Jackfruit.pdf

Indian Journal of Natural Products and Resources Vol. 3(3), September 2012, pp. 347-353

Study on functional properties of raw and blended Jackfruit seed flour (a non-conventional source) for food application A Roy Chowdhury1*, A K Bhattacharyya1 and P Chattopadhyay2 1

Department of Food Technology, Techno India, E.M. 4/1, Sector- V, Salt Lake, Kolkata-700 091, West Bengal, India 2

Department of Food Technology & Biochemical Engineering, Jadavpur University, Kolkata-700 032 Received 20 June 2011; Accepted 30 June 2012

Jackfruit (Artocarpus heterophyllus Lam.) is widely cultivated in India and its neighbouring countries as well as in parts of Africa. After the consumption of the edible portion of the ripe fruit, the seeds, rich in carbohydrate and protein, are usually discarded as a waste. The present work was undertaken to investigate the functional properties of raw and blended jackfruit seed flours with a view to provide useful information for its effective utilization along with wheat flour for various food formulation. It was observed that lye-peeled seeds are low in nutrient content, but had a better acceptability in terms of colour and flavour. The present study revealed that jackfruit seed flour has a great potential for new food formulation along with wheat flour. The factors affecting the functional behaviours of the raw and blended jackfruit seed flours were studied. As the flour and its blends have good water and oil absorption capacities along with other desirable properties, such a blend can be used for developing bakery products and as protein supplements and functional ingredients in food formulations. Keywords: Artocarpus heterophyllus, Flour blending, Food formulation, Functional properties, Jackfruit seed flour, Wheat flour. IPC code; Int. cl. (2011.01)  A23L 1/00

Introduction Jackfruit (Artocarpus heterophyllus Lam.), a member of the family Moraceae is a popular fruit of the tropics. It grows widely and abundantly in India, Bangladesh1, South-East Asia and in the evergreen forest zone of West Africa2. The edible bulbs of ripe jackfruit are usually consumed fresh or processed into canned products; 10-15% of the total fruit weight is considered as its seed weight3,4. Though the seeds are rich in carbohydrate and protein3,4, jackfruit seed is used occasionally as a minor supplement in culinary recipes but are mostly wasted. Keeping the colossal waste of this nutritious seed in view, the present study focuses on making seed flour which can be stored for longer period and find varied industrial applications. The jackfruit seed flour may also be blended with wheat flour to explore the potential of low cost flour from jackfruit seed as an alternative raw material for bakery and confectionary products. The Jackfruit seed flour is not only a rich source of protein, starch and dietary fibres but can also be regarded as an abundant yet cheap source of the said nutrients2. —————— *Correspondent author: E-mail: [email protected]; Tel : 91 9831424591, 03323577582-84

Lectin, a class of glycoproteins found in jackfruit seed, has been reported to possess antibacterial, antifungal and anticarcinogenic properties5. The present work is carried out to investigate the functional characteristics of jackfruit seed flour blends with wheat flour for new food formulations. Functional properties of jackfruit seed flour and its protein digestibility as well as a comparative study on functional properties of raw and heat processed Jackfruit seed flour have also been reported6,7. Not much information is available on functional properties of such blended flours. In India, malnutrition is prevalent due to inadequate intake of protein. In view of this, effort was made for identifying and evaluating under-utilized non-conventional cheap protein sources like jackfruit seed as an alternative. For efficient utilization of jackfruit seed flour, it is desirable to study the functional properties. The functionality of plant proteins in food system is influenced by the inherent chemical characteristics of the seed8. Processing and environmental conditions also influence the functional properties of seed proteins9. The successful utilization of seed flour as a food ingredient and its blending with wheat flour

348

INDIAN J NAT PROD RESOUR, SEPTEMBER 2012

depends on functional characteristics and sensory attributes which it would impart to the end-product thus affecting consumers’ acceptance. The functional properties also play an important role in the physical behaviour of foods or their ingredients during preparation, processing and storage. The efforts have geared towards jackfruit seeds as a cheap non-conventional protein source. Jackfruit seed could be a potential source of protein for many developing as well as under developed nations. Jackfruit seed flour and its blends with wheat flour can be sold as a low cost flour meeting up the requirement for protein for poor people. Various functional properties were studied which include foaming, emulsifying and gelation properties, water and oil absorption capacities and protein solubility. This study will provide the useful information towards effective utilization of jackfruit seed flour and wheat flour blends in various food formulation applications.

