The research, published in the reputable journal ACS Food Science & Technology, explores the biochemical composition and heat stability of proteins extracted from dried marigold flowers. By employing a series of sequential liquid extractions, scientists were able to isolate different groups of proteins from powdered marigold samples, allowing for comprehensive profiling of amino acid composition and physico-chemical properties. This methodical approach opens new doors to understanding how plant proteins beyond the usual legumes and grains can be harnessed for human consumption.

One of the striking findings from the study is the high concentration of umami-related amino acids such as glutamic acid and aspartic acid within certain marigold protein fractions. These amino acids are responsible for imparting savory flavors, which have significant applications in food formulation as natural flavor enhancers. Their presence suggests that marigold-derived proteins could add a desirable umami taste to a variety of plant-based products, offering food developers a novel ingredient that improves palatability without added chemical flavoring agents.

Heat stability is another critical factor in food protein functionality, particularly concerning processing techniques involving cooking and baking. Unlike many plant proteins extracted from pea or chickpea, which can denature at relatively low temperatures, the proteins isolated from pot marigold flowers demonstrated remarkable thermal resilience. They maintained structural integrity at temperatures as high as 105 degrees Celsius (221 degrees Fahrenheit), conditions that typically degrade other plant proteins. This robustness implies that marigold proteins can retain their nutritional and functional characteristics even after exposure to high heat, making them highly suitable for inclusion in thermally processed food products.

Another standout feature of the marigold proteins studied is their exceptional emulsifying capacity. Emulsification refers to a protein’s capability to stabilize mixtures of oil and water by reducing surface tension and preventing phase separation. Two distinct marigold protein extracts showed excellent performance in this area, which is a desirable trait for creating stable emulsions used in salad dressings, mayonnaise analogs, and dairy-free food substitutes. These findings position marigold proteins as promising functional ingredients for reformulating classic foods into plant-based versions with improved texture and shelf life.

Beyond tastiness and heat tolerance, the researchers observed that marigold proteins also possess effective hydration and antioxidant properties. Hydration capacity plays a vital role in food texture, influencing the mouthfeel and moisture retention of products like baked goods. Concurrently, antioxidant functionality suggests that marigold proteins could help inhibit oxidative spoilage and enhance the nutritional profile of foods by scavenging free radicals. Such multi-functional attributes amplify the potential of these proteins in creating not only sustainable but also health-promoting food formulations.

The valorization of agricultural byproducts is a growing trend in food science, driven by the need to reduce waste and promote circularity in food systems. Approximately 40% of pot marigold production is currently discarded post-ornamental use, a figure that demonstrates vast underutilization of a potentially valuable resource. This research highlights the critical opportunity to upcycle these otherwise wasted flowers into high-value protein ingredients, adding economic and environmental incentives to pursue their cultivation and processing.

Current knowledge about plant proteins largely centers on legumes, cereals, and oilseeds, but edible flowers and other horticultural commodities remain largely untapped. This study challenges conventional boundaries by characterizing flower proteins with rigorous biochemical analyses and functional assays, setting a precedent for further explorations into similar plant sources. The emphasis on detailed amino acid profiling and heat stability evaluation underscores the scientific rigor and practical relevance of this work in food innovation.

Looking ahead, the research team plans to expand their investigation to assess the health benefits of marigold proteins, including potential antioxidant activities and digestibility in human nutrition. Subsequent efforts will target product development, leveraging marigold proteins in baked goods and emulsion-based foods to evaluate sensory acceptance among consumers. This holistic approach from biochemical characterization to consumer testing ensures that the potential for marigold proteins moves beyond the lab towards real-world applications.

The implications of this work extend beyond mere protein sourcing, touching upon themes of sustainability, food security, and culinary innovation. As the global population grows and environmental concerns mount, tapping into overlooked agricultural waste streams aligns with broader goals to develop resilient and environmentally conscious food systems. Marigold proteins exemplify how such innovative pathways can be scientifically validated and technologically feasible.

Moreover, the study underscores the importance of interdisciplinary collaboration in addressing complex food challenges. By integrating agricultural science, protein chemistry, food technology, and sensory science, the research presents a model of how emerging food ingredients should be developed and evaluated comprehensively. This integrated methodology ultimately supports the transition towards more diverse, nutritious, and sustainable plant-based diets.

