Antinutritional factors in pulses

The presentation shares the information about the major antinutritional factors found in legume crops and the methods to overcome or minimize their effect in diet through various ways.

1. ANTINUTRIONAL FACTORS IN PULSES AND METHODS TO OVERCOME GPB 608 Breeding pulses and Oil seed Crops (3+1) Submitted by Ananda lekshmi .L 2018600801

2. D efined as a chemical substance, which, when present in human or animal food, impairs growth and normal functioning of the body. Anti-nutritional factors mainly occur in pulses and grain legumes and foods and feed material prepared from grain legumes and pulses. Anti-nutritional factors can cause detrimental effects to human and animal growth and performance by impairing intake, uptake, or utilization of other food and feed components, or by causing discomfort and stress to human and animals . Anti Nutritional Factors

3. A substance which when present in human or animal feed interferes with assimilation of certain nutrients showing toxic or undesirable physiological effects, such as flatulence. Nevertheless such ANFs provide a protective role against insects, predators and pathogens attacks. These compounds range in effect from relatively inoffensive polyphenols to the relatively harmful protease inhibitors. grain legumes with comparably large and protein-rich seed which often contain substantial amounts of "anti-nutritive" factors (ANF),

4. Lectins Tanins Protease inhibitors Phytic acid Lathyrogen Saponin oligosacchride Antinutritional factors in pulses:

5. Lectins are proteinaceous in nature and commonly found in some of the beans. Seeds of some of the edible species of pulses such as lentil and pea also contain phytohemagglutinins . These are proteins which possess a specific affinity for certain sugar molecules . Most of the lectins contain 4 to 10% carbohydrates . The lectins from mungbean are non toxic, whereas the lectins obtained from immature seeds of pigeon pea and ricebean are harmful (De- Muelenaere , 1965, Ikegwuonu and Bassir , 1977, Manage et al., 1972). LECTINS:

6. Lectins reduce the bioavailability of nutrients , which is due to direct action of lectin on digestive enzymes ( Jindel et al., 1982, Rea et al., 1985). Preliminary soaking prior to autoclaving or cooking is required for complete elimination of the toxicity of lectins ( Liener , 1976, Kute et al., 1984). deleterious effects associated with lectins are food poisoning, vomiting, bloating, and diarrhoea in humans .

7. Tannin (Polyphenol) is known to form complexes with proteins under certain pH conditions . Tannins-protein complexes are reported to be responsible for low protein digestibility, decreased amino acid availability and increased fecal nitrogen . Among pulses , pigeonpea , urdbean and pea have highest tannins in seeds . It appears that tannins content in pulses varies with colour of the seed coat . Lower amount of tannins, in general are observed in light coloured seeds than brown dark coloured pulses . White seeded varieties of Phaseolus vulgaris are contain almost negligible tannins, while coloured varieties contain large quantities of tannins ( Deshpande et al., 1982, Deshpande and Cheryan , 1983 ). TANNINS:

8. Single gene mutation has a pleiotropic effect eliminating tannins from seed coat and determining a white flower trait in pea and faba bean. Zero-tannin trait in lentil is controlled by a single recessive gene ( tan)

9. The tannins content in beans changes during seed maturation ( Kadam et al., 1982). Tannins are mainly located in seed coat of pulses, hence physical removal of seed coat by either dehulling or milling and separating hulls decreases the tannin content of pulses and improves their nutritional quality . Dehulling eliminates about 68 to 99% of tannins in seed. Soaking of seeds before cooking is a common household practice and, used to soften the texture and hasten the process of cooking . Leaching of tannins increases with the time of soaking in distilled water .

