Open Access Article
Si
Qin
a,
Sunantha
Ketnawa
b and
Nattaya
Konsue
*bc
aCollege of Food Science and Technology, Hunan Agricultural University, Changsha 410128, China
bFood Science and Technology Program, School of Agro-Industry, Mae Fah Luang University, Muang, Chiang Rai 57100, Thailand. E-mail: nattaya.kon@mfu.ac.th
cResearch Center of Innovative Food Packaging and Biomaterials, Mae Fah Luang University, Muang, Chiang Rai 57100, Thailand
First published on 24th September 2025
This study investigated the impact of boiling and in vitro gastrointestinal digestion on the nutritional properties of seven commercially available mushroom species: Volvariella volvacea, Lentinus polychrous, Lentinus squarrosulus, Pleurotus ostreatus, Astraeus odoratus, Lentinula edodes, and Auricularia auricula-judae. Boiling altered the mushroom microstructure, enhancing the release of nutrients and bioactive compounds. It increased crude protein (5–35%), amino acids (3–75%), minerals (3–30%), and phenolic compounds (1–2-fold), though the effects varied by species. A. odoratus showed the highest crude protein content (37.30%), while A. auricula-judae demonstrated the highest nutrient bioaccessibility during digestion. V. volvacea exhibited the greatest amino acid content (74.50 mg g−1). Simulated digestion further improved amino acid and phenolic availability. L. edodes and A. auricula-judae exhibited the highest phenolic bioaccessibility, likely due to lower dietary fiber. Boiling increased the total phenolic and flavonoid content in A. odoratus, suggesting the presence of heat-resistant polyphenols, but led to reductions in other species due to leaching. Antioxidant activity, assessed by DPPH and FRAP assays, increased after digestion across all species. Boiling enhanced antioxidant activity in A. odoratus and A. auricula-judae, likely due to stable compounds such as β-glucans and ergothioneine. Correlation analysis identified total phenolic content as the primary contributor to antioxidant potential, while flavonoid effects varied. These findings underscore the role of mushrooms as sustainable, nutrient-rich foods. Their efficient growth on low-input substrates and improved functionality through processing support their use in plant-based diets, meat analogues, and nutritional supplements for sustainable food system innovation.
Sustainability spotlightThis investigation promotes sustainable food systems by improving the bioaccessibility and nutritional value of edible mushrooms, which are fast-growing, low-impact crops that are cultivated on agro-waste. The work promotes the development of eco-efficient, plant-based protein alternatives by illustrating enhanced protein, amino acid, and mineral content through straightforward thermal processing. By fostering resource-efficient food innovation that reduces dependence on animal-derived proteins and mitigates environmental impact, these findings directly contribute to the United Nations sustainable development goals, particularly goal 2 (zero hunger), goal 12 (responsible consumption and production), and goal 13 (climate action). This research emphasizes the significance of mushrooms in the provision of sustainable, scalable nutrition to a burgeoning global population. |
Beyond their nutritional value, mushrooms are environmentally efficient to cultivate. They require minimal land, grow rapidly, and thrive on agricultural or industrial waste substrates, reducing food system waste and resource use. Compared to animal-based proteins, mushroom production generates significantly lower greenhouse gas emissions and conserves water and energy, making it an attractive option for sustainable protein development.1,2 As global interest in reducing reliance on meat intensifies, mushrooms are gaining recognition as functional, scalable alternatives in meat analogues, nutritional supplements, and health-focused foods.
