Skip to main content
PMC home page
Preventive Nutrition and Food Science logoLink to Preventive Nutrition and Food Science
. 2022 Mar 31;27(1):14–19. doi: 10.3746/pnf.2022.27.1.14

Tannins in Foods: Nutritional Implications and Processing Effects of Hydrothermal Techniques on Underutilized Hard-to-Cook Legume Seeds–A Review

Moses Ayodele Ojo 1,✉
PMCID: PMC9007702  PMID: 35465118

Abstract

Tannins, water-soluble phenolic compounds, have been reported to have the ability to form complexes with nutritionally important nutrients such as protein and mineral elements thereby making them unavailable for absorption and utilization. Toxicity of tannin has been demonstrated in experimental animals although no deleterious effect of ingestion of legume tannin on human physiology has been reported. This report highlights the processing effects of soaking and hydrothermal techniques on some underutilised hard-to-cook legume crops and the importance of tannin in legume nutrition. Soaking and hydrothermal processing reduce the tannin content of processed legume seeds and hence improve the availability of protein and mineral elements. In view of the recent findings of the health benefits, classification of tannin which is traditionally regarded as an antinutrient should be reconsidered. Provision of these information will enhance knowledge of legume nutrition and economic utility. Increasing consumption of underutilized nutritionally important legume seeds, it is hoped, will alleviate the problem of protein energy malnutrition in many developing nations.

Keywords: hydrothermal techniques, legume seeds, nutritional implication, tannin

INTRODUCTION

In their natural form, tannins are water-soluble phenolic compounds with molecular weights in the range of 300 to 500 and have the ability to precipitate gelatin, alkaloids, and proteins (Mena et al., 2015). Tannins are secondary metabolites widely distributed in plants: they are polymeric phenolic substances with astringency properties (Agrawal et al., 2012; Lattanzio et al., 2012; Bone and Mills, 2013; Tamokou et al., 2017). Humans consume a number of foods containing considerable amounts of dietary tannins. Tannins are found in a huge variety of plants, including legume seeds, cider, cereals, cacao, peas, some leafy and green vegetables, coffee, tea, and nuts (Lochab et al., 2014; Suvanto et al., 2017; Fraga-Corral et al., 2020). In general, tannins can be classified into one of two classes on the basis of their structural features: hydrolyzable and condensed tannins (Hatew et al., 2016; Bee et al., 2017). In addition to other antinutritional components, such as phytic acid, hemagglutinin, saponin, goitrogen, and trypsin inhibitors, tannins are present in legume seeds at varying concentrations. These antinutritional components interfere with the digestive process and prevent the efficient utilization of nutrients (Luo and Xie, 2013; Sathya and Siddhuraju, 2015; Wu et al., 2016).

Legumes are the good source of nutritionally important nutrients such as mineral elements and dietary protein (Ojo et al., 2016; Ojo et al., 2017a; Ojo et al., 2018). Proteins from plants sources are preferable to animal sources because, unlike animal proteins, plant proteins are not usually associated with the occurrence of cardiovascular diseases. Legume seeds are good alternatives to animal protein. In recent years, there has been an increase in demand and consumption for plant protein, which has stimulated the search for more protein-rich plants (Adebowale et al., 2005; Ojo, 2015; Septiana and Analuddin, 2019). However, overdependence on common legumes has resulted in a sharp increase in prices (Ojo, 2015; Ojo et al., 2017a). Many legumes remain underutilized in South-West Nigeria, where they are planted mainly for subsistence purposes. Some of these underutilized legumes include Cajanus cajan, Cassia hirsuta, Canavalia ensiformis, Mallotus subulatus, Vigna racemosa, Sphenostylis sterocarpa, and Vigna subterranean. In many areas of the world, particularly in Africa, many underexploited legumes are regarded as security crops for fallow farmland in preparation for a new planning season (Nwosu, 2013; George et al., 2020). They are also cultivated as alternative food crops that are consumed during dry seasons, when other food crops are out of stock.

The phenomenon of prolonged cooking times and the presence of antinutritional components are prominent challenges facing the use of these underutilized legumes. The problem of prolonged cooking in legume seeds was reported to be alleviated by hydrothermal processing techniques (Ojo, 2018a). In this study, the nutritional implications of tannins in foods, as well as the effects of soaking at varying hydration levels followed by hydrothermal processing, are reported. Information on the effect of hydrothermal techniques on the tannin content of underutilized legume species before and after processing will enhance the current knowledge of legume processing and nutrition and foster economic utility.

