Using Yellow Pea Flours to Improvethe Glycemic Prof ile of Cereal Products

Pulses have a signifi cantly lower glycemic index (GI) (39-55) than white rice (80), white bread (100) and potatoes (121)1 and are a valuable means of lowering the glycemic index of the diet.

There is a growing body of evidence that shows pulse fl ours and fracti ons may also have a low glycemic response; however the impact of processing (such as milling technology) and thermal processing (such as extrusion) on glycemic response of these pulse products has not been fully investi gated.

Dry fi eld peas (Pisum sati vum) are a nutrient-dense food ingredient which have been increasingly used as fl our in value-added food applicati ons. The additi on of pea fl our to food products can increase the protein, fi ber, vitamin and mineral content in many foods.

1Foster-Powell K, Holt, S.H.A. and Brand-Miler, J.C. 2002. Internati onal table of glycemic index and glycemic load values: 2002. Am J. Clin. Nutr. 76-5-56.

• The additi on of peasemolina or fl our into extruded breakfast cereal led to a lower in vitro glucose release compared to an all-corn extruded breakfast cereal.

• Inclusion of pulse fl ours can help to improve the glycemic profi le of cereal-based food products.

Key Findings

Overs Yield 16.7%(hull and shorts)

Pin mill15k rpm

Pin mill20k rpm

Fine Semolinayield 22.2%(~400µm)

FIRST BREAK

GrainBin

Corrugated rollsbreak peas intocoarse particles

SIZING ROLLSCorrugated rolls

to resize andscratch semolina

Coarse Semolinayield 40.5%

(600µm)

REDUCTION ROLLSSmooth rolls reducingmiddlings to flour

WholeCoarse

Semolina

WholePea

Flour

Purif ier Purif ier

Flour

Sif ter

Sif ter

Sif terTHE GLYCEMIC INDEX is a measure of the eff ect of carbohydrates on blood sugar levels. Carbohydrates that break down quickly during digesti on and release glucose rapidly into the bloodstream have a high GI; carbohydrates that break down more slowly, releasing glucose more gradually into the bloodstream have a low GI.

Commercially, roller mills are the most common grinding method for the reducti on of grain, parti cularly wheat, into fl our. As this process produces moderately fi ne fl ours within a moderately narrow parti cle size range, it was chosen for further explorati on of processing whole and split yellow peas.

A pilot scale Bühler roller mill was set up in durum milling mode to produce a coarse semolina and fl our with fi ne semolina and overs as additi onal products of the mill fl ow (Figure 1). Split yellow peas and whole yellow peas were roller milled to produce four types of fl our: whole yellow pea fl our, whole yellow pea semolina, split pea (refi ned) yellow

MILLING TECHNOLOGIES

pea fl our and split pea (refi ned) yellow pea semolina, and analyzed for nutriti onal quality (Table 1). Protein was concentrated in the semolina products compared to the fl ours and whole yellow pea semolina contained higher levels of fi ber compared to the whole fl our or refi ned pea semolina and fl our.

Each fl our type was used in a cornmeal/pea-based breakfast cereal formulati on (Table 2) with opti mized extrusion process parameters (Table 3). Breakfast cereals made from both the refi ned and whole pea semolina-based cereals contain signifi cantly higher protein content compared to those made from refi ned or whole yellow pea fl our ingredients.

Research suggests that fl our parti cle size can impact the in vitro glycemic response and this was further explored for pulse fl ours. Refi ned coarse yellow pea semolina (~600µm parti cle size) was remilled into fl our (~150µm parti cle size). Results showed the coarse yellow pea semolina had a lower in vitro glucose release (g glucose per 100g sample) than the refi ned yellow pea fl our, suggesti ng the larger parti cle size impacted glucose release. When the pea fl our and semolina were subjected to high temperature direct expansion extrusion, the in vitro glucose release diff erences due to parti cle size were eliminated with both pea products having similar release profi les (Figure 2).