Ng and Rosman7 found that in vitro digestion, when combined with domestic cooking (boiling, steaming, microwaving, and pressure-cooking), enhanced total antioxidant activity and carbohydrate-digestive enzyme inhibitory potential in various mushrooms, including L. edodes and Pleurotus sajor-caju. Similarly, Soler-Rivas et al.8 demonstrated that while water-soluble antioxidants in Agaricus bisporus, L. edodes, and Boletus edulis were impacted by cooking, intestinal digestion increased their antioxidant capacity, and the Caco-2 cell model confirmed partial absorption and transformation of those antioxidants. More recently, Zeng et al.9 evaluated six cooking methods on L. edodes, showing that boiling and steaming reduced some nutrients, yet roasting improved amino acid bioaccessibility during simulated digestion, and cooking methods influenced antioxidant retention. While these studies offer valuable insights, comparative evaluations across multiple species, particularly those relevant to Southeast Asia, remain limited. Moreover, most existing work has focused on antioxidant metrics and enzyme inhibition; comprehensive analyses of protein quality, mineral bioaccessibility, microstructure, and other nutritional parameters across digestion remain rare.
In real-world contexts, mushrooms are consumed as food rather than medicine. Thus, understanding how cooking methods like boiling, combined with gastrointestinal digestion, affect their nutritional and functional properties is essential for optimizing their role in sustainable diets—without overstating therapeutic potential.
Boiling is one of the most widely used culinary and industrial processing methods for mushrooms. It can result in the loss of water-soluble nutrients through leaching and heat degradation, but it may also improve the release and bioaccessibility of certain nutrients and bioactives by disrupting the mushroom's cell wall and softening the matrix.3 These effects are highly species-specific and can either enhance or reduce the final nutritional quality.
One important factor that determines the nutritional impact is bioaccessibility, which is the fraction of nutrients that are liberated from the food matrix and may be absorbed after digestion.6 Evaluating only nutrient content before and after cooking does not capture the complete picture. In particular, protein quality and digestibility can vary considerably with species and processing conditions, affecting the role of mushrooms as a viable, sustainable protein source in plant-based food development.
This study examined the effects of boiling and simulated gastrointestinal digestion on seven commercially cultivated mushroom species in Thailand: Volvariella volvacea, Lentinus polychrous, Lentinus squarrosulus, Pleurotus ostreatus, Astraeus odoratus, Lentinula edodes, and Auricularia auricula-judae. Nutritional parameters (crude protein, amino acids, and minerals), bioactive compounds (total phenolic and flavonoid content), antioxidant activities (DPPH and FRAP), and microstructural changes were analyzed before and after digestion. By highlighting species-specific differences in nutrient retention and bioavailability, the findings support the strategic use of mushrooms as nutrient-rich, environmentally sustainable components in next-generation plant-based foods.
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10.10 Boiled samples were drained, cooled down, and pat-dried using a kitchen paper towel. After that, the boiled samples were packed in LDPE plastic zip-lock bags and labeled as ‘boiled’.
Both raw and boiled mushroom samples were collected before and after in vitro gastrointestinal digestion and immediately frozen at −40 °C overnight. The samples were then freeze-dried using a laboratory lyophilizer (CHRIST, Osterode am Harz, Germany) set to a condenser temperature of −80 °C and a vacuum pressure of 0.1 mbar until completely dried. All freeze-dried samples were vacuum-sealed in polyethylene bags, stored at −40 °C, and labeled as “lyophilized” for subsequent protein content and microstructure analyses.
![]() | (1) |
P 0 = protein content of the sample before digestion.
P 1 = protein content of the sample after digestion.
The estimation of bioaccessibility (%) of total amino acid content and total mineral content in raw and boiled mushroom samples was calculated using the following formula:12
![]() | (2) |
:
1
:
1 (v/v) ratio. A 0.4 mL sample aliquot was added to 2.6 mL of the FRAP reagent and incubated at 37 °C for 30 minutes. The content was mixed, transferred to a 96-well plate, and absorbance was measured at 595 nm using a microplate reader (Thermo Fisher Scientific, Multiskan GO, Finland). Ferrous sulfate (FeSO4) was used as the standard, and distilled water served as the blank. The ferric reducing antioxidant power was expressed as micromoles of FeSO4 equivalent per gram of dried sample.
The intestinal phase was then initiated by adding 23 mL of intestinal enzyme solution, which consisted of 0.184 g pancreatin from porcine pancreas, 0.0138 g invertase and 3.68 mL amyloglucosidase in intestinal fluid buffer. Samples were collected at 0, 30, 60, 90, and 120 minutes for both the gastric and intestinal stages. All samples were centrifuged at 10
000×g for 5 minutes, and the supernatant aliquots were collected for further analysis.
