Modelling the effects of ethanol on the solubility of the proteinogenic amino acids with the NRTL, Gude and Jouyban-Acree models

The addition of organic solvents, such as ethanol, to molecules in solution is an effective process for crystallization and is used in industrial settings (i.e. pharmaceutical production, downstream processing, etc.). In this study, we use solubility data of all proteinogenic α-amino acids in binary ethanol/water systems to model their excess solubility. We use the empirical and regressive models of Gude and NRTL and the predictive Jouyban-Acree model. Based on the results, we hypothesize that amino acids that are spherical and lack a reactive side chain show little or no excess solubility. Being rod-like and/or having a reactive side chain leads to a positive excess solubility in a mixed solvent of ethanol and water. The empirical and regressed models, NRTL and Gude, fit the data well and the predictive Jouyban-Acree model, not originally intended to be used for small molecules, is less accurate but offers insights into the thermodynamic properties of the amino acids

Sustainable scenarios for alkaline protein extraction from leafy biomass using green tea residue as a model material

Leaf protein can be extracted cost-efficiently using 0.1 mol dm-3 NaOH, but this process is less sustainable due to the generation of large amounts of sodium salts. KOH or Ca(OH)2 are considered as replacements for NaOH, as these salts can be reused. This work evaluates the economic and environmental sustainability of weak alkaline pectin extraction followed by KOH enhanced protein extraction, and Viscozyme® L-aided pectin extraction followed by Ca(OH)2 enhanced protein extraction. The evaluations are made for green tea residue and are compared to related processes using NaOH. The predicted profits using KOH are comparable to those using NaOH. Environmental sustainability improves for all impact categories in the case of KOH extraction. Further environmental benefits are obtained by substituting conventional K fertilizer with the K-rich salty waste water from the extraction process. The profits of the process using Ca(OH)2 are highly dependent on the extraction yield of the protein product. Protein extraction yields using Ca(OH)2 need to be higher than 70% to be more profitable than the same process with NaOH. The environmental benefits of Ca(OH)2 extraction include the absence of salty waste water and the net production of heat. This is accompanied by increased electricity consumption. Thus, the impact categories of climate change, fossil and water depletion, and particulate matter formation worsen. Photochemical oxidant formations remain the same, while the other impacts improve. This work has shown the potential and bottlenecks of NaOH, KOH and Ca(OH)2 protein extraction on different types of biomass in terms of environmental and economic sustainability

Valorisation of Proteins from Rubber Tree

Purpose: The objective of this study was to identify the availability, possible applications, and economic potential of proteins that are present in different parts of the rubber tree. Proteins from non-food sources can be used in e.g. animal feed or biochemicals production with no or little competition with food production, rendering them important biobased feedstock. Rubber tree is primarily grown for its latex that is used in rubber production. Indonesia has the largest rubber plantation area that is mostly owned and run by smallholder farmers. Using non-latex fractions from the rubber tree may generate additional income, and increase the economics of rubber plantations in general. Methods: Several biomass streams from the rubber tree and subsequent latex processing were considered. Data were compiled from literature, a case study, and interviews with researchers, smallholder farmers, and managers at rubber processing plant and plantation. Results: Latex waste streams, seeds, and leaves were considered to have the highest potential based on the amount of available proteins, and processes to isolate proteins from these streams were proposed. Isolation of specific functional properties from natural sources requires complex (and expensive) separation processes and therefore only economically feasible when specific use of the protein(s) for high value applications can be identified. Purification of many interesting proteins from latex fractions has already been described. Processing of seeds and leaves may also yield useful proteins for food, other purposes, and also still unknown high value applications. Conclusions: A biorefinery concept can be applied to obtain multiple products from the seeds and leaves, and protein extraction can be performed with available knowledge and technology. Small scale processing can be more beneficial for the farmers, especially if the products are used locally for feed

Partitioning of proteins and anti-nutrients in cassava (manihot esculenta crantz) leaf processing fractions after mechanical extraction and ultrafiltration

Cassava plays a major role in improving food security and reducing malnutrition. The purpose of this study was to evaluate the influence of mechanical pressing coupled with ultrafiltration (UF) on the quality of different fractions of cassava leaves. Cassava leaves harvested from the greenhouse at the University of Hohenheim were passed through a mechanical screw press to extract the juice and separate the press cake. The juice was centrifuged and filtered to separate the sediment and clear supernatant. The clear supernatant was filtered using a 10 kDa UF system. The nutritional contents of the different fractions were analyzed at each processing step. The total phenolic content was significantly lower in the press cake that had a higher fiber and ash content. The juice and sediment fractions had higher crude protein and total phenolic content. Processing did not negatively affect the concentrations of essential amino acids except for tryptophan in the juice fraction. Non-protein nitrogen was mainly present in the UF permeate, illustrating the potential of UF for upgrading soluble protein fractions. The results indicated that the different fractions during processing could be a possible source of protein for food, feed (juice, sediment, and retentate), or fiber (press cake) for ruminant feed

