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. 2012 Jul 29;51(10):2608–2615. doi: 10.1007/s13197-012-0787-8

Effect of fermentation on antinutrients, and total and extractable minerals of high and low phytate corn genotypes

Awad M Sokrab 1, Isam A Mohamed Ahmed 2,3, Elfadil E Babiker 4,✉
PMCID: PMC4190255  PMID: 25328202

Abstract

Two corn genotypes, Var-113 (high phytate) and TL-98B-6225-9×TL617 (low phytate) were fermented for 14 days. The fermented flour was dried and milled. Phytic acid and polyphenols contents and hydrochloric acid (HCl) extractability of minerals from the fermented flours were determined at intervals of 2 days during fermentation period. Phytic acid and polyphenols decreased significantly (P ≤ 0.05) with an increase in fermentation period, with a concomitant increase in HCl extractable minerals. For both genotypes the major and trace minerals content was increased with fermentation period. When the grains flour was fermented for 14 days, TL-98B-6225-9×TL617 genotype had higher extractable calcium (94.73 %) while Var-113 had higher extractable phosphorus (76.55 %), whereas iron recorded high extractability levels (84.93 %) in TL-98B-6225-9×TL617 and manganese recorded high extractability levels (81.07 %) in Var-113. There was good correlation between phytate and polyphenols levels reduction and the increment in extractable minerals with fermentation period.

Keywords: Corn, Genotype, Fermentation, Antinutrients, Minerals, HCl-extractability

Introduction

The increment in maize production resulted from additional land area planted, genetic improvement and more efficient technological field practices as well as from the introduction of new more highly productive varieties. Most of the production in the developing countries is for human consumption while that in the developed world it is mainly for industrial use and animal feed (FAO 1992). It is well established that the majority of the people in the developing countries depend mainly on cereal grains as their staple food due to limited income and the high prices of animal foods. A comparison of available data for wheat, corn and rice puts corn as the second most important cereal grain after wheat and before rice in terms of yield per hectare (FAO 1992). Because of the great importance of maize as a basic staple food for large population groups, particularly in developing countries, and its low nutritional value, mainly with respect to protein, many efforts have been made to improve the biological utilization of the nutrients it contains.

Maize in Sudan is usually consumed after processing such as cooking to prepare thick porridge (asida), or thin one (nasha) and muttala, a fermented maize bread, 20 cm thick and hard crusts on the top and on the bottom surfaces. In between the two crusts the bread is very white and has a spongy texture (Dirar 1993).

Like other cereals, the nutritive value of corn is inadequate due to its deficiency in essential amino acids (lysine and tryptophan), and the presence of antinutritional factors such as phytate, tannins and polyphenols (Fageer et al. 2004). These antinutritional factors chelate dietary minerals in the gastrointestinal tract reducing their bioacessibility and bioavailability as reported for millet (AbdelRahaman et al. 2007), sorghum (Idris et al. 2005) and corn (Sokrab et al. 2011). Minerals are involved in activation of intracellular and extracellular enzymes, in regulation of critical pH level in body fluids necessary for control of metabolic reactions and in osmotic balance between the cell and the environment. A deficiency of any one of the essential minerals can result in severe metabolic disorders and compromise the health of the body. The presence of phytate in the human diet has a negative effect on mineral uptake. Minerals of concern in this regard include zinc, iron, calcium, magnesium, manganese and copper (Konietzny and Greiner 2003). More than 60 % of the phosphorus in corn meal is in the form of phytate phosphorus, which is poorly available for absorption and utilization in the gastrointestinal tract. The inhibitory effect of phytate on trace mineral absorption can also be predicted in vitro by the molar ratio of phytate to such mineral. Domestic processing techniques have been found to reduce significantly the levels of phytates and tannins by exogenous and endogenous enzymes formed during processing. Reductions of such antinutritional factors by processing methods such as gamma irradiation, dehulling, soaking, sprouting, cooking, malting and fermentation have been documented by many researchers (Abdelhaleem et al. 2008; Bains et al. 2011; Ertas and Turker 2012; Gupta and Nagar 2012; Idris et al. 2005; Obizoba and Atii 1994; Osman et al. 2012) and still progressing. It has been reported that germination of various pearl millet cultivars increased significantly the HCl-extractable parts of both major and trace minerals, and also reduced significantly (P ≤ 0.01) the phytic acid and polyphenols contents of millet cultivars (AbdelRahaman et al. 2007). In Sudan, research into mineral content and extractability in corn as an important food has not been fully documented. Therefore, in this study we would like to evaluate the effect of fermentation on the antinutritional factor content and hydrochloric acid (HCl) extractability of minerals in high and low phytate corn genotypes.