Additional mushroom samples were collected before and after in vitro gastrointestinal digestion, frozen at −40 °C overnight and subsequently freeze-dried using a laboratory lyophilizer as previously described. The freeze-dried samples were stored in an electronically controlled humidity cabinet until further analysis, including scanning electron microscopy (SEM), protein quantification, and calculation of protein digestibility.
Raw V. volvacea exhibited a relatively porous and hyphal network (Fig. 2A), which appeared disrupted after digestion. Boiling reduced structural coherence, and digestion of the boiled sample resulted in near-complete collapse of the visible microstructure. Similar trends were observed in L. polychrous and L. squarrosulus (Fig. 2B and C), where raw samples retained mycelial networks, but digestion led to deformation. In L. squarrosulus, more apparent surface voids appeared after digestion, while boiling further deteriorated the structure, likely due to polysaccharide solubilization and hyphal shrinkage. P. ostreatus showed a fibrous, porous structure in raw form (Fig. 2D). Digestion led to denser aggregation, while boiling elongated hyphae. Post-digestion of the boiled sample caused structural collapse. A. odoratus displayed compact, low-porosity morphology (Fig. 2E), which became more disrupted after digestion. Boiling produced a denser but disorganized structure, and digestion of the boiled sample caused further disintegration. In L. edodes, a sponge-like, porous matrix was evident (Fig. 2F). Digestion caused hyphal disorganization, while boiling led to partial shrinkage and coarser surface textures post-digestion. A. auricula-judae exhibited a smooth, flattened surface (Fig. 2G) with limited porosity in raw form. Digestion appeared to increase visible structural discontinuities, while boiling induced a fibrous structure that fragmented post-digestion.
While these micrographs suggest the presence of altered structural patterns such as fragmentation, hyphal disorganization, and apparent voids, we acknowledge that these are qualitative observations. Quantitative analysis (e.g., porosity measurements or image-based morphometry) was not performed, and thus claims regarding porosity enhancement are interpreted with caution.
Nonetheless, these findings align with prior studies reporting microstructural damage from boiling, such as cell wall rupture and polysaccharide solubilization.18,19 Further enzymatic degradation during digestion may contribute to hyphal fragmentation and network disassembly, consistent with previous reports.19,20 The presence of visibly altered structures—particularly in species like L. squarrosulus, A. odoratus, and A. auricula-judae—may reflect carbohydrate content and fiber swelling, although these interpretations require further validation using objective structural metrics in future work.20,21
Boiling significantly reduced the crude protein content in all seven studied mushroom species, with losses ranging from 5% to 35%, as shown in Fig. 3a. The smallest reduction was observed in A. odoratus (5.44%), while the greatest was recorded in V. volvacea (34.72%). This decline may be attributed to the solubilization and leaching of nitrogenous compounds and minerals during the boiling process.27 A comparable trend was noted by Nie et al., who reported a 9.3% reduction in protein content for L. edodes which lower than the 14.89% observed in our study.18
The effect of boiling on crude protein content was relatively modest in A. odoratus and L. edodes (both <15%). In the case of A. odoratus, this could be attributed to its high total dietary fiber and glucan content (77.1 g/100 g DM and 26.1 g/100 g DM, respectively), which may help preserve protein during cooking by forming a rigid cell matrix.25 Additionally, L. edodes is known to have a high proportion (approximately 90%) of water-insoluble proteins, which are less susceptible to loss during boiling.28 Since boiling mainly affects water-soluble proteins, peptides, and amino acids, most of the protein content in L. edodes remained intact.