Flour blends

To study the functional properties, the jackfruit seed flour (lye peeled variety) was mixed in different proportions with wheat flour (Ganesh Maida) to have 10, 15 and 20% w/w blends. The various functional properties were determined along with unblended raw jackfruit seed flour as control. All the flour samples were packed in polyethylene bags (0.7 mm/0.7 × 10-3 m thickness) and stored at around 8°C/281 K. Proximate compositional analysis of whole seed and defatted jackfruit seed flour

The crude protein (Kjeldahl N × 6.25), fat (solvent extraction with petroleum ether, b.p. 40-60°C/313333 K), crude fibre, ash and moisture contents were determined according to standard methods of AOAC10. The digestible carbohydrates were calculated by the difference. Analyses were carried out in triplicates. Functional properties Bulk density

Indian Jackfruit seeds (58.43% average moisture content) with white seed coverings were collected from local markets of Bengal and were used for this study. Commercial wheat flour (Ganesh Maida Variety) was procured from local market.

This was determined by taking the flour sample in measuring cylinder filled up to a certain mark, the initial volume and the initial weight of the sample were recorded. Then the flour samples were given equal tapping and the final volume was recorded. The bulk density of the sample was calculated from these data. The method adopted was slightly modified from the method of Narayana & Narasinga Rao11.

Preparation of Jackfruit seed flour

Water and oil absorption capacity

The seeds (4 kg) were cleaned and the white seed covers were removed. Seeds with brown seed coats were then lye-peeled with 2% NaOH for 5 minutes under hot condition (~80°C/ 353 K) to remove the thin brown coat. After washing, the fleshy white cotyledons were collected by scrubbing. Seeds were sliced into thin chips by rotary slicer and then tray dried at around 60°C/333 K for about 16 h to reduce the moisture content to 10% level. The chips were ground to flour by using grinder (Bajaj make Grinder). The flour was sieved (100 mesh), collected and stored in plastic pouches at around 8°C/281 K till further use. The yield of the flour was 46%. Another variant of flour was prepared without removing the outer brown seed coat followed by drying the chips at ~ 60°C/333 K and grinding. The colour of the flour thus obtained was brown and was collected in polyethylene pouch pack after passing through a 100 mesh sieve and was stored at 8°C/281 K.

Water absorption capacity was evaluated following Abbey & Ibeh12 method with minor modifications. 1 g (0.001 kg) of flour was dissolved in 25 ml (25 × 10-6 m3) of distilled water and vortexed thoroughly and centrifuged at 2500 g for 10 minutes. The residue obtained upon decanting the soluble fraction was weighed. The water absorption capacity was expressed as ml of water absorbed by 1 g of flour or in % (v/w) (% values remain unaltered in SI units). Oil absorption capacity was determined using 1 g (0.001 kg) of flour and 10 ml (10 × 10-6 m3) of refined vegetable oil (sunflower oil, ITC brand, density 0.89 g/ ml). The method of Beuchat13 was employed for the oil absorption capacity determination. The sample was then allowed to stand at room temperature (30+/- 2°C/303+/-2 K) for 30 min followed by the centrifugation at 5000 g for 30 minutes. The volume of the supernatant was noted in a 10 ml measuring cylinder. It was expressed as ml of oil absorbed by 1 g of flour or in % value (for SI unit also).

Materials and Methods Materials

ROY CHOWDHURY et al: FUNCTIONAL PROPERTIES OF RAW AND BLENDED SEED FLOUR OF JACKFRUIT

Foaming capacity

Foaming capacity and stability were measured following method of Lawhon et al14 with slight modifications. A weighed amount of flour was dissolved in 100 ml/ 100 × 10-6 m3 distilled water, stirred at room temperature for 5 min with the help of a magnetic stirrer at high speed. The material was immediately transferred to a measuring cylinder. Volume of foam (ml/10-6 m3) after mixing was expressed as foaming capacity. The volume of foam recorded over a time period of 20-120 min is foam stability for mentioned time period. Foam capacity measurements were also done using NaCl solution of 0.2-1.0 M/Mol concentrations. The percentage volume increase was calculated as follows: % volume increase = (V2 – V1) / V1 × 100 Where V2 is the volume of the solution after whipping and V1 is the original volume of the flour suspension. Emulsifying capacity