Anand Mohan, the corresponding author, aptly summarizes the societal importance of this research: it not only reveals the hidden potential of a common flower but also aligns with public interest in reducing food waste and diversifying protein sources. Such science-driven narratives resonate widely as consumers and industry stakeholders alike seek solutions that are scientifically sound, ethically responsible, and environmentally sustainable.

Scientific funding from the U.S. Department of Energy’s Office of Science supported the identification of marigold protein amino acid profiles, reflecting the critical role of public agencies in advancing food innovation. The publication of these findings in ACS Food Science & Technology ensures wide dissemination to both the academic community and food industry professionals poised to translate research insights into novel products.

In summary, the exploration of pot marigold flowers as a sustainable plant protein source epitomizes the convergence of food waste valorization, functional food ingredient development, and plant-based nutrition innovation. With promising heat stability, umami enhancement potential, emulsifying properties, and health-related functionalities, marigold proteins hold remarkable promise for next-generation food applications that are tasty, nutritious, and environmentally responsible.

Subject of Research: Protein content and functional properties of pot marigold flowers (Calendula officinalis) as a sustainable source of plant-based protein.

Article Title: Marigold flowers show potential as a source of plant-based protein

News Publication Date: 29-Apr-2026

Web References:
10.1021/acsfoodscitech.5c01215

Keywords: Plant proteins, protein functionality, marigold flowers, Calendula officinalis, sustainable food ingredients, heat stability, emulsification, umami amino acids, antioxidant properties, food waste valorization

The significance of this research lies in its innovative use of CO₂ as a processing aid in texturizing plant proteins—a method poised to revolutionize the field. Unlike conventional mechanical or chemical modification techniques, the controlled application of high-pressure CO₂ provides a unique mechanism to induce structural changes in proteins, enhancing their water retention, gelation behavior, and fibrous texture. These qualities are paramount in mimicking the mouthfeel and bite of animal-derived meat, which have long posed challenges for plant-based alternatives. This approach offers a cleaner, potentially more cost-effective, and environmentally friendly solution that aligns with rising consumer demand for both sustainable and delicious food options.

At the core of the study is isolated pea protein, a rapidly advancing meat alternative base known for its favorable amino acid profile, hypoallergenic nature, and broad availability. Despite its advantages, pea protein often suffers from a gritty texture and suboptimal binding capacity, which impede its ability to convincingly replicate meat. The researchers hypothesized that CO₂ injection under controlled pressure could disrupt pea protein aggregates, facilitating a rearrangement in molecular interactions that culminates in improved physicochemical properties. This concept hinges on leveraging the solubilizing and acidifying effects of dissolved CO₂, which can modulate protein charge and thus influence network formation during protein structuring processes.

Experimentally, the study employed a range of CO₂ injection pressures, meticulously calibrated to ascertain their effect on key quality indicators, including protein solubility, water holding capacity, gel strength, and overall texture profile analysis. The utilization of advanced rheological measurements and microscopic imaging technologies allowed for an unprecedented visualization of protein matrix transformations. The results demonstrated a clear correlation: increasing CO₂ pressure up to an optimal point enhanced protein unfolding and facilitated stronger intermolecular bonding, which translated into a more cohesive and fibrous meat analog structure. Exceeding this optimal pressure, however, led to detrimental protein degradation, highlighting the critical importance of process precision.

An equally compelling aspect of this research is its environmental implication. As the food sector grapples with climate change concerns and ethical demands, producing meat analogs with reduced resource input and minimal chemical additives is imperative. The use of CO₂—a greenhouse gas that is already captured and repurposed in various industrial applications—introduces a sustainable angle to protein texturization. By utilizing CO₂ in this manner, the process not only leverages its physicochemical properties but also potentially contributes to carbon circularity initiatives, making pea protein-based meat analogs even more attractive from an ecological perspective.

Moreover, the detailed evaluation of textural enhancements affirms that CO₂ treatment imparts a juicier and tender bite to the pea protein matrix, addressing one of the critical sensory shortcomings faced by plant-based meat developers. Sensory panel feedback indicated noticeable improvements in chewiness and mouthfeel, bringing the product closer to consumer expectations rooted in traditional meat experience. These advances hint at the possibility of tailoring meat analog texture profiles through specific CO₂ injection parameters, thus allowing manufacturers to customize products for diverse culinary applications—ranging from burgers to nuggets and beyond.