10. Raising the period of soaking from 6 to 12 and 18 hrs further reduces tannin content of seed Cooking and discarding the cooking water results in about 37.5 to 77% decrease in tannin content of seeds (Reddy et al., (1985). Overnight soaking in water and subsequent germination for 48 hrs removes more than 50% of the tannins in pigeonpea , chickpea, mungbean and urdbean ( Jood et al., 1987, Kataria et al., 1989

11. Trypsin inhibitors belong to a broad class of proteins (protease inhibitors) that inhibit proteolytic enzymes . Trypsin inhibitor activity increases as seed maturation progresses ( Kute et al., 1984). Most of the plant protease inhibitors are destroyed by heat resulting in enhancement of nutritive value of protein ( Liener , 1962). The moisture content, time, temperature and pressure are the major factors that influence cooking rates , inactivation of the trypsin inhibitor, and subsequent increase in nutritive value . Moist heat has been shown to be effective in destroying trypsin inhibitor activity in pulses ( Rackis , 1981). Protease inhibitors:

12. Germination also influences the trypsin inhibitors activity ( Hobday et al., 1973, Kadam et al., 1986). The application of dry heat to the seeds and meal is not effective in inactivating the trypsin inhibitor and chymotrypsin inhibitory activity of pigeon pea, but soaking for 24 hrs followed by cooking for 20 min is effective in destroying trypsin activity ( Mulimani and Paramjyothi , 1994).

13. Phytic acid is another antinutritional factor and is a major storage form of phosphorus in plants (60-90% of total seed phosphorus ). It is ubiquitous in seed comprising 1-3% of all nuts, cereals, legumes and oil seeds. It is present as crystals inside protein bodie s in discrete regions of seeds. Phytic acid is considered as one of the antinutrients mainly due to its ability to bind to essential dietary minerals as well as proteins and starch , consequently reducing their bioavailability in humans . Phytic acid:

14. However, on food processing , phytates can be dephosphorylated to produce degradation products roasting and autoclaving has been reported to decrease phytic acid in dry bean .

15. Seeds of V. faba can trigger the onset of Favism , an acute haemolytic disease which affects individuals lacking sufficient activity of the NADPH producing enzyme glucose-6-P-dehydrogenase (G6PD) in their red blood cells . ( Mager et al., 1980; Marquardt,1989) The glycosides vicine and convicine (VC) are concentrated in cotyledons of faba bean seeds . Conventional cultivars contain from 6 to 14 g/kg of VC in mature seed A mutant allele vc has been discovered which reduces 10 to 20 fold VC content. ( Duc et al. 1989). This allele has a positive effects on egg production by laying hen and energy value of feeds for chicken Vicine and convicine

16. Lathyrogen toxin is one of the natural toxins found in the seeds of lathyrus , commonly known as khesari or teora , which is known to cause lathyrism . If consumed in excess quantity for long time, it causes paralysis in the legs in susceptible individuals and is believed to be caused by a toxic amino acid known as N- Oxalyl amino alanine (BOAA ). The BOAA content of seed of lathyrus varies from 0.05 to 0.4% ( Srivastava et al., (2000). Less than 0.2% BOAA is considered safer from health point of view ( Siddiqu , 1995). The concentration of BOAA is maximum in the germ portion of the seed of lathyrus ; therefore the degerming of the seed cotyledons greatly reduces the neurotoxin content of lathyrus seed . Lathyrogen :

17. Processing techniques like soaking, parboiling, roasting and degerming eliminates neurotoxin to a large extent . Pre-cooking soaking of pulse removes 30-40% of toxin ( Srivastava and Srivastava , 2002 ). Roasting of seeds for about 15-20 min removes most of the toxin of lathyrus ( Rao et al., 1969). Preboiling of lathyrus seeds removes more than 80% of the toxin and produces minimum change in nutritive value ( Nagrajan et al., 1965).

18. Saponins are secondary plant metabolites present in pulses . The chickpea, mungbean and pigeonpea contain saponins ranging from 0.05 to 0.23%. Though saponin reduces the nutritive value of pulses, but the saponins appear to be beneficial as they are responsible for lowering the cholesterol in body and may be important in human nutrition in reducing the risk of heart diseases and also inhibited colon cance r . Processing techniques like soaking, germination and cooking helps in reducing the saponin contents of pulses. Saponins:

19. Soaking of pulses reduces 5 to 20% saponin in pulse. Germination reduces saponin content of various pulses. Forty eight hours sprouting results in 22% reduction of saponin in urdbean ( Jood et al., 1988, Kataria and Chauhan , 1988). The loss of saponin increases with increase in the germination period. Cooking also reduces saponin content of seed/ grain in chickpea, mungbean and urdbean ( Jood et al., 1987, Kataria et al., 1989, Sharma and Sehgal , 1992),

20. Ingestion of large quantities of pulses is known to cause flatulence in human beings. Accumulation of flatus in the intestinal tract results in discomfort, abdominal rumblings, cramps, pain, diarrhoea etc. The oligosaccharides of the raffinose family sugars viz ., raffinose , stachyose and verbascose from pulses are causative agent of flatulance in humans ( Rao , and Belvady , 1978). Raffinose is not digested by man because the intestinal mucosa lacks the hydrolytic enzyme a1, 6-galactosidase ( Cristotaro and Wuhrmann , 1974). Oligosaccharides:

21. Microflora in the lower intestinal tract metabolise these oligosaccharides and produce large amount of carbon dioxide, hydrogen and small quantity of methane , which causes flatus production ( Rackis , 1974). Varieties with low raffinose sugars can be developed and also be used for reducing the oligosaccharides, which are removed as a result of soaking ( Iyenger and Kulkarni , 1977). Discarding cooking water also reduces the raffinose contents in beans (Reddy and Salunkhe , 1980). Raffinose sugars can also be removed from pulses by germination (Gupta and Wagle , 1980, Rao and Belvady , 1978).

22. There can be no doubt that the so called "anti-nutrients" of legumes have a biological function. They are certainly important in the physiology of seedlings as N or C storage compounds and to facilitate nutrient uptake and rhizosphere establishment . Since they are also toxic to animals and sometimes even to microorganisms, viruses and other plants, they exhibit defence functions at the same time. Can "anti-nutrients" be even useful?

23. Anti nutritional factors play important role in Seed germination Preservation of seed longevity Desiccation tolerance Stored carbon reserves in seeds will be released during seed germination. --- polysaccharides , sugars, oil and proteins Dessication tolerance in legumes could be the result of antinutritional factors protecting membrane-bound proteins

24. An important question arising in the context of selection for low-toxin lines is whether the genetic reduction of anti- feedant and anti-nutritional factors is going to have a negative effect on the ecological fitness of the resulting cultivars? In the words of Bell (1977) who reviewed the ecological function of non-protein amino acids, "The development of a toxin-free crop would be totally impractical if the reduction in toxicity to man or domestic animals was accompanied by an equal or greater reduction in toxicity to predatory insects which might destroy the crop before it could be harvested ".

25. the selection of genotypes with low levels of ANF factors , thus enabling the development of more palatable and less toxic cultivars. The general aim is a selection of non-toxic and palatable genotypes requiring efficient screening techniques to expedite the quantitative detection of individual ANFs for the selection of improved grain legume cultivars. Sometimes simple colour reagent s might work for an initial test, such as Reifers reagent for quinolizidine alkaloids in lupins (it produces a brown precipitate with alkaloids; Wink, 1993 ). Elimination of ANFs through genetic modification

26. Immunological methods such as ELISA to detect specific proteins can also be established for low molecular weight compounds such as alkaloids (Wink 1993). Living systems can also be useful for selection: Whereas alkaloid rich bitter lupins are avoided by rabbits and aphids, sweet alkaloid poor varieties are readily accepted (Wink 1998, 1992 ). Mass screening is still a labour and capital intensive strategy. Tolerance levels for individual ANFs and applications need to be known so that plant breeders can define target levels in their breeding programs.

27. If the gene is known which encodes a toxic protein, genetic engineering offers a set of methodologies at present to downregulate or to knock out the respective activity. Strategies include the expression of antisense mRNA, of gene targetting , and of synthetic oligonucleotides or ribozymes. Obstacles are often encountered in that relevant genes have not been detected so far which is usually the situation for biosynthetic enzymes of ANFs. Transformed plants need to be regenerated which is a severe problem in most legumes . Genetic engineering options

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