Soybean: The Future Food Protein Source for Humans

Srinivasan Damodaran Department of Food Science

University of Wisconsin-Madison

The Issue

World Population:

> 7 billion and growing.

Expected to reach 10 billion by 2050

Do we have enough food proteins to feed the population?

Global Soybean Production (2012-13)

Country Current (2012/13)

World 258.1 MMT (251 MMT in 2011/2012)

Brazil 83.5

USA 82.1

Argentina 53.0 (48 MMT in 2011/12)

China 12.6

India 11.5

Almost all of soymeal produced worldwide is used as cattle feed.

The efficiency of conversion of plant proteins to animal protein is 8:1 (i.e., ~ 12%).

Nutritional Value of Soy Protein

Protein source Chemical Score(%)

Egg Cow’s milk Beef Fish Wheat Rice Maize Barley Soybean Pea Peanut

100 100 100 100 40 59 43 55 100 82 67

Based on FAO/WHO amino acid pattern, 1985

Two major Issues limiting expanded use of soy protein isolate in foods:

1. The first one is its “beany, grassy, cardboardy” off-flavor.

Two-thirds of the world population is averse to this “beany” off-flavor.

The source of these off-flavors is residual phospholipids in SPI.

Source of Phospholipids: Soybean Oil bodies

Phospholipid

Hydroperoxide

R

O2

R o o

H

Pentyl Pyridine, Hexanal, and other carbonyl compounds.

Formation of Off-Flavors

Decomposition

2. Phyto-estrogens

• Prevent breast and prostate cancer • Reduce the risk of coronary artery disease • Improve bone health

Lingering Question: Do they reduce the testosterone level in men?

We need to develop a single technology that can solve both these issues

Structure of bCD

Toroidal view of bCD

=O

6.5Å

8Å

Beta-Cyclodextrin (bCD)

Challa et al., 2005

Salient Features of the New Technology…

Soy Protein-bound Phospholipid

Phospholipase A2

LPL FFA

b-Cyclodextrin

pH 4.5

Precipitate (Protein)

Supernatant

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

2,0

Removal of Phospholipids by PLA2/b-Cyclodextrin Treatment

Ph

osp

ho

lipid

co

nte

nt

of

SPI (

%)

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

2,0

70

80

90

100

4 5 6 7 8

Cavity diameter of cyclodextrin (Å)

% R

ed

uc

tio

n o

f P

L

120 U PLA2, 8 mM CD, pH8

Ph

osp

ho

lipid

co

nte

nt

of

SPI (

%)

Relative effects of a, b, and g-Cyclodextrins on Phospholipid removal

Compound Fresh Samples 90 Day Storage

Odor

Threshold 1

Flavor

Threshold 1

Control

(ppb)

Treated

(ppb)

Control

(ppb)

Treated

(ppb) ppb ppb

Hexane 1.92 0.00 0.00 0.00 Pentanal 0.00 0.00 6.04 0.00 12-42 31

3 Methyl Butanal 1.28 1.96 0.00 0.00

2 Ethyl Furan 0.00 0.00 4.90 1.98

Dimethyl

Disulfide 0.00 0.00 0.00 1.82 0.16-12 0.06-30 1-Pentanol 0.00 0.00 4.89 0.00 4000

Hexanal 14.31 0.00 184.79 23.17 4.5-5.0 16-76 (E)- 2-Nonenal 0.00 0.00 4.53 0.00 0.08-0.1 6

