Browsing by Subject "pea protein isolate"
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Item Characterization and Modification of Scaled-Up Pea and Chickpea Protein Isolates Extracted using Salt Solubilization Coupled with Membrane Filtration in Comparison to Commercial Proteins(2023-12) Yaputri, BrigittaThe demand for plant protein ingredients continues to grow, along with growing interest in plant-based products, such as meat analogues. Soy protein is the most common plant protein source in the market due to availability, low cost, excellent nutritional quality, and good functional properties. In the meat analogue sector, soy protein is commonly combined with wheat gluten to form a meat-like fibrous texture via high moisture extrusion. However, soy protein and gluten are among the “Big Nine” allergens in the U.S., in addition to soy being a genetically modified (GMO) crop, which raises concerns and skepticism among consumers, creating demand for alternative plant protein sources. Among legume crops, pea and chickpea have been known to be good sources of protein. Pea protein is a major protein source that has been used in many food and beverage applications. Chickpea protein is a rather emerging protein source and is less studied compared to pea protein. There remains a limited availability of commercial chickpea protein ingredients in the market. As legumes, pea, chickpea, and soy share similar protein profile and structure, indicating the potential for pea and chickpea protein to substitute soy protein. However, pea and chickpea proteins have inferior functionality compared to soy protein, particularly gel strength. Protein functionality not only depends on the inherent protein structure and amino acid compositions but also on external factors, such as extraction methods. Currently, alkaline extraction coupled with isoelectric precipitation (AE-IEP) is the most common extraction method used in the industry to produce plant protein isolates. Extreme alkaline conditions may cause damage to the protein’s native structure due to excessive denaturation, which can impair protein functionality. Therefore, to compete with soy protein, there is a need to explore and optimize a milder extraction process to produce functional pea and chickpea protein isolates (PPI and ChPI). One method that is gaining traction is salt solubilization coupled with membrane filtration, which has mostly been performed at lab-scale to produce soy and pea protein isolates. To conduct a comprehensive evaluation, the industrial feasibility of such extraction process, following lab-scale optimization for ChPI, and its impact on the protein’s structure and function, must be determined. In addition to the extraction method, structural modification can also be used to further enhance targeted protein functionality. For meat analogue applications, good protein network, demonstrated by high gel strength, is important for the formation of meat-like fibrous texture. Enzyme transglutaminase (TG) has been used in the food industry to catalyze the formation of inter and intra-molecular crosslinks between the amino acids lysine and glutamine. Pea and chickpea are high in lysine, making them suitable substrates for TG. As research on this topic is limited, the selection of treatment parameters, along with protein structural and functional characterization, need to be done to determine the impact of TG on pea and chickpea protein. Therefore, the objectives of this study were: (1) to investigate the feasibility of scaling-up salt extraction coupled with membrane filtration and its impact on the structure and function of chickpea protein in comparison to pea protein and (2) to investigate the impact of transglutaminase treatment on the structure and function of pea and chickpea proteins. For objective 1, the salt solubilization conditions, including salt concentration and temperature were optimized for ChPI on benchtop based on protein purity and yield. Optimized benchtop extraction was then scaled-up at pilot scale to evaluate the scalability based on purity and yield of the chickpea protein. For comparison purposes, scaled-up (SU) PPI was produced following the same extraction method, according to our previous study. Structural characteristics of the SU PPI and SU ChPI were compared to benchtop and commercial isolates by determining the protein profile via SDS-PAGE, protein denaturation via differential scanning colorimetry (DSC), surface charge via zeta potential, and surface hydrophobicity by a spectrophotometric method. Functional characteristics of the SU isolates in comparison to benchtop and commercial counterparts, which included solubility, gel strength, water holding capacity, and emulsification properties, were also assessed. For objective 2, SU isolates were further treated with TG to induce polymerization. Different treatment conditions, including enzyme concentration and treatment time were tested and selected based on degree of polymerization, protein denaturation, and gel strength, as determined by SDS-PAGE, DSC, and thermal-induced gelation. The structural characteristics of the modified isolates (TG PPI and TG ChPI) were determined by evaluating the protein profile via SDS-PAGE, protein molecular weight distribution via SE-HPLC, protein denaturation by DSC, secondary structure via FTIR, surface charge via zeta potential, and surface hydrophobicity