Standard method of Beuchat et al13 was followed as a procedure for this study at room temperature. 5 g/ 0.005 Kg of flour sample was mixed with 65ml/ 65/10-6 m3 of distilled water or NaCl (0.2-1.0 M/ Mol) solution and were agitated in a mixer. Along with the previous dispersed content, 2 ml/2 × 10-6 m3 oil (refined vegetable oil- ITC brand, density 0.89 g/ml) was added drop-wise at a time from the burette and blending was continued until emulsion break point was reached. After getting the separation into two layers, emulsion capacity was calculated as ml/10-6 m3 of oil that was emulsified by 1 g/0.001kg of flour sample. Gelation study

To study the gelation capacity of raw and blended jackfruit seed flour, 5 ml/5×10-6 m3 distilled water was mixed with flour sample taken in test tubes to obtain suspension of 2-15% (w/v) concentration. Gel stability was studied following method of Coffman & Garcia15 as modified by Abbey & Ibeh12. The test tubes were heated in a boiling water bath for hours till gel are formed. It was immediately cooled rapidly and further cooled under refrigerated condition at 4~8°C/ 277-281 K. All the samples were then cooled for 10 h and least gelation concentration was assessed as that concentration which would hold the sample tightly on the wall of the inverted test tube and the sample did not fall or drop. Protein solubility

Protein solubility of raw and blended jackfruit seed flours were studied by application of the method of

349

Narayana & Narasinga Rao16 suggested for nitrogen solubility in varied pH (2-12) range, using 2 g/0.002 kg flour and 100 ml/100 × 10-6 m3 of distilled water (flour: water =1:50) shaken for 30 min with the help of a magnetic stirrer at high speed. After extraction, the suspension was centrifuged for 20 min at 4500 rpm at room temperature and the soluble protein extracted was estimated by Lowry method17. All extractions and determinations were performed in triplicates. Results and Discussion Proximate composition

The proximate analyses of the base flour (Ganesh maida) and Bengal variety jackfruit seed (j.f.s) flour have been shown in the Table 1. The flour composition of the present study reveals that there is variation in the amount of protein content in the two flours obtained with or without lye-peeling. It is observed that the removal of seed coats by lye-peeling has an effect on the proximate composition of flour. However, lye-peeled flour had better acceptability in terms of colour and flavour and was used for subsequent studies. Different blends of jackfruit seed were prepared by supplementation of the base flour with jackfruit seed flour to study the various functionalities. The compositions of the blends are: 100% wheat flour, wheat flour blended with 10, 15 and 20% jackfruit seed flour and 100% jackfruit seed flour. Water absorption and oil absorption capacity

These capacities of the jackfruit seed flour and its blends are reported in Table 2 which indicates that jackfruit seed flour has very high water absorption capacity compared to wheat flour whereas for the blends of 10, 15 and 20% (w/w), it goes on increasing with supplementation. Protein and carbohydrate play Table 1  Proximate analysis of wheat flour and Jackfruit seed flour (sieved through 100-mesh) Proximate analysis (%)

Wheat flour

Moisture content Crude protein Ash Crude fat Crude fibre Total digestible carbohydrate

11.5 8.9 0.63 1.4 0.78 76.79

Flour with Flour without Brown seed Brown seed coat coat (without (with Lye-peeling) Lye-peeling) 10.7 14.02 2.54 4.08 1.8 66.86

10.1 12.6 2.24 3.37 1.47 70.22

INDIAN J NAT PROD RESOUR, SEPTEMBER 2012

350

an important role in binding water16. It can be suggested that the proteins in Jackfruit seed consist of more hydrophilic subunit structure than wheat flour protein which can bind more water. This could be the reason for higher water absorption by higher % of blends of jackfruit seed flour with wheat flour. The high value of carbohydrate (may be presence of hydrocolloids, starch) could lead to increased water absorption on higher supplementation16. The jackfruit seed flour was prepared by dry milling method. However, the process of lye-peeling and milling equipment and milling time can affect the properties of jackfruit seed flour. It may affect the starch quality which is reflected on higher water absorption value. Fat absorption is an important property in food formulations because fats improve the flavour and mouth feel of food18. The significance of proteinlipid interactions was examined by Chung & Pomeranz19 in bread making. High oil absorption suggests the hydrophobic structures of jackfruit seed protein in protein subunits. The oil absorption capacity of jackfruit seed flour and its blends suggests Table 2  Functional properties of raw and blended Jackfruit seed flour: Bulk density, Water & Oil absorption capacity Flour type