HEALTH IMPLICATION OF TANNINS IN DIETS

Traditionally, tannins are considered to have antinutritional properties (Ojo, 2018b). However, recent evidence has shown that the consumption of tannins can have health benefits. The effects of tannin on human and animal biology vary considerably and depend on the composition of the diet and dietary patterns. Tannins have the ability to form complexes with carbohydrates, proteins, and certain mineral ions in foods (Kunyanga et al., 2011). The formation of such complexes depends on a requirement for suitable conditions such as pH, temperature, and concentration. Tannins have greater tendency to form complexes with proteins than carbohydrates and other food polymers because of the strong hydrogen bond affinity of the carboxyl oxygen of the peptide group. Complexes formed by tannins and proteins have been reported to be responsible for growth depression, low protein digestibility, decreased availability of amino acid, and increased fecal nitrogen (Waghorn, 2008; Woodward et al., 2009; Dijkstra et al., 2013; Grosse Brinkhaus et al., 2016).

Although the consumption of legume seeds has been reported to confer health benefits, a number of reports have described the harmful effects of tannic acid on the gastrointestinal tissues (Maphosa and Jideani, 2017; George et al., 2020). The toxicity of orally ingested tannins is relatively low: the rectal toxicity of tannic acid is approximately twice its oral toxicity (George et al., 2020; Hassan et al., 2020). The ingestion of tannic acid has been reported to cause hardening of the gastrointestinal mucosa, which results in a reduction in the gastrointestinal absorption of nutrients. Sorghum, which contains tannins, has been implicated in the occurrence of esophageal cancer (Wexler, 2014). It is important to consider that most of the toxicity studies of tannins in experimental animals are conducted using commercially available samples of tannins or tannic acid. There was no evidence of toxicity in sheep and cattle fed diets containing tannin (Wen et al., 2002). It is therefore extremely difficult to extrapolate if tannins in legume seeds used in feeds will have similar toxicities upon ingestion. There are conflicting reports. Recently, tannins have been reported to be useful in the control of zoonotic pathogens, such as Salmonella, in monogastric animals (Hassan et al., 2020). There have been contrasting reports about the relationship between condensed tannins and bioactivities in animals. It has been reported that condensed tannins from forage legumes fed to ruminants resulted in improved growth, milk production, and fertility, and reduced methane emissions and ammonia volatilization from the lung and the urine (Mueller-Harvey et al., 2019). Forage legumes containing condensed tannins have been reported to be beneficial in combating the effect of gastrointestinal parasitic nematodes (Hoste et al., 2012; Mueller-Harvey et al., 2019). Tannins bind excess plant proteins in ruminant, causing them to precipitate them out of the rumen and thus preventing the creation of the stable form that is characteristic of pasture bloat (MacAdam and Villalba, 2015).

Conversely, tannic acid used to be administered for the treatment of diarrhea and the dressing of skin burn. A precipitant of proteins affecting the colloidal stability of beer, tannic acid removes some metals (such as Al, Zn, Pb, and Fe) and some polyphenols when they are bound to proteins. Tannic acid has been reported to be effective against staling, flavor, and light instability (Wexler, 2014). It has been reported that tannins in Lotus corniculatus seeds bind excess plant proteins in the rumen of cattle and sheep, preventing bloating. Therefore, it can be included as 50% or more in the forage mixture without the risk of bloating. Moreover, tannins in L. corniculatus seeds have been reported to reduce the enteric methane production of dairy cows (Woodward et al., 2004). As a result of the low pH in the abomasum, tannins release proteins, which are then digested and absorbed in the small intestine (Wen et al., 2002; MacAdam and Villalba, 2015). In humans, no evidence of toxicity arising from the consumption of excessive amounts of legume tannins has ever been reported. Excess tannins may have been attributed to the increased incidence of tumorigenic diseases or carcinogenesis in some areas of the world; however, the minimum amount of tannins in the human diet that can cause physiological disorder is not known. There is a dearth of information on the effects of legume tannins on the incidence of carcinogenesis. The acetonic extract of some processed legumes, such as field bean and pigeon pea, have been reported to have antioxidant and antidiabetic properties (Kunyanga et al., 2011). Polyphenols, including tannins, have been reported to be some of the major antioxidants in our daily diets (Montes-Ávila et al., 2018). Legume tannins are astringent and decrease the palatability of forage, leading to low feed intake, poor nutrient digestibility, and poor production performance in livestock. The growth suppression and protein digestibility effects of bean tannin may be related to their astringent taste, which decreases feed consumption, and their ability to form stable and insoluble complexes with dietary proteins (Bone and Mills, 2013; Wang et al., 2015; Tamokou et al., 2017; Gutierrez and Torres, 2019). Moreover, tannic acid has non-food uses in the manufacture of rubber and inks, and as a fixative of dyes.