Boiling led to a reduction in total mineral content ranging from 3% to 30%. The smallest loss was observed in Lentinula edodes, while Lentinus squarrosulus experienced the greatest decrease. After boiling, the ranking of total mineral content (mg g−1 DM) among the species was as follows: Volvariella volvacea (14.33) > Pleurotus ostreatus (12.96) > L. edodes (10.26) > L. squarrosulus (9.96) > Lentinus polychrous (6.21) > Astraeus odoratus (3.54) > Auricularia auricula-judae (2.32). In addition to the overall reduction in mineral content, significant losses were recorded in individual macro- and trace elements, including potassium, magnesium, calcium, manganese, iron, zinc, copper, and selenium. These findings suggest that boiling promotes the leaching of minerals into the cooking water, as detailed in SI Table S5. This trend is consistent with the findings of Lee et al. (2019), who investigated the effects of boiling on L. edodes.30 Their study reported notable decreases in potassium, magnesium, and phosphorus following boiling.
The observed reduction in both protein and mineral content following boiling is primarily attributed to the diffusion of minerals into the cooking water.31 This finding aligns with the previous work of R. Puupponen-Pimiä et al.,32 who reported that mineral losses during cooking are due to leaching rather than degradation. Interestingly, while boiling reduces mineral content, it can also improve the nutritional quality of mushrooms by lowering levels of antinutritional factors. Traditional cooking methods, such as boiling, are known to reduce compounds like phytic acid, polyphenols, and certain fibers that bind minerals and limit their bioavailability.33 Therefore, although boiling causes some mineral loss, it may enhance the overall bioavailability of remaining minerals by decreasing the impact of antinutrients and breaking down structural barriers within the mushroom matrix.
The results of this study broadly align with previous findings, although reported amino acid values vary considerably depending on mushroom species, cultivation conditions, substrate composition, and analytical methodology on amino acid quantification. For instance, total amino acid contents have ranged from 4.4 mg g−1 in L. polychrous to over 100 mg g−1 in species such as P. ostreatus and L. edodes.26,34 Amino acids contribute significantly to the nutritional quality and characteristic flavor profiles of mushrooms.2 These results highlight V. volvacea and P. ostreatus as particularly rich sources of amino acids, underscoring their potential as valuable dietary protein supplements. Moreover, the species-specific differences in amino acid composition may inform their selection for use in functional food products or targeted nutritional applications.
Boiling significantly reduced total amino acid content across all species, with losses ranging from approximately 3% to 75% (Fig. 3c, Tables S3 and S4). The smallest reduction was observed in A. odoratus, while V. volvacea experienced the greatest loss. After boiling, the ranking of total amino acid content changed to: L. edodes (28.08) > L. polychrous (22.94) > V. volvacea (17.68) > P. ostreatus (15.37) > A. odoratus (14.33) > L. squarrosulus (10.99) > A. auricula-judae (2.43), as shown in Fig. 3c. The observed reduction in amino acid content is consistent with prior studies demonstrating that heat treatment can compromise the protein structure and reduce amino acid retention. For instance, it has been reported that free amino acids in L. edodes significantly (p < 0.05) decreased by 58.60% (from 5.03 to 2.09 mg g−1) following boiling.18 In comparison, our study noted a 25% reduction in total amino acids for the same species (from 37.85 to 28.08 mg g−1 DM). This decline is largely attributed to the high water solubility of free amino acids, which are readily leached into the cooking water during boiling. Consequently, the consumption of mushroom broth may help recover some of the lost amino acid content and enhance dietary intake.18
