and 34% (solubility of 94.4%) for pH 7.0, respectively. The whey concentrate powder present particle size distribution between 0.4-110 um. The whey at pH 5.7 and 7.0 was not observed significant differences in the resistance parameters of the oil/water layer interface. The interfacial film formed by the proteins presented an essentially elastic behavior in both pH, and in pH 5.7 the emulsion was more stable with lower diameter droplets. The concentrate whey showed techno-functional properties (emulsification and solubility), which allow the use as ingredients in products of industrial interest in food products such as mayonnaise, ice cream, sauces, and others.

Rice bran is a by-product of the rice milling process, found worldwide in abundance and highlighted due its protein content. This study optimized the conditions for ultrasonic-assisted extraction of protein from defatted rice bran (DRB) and characterized the rice bran protein concentrate (RBPC). A sequential strategy of experimental design was employed; the effect of pH, temperature, ultrasound exposure time, and amplitude were evaluated regarding the percentage of protein extraction by a Full factorial design (FFD) with a fixed frequencies (FFD-A: 37 kHz; FFD-B: 80 kHz). Subsequently, the percentage of protein extracted was optimized employing a Central composite rotatable design (variables: pH and ultrasound exposure time) and RBPC obtained was characterized regarding chemical and functional properties. The pH and ultrasound exposure time had positive effect (P ≤ 0.05) on percentage of protein extraction; moreover, 37 kHz frequency was more effective in protein extraction. The optimized condition (frequency: 37 kHz; temperature: 30 °C; pH: 10; ultrasound exposure time: 30 min; and amplitude: 100%) allowed 15.07% of protein recovery and the RBPC presented 84.76 g 100 g-1 of protein. Magnesium and copper were the main mineral in RBPC (34.4 and 25.5 µg g-1, respectively), while leucine was the limiting amino acid (0.42) and threonine presented the highest chemical score (1.0). The RBPC solubility was minimal at pH 4 and higher at pHs 6-10; the water and oil absorption capacity were higher than bovine serum albumin (BSA) and the emulsifying capacity was comparable to BSA, with a suitable stability. It was possible to obtain a higher purity RBPC than described in the literature, due to the optimization in the extraction process steps, with functional properties suitable for application in food products, especially emulsified ones. RESUMO: O farelo de arroz é um subproduto do processo de moagem do arroz, encontrado em abundância em todo o mundo e destacado devido ao seu teor de proteínas. Este estudo otimizou as condições para a extração assistida por ultrassom da proteína do farelo de arroz desengordurado (DRB) e caracterizou o concentrado de proteína do farelo de arroz (RBPC). Uma estratégia sequencial de desenho experimental foi empregada; o efeito do pH, temperatura, tempo de exposição ao ultrassom e amplitude foram avaliados em relação à porcentagem de extração proteica por um Delineamento Fatorial Completo (FFD) com frequências fixas (FFD -A: 37 kHz; FFD-B: 80 kHz). Posteriormente, a porcentagem de proteína extraída foi otimizada empregando um Planejamento Composto Central (variáveis: pH e tempo de exposição ao ultrassom) e o RBPC obtido foi caracterizado quanto às propriedades químicas e funcionais. O pH e o tempo de exposição ao ultrassom tiveram efeito positivo (P ≤ 0,05) na porcentagem de extração proteica. Além disso, a frequência de 37 kHz foi mais eficaz na extração de proteínas. A condição otimizada (frequência: 37 kHz; temperatura: 30 °C; pH: 10; tempo de exposição ao ultrassom: 30 min; e amplitude: 100%) permitiu 15,07% de recuperação de proteínas e o RBPC apresentou 84,76 g 100 g-1 de proteína. Magnésio e cobre foram os principais minerais da RBPC (34,4 e 25,5 µg g-1, respectivamente), enquanto a leucina foi o aminoácido limitante (0,42) e a treonina apresentou o maior escore químico (1,0). A solubilidade do RBPC foi mínima em pH 4 e superior em pH 6-10; a capacidade de absorção de água e óleo foi maior que a albumina sérica bovina (BSA) e a capacidade de emulsificação foi comparável à BSA, com uma estabilidade adequada. Assim, foi possível obter um RBPC com elevada pureza, maior do que o descrito na literatura, devido à otimização nas etapas do processo de extração, com propriedades funcionais adequadas para aplicação em produtos alimentícios, principalmente emulsificados.