1-Hexanol 1.80 0.00 4.71 0.00 2500

2-Heptanone 0.00 0.00 37.64 7.83 140-3000 1000

Heptanal 0.00 0.00 15.53 0.00 3 21

2 Ethyl Hexanal 5.93 0.00 3.10 0.00

1-Heptanol 0.00 0.00 1.99 0.00 3 31

1-octen-3-ol 0.00 0.00 9.53 1.13 1

5-Hepten-2-one, 6-

methyl- 0.00 0.00 3.97 2.18 50

2 Pentyl Furan 3.63 1.53 208.73 35.57 6

Octanal 0.00 0.00 17.56 0.00 0.7 5-45

3-Hepten-2-one, 5-

methyl- 0.00 0.00 10.53 0.00

3 Octen-2-one 0.00 0.00 1.76 0.00

2-Octenal, (E)- 0.00 0.00 1.31 0.00 3 90

2-ethyl-3,5-dimethyl-

Pyrazine 0.00 0.00 0.00 1.90 1

2-nonanone 0.00 0.00 5.56 0.00 5-200

Nonanal 1.80 0.00 6.41 2.49 1 6-12

2-Decanone 0.00 0.00 5.49 0.00

Decanal 0.00 0.00 2.59 1.89 0.1-2 7

2-butyl- 2-Octenal 0.00 0.00 5.54 2.25

Headspace Volatiles after Accelerated Storage at 40 oC for 90 days…

0

20

40

60

80

100

120

140

160

Diadzin Genistin Diadzein Genistein

Control

Treated

Co

nce

ntr

atio

n (

mg

/10

0 g

SP

I)

Removal of Phytoestrogens (Isoflavones)

8% Soy Protein solution

(pH 8.0)

Add PLA2; incubate for 3 h at 37 oC

Add 10 mM bCD and mix the solution for 30 - 60 min.

Diafilter the solution using a

10K ultrafiltration membrane in

a continuous diafiltration mode

to remove bCD and bCD-PL

complex

Adjust the pH to 4.5.

Centrifuge to recover the

protein precipitate. Wash the

precipitate with water at pH

4.5. Re-dissolve the protein

in water at pH 8.0

Spray dry

The Process…

OR

Recrystallize bCD

Supernatant

Extract with ethanol

bCD Ethanol extract

Lyso-phospholipids, FFA, Isoflavones

Non-food Uses of Soy Flour…..

Soy flour biomass can be used as a feedstock for fabricating several industrial polymers: Examples: • Hydrogels • Soy flour-based wood adhesive

Non-food Uses of Soy Flour…..

Soy Flour-based Wood Adhesive

• The use of Urea-formaldehyde adhesive in interior-used plywood and other wood products is being phased out in the US.

• There is a need to develop safe and environmentally friendly wood

adhesives using renewable biomass.

Rationale…

Issues… Soy Flour-based wood adhesives have very poor wet

bonding properties when used in wood composites.

OH

H2N

+ POCl3

O – P - OH

HN

O

OH

O

OH

HO - P -

O – P – O

HN

O

OH

O

OH

O - P -

High pressure (1.2 MPa) and temperature (150 oC)

Plywood panels

Our Approach….

Proteins and polysaccharides

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

SF PSF PSF + 0.8%NaClO2

PSF + 1.8%Ca(NO2)2

120 C

140 C

Wet

bo

nd

ing

stre

ngt

h (

MP

a)

Wet Bonding Strength of Phosphorylated Soy Flour Adhesive in Wood veneers

Adhesive Number of specimens failed in the three-cycle soak test

1st Cycle 2nd Cycle 3rd Cycle

SF 7/7 7/7 7/7

PSF + 1.8% Ca(NO2)2 0/7 0/7 1/7

Three Cycle Soak Test: Soak the specimen in water at 25 oC for 4 h and then dry at 50 oC for 19 h. Repeat the cycle three times.

Water Resistance of PSF Adhesive in plywood Samples in the three-cycle soak test

Summary Soy Flour has great potential for use in both food and non-food applications: • Off-flavors in SPI can be minimized using the cyclodextrin

technology. • Phytoestrogens can be removed from SPI using the

cyclodextrin technology.

• Phosphorylated soy flour has great potential as an environmentally safe wood adhesive.

Acknowledgement:

This research was funded by grants from

USDA-National Institute of Food and Agriculture – Agriculture and Food Research Initiative

AND

USDA Forest Service

Oleosin-PL Complex

Sterically not favored

bCD-PL complex

Oleosin-PL Complex

FA

LAL

PLA2

0.2–0.5 mm

Oleosin

Phospholipid

Triglycerides

11nm

-

Phospholipid

Oleosin -

+ +

-

11 nm Hydrophobic Domain

Proline Knot

N-Terminal C-Terminal

Oil Body

Functional Roles of Proteins in Foods

• Solubility • Emulsification • Foaming • Gelation • Texturization • Fat and Flavor Binding