by spectrophotometric method in comparison to SU isolates and commercial ingredients. The functional properties of TG PPI and TG ChPI were determined by evaluating the protein’s solubility, gel strength, and emulsion capacity. The optimum salt solubilization conditions for ChPI were 0.5 M NaCl at room temperature, similar to those used for PPI, followed by ultrafiltration and dialysis. The benchtop and SU isolates had comparable protein purity with >90% protein and low ash content. The production of SU ChPI resulted in lower yield (41%) compared to benchtop production (52%), which was also observed for SU PPI, due to unavoidable losses during large scale production. The SU and benchtop isolates shared a similar protein profile. However, SU isolates experienced partial protein denaturation, higher surface hydrophobicity, and some polymerization due to thermal treatments during pasteurization, evaporation, and spray drying. Changes in structural characteristics of the SU isolates significantly impacted their functionality, including superior gel strength compared to their benchtop counterparts. Compared to the commercial pea and chickpea proteins, SU isolates were less denatured and polymerized, confirming that the adopted SE-UF process is milder compared to commercial isolation processes. Further, TG treatment of SU isolates resulted in a high degree of polymerization and a significant increase of intermolecular β-sheet. Heat treatment during enzyme incubation and inactivation step resulted in complete protein denaturation. TG-modified isolates had significantly lower solubility compared to their SU counterparts due to the formation of insoluble high molecular weight (MW) polymers and relatively high surface hydrophobicity. In contrast, TG isolates showed significantly stronger gel strength compared to the SU isolates, which was attributed to TG-induced polymerization. On the other hand, TG ChPI had significantly lower EC compared to SU ChPI, whereas that of TG PPI was not impacted, which was attributed to differences in legumin to vicilin ratio between pea and chickpea proteins. This study, for the first time, successfully demonstrated the scalability of chickpea protein isolate production following a mild SE-UF process. SU extraction resulted in protein isolates with high protein purity and good yield and preserved the protein’s structural integrity in comparison to the commercially produced ingredients, leading to better functionality. In addition, this study uniquely demonstrated the holistic impact of TG on the structure and function of SU PPI and SU ChPI, which could be leveraged to enhance texturization potential for meat analogues applications.Item Impact of Cold Atmospheric Plasma on the Structure and Functionality of Pea Protein(2021-04) Bu, FanIncreased consumer demand for alternative plant protein sources other than soy, which is a GMO crop and “Big Eight” allergen, is driving the growth of the pea protein ingredient market. Yellow field peas (Pisum sativum L.), an easy to grow environment-friendly non-GMO crop, with currently low occurrence of allergenicity, have similar protein profile and nutritional quality compared to soy. Therefore, pea protein has the potential to replace soy protein in the global plant protein ingredient market. The functional properties of pea protein, however, are inferior to that of soy protein counterparts, hindering its expanded use. Current breeding efforts, extraction and processing advances, and traditional modification strategies are limited in improving the functional properties of pea protein while maintaining nutritional quality as well as feasible production cost. Cold atmospheric plasma (CAP), a physical nonthermal processing technology that has been explored in electronics, material science, medicine, and agriculture, is being explored as a novel protein modification approach. Several studies reported unfolding and polymerization of proteins and corresponding improvements in functional properties after CAP treatment. However, the link between different plasma reactive species and observed structural changes, and consequent functional enhancement, has not been demonstrated. Additionally, only plasma sources that produce long-lived species (O3, H2O2, NO2-, and NO3-) have been investigated in protein modification studies. Other plasma sources that can generate various short-lived species (such as OH radicals) are worth investigating to optimize CAP conditions for a directed enhancement in pea protein functionality. Therefore, the objectives of this study were: (1) investigate the impact of plasma reactive species, as well as pH conditions and salt content, on pea protein structure and functionality; (2) investigate the impact of different plasma configurations, gas mixtures, and treatment time on pea protein structure and functionality. For objective 1, the impact of RNS and ROS (O3, NxOy, H2O2 and OH) at two pH conditions (pH 2 and pH 7), on the color, structure, and functionality of pea protein isolate (PPI) was evaluated. Structural characteristics of modified pea protein isolates (mPPIs) and PPI were compared by determining the protein profile using SDS-PAGE and SE-HPLC, protein denaturation by DSC, surface charge by measuring zeta potential, surface hydrophobicity as measured by a spectrophotometric method, and protein secondary structure by FTIR. Protein