Material and methods

Materials

Two corn genotypes Var-113 (high phytate) and TL98B-6225-9×TL617 (low phytate) were obtained from the Department of Agronomy, University of Khartoum. The samples were carefully cleaned and freed from foreign materials and part of the grains was ground to pass a 0.4-mm screen and kept in polyethylene bags at 4 °C for further analysis. All chemical used in this study were commercially available and of reagent grade.

Fermentation process

Corn flour of the genotypes was fermented according to the traditional method (lactic acid fermentation) practiced by the Sudanese housewives (El Tinay et al. 1985). Initially, however, a natural fermentation was performed by the original microorganisms present in the corn flour. Approximately, 95 g flour was mixed with 200 ml of sterile deionized water and then 5 g starter obtained from previously fermented dough were added and mixed well with a glass rod. The slurry was allowed to ferment at 30 °C (temperature used in a traditional Sudanese kitchen) for 14 h. Samples were withdrawn at zero time and at 2 h intervals throughout the fermentation period. The pH was measured after each withdrawal of sample using a pH meter (model 315i, WTW, Weilheim, Germany). Then samples were dried in a hot air oven (Heraeus UT 5042, Germany) at 60 °C for 16 h. Dried samples were ground in a mortar and pestle to pass through 0.4 mm screen and stored at 4 °C in tightly closed containers until used for determination of phytic acid, polyphenols and HCl extractability of minerals.

Phytic acid determination

Phytic acid content of the samples was determined by the method described by Wheeler and Ferrel (1971). Briefly, 2 g of corn flour was extracted with 50 ml of 3 % trichloroacetic acid (TCA) for 3 h with shaking and precipitated as the ferric salt. The iron content of the precipitate was determined colorimetrically (Hach DR3 spectrophotometer, Loveland, Colorado, USA). The phytate content calculated from this value assuming a constant 4 Fe: 6 P molecular ratio in the precipitate. The iron content in the unknown samples was read from the previously prepared standard curve (different solution of ferric nitrate having varied concentration of Fe+++). Phytic acid content was determined by multiplying the phytate phosphorus content by a constant factor of 3.55.

Polyphenols determination

Total polyphenols were determined according to the Prussian blue spectrophotometric method (Price and Butler 1977) with a minor modification. Sixty milligrams of ground sample were shaken manually for 1 min in 3 ml methanol. The mixture was filtered. The filtrate was mixed with 50 ml distilled water and analyzed within 1 h. About 3 ml of 0.1 M FeCl3 in 0.1 M HCl was added to 1 ml filtrate, followed immediately by timed addition of 3 ml freshly prepared K3Fe(CN)6. The absorbance was monitored on a spectrophotometer (Pye Unicam SP6-550 UV, London, UK) at 720 nm after 10 min from the addition of 3 ml of 0.1 M FeCl3 and 3 ml of 0.008 M K3Fe(CN)6. A standard curve was obtained, expressing the result as tannic acid equivalents; that is, the amount of tannic acid (mg/100 g) that gives a color intensity equivalent to that given by polyphenols after correction for blank.

Minerals composition

Minerals were determined from the samples by the dry ashing method that described by Chapman and Pratt (1982). Briefly, 2 g of corn flour were weighed in dry crucible and placed in a muffle furnace for 3 h at 550 °C. After cooling, samples were transferred to 250 ml beaker and then 12 ml of 5 N HCl and 3 ml of concentrated HNO3 were added. The beaker was placed in a sand bath to boil for 10 min. Thereafter, 100 ml distilled water were added and allowed to boil for another 10 min. The contents were filtered through Whatman ashless filter paper No. 41. The filtrate was made up to 250 ml with double-distilled water and was used for determination of total minerals. Calcium was determined by a titration method. Phosphorus was determined spectrophotometerically by using molybdovanadate method. All other minerals were determined by atomic absorption spectrophotometer (Perkin–Elmer 2380, Norwalk, Connecticut, USA).