INFLUENCE OF SOAKING ON TANNIN CONTENT OF LEGUME SEEDS

The seeds of some underutilized hard-to-cook legumes were soaked in distilled water at various hydration levels (0, 10, 25, 50, 75, and 100%) for a period of 24 h at an ambient temperature of 23°C to 28°C (Ojo, 2015; Ojo et al., 2017a; Ojo et al., 2018). The changes in the concentrations of tannins in the seeds before and after soaking were determined (Table 1). For each of the legume seeds, there was a significant difference (P<0.05) in the concentration of tannins at the different hydration levels. The lowest percentage reduction in tannin content after soaking (0.61%) was observed for C. hirsuta at the 10% hydration level. For V. racemosa, percentage reduction of 3.21% was recorded at 10% hydration level while 15.53% was recorded for both 75% and 100% hydration levels. The raw sample of S. sterocarpa contained 39.88 mg/g tannin. This quantity was reduced by 4.11, 7.07, 13.87, and 14.29% when the seed was soaked at the 10, 25, 50, and 100% hydration levels, respectively. As presented in Table 1, the percentage reduction for other legumes was in the range of 3.81% to 14.52% for M. subulatus (white species), 0.61% to 8.73% for C. hirsuta, and 3.53% to 13.79% for C. ensiformis (Ojo et al., 2017a; Ojo et al., 2018; Ojo, 2018b). In a study on kidney beans, soaking, boiling, and pressure cooking yielded a significant decrease in tannin content (Khattab and Arntfield, 2009).

Table 1.

Concentration of tannins in legume seeds before and after soaking at various hydration levels (unit: mg/g)

Legume sample Hydration level
0 10 25 50 75 100
Mallotus subulatus 1 (white variety) 28.10±1.22f 27.03±0.10e 26.07±0.14d 25.32±0.21c 24.28±0.07b 24.02±0.11a
(3.81) (7.22) (9.89) (13.59) (14.52)
Cassia hirsuta 62.31±0.37f 61.93±0.51e 61.37±0.42d 60.17±0.22c 59.48±0.60b 56.87±0.50a
(0.61) (1.51) (3.43) (4.54) (8.73)
Canavalia ensiformis 27.47±0.44f 26.50±0.12e 26.37±0.21d 26.12±0.03c 24.70±0.10b 23.68±0.11a
(3.53) (4.00) (4.91) (10.08) (13.79)
Vigna subterranean 1 (mottled colored) 31.58±0.31f 30.20±0.13e 28.88±0.24d 26.72±0.17c 25.87±0.25b 25.41±0.10a
(4.36) (8.55) (15.39) (18.08) (19.54)
Vigna racemosa 28.97±0.32e 28.04±0.10d 27.16±0.02c 26.55±0.13b 24.47±0.24a 24.47±0.24a
(3.21) (6.25) (8.35) (15.53) (15.53)
Mallotus subulatus 2 (brown variety) 38.87±0.41f 36.42±0.21e 35.26±0.32d 34.87±0.24c 34.23±0.10b 33.08±0.12a
(6.30) (9.29) (10.29) (11.94) (14.89)
Vigna subterranean 2 (cream colored) 42.59±0.53e 40.08±0.12d 38.14±0.10c 37.52±0.30b 37.34±0.21a 37.34±0.21a
(5.89) (10.45) (11.90) (12.33) (12.33)
Sphenostylis sterocarpa 39.88±0.24e 38.24±0.21d 37.06±0.10c 34.35±0.22b 34.18±0.30a 34.18±0.20a
(4.11) (7.07) (13.87) (14.29) (14.29)
Open in a new tab

Values are presented as mean±SD (n=3) on dry basis and values in parentheses represent the percentage loss.

Different letters (a-f) in the same row indicate significant differences (P<0.05).

Data from the article of Ojo (2015), Ojo et al. (2017a), and Ojo et al. (2018).