FIGURE 1

Roller milling of whole yellow peas into whole and refi ned yellow pea semolina and fl our

Using Yellow Pea Flours to Improve the Glycemic Profi le of Cereal Products

Overs Yield 16.7%(hull and shorts)

Pin mill15k rpm

Pin mill20k rpm

Fine Semolinayield 22.2%(~400µm)

FIRST BREAK

GrainBin

Corrugated rollsbreak peas intocoarse particles

SIZING ROLLSCorrugated rolls

to resize andscratch semolina

Coarse Semolinayield 40.5%

(600µm)

REDUCTION ROLLSSmooth rolls reducingmiddlings to flour

WholeCoarse

Semolina

WholePea

Flour

Purif ier Purif ier

Flour

Sif ter

Sif ter

Sif ter

Protein%

Total Fiber%

Folic Acidµg/100g

Thiamine (Vit B1) mg/100g

Riboflavin (Vit B2) mg/100g

Niacinmg/100g

Ironmg/100g

Potassiummg/100g

23.6

23.4

28.98

0.77

0.13

3.42

5.36

941

WHOLEYELLOW PEAS

26.7

9.5

107.21

0.8

0.24

4.58

5.68

1050

REFINED PEA SEMOLINA

22.5

7.8

30.56

0.67

0.17

4.10

6.47

902

REFINED PEA FLOUR

25.7

20.2

97.23

0.86

0.17

4.11

5.74

953

WHOLE PEA SEMOLINA

21.7

14.8

52.71

0.64

0.14

3.79

6.18

817

WHOLE PEA FLOUR

TABLE 1

Eff ect of roller milling on nutriti onal quality of whole and split (refi ned) yellow peas

Corn meal

Pea flour or pea semolina

Pea fiber

Salt

Sugar

INGREDIENT

31.5

56.5

6.5

0.5

5.0

AMOUNT (%)

TABLE 2

Opti mized breakfast cereal formulati on Water Flow Rate

kg/h

Blend Feed Ratekg/h

Screw Speedrpm

Cutter Speedrpm

Temperature°C

PressurekPa

2.1, 2.4

36, 36

537, 650

1178, 1207

107, 109

700, 300

WHOLE PEA SEMOLINA

REFINED PEA SEMOLINA

WHOLE PEA FLOUR

REFINED PEA FLOUR

TABLE 3

Extrusion processing: Opti mized pea-based breakfast cereal products

2.1, 2.1

36, 36

655, 655

1079, 1122

106, 106

400, 400

2.5, 2.2

36, 36

602, 602

1051, 1221

109, 110

300, 300

2.5, 2.5

36, 36

537, 673

1093, 1122

109, 109

300, 200

Conditions – rep 1, rep2

Both yellow pea semolina and fl our were incorporated into the extruded breakfast cereal formulati on and all products analyzed for in vitro glucose release. Results showed that the additi on of the pea semolina or fl our into extruded breakfast cereal led to a lower in vitro glucose release over 360 minutes compared to an all-corn extruded breakfast cereal (Figure 3). These results suggest the incorporati on of pulse fl ours into commercially prepared cereal blends may help improve the glycemic profi le.

100

90

80

70

60

50

40

30

20

10

0

Glucoseg/100g

dry basis

Time, minutes

0 100 200 300

EFFECT OF PARTICLE SIZE AND EXTRUSION – AVERAGE OF 2 REPS

100% PEA SEMOLINA

100% PEA FLOUR

100% PEA SEMOLINA– EXTRUDED

100% PEA FLOUR– EXTRUDED

FIGURE 2

The eff ect of parti cle sizeand extrusion on the in vitro

glucose release of yellow pea fl our

and semolina

100

90

80

70

60

50

40

30

20

10

0

Glucoseg/100g

dry basis

Time, minutes

0 100 200 300

BREAKFASTCONTROL(corn meal, salt, sugar, fiber)

BREAKFAST BLEND(refined yellow peaflour, salt, sugar, fiber)

BREAKFAST BLEND(corn meal, refined yellow peasemolina, salt, sugar, fiber)

100% CORN MEAL

EXTRUDED CEREALS - AVERAGE OF 2 REPSFIGURE 3

The eff ect of the additi on of

yellow pea fl our and semolina

to extruded breakfast cereals

on the in vitro glucose release

over ti me

This research was conducted by the Canadian International Grains Institute and by Dr. Nancy Ames of Agriculture Agri-Food Canada with support from the Canadian Pulse Growers.

For more information, contact:Pulse Canada: o� ce@pulsecanada.com | 204-925-4455 | www.pulsecanada.com