HCl extractability of minerals (in vitro bioavailability)

Minerals in the samples were extracted by the method described by Chauhan and Mahjan (1988). About 1 g of the sample was shaken with 10 ml of 0.03 M HCl for 3 h at 37 °C and then filtered. The clear extract obtained was oven-dried at 100 °C and then acid-digested. The amount of the extractable minerals was determined by the methods described above. HCl extractability of minerals (%) was determined as follows:

graphic file with name M1.gif

Statistical analysis

Three separate batches, for a particular treatment, were taken and analyzed separately and the results were then averaged. Data were assessed by analysis of variance (ANOVA) (Snedecor and Cochran 1987) and by Duncan’s multiple range test with a probability P ≤ 0.05 using SAS/STAT software.

Results and discussion

Effect of fermentation on antinutritional factors content and phytate/phosphorus ratio of corn genotypes

Table 1 shows the effect of fermentation on antinutritional factors content and phytate/phosphorus ratio of corn genotypes. Phytate content of untreated genotypes was 1047.00 and 87.16 mg/100 g for Var-113 and TL-98B-6225-9×TL617, respectively while polyphenols content was 460.50 and 363.70 mg/100 g for the genotypes, respectively. Variations in phytate and polyphenols contents between the two genotypes can be attributed to both genetic and environmental conditions. The value of phytate for Var-113 was much higher than those reported for white and yellow corn (Marfo et al. 1990) but much lower than that of TL-98B-6225-9×TL617. Khan et al. (1991) reported very high levels (715–760 mg/100 g) of phytate for maize products when compared with that of genotype TL-98B-6225-9×TL617 genotype but much lower than that of Var-113 genotype. Deshmukh et al. (1995) reported phytate phosphorus content ranging from 132 to 234 mg/100 g of maize varieties. Compared to TL-98B-6225-9×TL617 genotype (14.47 %), Var-113 had low protein content (11.70 %) but higher value of phytate. It has been reported that appreciably high amount of protein was observed to be associated with phytate content and it was found that as the protein content increased, phytate levels also increased (Reddy and Pierson 1994). This observation is a departure from an otherwise good correlation between protein content and phytate level. The explanation for this deviation is not clear, but may lie in chemical (as well as quantitative) differences between the protein and phytate of the genotypes. As shown in Table 1 the ratio of phytic acid/total phosphorus for corn genotypes was 11.34 and 0.49 with an average value of 5.91. AbdelRahaman et al. (2007) stated that phytic acid represents more than 70 % of total phosphorus in pearl millet. Results obtained in this study showed a linear relation between phytic acid and total phosphorus. Raboy et al. (1991) concluded that, in various seeds, phytic acid positively correlates with total phosphorus, correlation coefficients for some cultivars being greater than 0.90. Factors that affect the total phosphorus content, such as soil, available phosphorus and fertilizers, can influence the phytic acid concentration. Polyphenols content was also varied between the two genotypes and this variation is likely to be due to the fact that the amounts of such factor depend on variety, stage of maturity, edible portion and storage conditions.

Table 1.

Effect of fermentation on anti-nutritional factors content (mg/100 g) and phytate/P ratio of two corn genotypes (Var-113 and TL-98B-6225-9×TL617)

Fermentation time (h) Var-113 TL-98B-6225-9×TL617
Phytic acid % reduction Phytate/P Polyphenols % reduction Phytic acid % reduction Phytate/P Polyphenols % reduction
0 1047.00a – 11.34 460.50a – 87.16a – 0.49 363.70a -
2 1047.00a 0.00 8.63 159.40b 65.38 38.71b 55.59 0.21 217.60b 40.17
4 968.30b 7.52 4.60 155.10c 66.32 24.70c 71.66 0.12 205.30c 43.55
6 819.40c 21.74 3.89 121.50d 73.62 13.20d 84.85 0.07 182.90d 49.71
8 303.50d 71.01 1.40 98.17e 78.68 9.60e 88.98 0.05 175.10e 51.86
10 223.10e 78.69 1.01 95.95 f 79.16 3.40f 96.10 0.02 172.90f 52.46
12 187.50f 82.09 0.80 91.50g 80.13 1.54g 98.23 0.01 171.90g 52.73
14 155.00g 85.20 0.69 91.40g 80.14 0.31h 99.64 0.001 151.70h 58.29
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Values are means of three replicates. Means not sharing a common superscript letter in a column are significantly different at P ≤ 0.05 as assessed by Duncan’s multiple range test