Further exploration into the chemical modifications induced by CO₂ injection revealed a shift towards enhanced protein-protein cross-linking and a more ordered secondary structure, as evidenced by spectroscopic analyses. This level of structural refinement is crucial for achieving the textural robustness demanded by consumers. Additionally, the process was found to preserve the nutritional integrity of the pea protein, a vital consideration as meat analogs strive to not only emulate sensory qualities but also meet or exceed nutritional standards intrinsic to animal proteins.

The technical sophistication introduced by integrating CO₂ under pressure also carries significant implications for scalability. The method lends itself to integration with existing extrusion and protein structuring technologies commonly used in the plant-based food industry. By optimizing key operational parameters such as pressure, temperature, and protein concentration, producers could feasibly scale this process without substantial capital investment. This scalability could accelerate market entry of next-generation meat analogs that offer improved texture and nutritional profiles at competitive price points, making plant-based diets more accessible worldwide.

Critically, the study underscores the delicate balance between process conditions and protein functionality. It offers a valuable framework for future research aimed at fine-tuning gas injection interventions to achieve desired product characteristics. This approach can potentially be extended beyond pea protein to other legume- or grain-based proteins, broadening the impact across various plant substrates. Such versatility enhances the prospects for diversifying meat analog offerings and responding dynamically to fluctuating raw material availability or consumer preferences.

From a molecular perspective, the controlled acidification through CO₂ dissolution was found to modify electrostatic interactions within the protein matrix, facilitating superior water binding and gel network formation. These phenomena are instrumental in replicating the succulent, juicy experience of animal meat. Understanding these biochemical mechanisms equips food scientists with powerful tools for rational design of plant-based meat textures, enhancing product innovation and differentiation in an increasingly crowded marketplace.

Consumer interest in plant-based meats continues to surge, driven by environmental, ethical, and health motivations. However, overcoming textural deficits remains paramount to widespread adoption. This research addresses this challenge head-on with tangible, science-backed solutions that promise to elevate pea protein’s functional capabilities. As the food industry pivots toward sustainability, breakthroughs such as these not only support market growth but also fortify public confidence in plant-derived proteins as viable, enjoyable alternatives.

Looking ahead, the application of CO₂ injection pressure technology could catalyze next waves of innovation in meat analog development, complementing genetic, enzymatic, and formulation advances. Collaborative efforts between academia and industry could refine these findings further, enabling the production of meat substitutes that rival or surpass conventional meat in consumer sensory tests. Such progress aligns perfectly with global sustainability goals, offering a pathway for reducing reliance on animal agriculture while satisfying escalating protein demands.

Ultimately, this study illustrates how interdisciplinary research catalyzes transformative changes in food science. Leveraging a common yet powerful molecule like CO₂ in novel ways enhances the physicochemical and sensory landscape of plant-based proteins, advancing the quest for sustainable nutrition. As these findings reverberate through research labs and food production lines alike, one can envision a near future where pea protein-based meat analogs are no longer merely alternatives but preferred staples in kitchens worldwide, embodying a fusion of technology, sustainability, and culinary excellence.

This breakthrough represents not just a technical milestone but a beacon of possibility within the evolving narrative of global food security. Increasingly sophisticated manipulation of plant proteins promises to dissolve barriers between traditional and alternative proteins, enriching diets while safeguarding planetary health. The utilization of CO₂ injection pressure to enhance pea protein’s textural and physicochemical properties thus heralds a new chapter in sustainable food innovation—one poised to satisfy palates and preserve ecosystems alike.

Against this backdrop, the study calls for renewed investments in research infrastructures and cross-sector partnerships to fully harness the potential of gas-assisted protein texturization. By integrating insights from material science, food chemistry, and sensory science, the food industry is primed to deliver meat analogs that do not compromise on taste or texture. This convergence of science and technology exemplifies the paradigm shift underway in protein production—ushering in an era where plant-based meats can convincingly compete with traditional animal products and contribute meaningfully to a sustainable food future.

Subject of Research: The effects of CO₂ injection pressure on the physicochemical and textural properties of isolated pea protein-based meat analogs.

Article Title: Effects of CO₂ injection pressure on physicochemical and textural properties of isolated pea protein-based meat analog.