The percentage reduction in tannin content of the legumes studied was similar to, but comparatively lower than, those of a previous report on Mucuna flagellipes, which ranged from 58.4% at 6 h of soaking to 74.9% at 24 h of soaking (Udensi et al., 2008). The smaller reduction might be due to varietal differences. The reduction in tannin content of some beans by soaking in different solutions has also been reported (Vijayakumari et al., 2007). Pinto beans with a high tannin content exhibited the greatest reduction in tannin content after soaking, whereas cranberry beans with low tannin content lost less tannins during soaking.

The reduction in the tannin content may be due to leaching of the polyphenols into the soaking water (Wu et al., 2016; Ojo et al., 2018). Tannins are polyphenols and polyphenolic compounds are mostly water-soluble in nature and mostly located in the seed coat. Therefore, it can be inferred that a pre-processing method, such as soaking, can be used to reduce the level of some water-soluble/leachable antinutritional factors, such as tannins (Ojo et al., 2017a; Ojo et al., 2018; Ojo, 2018b).

IMPACT OF HYDROTHERMAL TECHNIQUES ON TANNIN CONTENT OF UNDERUTILIZED LEGUME SEEDS

Four hydrothermal techniques [atmospheric boiling (AB), atmospheric steaming (AS), pressure boiling (PB), and pressure steaming] were employed to process the seeds of some underutilized hard-to-cook legume seeds (Ojo, 2015; Ojo et al., 2017a; Ojo et al., 2018). The effects of hydrothermal processing techniques on the levels of tannins in the seeds are presented in Table 2. The hydrothermal techniques caused a reduction in the concentration of tannins in the legume seeds. All the hydrothermal processing methods (i.e., boiling and steaming at atmospheric pressure, as well as boiling and steaming at elevated pressure) had significant effects (P<0.05) at varying percentages on the level of tannins in the legume seeds.

Table 2.

Tannin content of legume seeds as influenced by hydrothermal processing techniques (unit: mg/g)

Legume sample Processing condition
Raw dried sample Atmospheric boiling Atmospheric steaming Pressure boiling Pressure steaming
Mallotus subulatus 1 (white variety) 28.10±0.22e 6.85±0.32a 7.84±0.40c 7.57±0.05b 8.15±0.13c
(75.62) (72.10) (73.06) (70.99)
Cassia hirsuta 62.31±0.37d 13.42±0.33a 15.38±0.32b 13.42±0.61a 16.67±0.80c
(78.46) (75.32) (78.46) (73.25)
Canavalia ensiformis 27.47±0.44d 9.70±0.41a 10.60±0.34c 10.03±0.20b 10.64±0.32c
(64.69) (61.41) (63.49) (61.27)
Vignasubterranean 1 (mottled colored) 31.58±0.31d 11.49±0.24a 12.82±0.31b 12.31±0.57b 13.19±0.60c
(63.62) (59.40) (61.02) (58.23)
Vigna racemosa 28.97±0.32c 9.02±0.13a 10.15±0.21b 9.38±0.34a 10.13±0.42c
(68.86) (64.96) (67.62) (65.03)
Mallotus subulatus 2 (brown variety) 38.87±0.41c 9.20±0.18a 10.74±0.52b 9.61±0.29a 10.77±0.61b
(76.33) (72.37) (75.28) (72.29)
Vigna subterranean 2 (cream colored) 42.59±0.53 14.57±0.57a 16.13±0.60b 15.20±0.70a 16.16±0.42b
(65.79) (62.13) (64.34) (62.06)
Sphenostylis sterocarpa 39.88±0.24d 10.07±0.15a 11.76±0.23b 11.01±0.40b 11.93±0.37c
(74.75) (70.51) (72.39) (70.09)
Open in a new tab

Values are the mean±standard deviation (n=3) on dry basis and values in parentheses represent the percentage loss.

Different letters (a-e) in the same row represent significant differences (P<0.05).

Data from the article of Ojo (2015), Ojo et al. (2017a), and Ojo et al. (2018).