As shown in Table 1 and for the two genotypes, polyphenols content decreased significantly (P ≤ 0.05) within the first 2 days of fermentation but phytic acid significantly (P ≤ 0.05) decreased within the first 4 days of fermentation. Thereafter, they decreased at a higher rate from day 6 to day 14 of fermentation and the reduction exceeded 85 % for phytate and 58 % for polyphenols at the end of fermentation process for both genotypes. The results showed that fermentation as a source of degrading enzymes had significantly (P ≤ 0.05) reduced phytic acid and polyphenols contents of the genotypes grains with time. Generally, cereal has been regarded as the major source of dietary phytate. The majority of ingested phytate is undergraded during transit through the gastrointestinal tract (Graf and Easton 1990). During digesta movement in the human body, dietary phytate-mineral complexes may dissociate and may form other complexes through the gastrointestinal tract. In the upper part of the small intestine, which is characterized by maximum mineral absorption, the insoluble complexes are highly unlikely to provide absorbable essential elements. Thereby, the chemical interactions of phytate in the upper gastrointestinal tract are of particular concern since the site and degree of phytate degradation can affect the nutritional value of a phytate-rich diet (Kumar et al. 2010). One phytate molecule can bind up to six divalent cations, and the metal could possibly bridge at least two phytate molecules, depending on the redox state (Graf and Easton 1990). Phytic acid is a powerful inhibitor of iron-driven hydroxyl radical formation because it forms a catalytically inactive iron chelate. Abdelseed et al. (2011) have observed decrease in phytic acid contents of sorghum grains as a result of fermentation. The decrease in the level of phytic acid during fermentation may be attributed to the action of the enzyme phytase released during fermentation. Other researchers have reported a decrease in the level of phytic acid during fermentation due to phytase activity in the fermented flour (Kerovuo et al. 2000; AbdelRahaman et al. 2005; Idris et al. 2005). The polyphenols content for both genotypes was also significantly (P ≤ 0.05) decreased with fermentation of genotypes flour and the reduction exceeded 58 % for both genotypes. Many researchers reported that fermentation greatly decreased polyphenols contents (AbdelRahaman et al. 2005; Idrir et al. 2005). Moreover, fermentation of malted samples caused further reduction in polyphenols as reported for sorghum (Abdelhaleem et al. 2008). The reduction in polyphenols content after fermentation is due to the action of tannase enzyme which is released by the microorganisms during fermentation (Barthamuef et al. 1994)

Effect of fermentation on total and extractable minerals of corn genotypes

The effect of fermentation on major minerals content and HCl extractability of corn genotypes grains is shown in Table 2. The major mineral content varied between the genotypes. The data obtained for unfermented flour indicated that phosphorus and potassium were the major mineral constituents of the genotypes grains. For genotype Var-113, total phosphorus was 92.33 mg/100 g and out of this amount about 33 % was extractable while that of genotype TL-98B-6225-9×TL617 was 178.70 mg/100 g and out of this amount about 27.40 % was extractable. For both genotypes calcium of unfermented flour represents the third mineral but the amount extractable was higher compared to all minerals. The variation in mineral content between the genotypes may be due to genetic as well as environmental factors. As shown in Table 2 the major minerals content of fermented samples was increased significantly (P ≤ 0.05) with the fermentation period as well as the HCl extractability of such minerals. The extractability of minerals of nutritional importance (calcium and phosphorus) significantly (P ≤ 0.05) increased with the fermentation period, with maximum values obtained at day 14. Genotype TL-98B-6225-9×TL617 gave higher extractable calcium (94.73 %) compared to that of genotype Var-113 (82.53 %) after 14 days of fermentation. In a similar study, Abdelseed et al. (2011) observed an increase in the HCl extractability of calcium of sorghum lines after fermentation. Moreover, Eltayeb et al. (2008) reported that malting of millet followed by fermentation greatly improved the HCl extractability of calcium due to reduction in antinutrients level.

Table 2.