Article References:
Zhang, Y., Ryu, G.H. & Gu, B.J. Effects of CO₂ injection pressure on physicochemical and textural properties of isolated pea protein-based meat analog. Food Sci Biotechnol (2026). https://doi.org/10.1007/s10068-026-02101-3

Image Credits: AI Generated

DOI: 01 February 2026

As global consumers increasingly pivot towards meat alternatives, driven by environmental concerns, health awareness, and ethical considerations, demand for products that genuinely mimic the texture, flavor, and mouthfeel of traditional meat is surging. TVP, a well-established plant protein ingredient derived predominantly from soy, has emerged as a cornerstone in crafting meat analogues due to its fibrous structure and protein content. However, the inherent complexity of replicating meat’s multifaceted organoleptic profile requires sophisticated formulation strategies, a challenge this new research boldly addresses.

The study employed a mixture experimental design—a statistical approach uniquely suited for optimizing the proportions of complex ingredient blends. This method allows researchers to systematically vary component ratios and evaluate their combined effects on product attributes without resorting to exhaustive trial-and-error. By harnessing this design, the team meticulously explored varying ratios of TVP with complementary binders, flavor enhancers, and texture modifiers, seeking an optimal balancing point that harmonizes all key quality parameters.

Central to the endeavor was the performance of the resultant sausage in terms of texture, juiciness, firmness, and flavor release—attributes that collectively shape consumer satisfaction. The researchers evaluated a series of formulations, analyzing how subtle shifts in the mixture composition influenced these properties through instrumental texture analysis and sensory evaluation panels. This dual approach ensured that both objective measurements and subjective consumer perceptions informed the optimization.

Findings revealed that specific ratios of TVP combined with a strategic blend of hydrocolloids and plant-based fats dramatically improved the bite and cohesiveness of the sausages, closing the gap with conventional meat products. The incorporation of tailored binders not only enhanced water retention and juiciness but also stabilized the structure, preventing common issues of crumbliness often observed in plant-based substitutes. Flavor delivery was markedly improved through the introduction of natural umami-rich ingredients, which complemented the inherent nutty notes of soy protein.

Beyond texture and flavor, nutritional profiles were also significantly impacted by the optimized mixture. The ideal blends featured enhanced protein density while maintaining low fat and carbohydrate contents, aligning well with contemporary consumer demands for healthier yet indulgent food options. This demonstrates that functional formulation can simultaneously address sensory appeal and nutritional integrity—a dual imperative in food science.

Perhaps equally noteworthy is the study’s contribution to process scalability and industrial applicability. By elucidating precise mixing ratios, the research offers manufacturers a scientifically validated blueprint to streamline production, minimize ingredient waste, and ensure consistent product quality. This translates into potential cost savings, greater market competitiveness, and expanded consumer accessibility for plant-based sausage options.

The research team underscores that such optimization frameworks extend beyond sausages to other protein-rich alternative foods, highlighting a versatile methodology capable of accelerating innovation across the plant-based sector. The utilization of mixture experimental designs constitutes a sophisticated toolset that can unravel the complex interplay of multi-component food systems, shedding light on innovative ingredient synergies previously unexplored.

Industry experts predict that studies like this will catalyze a new wave of next-generation meat analogues that not only cater to vegetarian and vegan consumers but also entice flexitarians seeking flavorful, nutritious, and environmentally responsible choices. The refinement of texture and taste profiles to near-parity with animal-derived products represents a critical milestone in mainstreaming alternative proteins.

Moreover, this research taps into the growing trend of hybrid product formulations—where plant proteins combine with minimal animal derivatives or novel functional ingredients to deliver cost-effective, sustainable, yet highly palatable solutions. Optimization of mixing ratios becomes indispensable in fine-tuning such complex matrices, enabling bespoke customization according to regional preferences, market trends, or nutritional guidelines.

While the study primarily focuses on soy-based TVP, the underlying principles hold promise for integration with emerging protein sources such as pea, lentil, or mycoprotein. This adaptability can drive diversification of plant-based portfolios, reduce allergen concerns, and foster innovation that resonates with wider demographics.

This work also opens avenues for incorporating functional additives that may extend shelf life, improve textural stability under varying storage conditions, or enhance micronutrient profiles. By understanding how each component interacts within optimized formulations, formulators can engineer multifunctional, high-performance products meeting the demands of a dynamic food ecosystem.