The lowest value of tannins (6.85 mg/g) was recorded for the white variety of M. subulatus, which was boiled at normal atmospheric pressure, whereas the highest value (8.15 mg/g) was recorded after steaming at elevated pressure. The same percentage reduction, of 78.46%, was observed for C. hirsuta using conventional boiling and PB (Ojo et al., 2018). For C. ensiformis, the two processing methods, i.e., AB and AS, resulted in the reduction in tannins of 64.69% and 61.41%, respectively, whereas boiling and steaming at high pressure resulted in a reduction of 63.49% and 61.27%, respectively (Ojo et al., 2018). For the other legumes investigated, the mottled colored variety V. subterranean, V. racemosa, M. subulatus, cream-colored variety V. subterranean, and S. sterocarpa, there were similarities in the trend in tannin reduction when each of the four hydrothermal processing techniques was used (Ojo, 2015; Ojo et al., 2017a; Ojo et al., 2017b).

As recorded in Table 2, pressure processing, both boiling and steaming, resulted in relatively smaller losses of tannin than the atmospheric processing of boiling and steaming. This observation is true for all the legumes studied, except for C. hirsuta, in which the percentage loss of 78.46% was reported for both boiling processing methods (Ojo, 2018b). Pressure processing causes relatively lower losses because of the shorter processing times. These results agree with the study of Xu and Chang (2009) on green pea, yellow pea, and chickpea. In 2016, Fabbri and Crosby also reported that cooking improved the digestibility of beans that contained high concentrations of antinutrients, including tannins. In another study on asparagus beans (Vigna sesquipedalis), the tannin content was reduced by 49% after boiling (Nzewi and Cemaluk, 2011). The tannin content of varieties of Phaseolus vulgaris in Tanzania was investigated after conventional cooking and the percentage of tannin reduction was in the range of 20% to 81% (Mamiro et al., 2017). Percentage reductions of 65.8, 65.8, 74.3, and 74.3% were recorded after regular boiling of M. flagellipes for 30, 45, 60, and 90 min, respectively (Udensi et al., 2008). Similarly, the thermal treatment of C. cajan seeds resulted in a 47.06% reduction in tannins (Iorgyer et al., 2009).

CONCLUSION

The processing of these underutilized legume seeds must be performed such that the tannins will be reduced to a safe level/concentration. Although there is no standardized safe limit for legume tannins, it is well established that tannins form complexes with nutritionally important compounds, such as proteins and some mineral elements, making them unavailable for absorption. Soaking and hydrothermal techniques reduce tannin concentrations in legume seeds and hence improve the bioavailability of protein and mineral elements. Although the toxicity of synthetic/commercially available tannins has been demonstrated in experimental animals, legume seed tannins have not been reported to cause any known toxicities or physiological disorders upon ingestion. Considering the recent evidence showing the health benefits, the classification of tannins that have been hitherto regarded as an antinutrient should be reconsidered. Therefore, the provision of information on the importance of tannins in legume nutrition is anticipated to foster economic utility, encourage cultivation, and prevent the imminent extinction of these lesser known legume food crops. Increasing the consumption of nutritionally important underutilized legume seeds will alleviate the problem of protein energy malnutrition in developing nations.

Footnotes

FUNDING

None.

AUTHOR DISCLOSURE STATEMENT

The author declares no conflicts of interest.