Effect of fermentation on major minerals content (mg/100 g) and HCl-extractability (%) of two corn genotype (Var. 113 and TL-98B-6225-9×TL617)

Genotype Fermentation time (h) pH Na K Mg Ca P
Total Extractable Total Extractable Total Extractable Total Extractable Total Extractable
Var-113 0 5.94 13.28g 38.00h 206.17e 57.1h 51.67g 67.87h 74.50h 69.80g 92.83h 33.00h
2 5.83 14.32f 54.57g 219.70de 60.33g 52.03g 68.27g 78.23g 70.57 f 121.30g 35.15g
4 5.48 14.49f 65.33f 241.90cde 68.30f 55.11f 74.13f 84.00f 74.13e 160.40f 43.46ef
6 4.93 16.22e 72.61e 251.10bcd 76.30e 56.63e 75.73e 87.27e 76.13d 210.70e 47.11de
8 4.53 17.97d 78.22 d 266.10abc 81.82d 59.19d 79.36d 90.40d 79.10c 218.00d 54.87d
10 4.23 20.30c 82.07c 286.80ab 93.20c 62.63c 82.42c 93.19c 81.34 b 222.10c 62.12c
12 4.09 22.28b 88.70b 299.60a 99.33b 67.33b 84.48b 95.23b 82.08 a 233.50a 66.05b
14 3.92 23.07a 96.80a 305.30a 103.40a 68.33a 87.23a 96.76a 82.53a 225.20b 76.55a
TL-98B-6225-9×TL617 0 5.85 10.80h 39.77h 125.00cde 37.50h 43.33h 62.90h 69.67f 79.10h 178.70g 27.40h
2 5.76 12.12g 45.03g 123.40e 46.05g 45.27g 68.14g 72.33e 81.17g 185.10f 30.63g
4 5.19 14.47f 52.28f 131.60de 57.29f 47.15f 72.88f 74.63d 83.42f 199.10e 34.42f
6 4.76 16.21e 58.51e 150.80bcd 62.09e 49.50e 81.14e 76.05c 86.30e 200.90d 38.26e
8 4.35 20.13d 62.25d 162.20abc 67.54d 50.81d 84.23d 77.30c 92.40d 200.90d 44.36d
10 4.21 21.68c 68.90c 164.10abc 72.33c 52.07c 86.30c 78.93b 93.15c 204.30c 52.10c
12 4.06 23.42b 76.66b 175.80ab 80.50b 53.87b 87.84b 81.10a 94.30b 206.10b 61.76b
14 3.85 27.20a 83.53a 180.30a 88.13a 56.32a 91.72a 82.07a 94.73a 213.30a 66.10a
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Values are means of three replicates. Means not sharing a common superscript letter in a column are significantly different at P ≤ 0.05 as assessed by Duncan’s multiple range test

Another important mineral considered in this study, having a significant role in nutrition, is phosphorus. The phosphorus content for both genotypes significantly (P ≤ 0.05) increased with the fermentation time. The increment in phosphorus content may be due to hydrolysis of phytate by the enzyme phytase, which is released after fermentation. Phosphorus extractability increased significantly (P ≤ 0.05) with increase in fermentation period (Table 2) for both genotypes. Despite it contains higher level of phytate, genotype Var-113 gave higher extractable phosphorus (76.55 %) compared to that of TL-98B-6225-9×TL617 (66.10 %) after 14 days of fermentation. Variation in extractable phosphorus at different periods of fermentation was observed by Eltayeb et al. (2008) for millet cultivars. For both genotypes, all other minerals studied (sodium, potassium and magnesium) gave an HCl extractability trend similar to that obtained for calcium and phosphorus. According to FAO (1992), the corn germ is relatively rich in minerals, with an average value of 11 % as compared with less than 1 % in the endosperm. The germ provides about 78 % of the whole kernel minerals. The most abundant mineral is phosphorus, found as phytate of potassium and magnesium.