In summary, this pioneering research delivers not only a rigorously validated optimized mix for TVP-based sausages but also advances the methodological paradigm in product development. Through precise manipulation of mixture components guided by experimental design, the study elevates plant-based meat alternatives closer than ever to their animal-based counterparts, promising a tastier, healthier, and more sustainable future for protein consumption worldwide.

As consumer appetite for alternative meats intensifies, scientific breakthroughs such as these will underpin the industry’s ability to innovate responsibly and competitively. The convergence of food technology, sensory science, and nutritional optimization showcased here exemplifies the frontier of food innovation—where data-driven craftsmanship creates the next culinary revolution.

Continued interdisciplinary collaborations and investment in such research hold the key to unlocking the full potential of plant proteins, ultimately contributing to more sustainable food systems and global food security. The transformative impact of optimized TVP mixtures is thus not merely incremental but foundational, heralding a new era in meat analogue excellence.

Subject of Research: Optimization of mixing ratios for TVP-based plant protein sausages using mixture experimental design to enhance sensory qualities and nutritional value.

Article Title: Optimization of mixing ratio for a TVP-based alternative sausage using mixture experimental design

Article References:
Song, H.Y., Jeong, D.H., Jung, Y.J. et al. Optimization of mixing ratio for a TVP-based alternative sausage using mixture experimental design. Food Sci Biotechnol (2025). https://doi.org/10.1007/s10068-025-02077-6

Image Credits: AI Generated

DOI: 10.1007/s10068-025-02077-6 (Published 11 December 2025)

Pea protein hydrolysates are derived from the enzymatic or chemical breakdown of proteins found in peas, resulting in a complex mixture of small peptides and free amino acids. These hydrolysates are gaining momentum in the food industry due to their favorable digestibility, balanced amino acid profiles, and capacity to promote feelings of fullness. Yet, their prominent bitter flavor often limits widespread usage and consumer enthusiasm, a problem that nutrition scientists and food technologists have grappled with for years. The current study pivots on addressing this challenge—whether the bitterness that contributes to satiety could be diminished without compromising the health-promoting effects of these protein derivatives.

The research, spearheaded by doctoral candidate Katrin Gradl under the guidance of principal investigator Prof. Dr. Veronika Somoza, acknowledges a critical paradox: bitter peptides in the stomach can stimulate satiety via activation of bitter taste receptors (TAS2Rs), yet the unpleasant flavor they impart undermines palatability. Intriguingly, the team’s prior studies examining milk protein hydrolysates suggested that some bitter peptides don’t necessarily have to be present in the initial food product. Instead, these bioactive fragments can be generated dynamically during digestion within the gastric environment by the action of gastric fluids. This insight fueled their hypothesis that similar processes might occur with pea protein hydrolysates, allowing less bitter formulations to maintain or even enhance satiety signaling post-ingestion.

To explore this, the researchers simulated gastric digestion in vitro using artificial gastric fluid and subjected both more bitter and less bitter variants of pea protein hydrolysates to digestive conditions mimicking the human stomach. This carefully controlled experimentation was paired with advanced analytical techniques, including mass spectrometry and computational peptide profiling, to identify the spectrum of peptides produced after digestion. Their goal was to discover whether newly formed peptides in less bitter hydrolysates could activate the molecular pathways responsible for satiety as effectively as those found in more bitter counterparts.

The results were both unexpected and enlightening. In each digestion product, three distinct bitter peptides were detected, totaling six key peptides that shared bioactivity in stimulating gastric acid secretion and serotonin release in cultured human parietal stomach cells. Remarkably, peptides originating from the less bitter hydrolysate exhibited even stronger stimulation of serotonin release—a central hormone regulating appetite and satiety than previously anticipated. These findings suggest that bitterness in the original product is not the sole determinant of the final satiety-inducing effect. Instead, digestion-generated peptides may potentiate the physiological response, thereby dissociating taste intensity from functional efficacy.

The study further uncovered that the satiety signals were mediated through specific bitter taste receptors located on stomach parietal cells, particularly TAS2R4 and TAS2R43. These receptors, part of the extensive family of G-protein coupled bitter taste receptors, traditionally recognized for their role in taste perception on the tongue, are now understood to have extraoral functions including the regulation of gastrointestinal hormone release. Activation of these receptors by bitter peptides triggers secretion of gastric acid and serotonin, both integral to the complex cascade signaling the brain to reduce hunger and delay gastric emptying, thus promoting satiety.