Raw jackfruit seed flour (100mesh) Without seed coat 10% blend 15% blend 20% blend Wheat flour

Water Oil absorption Bulk density absorption capacity g/cc capacity (%) (%) (103 kg / M 3) 203.4

97

0.80

74.6 79.3 86.1 65.5

88 89.8 90.2 86

0.74 0.76 0.77 0.73

that they may find useful application in formulation of bakery products like cake and cookies. Bulk density

There is no appreciable change in bulk density value (Table 2) of wheat flour with raw and blended jackfruit seed flour. Raw jackfruit seed flour (100-mesh) was compared with the flour having seed coat which has got high bulk density value which is in accordance with its high ash content value. However when the blends are concerned, bulk density goes on increasing with increase in blend % compared to control. Foam capacity and foam stability

The foaming capacity of flours is related to the amount of native protein20. Yasumatsu et al21 have shown that native protein gives higher foam stability than the denatured protein. Upon continuation of blending, foam stability increases. Surface active proteins control aeration and the texture by allowing the uniform distribution of fine air cells throughout the matrix22. Hence, it may be suggested that jackfruit seed protein has high surface viscosity property from the viewpoint of foam stability (Tables 3 a & 3 b) and upon blending with wheat flour, surface activity increases which allows more air to get entrapped for a longer time period. Simultaneously the hydrophobic nature of the protein matrix goes on increasing upon blending which is reflected in the noted data. This property may be utilised for aerated health drink. Emulsifying capacity

The emulsifying capacity of the jackfruit seed flour and its blends are reported in Table 4 a & b which indicate that jackfruit seed flour showed less

Table 3a  Foam Capacity ( at 0 hr. ) and Foam stability of Jackfruit seed flour blends Time in minute Jackfruit Seed Flour,60oC, Lye peeled 10% blend 15% blend 20% blend Wheat flour

Volume of foam in ml /(1× 10-6 M3 )

0 10 6 7 7.6 5

20 7 5.4 6.0 6.2 4

40 5 4.0 5.8 6.0 3.2

60 5 3.6 5.2 5.8 3.0

120 4 2.8 5.2 5.8 2.2

Table 3b  Effect of Varying NaCl concentration on Foaming Capacity ( ml / 1× 10-6 M3 ) NaCl Conc. Mol/dm3 Jackfruit Seed Flour,600C, Lye peeled 10% blend 15% blend 20% blend Wheat flour

0.0 10 6 7 7.6 5

0.2 11.4 7.1 8.0 8.8 6.2

0.4 11.6 7.4 8.4 8.2 6.4

0.6 10.8 7.4 7.8 7.8 6

0.8 10.4 6.8 7.4 7.4 5.4

1 10.2 6.4 7.2 7.4 4.8

ROY CHOWDHURY et al: FUNCTIONAL PROPERTIES OF RAW AND BLENDED SEED FLOUR OF JACKFRUIT

351

emulsifying capacity in comparison with wheat flour whereas that could be extended with increase in blend percentage with wheat flour. The result of emulsifying capacity by varying NaCl concentration revealed that this functional property was initially increased upon increase in molar concentration up to 0.4-0.6 and decrease in value with higher concentration of NaCl. The result might be due to the fact that within a composite matrix there could be interaction of starch and protein both. Though the flour showed a very high water and oil absorption values in comparison to wheat flour, still the emulsifying capacity of protein in a cohesive or composite matrix showed a reverse observation.

charge on protein to its hydrophobicity is a better predictor than hydrophobicity alone, of the type of gel network formation (coagulum type gel and translucent type gel). 20% (w/w) concentration of 15% (w/w) blend was found effective in gel formation which can be utilized as a gelling agent for developing new food items like soup, sauces, pudding and cake and can be used in food additives. Hermansson25 discussed the significance of aggregation and denaturation of protein in gel formation. In association with starch and carbohydrate, the protein-protein interaction involving non-covalent bonds was found to be increasing on blending. This indicates that jackfruit seed proteins aggregate and get denatured to make gel.