REFERENCES

  1. Adebowale YA, Adeyemi IA, Oshodi AA. Functional and physicochemical properties of flours of six Mucuna species. Afr J Biotechnol. 2005;4:1461–1468. [Google Scholar]
  2. Agrawal AA, Hastings AP, Johnson MT, Maron JL, Salminen JP. Insect herbivores drive real-time ecological and evolutionary change in plant populations. Science. 2012;338:113–116. doi: 10.1126/science.1225977. [DOI] [PubMed] [Google Scholar]
  3. Bee G, Silacci P, Ampuero-Kragten S, Čandek-Potokar M, Wealleans AL, Litten-Brown J, et al. Hydrolysable tannin-based diet rich in gallotannins has a minimal impact on pig performance but significantly reduces salivary and bulbourethral gland size. Animal. 2017;11:1617–1625. doi: 10.1017/S1751731116002597. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Bone K, Mills S. Principles of herbal pharmacology. In: Bone K, Mills S, editors. Principles and Practice of Phytotherapy: Modern Herbal Medicine. 2nd ed. Churchill Livingstone; Edinburgh, UK: 2013. pp. 45–55. [Google Scholar]
  5. Dijkstra J, Oenema O, van Groenigen JW, Spek JW, van Vuuren AM, Bannink A. Diet effects on urine composition of cattle and N2O emissions. Animal. 2013;7:292–302. doi: 10.1017/S1751731113000578. [DOI] [PubMed] [Google Scholar]
  6. Fabbri ADT, Crosby GA. A review of the impact of preparation and cooking on the nutritional quality of vegetables and legumes. Int J Gastron Food Sci. 2016;3:2–11. doi: 10.1016/j.ijgfs.2015.11.001. [DOI] [Google Scholar]
  7. Fraga-Corral M, García-Oliveira P, Pereira AG, Lourenço-Lopes C, Jimenez-Lopez C, Prieto MA, et al. Technological application of tannin-based extracts. Molecules. 2020;25:614. doi: 10.3390/molecules25030614. https://doi.org/10.3390/molecules25030614. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. George TT, Obilana AO, Oyeyinka SA. The prospects of African yam bean: past and future importance. Heliyon. 2020;6:e05458. doi: 10.1016/j.heliyon.2020.e05458. https://doi.org/10.1016/j.heliyon.2020.e05458. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Grosse Brinkhaus A, Bee G, Silacci P, Kreuzer M, Dohme-Meier F. Effect of exchanging Onobrychis viciifolia and Lotus corniculatus for Medicago sativa on ruminal fermentation and nitrogen turnover in dairy cows. J Dairy Sci. 2016;99:4384–4397. doi: 10.3168/jds.2015-9911. [DOI] [PubMed] [Google Scholar]
  10. Gutierrez N, Torres AM. Characterization and diagnostic marker for TTG1 regulating tannin and anthocyanin biosynthesis in faba bean. Sci Rep. 2019;9:16174. doi: 10.1038/s41598-019-52575-x. https://doi.org/10.1038/s41598-019-52575-x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Hassan ZM, Manyelo TG, Selaledi L, Mabelebele M. The effects of tannins in monogastric animals with special reference to alternative feed ingredients. Molecules. 2020;25:4680. doi: 10.3390/molecules25204680. https://doi.org/10.3390/molecules25204680. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Hatew B, Stringano E, Mueller-Harvey I, Hendriks WH, Carbonero CH, Smith LM, et al. Impact of variation in structure of condensed tannins from sainfoin (Onobrychis viciifolia) on in vitro ruminal methane production and fermentation characteristics. J Anim Physiol Anim Nutr. 2016;100:348–360. doi: 10.1111/jpn.12336. [DOI] [PubMed] [Google Scholar]
  13. Hoste H, Martinez-Ortiz-De-Montellano C, Manolaraki F, Brunet S, Ojeda-Robertos N, Fourquaux I, et al. Direct and indirect effects of bioactive tannin-rich tropical and temperate legumes against nematode infections. Vet Parasitol. 2012;186:18–27. doi: 10.1016/j.vetpar.2011.11.042. [DOI] [PubMed] [Google Scholar]
  14. Iorgyer MI, Adeka IA, Ikondo ND, Okoh JJ. The impact of boiling periods on the proximate composition and level of some anti-nutritional factors in pigeon pea (Cajanus cajan) seeds. PAT. 2009;5:92–102. [Google Scholar]
  15. Khattab RY, Arntfield SD. Khattab RY, Arntfield SD. Nutritional quality of legume seeds as affected by some physical treatments 2. Antinutritional factors. LWT-Food Sci Technol. 2009;42:1113–1118. doi: 10.1016/j.lwt.2009.02.004. [DOI] [Google Scholar]