Understanding that less bitter hydrolysates can exert substantial satiating effects via these digestion-derived peptides is a breakthrough for the field of protein research and plant-based nutrition. It suggests that the food industry can formulate protein hydrolysate-containing products that achieve consumer acceptability through milder taste profiles without sacrificing appetite control benefits. This advance holds promise for developing plant-based foods that marry health, sustainability, and sensory pleasure—a critical trifecta in moving diets towards more environmentally friendly options that also support obesity management.

Nonetheless, the authors emphasize that these molecular and cellular findings, while promising, require further substantiation through clinical trials involving human subjects. Only rigorously designed in vivo studies can confirm the extent to which these in-vitro satiety mechanisms translate into measurable effects on food intake, appetite regulation, and weight control in real-world dietary settings. Human metabolism and behavior are influenced by myriad additional factors, and thus dedicated research is essential before definitive nutritional recommendations can be made based on these observations.

The implications of the study resonate beyond the scope of food chemistry and physiology; they underscore the growing importance of plant proteins as sustainable, health-supporting nutritional ingredients. Plant-based proteins have a substantially lower environmental footprint compared to animal-derived proteins, requiring drastically less land, water, and energy. Integrating bioactive peptides that modulate satiety into plant-based food products could therefore contribute significantly to public health efforts addressing obesity—a global epidemic closely linked to serious comorbidities such as type 2 diabetes and certain cancers.

By dissecting the molecular interactions between bitter peptides and gastric receptors, this research also enriches the broader understanding of gut-brain communication pathways and the complex role of taste receptors beyond their conventional sensory functions. The recognition that gastrointestinal bitter taste receptors detect and respond to diet-derived peptides adds a nuanced layer to how we conceptualize appetite signaling networks and their modulation by dietary components. It opens fresh prospects for targeted interventions that optimize nutrient sensing and hormonal responses to promote healthier eating behaviors.

Serotonin, a pivotal neurochemical in appetite regulation, emerges as a key player in this research. The majority of serotonin in the human body is synthesized and stored in cells of the gastrointestinal mucosa, where it acts locally to influence gastric motility, secretion, and signaling to the central nervous system. Stimulating its release through specific peptide interactions with bitter taste receptors highlights a functional mechanism by which dietary proteins can influence the physiology of satiety and fullness.

Conclusively, this pioneering study by the Leibniz Institute for Food Systems Biology exemplifies how innovative cross-disciplinary approaches—melding food chemistry, cell biology, and computational analysis—can unravel sophisticated biological effects of food components. It encourages a paradigm shift in how protein hydrolysates are developed and utilized, prioritizing not only their nutritional benefits but also their sensory characteristics and molecular bioactivity. Such comprehensive investigations are vital as the global community seeks sustainable solutions to nutrition-related health challenges.

Future research inspired by these findings is expected to map the precise peptide sequences involved, explore their receptor binding dynamics in greater detail, and assess the potential for formulating bespoke protein hydrolysates tuned to optimize satiety signaling. This could herald a new era of smart, plant-based functional foods calibrated at the molecular level to target appetite regulation and metabolic health—a timely advance in the face of escalating dietary and environmental concerns.

Subject of Research: Cells

Article Title: Bitter peptides formed during in-vitro gastric digestion induce mechanisms of gastric acid secretion and release satiating serotonin via bitter taste receptors TAS2R4 and TAS2R43 in human parietal cells in culture.

News Publication Date: 1-Apr-2025

References:
Gradl, K., Richter, P., and Somoza, V. (2025). Bitter peptides formed during in-vitro gastric digestion induce mechanisms of gastric acid secretion and release satiating serotonin via bitter taste receptors TAS2R4 and TAS2R43 in human parietal cells in culture. Food Chem 482, 144174. 10.1016/j.foodchem.2025.144174.

Image Credits: Photo by Joseph Krpelan / Leibniz-LSB@TUM

Keywords: Pea protein hydrolysates, bitter peptides, satiety, gastric acid secretion, serotonin release, bitter taste receptors TAS2R4, TAS2R43, gastric digestion, plant-based protein, functional food, obesity management, in vitro digestion