Gelation

Protein solubility

Variations in gelation (Table 5) of different flours (raw jackfruit seed and their blends with wheat flour) can be attributed to the change in the ratios of different constituents such as carbohydrate, lipids and protein. The gelling capacity of flours has been attributed to denaturation, aggregation and thermal degradation of starch23. Gelation involves the swelling of starch and protein components in flour matrix on heating. According to Damodaran24 the ratio of net

Protein solubility of flours is presented in Fig. 1. The result indicates that minimum solubility for jackfruit seed flours and its blends with wheat flour is at around pH 4 -6, while in all cases, the maximum solubility was observed at pH 10. Normally, solubility gets increased as the pH increases whereas least solubility was observed at pH 4, followed by gradual increase in solubility profile as pH increases. Maximum solubility was achieved around pH 10 for flour blends. Similar results have been reported for flours of different kinds such as mung bean26 and black gram27. The minimum protein solubility of 23% at pH 4.5 for winged bean16 and 19.36% at pH 4 for cowpea powder28 had been reported. Low protein solubility of heat-treated jackfruit seed flour may be due to the protein denaturation. High temperature causes irreversible denaturation, association and

Table 4a  Emulsifying capacity of Jackfruit seed flour blends Flour type

Emulsifying capacity ml/g ( × 10-3 M3 /kg )

Jackfruit seed flour 10% blend 15% blend 20% blend Wheat Flour

8.1 9.0 10.5 11 13

Table 4b  Effect of NaCl concentration on Emulsification capacity ml/g ( × 10-3 M3 / kg ) NaCl Conc. Mol/dm3 Jackfruit Seed Flour,60oC, Lye peeled 10% blend 15% blend 20% blend Wheat flour

0.0 8.1 9.0 10.5 11.0 13

0.2 8.6 9.8 11.2 12.1 13.6

0.4 9.0 10.2 11.8 12.8 13.8

0.6 8.2 9.6 10.5 11.1 12.8

0.8 7.2 8.4 9.6 10.4 12

1 6.1 8.0 8.8 9.0 11.1

Table 5  Gelation properties of Jackfruit Seed Flour Blends a Flour concentration ( %, w/v ) Flour Type Jackfruit Seed Flour 10% blend 15% blend 20% blend Wheat Flour a

2 -

4 +/+/+/-

- not gelled ; +/- slightly gelled ; + gelled

6 + +/+ + +/-

8 + + + + +/-

10 + + + + +

12 + + + + +

14 + + + + +

16 + + + + +

18 + + + + +

20 + + + + +

352

INDIAN J NAT PROD RESOUR, SEPTEMBER 2012

developing bakery and confectionary items, extended meat batters, etc in non-wheat producing countries and even during scarcity for wheat production or unavailability of wheat flour in local market. References

Fig. 1Effect of pH on protein solubility of raw and blended jackfruit seed flour

followed by precipitation of polypeptide chain as high molecular weight compound29. Mild heat treatment on protein may not drastically reduce its solubility30. Conclusion The present study reveals that jackfruit seed flour has a great potential in new food formulation along with wheat flour. The different functional behaviors of the raw and blended jackfruit seed flour are influenced by milling operation, concentration of NaCl, effect of pH and on heating. As the flour and its blends have good water and oil absorption capacities up to 15% (w/w) blending could be suggested to use in developing bread with comparable sensory and chemical evaluation with control. The flour blends could be used as protein supplements and functional ingredients in human diets. The raw seed flour and its blends with wheat flour could also be used in