  16. Kunyanga CN, Imungi JK, Okoth M, Momanyi C, Biesalski HK, Vadivel V. Antioxidant and antidiabetic properties of condensed tannins in acetonic extract of selected raw and processed indigenous food ingredients from Kenya. J Food Sci. 2011;76:C560–C567. doi: 10.1111/j.1750-3841.2011.02116.x. [DOI] [PubMed] [Google Scholar]
  17. Lattanzio V, Cardinali A, Linsalata V. Plant phenolics: a biochemical and physiological perspective. In: Cheynier V, Sarni-Manchado P, Quideau S, editors. Recent Advances in Polyphenol Research. Wiley-Blackwell; Chichester, UK: 2012. pp. 1–39. [DOI] [Google Scholar]
  18. Lochab B, Shukla S, Varma IK. Naturally occurring phenolic sources: monomers and polymers. RSC Adv. 2014;4:21712–21752. doi: 10.1039/C4RA00181H. [DOI] [Google Scholar]
  19. Luo Y, Xie W. Relative contribution of phytates, fibers and tannins to low iron in vitro solubility in faba bean (Vicia faba L.) flour and legume fractions. Br Food J. 2013;115:975–986. doi: 10.1108/BFJ-11-2010-0204. [DOI] [Google Scholar]
  20. MacAdam JW, Villalba JJ. Beneficial effects of temperate forage legumes that contain condensed tannins. Agriculture. 2015;5:475–491. doi: 10.3390/agriculture5030475. [DOI] [Google Scholar]
  21. Mamiro PS, Mwanri AW, Mongi RJ, Chivaghula TJ, Nyagaya M, Ntwenya J. Effect of cooking on tannin and phytate content in different bean (Phaseolus vulgaris) varieties grown in Tanzania. Afr J Biotechnol. 2017;16:1186–1191. doi: 10.5897/AJB2016.15657. [DOI] [Google Scholar]
  22. Maphosa Y, Jideani VA. The role of legumes in human nutrition. In: Hueda MC, editor. Functional Food–Improve Health through Adequate Food. IntechOpen; London, UK: 2017. pp. 116–124. [DOI] [Google Scholar]
  23. Mena P, Calani L, Bruni R, Del Rio D. Bioactivation of high-molecular-weight polyphenols by the gut microbiome. In: Tuohy K, Del Rio D, editors. Diet-Microbe Interactions in the Gut: Effects on Human Health and Disease. Academic Press; San Diego, CA, USA: 2015. pp. 73–101. [DOI] [Google Scholar]
  24. Montes-Ávila J, López-Angulo G, Delgado-Vargas F. Tannins in fruits and vegetables: chemistry and biological functions. In: Yahia EM, editor. Fruit and Vegetable Phytochemicals: Chemistry and Human Health. 2nd ed. John Wiley & Sons; Chichester, UK: 2018. pp. 221–268. [DOI] [Google Scholar]
  25. Mueller-Harvey I, Bee G, Dohme-Meier F, Hoste H, Karonen M, Kölliker R, et al. Benefits of condensed tannins in forage legumes fed to ruminants: importance of structure, concentration, and diet composition. Crop Sci. 2019;59:861–885. doi: 10.2135/cropsci2017.06.0369. [DOI] [Google Scholar]
  26. Nwosu JN. Evaluation of the proximate composition and antinutritional properties of African yam bean (Sphenostylis sternocarpa) using malting treatment. Int J Basic Appl Sci. 2013;2:159–169. [Google Scholar]
  27. Nzewi DC, Cemaluk EAC. Effect of boiling and roasting on some anti-nutrient factors of asparagus bean (Vigna sesquipedalis) flour. Afr J Food Sci Technol. 2011;2:75–78. [Google Scholar]
  28. Ojo MA, Ade-Omowaye BI, Ngoddy PO. Impact of hydrothermal techniques on the chemical components of Mallotus subulatus. Pak J Nutr. 2017a;16:813–825. doi: 10.3923/pjn.2017.813.825. [DOI] [Google Scholar]
  29. Ojo MA, Ade-Omowaye BI, Ngoddy PO. Influence of soaking and hydrothermal techniques on antinutritional components and in vitro multienzymes protein digestibility of Vigna racemosa–an underutilised hard-to-cook legume. Ann Food Sci Technol. 2017b;18:385–394. [Google Scholar]
  30. Ojo MA, Ade-Omowaye BI, Ngoddy PO. Mineral elements in Canavalia ensiformis: influence of hydrothermal processing techniques. Ann Food Sci Technol. 2016;17:548–555. [Google Scholar]
  31. Ojo MA, Ade-Omowaye BI, Ngoddy PO. Processing effects of soaking and hydrothermal methods on the components and in vitro protein digestibility of Canavalia ensiformis. Int Food Res J. 2018;25:720–729. [Google Scholar]
  32. Ojo MA. Alleviation of hard-to-cook phenomenon in legumes: effects of hydrothermal processing techniques on two species of Vigna subterranean. Am J Food Sci Technol. 2018a;6:103–107. [Google Scholar]