| Mushroom samples | Treatment | Estimated in vitro digestibility (%) | Estimated in vitro bioaccessibility (%) | |||||
|---|---|---|---|---|---|---|---|---|
| Total crude protein | Total mineral content | Total amino acid content | Total phenolic content (TPC) | Total flavonoid content (TFC) | DPPH radical scavenging activity (DPPH) | Ferric reducing antioxidant power (FRAP) | ||
| a Values represent the mean and standard deviation (n = 3). Values of estimated in vitro digestibility and estimated in vitro bioaccessibility (%) were obtained from eqn (1) and (2). Small letters indicate significant differences between samples within the same treatment (p < 0.05). | ||||||||
| V. volvacea | Raw | 24.27 ± 1.46c | 25.71 ± 0.21e | 106.47 ± 5.80d | 342.72 ± 17.26b | 110.99 ± 5.14c | 129.81 ± 2.24c | 193.13 ± 10.12b |
| Boiled | 32.85 ± 1.01d | 29.03 ± 0.53cd | 350.11 ± 15.98b | 997.51 ± 51.53bc | 116.79 ± 0.20b | 133.87 ± 0.51b | 341.70 ± 6.64a | |
| L. polychrous Berk | Raw | 38.10 ± 1.44b | 58.65 ± 0.92bc | 149.51 ± 3.63d | 446.00 ± 22.26b | 62.51 ± 1.06e | 142.60 ± 0.21b | 150.37 ± 2.49bc |
| Boiled | 43.22 ± 3.01bc | 29.77 ± 2.54cd | 193.02 ± 7.58d | 1206.77 ± 56.86bc | 91.67 ± 6.48c | 141.09 ± 3.54ab | 157.20 ± 12.53c | |
| L. squarrosulus | Raw | 40.83 ± 1.17b | 38.56 ± 0.50d | 190.71 ± 13.39cd | 494.21 ± 45.91b | 72.22 ± 2.35e | 135.13 ± 3.82bc | 140.35 ± 2.35c |
| Boiled | 44.22 ± 0.52bc | 21.08 ± 1.48d | 365.78 ± 17.19b | 1189.59 ± 222.92bc | 90.51 ± 3.00c | 143.37 ± 5.25a | 127.32 ± 10.84d | |
| P. ostreatus | Raw | 37.93 ± 0.49b | 37.58 ± 0.57d | 137.73 ± 9.34d | 600.20 ± 37.92b | 133.56 ± 0.18b | 154.64 ± 3.69a | 157.04 ± 6.55bc |
| Boiled | 38.22 ± 1.84cd | 23.76 ± 0.40cd | 232.15 ± 6.18 cd | 1518.24 ± 176.11b | 66.97 ± 3.86d | 149.55 ± 0.36a | 174.54 ± 7.68 bc | |
| A. odoratus | Raw | 39.70 ± 1.87b | 62.71 ± 0.73b | 355.82 ± 29.39b | 410.80 ± 58.42b | 114.20 ± 15.95c | 128.72 ± 5.45c | 182.14 ± 4.83bc |
| Boiled | 55.31 ± 1.27a | 54.41 ± 1.45b | 264.68 ± 4.44c | 436.27 ± 32.16c | 117.57 ± 7.92b | 144.07 ± 2.77a | 200.26 ± 12.60b | |
| L. edodes | Raw | 39.07 ± 0.02b | 51.29 ± 0.20c | 314.21 ± 32.80bc | 1139.36 ± 201.62a | 169.01 ± 1.45a | 158.58 ± 6.49a | 318.03 ± 43.55a |
| Boiled | 39.87 ± 0.88c | 32.35 ± 0.50c | 130.83 ± 3.37e | 1406.20 ± 74.70bc | 71.05 ± 2.36d | 148.99 ± 3.80a | 186.12 ± 15.59bc | |
| A. auricula-judae | Raw | 50.71 ± 1.17a | 99.89 ± 6.62a | 1483.09 ± 97.88a | 1451.48 ± 378.26a | 94.18 ± 5.18d | 156.53 ± 7.04a | 160.83 ± 19.60bc |
| Boiled | 49.68 ± 2.22ab | 110.40 ± 6.63a | 1002.74 ± 19.45a | 3520.55 ± 1140.72a | 136.75 ± 15.36a | 143.52 ± 5.84a | 173.61 ± 18.70bc | |
Protein digestibility is significantly influenced by the structural complexity of proteins and the accessibility of peptide bonds for enzymatic hydrolysis. Proteins embedded within complex matrices, such as polysaccharides, are less accessible to digestive enzymes, leading to reduced digestibility.37 For instance,20L. squarrosulus exhibited a protein content of 30.84%, which decreased to 11.91% after simulated intestinal digestion, corresponding to a hydrolysis rate of 59.79%. In contrast, our study found lower digestibility in raw L. squarrosulus (40.82%), which increased to 58.78% upon boiling. This suggests that the structural matrix of the mushroom may hinder enzymatic access to proteins, thereby affecting digestibility.38
The presence of polysaccharides such as β-glucans in mushroom cell walls can hinder protein digestion by increasing gastrointestinal viscosity and forming glycoprotein complexes that resist enzymatic breakdown.38 These interactions reduce protein bioavailability. Additionally, the degree of hydrolysis and type of protease used are key factors; endopeptidases, for instance, enhance digestibility by producing smaller, absorbable peptides.39 Protease treatment, as shown in Pleurotus eryngii, improves digestibility by increasing amino acid release.38 Overall, protein digestibility in mushrooms is shaped by structural complexity and polysaccharide interactions, emphasizing the need for targeted processing strategies to improve bioavailability.