Fibrous Structures from Starch and Gluten

Starch is added to meat analogues for binding and water holding. In this study, we investigate whether starch can have an additional role as a structuring agent. Therefore, different types of starch were combined with wheat gluten at various amounts and sheared in a High Temperature Shear Cell to determine how starch influences the structuring behavior of gluten–starch blends. The starches were chosen based on their diverse amylose contents, leading to different technological properties. Remarkable differences were found between the starches investigated. The addition of Amioca starch (containing 1% amylose) had a strong negative influence on the ability of gluten to form fibers. Maize starch (25% amylose) and Hylon VII (68% amylose) formed fibrous materials up to high starch additions. The pre-gelatinizing of maize starch further increased the ability of gluten–starch mixtures to form fibrous structures. The influence of the different types of starch on the hardness, deformability, and stiffness of the sheared samples was also assessed, revealing a spectrum of achievable properties through the addition of starch. Most remarkable was the formation of a material with anisotropy in Young’s modules. This anisotropy is also found in chicken meat, but not in protein-based fibrous materials. Furthermore, it was observed that the pre-gelatinization of starch facilitated fiber formation. A similar effect of pre-gelatinizing the starch was found when using faba bean meal with added wheat gluten, where fibrous structures could even be formed in a recipe that previously failed to produce such structures without pre-treatment

Quantifying water distribution between starch and protein in doughs and gels from mildly refined faba bean fractions

The development of novel and sustainable food products, such as cheese- and meat analogues, requires a better understanding of the use of less refined ingredients. We investigated the distribution of water between the protein and starch phase of doughs and heat-induced gels made from air-classified faba bean fractions by developing a method suited for investigation of such multi-component ingredients. The moisture contents of the protein and starch phases in the dough were determined using a method based on partial sorption isotherms of mixed doughs of protein- and starch-rich fractions at high water activity. Water content of the protein phase is higher than that of the starch phase in dough, showing that protein takes up more water than starch at room temperature. Also, the moisture content of the protein phase in the gels was calculated using a model based on the denaturation temperature of legumin. From the experiments and the modelling, it became evident that the moisture content of the protein phase in the gel is lower than the moisture content of the protein phase in the dough, showing the importance of considering moisture migration from the protein to the starch during heating

Pulsed Electric Field as an Alternative Pre-treatment for Drying to Enhance Polyphenol Extraction from Fresh Tea Leaves

Drying is an essential pre-treatment prior to extraction of tea polyphenols from tea leaves, which is a time and energy-intensive process. In this study, pulsed electric field (PEF) was utilized to replace the conventional thermal dehydration procedure before the phenolic extraction. The influence of different PEF conditions on total polyphenol yield from fresh tea leaves combined with a solid-liquid extraction were compared. PEF treatment at 1.00 kV/cm electric field strength, 100 pulses of 100 μs pulse duration, and 5 s pulse repetition, which delivered 22 kJ/kg and induced 1.5 °C of temperature increase, was used for further study on the extraction kinetics of green tea catechins. The results indicated that compared to oven drying, PEF pre-treatment increased the extraction rate by approximately two times, without significantly altering the phenolic profiles, as revealed by using liquid chromatography combined with mass spectrometry. Scanning electron microscopy imaging revealed that PEF pre-treatment induced the formation of inhomogeneously distributed pores and protuberances on the surface of leaf tissues, which might facilitate the penetration of extraction solvent and the migration of phenolics. This study demonstrates that PEF as a time and energy efficient processing method is a promising alternative for the conventional drying process before further tea polyphenol extraction.</p

Improving yield and composition of protein concentrates from green tea residue in an agri-food supply chain: Effect of pre-treatment

Rather than improving crop-production yield, developing biorefinery technology for unused biomass from the agri-food supply chain may be the crucial factor to reach sustainable global food security. A successful example of food-driven biorefinery is the extraction of protein from green tea residues, however, alkali usage is high and the resulting low protein quality limits its application. The research objective was to investigate the influence of pre-treatments with ethanol, Viscozyme® L and/or H2O2 on the subsequent alkaline protein extraction, and on their possible products for food applications. Polyphenols and/or pigments can be obtained by ethanol pre-treatment. Galacturonic acid and glucose can be obtained using Viscozyme® L. Pre-treatments using ethanol or Viscozyme® L individually reduced alkali consumption by 25% and improved protein extraction yield and purity. Their combination has the best effect. Additionally, pre-treatment using 50% ethanol reduced browning by 59% while pre-treatment using Viscozyme® L increased contents of arginine, threonine, and serine in the final alkaline protein extract. H2O2 pre-treatment had a negative effect on the alkaline protein extraction. These pre-treatments and protein extraction can be added to the existing process

Solubility of the Proteinogenic α‑Amino Acids in Water, Ethanol, and Ethanol–Water Mixtures

The addition of organic solvents to α-amino acids in aqueous solution could be an effective method in crystallization. We reviewed the available data on the solubility of α-amino acids in water, water–ethanol mixtures, and ethanol at 298.15 K and 0.1 MPa. The solubility of l-alanine, l-proline, l-arginine, l-cysteine, and l-lysine in water and ethanol mixtures and the solubility of l-alanine, l-proline, l-arginine, l-cysteine, l-lysine, l-asparagine, l-glutamine, l-histidine, and l-leucine in pure ethanol systems were measured and are published here for the first time. The impact on the solubility of amino acids that can convert in solution, l-glutamic acid and l-cysteine, was studied. At lower concentrations, only the ninhydrin method and the ultraperfomance liquid chromatography (UPLC) method yield reliable results. In the case of α-amino acids that convert in solution, only the UPLC method was able to discern between the different α-amino acids and yields reliable results. Our results demonstrate that α-amino acids with similar physical structures have similar changes in solubility in mixed water/ethanol mixtures. The solubility of l-tryptophan increased at moderate ethanol concentrations