  33. Ojo MA. Changes in some antinutritional components and in vitro multienzymes protein digestibility during hydrothermal processing of Cassia hirsutta. Prev Nutr Food Sci. 2018b;23:152–159. doi: 10.3746/pnf.2018.23.2.152. [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Ojo MA. Effects of hydrothermal processing methods on nutrients, antinutritional components and protein digestibility of selected underutilised legumes in Nigeria. Dissertation. Ladoke Akintola University of Technology; Ogbomoso, Nigeria: 2015. [Google Scholar]
  35. Sathya A, Siddhuraju P. Effect of processing methods on compositional evaluation of underutilized legume, Parkia roxburghii G. Don (yongchak) seeds. J Food Sci Technol. 2015;52:6157–6169. doi: 10.1007/s13197-015-1732-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  36. Septiana A, Analuddin K. Evaluation of nutritional and antioxidant capacity of marine bean grown in coastal areas, Southeast Sulawesi, Indonesia. Pak J Nutr. 2019;18:271–277. doi: 10.3923/pjn.2019.271.277. [DOI] [Google Scholar]
  37. Suvanto J, Nohynek L, Seppänen-Laakso T, Rischer H, Salminen JP, Puupponen-Pimiä R. Variability in the production of tannins and other polyphenols in cell cultures of 12 Nordic plant species. Planta. 2017;246:227–241. doi: 10.1007/s00425-017-2686-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
  38. Tamokou JDD, Mbaveng AT, Kuete V. Antimicrobial activities of African medicinal spices and vegetables. In: Kuete V, editor. Medicinal Spices and Vegetables from Africa: Therapeutic Potential Against Metabolic, Inflammatory, Infectious and Systemic Diseases. Academic Press; San Diego, CA, USA: 2017. pp. 207–237. [DOI] [Google Scholar]
  39. Udensi EA, Arisa NU, Maduka M. Effects of processing methods on the levels of some antinutritional factors in Mucuna flagellipes. Niger Food J. 2008;26:53–59. doi: 10.4314/nifoj.v26i2.47437. [DOI] [Google Scholar]
  40. Vijayakumari K, Pugalenthi M, Vadivel V. Effect of soaking and hydrothermal processing methods on the levels of antinutrients and in vitro protein digestibility of Bauhinia purpurea L. seeds. Food Chem. 2007;103:968–975. doi: 10.1016/j.foodchem.2006.07.071. [DOI] [Google Scholar]
  41. Waghorn G. Beneficial and detrimental effects of dietary condensed tannins for sustainable sheep and goat production–progress and challenges. Anim Feed Sci Technol. 2008;147:116–139. doi: 10.1016/j.anifeedsci.2007.09.013. [DOI] [Google Scholar]
  42. Wang Y, McAllister TA, Acharya S. Condensed tannins in sainfoin: composition, concentration, and effects on nutritive and feeding value of sainfoin forage. Crop Sci. 2015;55:13–22. doi: 10.2135/cropsci2014.07.0489. [DOI] [Google Scholar]
  43. Wen L, Kallenbach RL, Williams JE, Roberts CA, Beuselinck PR, McGraw RK, et al. Performance of steers grazing rhizomatous and nonrhizomatous birdsfoot trefoil in pure stands and in tall fescue mixtures. J Anim Sci. 2002;80:1970–1976. doi: 10.2527/2002.8071970x. [DOI] [PubMed] [Google Scholar]
  44. Wexler P. Encyclopedia of toxicology. 3rd ed. Academic Press; San Diego, CA, USA: 2014. p. 157. [Google Scholar]
  45. Woodward SL, Waghorn GC, Laboyrie PG. Condensed tannins in birdsfoot trefoil (Lotus corniculatus) reduce methane emissions from dairy cows. NZSAP. 2004;64:160–164. [Google Scholar]
  46. Woodward SL, Waghorn GC, Watkins KA, Bryant MA. Feeding birdsfoot trefoil (Lotus corniculatus) reduces the environmental impacts of dairy farming. NZSAP. 2009;69:179–183. [Google Scholar]
  47. Wu G, Johnson SK, Bornman JF, Bennett SJ, Singh V, Simic A, et al. Effects of genotype and growth temperature on the contents of tannin, phytate and in vitro iron availability of sorghum grains. PLoS One. 2016;11:e0148712. doi: 10.1371/journal.pone.0148712. https://doi.org/10.1371/journal.pone.0148712. [DOI] [PMC free article] [PubMed] [Google Scholar]
  48. Xu B, Chang SK. Phytochemical profiles and health-promoting effects of cool-season food legumes as influenced by thermal processing. J Agric Food Chem. 2009;57:10718–10731. doi: 10.1021/jf902594m. [DOI] [PubMed] [Google Scholar]

Articles from Preventive Nutrition and Food Science are provided here courtesy of Korean Society of Food Science and Nutrition (KFN)

RESOURCES