These variations highlight the complex interplay between mushroom cell wall composition, the presence of antinutritional factors, and mineral bioaccessibility. Polysaccharides, such as β-glucans and chitin, prevalent in mushroom cell walls, can form complexes with minerals, reducing their solubility and hindering enzymatic breakdown during digestion.38 Additionally, compounds like phytic acid, oxalic acid, and tannins can bind minerals, further decreasing their bioavailability.33
Processing methods, including boiling, can influence the release of minerals from these complexes. For instance, boiling may facilitate the leaching of minerals into the cooking water, as observed in some species, while others may retain minerals more effectively. Understanding these dynamics is crucial for optimizing the nutritional value of mushrooms through appropriate culinary practices. In summary, the bioaccessibility of minerals in mushrooms is influenced by their intrinsic cellular structures and the presence of antinutritional factors. Species-specific responses to processing methods underscore the need for tailored approaches to enhance the nutritional benefits of edible mushrooms.
Proteolytic enzymes during digestion convert proteins into smaller peptides and free amino acids, making them more bioavailable.19 However, raw V. volvacea and P. ostreatus extracts exhibited notable reductions in total amino acids after digestion, whereas other mushroom species showed an increase. This discrepancy may be explained by the high mineral content of V. volvacea and P. ostreatus, which likely facilitates peptide-mineral complex formation during in vitro digestion. As proteins are hydrolyzed into amino acids and peptides, some exhibit strong metal-binding properties, particularly with iron, leading to reduced free amino acid levels but improved mineral bioavailability. The nitrogen of the ε-amino group from lysine and the imidazole group from histidine play a crucial role in chelation, while proline residues contribute to peptide folding, although they do not participate directly in metal complexation.40
Notably, the percentage bioaccessibility of total amino acids during in vitro digestion was higher in boiled mushrooms than in raw mushrooms, except for A. auricula-judae. Boiling mushrooms for 10 minutes generally enhanced amino acid bioaccessibility during in vitro digestion, despite a reduction in total amino acid content. This suggests that boiling facilitates the release and absorption of amino acids by denaturing proteins and increasing protease accessibility. However, excessive boiling can lead to nutrient loss and reduced digestibility due to protein aggregation and oxidation. For instance, studies on A. bisporus and L. edodes have shown that boiling can decrease free amino acid content, but the bioaccessibility of amino acids in the digestive tract may still improve due to better protein breakdown and solubility.
Conversely, A. odoratus exhibited the highest TPC after boiling, suggesting that its polyphenols may be more heat-resistant compared to other species. In addition, boiling may enhance the release and bioaccessibility of phenolic compounds in this species. Conversely, boiling generally reduced TPC in other mushroom species, likely due to the leaching of water-soluble phenols into the cooking water, a process that can significantly decrease antioxidant activity.42 In contrast, boiling V. volvacea resulted in a significant reduction in TPC, but in vitro digestion led to an overall increase in TPC, suggesting that digestive processes can enhance the bioaccessibility of phenolic compounds even after thermal degradation.