Table 3 shows the effect of fermentation on total and HCl extractable trace minerals of corn genotypes. The genotypes varied in total and extractable trace minerals. Iron content was 1.95 mg/100 g for Var-113 and out of this amount about 32.30 % was extractable while that of TL-98B-6225-9×TL617 was 4.57 mg/100 g and about 21 % was extractable. For both genotypes the trace minerals content and the HCl extractability increased significantly (P ≤ 0.05) with the fermentation period. The genotypes were significantly (P ≤ 0.05) differing in HCl extractability at various levels of fermentation. The HCl extractability of iron increased significantly (P ≤ 0.05) from the beginning of the fermentation and reached a maximum value at day 14. Genotype TL-98B-6225-9×TL617 gave higher HCl extractability of iron (84.93 %) while that of Var-113 was 60.18 %. The difference in iron extractability between the two genotypes is due to differences in level of phytate between them. In a similar study, Abdelseed et al. (2011) observed an increase in iron extractability of sorghum lines after fermentation. Moreover, Eltayeb et al. (2008) reported that malting of millet followed by fermentation greatly improved the HCl extractability of iron. Total and extractable zinc, manganese, copper and cobalt increased significantly (P ≤ 0.05) when the grains flour was fermented for 14 days. Similarly, Afoakwa et al. (2011) reported that fermentation significantly increased the copper content of the Ghanaian cocoa beans. The increment in HCl extractability of both major and trace minerals of corn genotypes is likely to be due to the reduction of antinutrients (phytate and polyphenols) as a result of fermentation during which phytase and tannase enzymes released during fermentation which hydrolyzed phytate and polyphenols, respectively. The mechanism of the release of minerals might be through the dephosphorylation of phytate in which the removal of phosphate groups from the inositol ring decreases the mineral binding strength of phytate, and thus, results in increased bioavailability of essential dietary minerals (Sandberg et al. 1999).

Table 3.

Effect of fermentation on trace minerals content (mg/100 g) and HCl-extractability (%) of two corn genotype (Var. 113 and TL-98B-6225-9×TL617)

Genotype Fermentation time (h) pH Fe Zn Mn Cu Co
Total Extractable Total Extractable Total Extractable Total Extractable Total Extractable
Var-113 0 5.94 1.95e 32.30h 1.25f 50.60 g 0.68f 68.40g 0.12 e 41.60h 0.70a 86.30g
2 5.83 2.20d 34.21g 1.40e 54.14f 0.71ef 69.35f 0.37d 43.23g 0.68a 86.41g
4 5.48 2.31d 35.33f 1.54d 54.14f 0.73def 70.25e 0.61c 46.25f 0.70a 87.07f
6 4.93 2.44d 39.85e 1.61d 56.43e 0.75cde 73.10d 0.63c 47.10e 0.73a 89.54e
8 4.53 3.33c 44.30d 1.74c 61.17d 0.77cd 76.69c 0.66bc 50.27d 0.76a 91.17d
10 4.23 3.72b 48.00c 1.83b 63.33c 0.82bc 76.53c 0.71b 57.23c 0.81a 96.27c
12 4.09 3.91b 55.30b 1.91a 64.07b 0.84ab 78.23b 0.77 a 59.62b 0.82a 96.93b
14 3.92 4.34a 60.18a 1.96a 66.34a 0.87a 81.07a 0.79a 62.09a 0.88a 98.57a
TL-98B-6225-9×TL617) 0 5.85 4.57d 21.00h 1.19g 47.90g 0.64f 33.30h 0.18f 49.10h 0.50f 52.00h
2 5.76 4.78cd 38.10g 1.42f 51.47f 0.71 e f 34.77g 0.54e 53.33g 0.63e 54.90g
4 5.19 4.99c 49.41f 1.54e 53.57e 0.77de 37.77f 0.62d 61.97f 0.71de 63.10f
6 4.76 5.21b 61.62e 1.67d 53.37e 0.79de 44.52e 0.66d 67.87e 0.76cd 66.67e
8 4.35 5.34b 68.39d 1.75cd 65.37d 0.83cd 55.59d 0.69d 73.50d 0.78cd 70.97d
10 4.21 5.61a 75.99c 1.79bc 68.94c 0.87bc 63.27c 0.90c 75.47c 0.82bc 74.22c
12 4.06 5.71a 78.73b 1.87ab 72.62b 0.93ab 71.07b 1.07b 79.00b 0.87b 76.14b
14 3.85 5.72a 84.93a 1.91a 79.16a 0.97a 73.22a 1.21a 81.93a 0.97a 80.34a
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Values are means of three replicates. Means not sharing a common superscript letter in a column are significantly different at P ≤ 0.05 as assessed by Duncan’s multiple range test

Conclusion

Fermentation is a powerful method in improving total and extractable major and trace minerals of corn genotypes by reducing the antinutritional factors (phytate and polyphenols) by the action of the enzymes released during fermentation.

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