1 Rahman M A, Nahar N, Mian A J and Mosihuzzaman M, Variation of carbohydrate composition of two forms of fruit from jack tree (Artocarpus heterophyllus Linn.) with maturity and climatic conditions, Food Chem, 1999, 65, 91-97. 2 Burkill H M, The Useful Plants of West Tropical Africa, Vol. 4, 2nd Edn, Royal Botanic Gardens, Kew, 1997, pp. 160-161. 3 Bobbio F O, El-Dash A A, Bobbio P A and Rodriguis L R, Isolation and characterization of the physico-chemical properties of the starch of Jackfruit seeds (Artocarpus heterophyllus), Cereal Chem, 1978, 55, 505-511. 4 Kumar S, Singh A B, Abidi A B, Upadhyay R and Singh A, Proximate composition of Jackfruit Seed, J Food Sci Technol, 1988, 25, 308-309. 5 Kely C C, Leandro L O, Camila F P, Patrícia E V, Roberto M et al, Therapeutic administration of KM+ lectin protects mice against Paracoccidioides brasiliensis infection via interleukin12, Amer J Path, 2008, 173 , 423-432 6 Singh A, Kumar S and Singh I S, Functional properties of Jackfruit seed flour, Lebensm – Will u Technol, 1991, 24, 373-374. 7 Odoemalam S A, Functional Properties of raw and heat processed Jackfruit (Artocarpus heterophyllus) Flour, Pak J Nutr, 2005, 4(6), 366-370. 8 Mattil K F, Considerations for choosing the right plant proteins, Food Prod Develop, 1973, 7, 40-42 9 Johnson D W, Functional properties of oilseed proteins, J Amer Oil Chem Soc, 1970, 47, 402-405. 10 AOAC, Official methods for analysis, 14th Edn.,Washington DC: Association of Official Analytical Chemists, 1984 11 Narayana K and Rao Narasinga M S, Effect of partial proteolysis on the functional properties of winged bean (Psophocarpus tetragonolobus) flour, J Food Sci, 1984, 49, 944-947. 12 Abbey B W and Ibeh G O, Functional Properties of raw and heat processed cowpea (Vigna unguiculata, Walp) flour, J Food Sci, 1988, 53, 1775-1777. 13 Beuchat L R , Cherry J P and Quinn M R, Physico-chemical properties of peanut flour as affected by proteolysis, J Agric Food Chem , 1975, 23, 617-620. 14 Lawhon J T, Cater C M and Mattil K F, A comparative study of whipping potential of an extract from several oil seed flours, Cereal Sci Today, 1972, 17, 240. 15 Coffman C W and Garcia V V, Functional Properties and amino acid content of protein isolate from mung bean flour, J Food Technol, 1977, 12, 473. 16 Narayana K and Rao Narasinga M S, Functional properties of raw and heat processed winged bean (Psophocarpus tetragonolobus) flour, J Food Sci, 1982, 47, 1534-1538. 17 Lowry O H, Rosebrough N J, Farr A L and Randall R J, Protein measurement with the Folin-Phenol reagents, J Biol Chem, 1951, 193, 265-275. 18 Kinsella J E, Functional Properties of proteins in food – A survey, Crit Rev Food Sci Nutr, 1976, 7, 219-280.

ROY CHOWDHURY et al: FUNCTIONAL PROPERTIES OF RAW AND BLENDED SEED FLOUR OF JACKFRUIT

19 Pomeranz Y and Chung O K, Interaction of lipids with proteins and carbohydrates in bread making, J Amer Oil Chem Soc, 1978, 55(2), 285-289. 20 Lin M J Y, Humbert E S and Sosulki F W, Certain functional properties of Sunflower meal product, J Food Sci, 1974, 39, 368-370. 21 Yasumatsu K, Sawada K, Moritaka S, Mikasi M, Toda J, Wada T and Ishi K, Whipping and emulsifying properties of soybean products, Agric Biol Chem, 1972, 36, 719-727. 22 Pomeranz Y, Functional Properties of Food Components, Academic Press, 1985. 23 Enwere N J and Ngoddy P O, Effect of heat treatment on selected functional properties of cowpea flour, J Trop Sci, 1986, 26, 223-232. 24 Damodaran S, Protein-stabilized foams and emulsions, Chapt 3, In: Food Proteins and Their Applications, by A Damodaran and A Paraf (Eds), Marcel Dekker : New York, 1997.

353

25 Hermansson A M, Aggregation and denaturation involved in gel formation, ACS symposium Series, 1978, 92, 81-104 26 Thompson L U, Preparation and evaluation of mung bean protein isolates, J Food Sci, 1977, 42, 202. 27 Sathe S K and Salunkhe D K, Functional properties of the great northern bean (Phaseolus vulgaris L.) proteins, emulsions, foaming, viscosity and gelation properties, J Food Sci, 1981, 46, 71. 28 Okaka J C and Potter N N, Physicochemical and functional properties of cowpea powders processed to reduce beany flavor, J Food Sci, 1979, 44, 1235-1240. 29 Wolf W J and Tamura T, Heat denaturation of soybean 11s protein, Cereal Chem, 1969, 46, 331-336. 30 Morr C V, German B, Kinsella J E, Regenstein J M, Van Buren JP et al, A collaborative study to develop a standard food protein solubility procedure, J Food Sci, 1985, 50(6), 1715-1718.