In this study, raw and boiled V. volvacea exhibited the highest total flavonoid content (TFC) both before and after in vitro digestion. Notably, boiling significantly increased TFC in A. odoratus, suggesting that boiling can enhance flavonoid release during digestion. Conversely, boiling led to a reduction in TFC in P. ostreatus, with the lowest TFC observed post-digestion. This variability underscores the influence of cooking methods on flavonoid stability and bioaccessibility.
Flavonoids are water-soluble and heat-sensitive, making them susceptible to degradation during cooking and digestion. In this study, boiling resulted in a significant decrease in TFC across various mushroom species, consistent with previous findings that attributed such reductions to the breakdown of mushroom tissue during heating, facilitating the release of these compounds from the food matrix.10 However, some studies suggest that certain cooking methods, such as steaming and microwaving, can enhance flavonoid content by increasing the extractability of these compounds from the cell matrix.36
The observed differences in TFC among mushroom species and cooking methods highlight the complex interplay between thermal processing and flavonoid stability. While boiling generally reduces TFC, it may also enhance the release of bound flavonoids during digestion, potentially increasing their bioaccessibility. Therefore, the impact of cooking on flavonoid content and bioaccessibility is multifaceted, depending on the specific mushroom species and cooking techniques employed.
Among the raw mushroom samples, L. squarrosulus and L. edodes showed the highest initial DPPH scavenging activity (211.66 and 207.96 mM TE/100 g DM, respectively; p < 0.05), with no significant difference between them. All raw mushrooms demonstrated increased DPPH activity following digestion. In contrast, A. odoratus exhibited the lowest initial activity (115.29 mM TE/100 g DM).
Boiling significantly enhanced DPPH activity in A. odoratus and A. auricula-judae, suggesting their antioxidant compounds—such as β-glucans, amino acids, and ergothioneine—are heat-resistant and likely extend beyond phenolics.42 Conversely, boiling reduced DPPH activity in other species, which could be due to processing depending on surface area exposure and cooking time.
FRAP values also increased after digestion across all raw mushrooms. However, A. auricula-judae, despite high DPPH activity, showed the lowest FRAP value (8.26 mM FeSO4/100 g DM). Post-digestion, the highest FRAP values were recorded in V. volvacea and L. edodes (34.5 and 32.11 mM FeSO4/100 g DM, respectively). Boiling reduced FRAP in all mushrooms; however, boiled A. odoratus initially had the highest FRAP value. During digestion, boiled V. volvacea showed a notable increase in FRAP. Flavonoid-related metal-chelation may also influence FRAP activity. This depends on the flavonoid structure, metal ion type, and pH.43 Since pH varies across the digestive tract, the stability and bioavailability of flavonoid–metal complexes may shift during digestion.
It is important to note that the TPC, TFC, DPPH, and FRAP values in this study were based on water extracts, which may not fully reflect the total antioxidant content. Some mushrooms may require alternative solvents—such as ethanol, diethyl ether, or mixed solvents—for more efficient extraction. Nevertheless, this study prioritized water-based extraction to better simulate real-life consumption conditions. Consequently, while the bioavailability of phenolic compounds may increase, the overall antioxidant capacity of the vegetable diminishes due to the loss of these compounds into the cooking medium.
TPC showed strong correlation with DPPH (R2 = 0.814–0.962) and moderate to strong correlation with FRAP (R2 = 0.668–0.987) across species. TFC also correlated with antioxidant activity in some species, such as V. volvacea, P. ostreatus, and L. edodes. These results suggest that phenolics are major contributors to antioxidant capacity. Notably, A. auricula-judae showed no DPPH-FRAP correlation, possibly due to assay differences and solvent effects.
Interestingly, L. squarrosulus had a negative correlation between TFC and antioxidant activity, despite strong TPC-TFC correlation, indicating that non-flavonoid phenolics—like gallic acid—may dominate antioxidant effects. L. polychrous had the highest TFC, while A. odoratus showed no significant TFC-antioxidant link, likely due to low TFC (Fig. 4). Overall, these findings support TPC as the primary antioxidant contributor in mushrooms.10,44,45
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