Vegetable-based proteins may be extracted from different sources using different extraction methods, among them, ultrasound-assisted extraction stands out. This review presents the current knowledge on ultrasound-assisted extraction (UAE) and the functional properties of extracted vegetable proteins. Ultrasound generates cavitation in a liquid medium, defined as gas and vapor microbubbles collapse under pressure changes large enough to separate them in the medium. Cavitation facilitates the solvent and solid interaction, increasing yield and reducing extraction periods and temperature used. Moreover, ultrasound treatment changed extracted protein properties such as solubility, hydrophobicity, emulsifying and foam, water and oil absorption capacity, viscosity, and gelatinization. Ultrasound-assisted extraction is a promising technique for the food technology sector, presenting low environmental impact, lower energy and solvent consumption, and it is in accordance with green chemistry technology and sustainable concepts.

The need to develop new sources of foods is growing, especially due to malnutrition in underdeveloped and developing countries. Also, the growth of the world’s population has led to the exploration of alternative food sources that can maintain food security. The high protein content of several macro and microalgal species would make them a great component of different foods, increasing their nutritional value. Parallel studies have shown that microalgae consumption may bring additional health benefits due to their variety of active biological compounds that are not found in other organisms. Considering this evidence and the potential commodity-scale production of algae, we aimed to conduct a survey of the biochemical, biological, and functional properties of different microalgae and to explore their techno-functional characteristics that can improve food processing, including their protein solubility, foaming, emulsifying, and gelling properties.

The objective of this study is to elaborate Serra da Estrela cheese with sheep's milk concentrate by ultrafiltration and characterize it in relation to protein, yield, proteolysis, amino acid profile, and acceptability. The cheese elaborated with concentrate milk (F2) presented an increase of 17% yield, and protein content was 2 times higher than cheese without concentrate milk (F1). On the 30thday of storage F2 presented an increase of the amino acids and also of proteolysis extension and depth index in relation to the 1st day. Also presented better sensorial characteristic in relation to F1. Were observed positive correlations (>0.85) between acceptability in relation to protein, depth index, extensionand extension index, valine, methionine, serine, phenylalanine aspartic acid, valine andproline. Cheese elaborated with concentrate milk and coagulated with thistle flower is one alternative to increase cheese yield with differential sensorial characteristics.

The nutritional composition of Spirulina platensis has been studied extensively, especially its proteins, amino acids, vitamins and mineral content. However, research on its protein properties, including its techno-functional properties, remains scarce. Therefore, S. platensis proteins were extracted and concentrated to produce a S. platensis protein concentrate (SpPC), which was characterized by its physicochemical and techno-functional properties. Response surface methodology (RSM) was applied to evaluate the influence of two variables, pH and SpPC concentration, on the techno-functional properties of the SpPC, instead of studying one variable at a time. The SpPC contained 75.97% proteins (dry weight); its minimum solubility was at pH 3.0, and its maximum solubility was at pH 9.0. The effects of the SpPC concentration and pH on the water absorption capacity and emulsifying and foaming properties were evaluated. The pH exhibited a positive effect on these properties, and the best conditions were far from the isoelectric point. The SpPC concentration also showed a positive effect, except water and oil absorption. Considerable concentrations of amino acids were found in the S. platensis protein concentrate; tryptophan had the highest chemical score. The most abundant secondary structure conformation was β-sheet. Consequently, the S. platensis protein concentrate may contribute technologically to food formulation, and facilitate industrial processing.