solubility, gelation, and emulsification properties were evaluated. For the second objectives three different CAP treatments, atmospheric pressure plasma jet (APPJ) coupled with Ar/O2 mixture, two-dimension dielectric barrier discharge (2D-DBD) coupled with Ar/O2 mixture, and nanosecond pulsed discharge (ns-pulsed) coupled with air, on the color, structure, functionality, and amino acid composition of PPI was evaluated. The effect of treatment time (5, 15, 30, and 45 min) was also determined. Structural characteristics and functional properties of PPI samples were determined following the same stated methods. The amino acid profile and non-protein components of the isolates were characterized using UPLC-MS. Pronounced structural and functional changes were observed upon treatment with reactive species at pH 2. All reactive species induced the formation of disulfide-linked soluble aggregates. Protein denaturation was observed after treatment with all reactive species. A significant increase in β-sheet content and surface hydrophobicity was only induced by treatment with O3 and OH, which resulted in the greatest enhancement in gelation and emulsification. While H2O2 enhanced PPI color by increasing whiteness, it had the least impact on protein structure and functionality. Results indicated that the plasma sources that can generate OH and O3 could be used for pea protein functionalization. Accordingly, different plasmas sources that can generate O3 and OH were further investigated in objective 2. All plasma treatments resulted in reduced yellow color of PPI, denaturation of the proteins, formation of disulfide-linked soluble aggregates, and increased surface hydrophobicity. The plasma-induced structural changes resulted in improvement of gel strength and emulsification capacity. The amino acid composition of PPI was not significantly impacted by 2D-DBD treatment, whereas a slight decrease in tyrosine content was observed after APPJ and ns-pulsed treatment. Results indicated that the 30-minute 2D-DBD (Ar + O2) treatment was the most desirable treatment because of moderate changes in protein structure coupled with significant improvement in the gelation and emulsification properties of PPI, with minimal impact on the amino acid composition. Overall, the study successfully demonstrated the link in structural changes induced by plasma reactive species (NxOy/O3, O3, H2O2, and OH) to improvement in functional properties. Results can be used to explain previously reported observations related to the impact of different CAP systems on the functional properties of proteins. Additionally, this work provided a detailed understanding of the potential of different CAP sources and associated reactive species in enhancing pea protein functionality.Item Mechanisms Of Texture And Flavor Formation In Meat Analogues Based On Pea Protein Isolate(2023-09) Tingle, ChristinaAs the global population continues to rise, we see a simultaneous increase in need for sustainable food sources. These can be found in plant proteins analogue. As consumers shift away from soy and gluten-containing protein sources, pea protein has emerged for a high-value, non-GMO, allergen-free, sustainable alternative. In an effort to convince habitual meat eaters to find substitutions in their diets, one attractive use for plant proteins is in high moisture meat analogues (HMMAs). There is much ongoing research into the textural properties of HMMAs, as well as into finding and optimizing novel plant protein sources that can produce a meaty texture. However, extracting protein from less-known sources produces quantities of protein too limited for use in even the smallest benchtop extruders. Developing a smaller-scale method is, therefore, of interest. This thesis delves into the intricate process of thermomechanical processing of plant proteins, with a particular focus on the development of high-moisture meat analogues (HMMAs).The study begins with an examination of micro compounding as an effective method for the thermomechanical processing of plant proteins. It highlights the challenges and solutions in loading hydrated protein concentrates into the micro compounder barrel, offering insights into the solubility and structural changes of pea protein isolate (PPI) post-processing. Ultimately, we offer a solution to the need for a small-scale extrusion device in the micro compounder. Transitioning to the realm of meat analogues, the research delves into their composition, underscoring the significance of organoleptic properties, and the current use of color and flavor additives. It underscores the paramount importance of color and flavor in determining consumer acceptance of these products. The research identifies the challenges in achieving meat-like color and flavor in HMMAs, especially given the natural color of most plant-based proteins. Through experimental setups and analyses, the study identifies volatile organic compounds (VOCs) that contribute to the aroma profile of cooked patties and explores the impact of grilling on the molecular structure of proteins. In conclusion, this thesis offers a holistic view of the thermomechanical processing of plant proteins, providing valuable insights for the future production of plant-based meat substitutes. The findings pave the way for enhancing the sensory attributes of HMMAs, making them more palatable and visually appealing to consumers.