Using NIRS to Predict Palmitic Fatty Acid in Peanut Seeds

Barry L. Tillman and George Person

Why are oleic, linoleic, and palmitic acid important?

• Dominant fatty acids in peanut oil

– High oleic acid• US Patent- 6,063,984, Knauft, Gorbet, Norden• Trait is simply inherited- two recessive genes

Oleic acid

(18:1)

Linoleic acid (18:2)

Palmitic acid

(16:0)Normal 50-60% 20-30% 8-12%High Oleic 74-84% 2-8% 5-7%

Relationship among Palmitic, Linoleic, and Oleic Acids

y = -0.1389x + 172.49R2 = 0.8532n = 13856

y = -0.8685x + 727.76R2 = 0.9806n = 13856

050

100150200

250300350

400

350 450 550 650 750 850

Oleic acid (g kg-1)

Con

tent

(g k

g-1)

Palmitic acid Linoleic acid

High oleic peanuts have commercial and health benefits.

• Commercial benefits– High oleic peanuts have 5x-15x the shelf life of normal peanuts

• Maintain flavor– Oil quality similar to olive oil

• Health (have more of what makes normal peanuts healthy)– High in monounsaturated fats

• Lowers total cholesterol • Lowers bad LDL cholesterol • Maintains beneficial HDL cholesterol • Lowers triglycerides

– May reduce risk of heart disease when eaten regularly

Developing high oleic (HO) peanut varieties is a priority

At Least 18 High oleic acid peanut cultivars have been released.

• SunOleic 95R• SunOleic 97R• GK7• VC-2• AT1-1• AT201• Flavor Runner• Georgia HiOL• Georgia 02C

• Olin• Tamrun OL01R• ANorden• Hull• Tamrun OL02R• AT3085RO • McCloud• York• Florida-07

How do we measure fatty acid content? • Gas chromatography (GC)

– Accurate– Always destructive/injurious– Time consuming (15-20 min./sample)

Can we reliably measure oleic, linoleic and palmitic acid content with NIR and replace GC? • We test about 800-900 samples per year using GC• Need to test 3-4 times that number

– Near infrared reflectance spectroscopy (NIR)• Less accurate• Can be non-destructive• Fast (3-5 min./sample)

NIR requires minimal sample preparation

NIR captures and stores light absorbance data

Absorbance data used to estimate chemical content based on calibration

NIR Calibration - Fatty Acids in Peanut

• Previous Calibration & Validation – Predicts Oleic and Linoleic acids– Misclassifies 4-5% of single seeds tested

(Crop Sci. 46:2121–2126 (2006))

• Goals of New Calibration– Predict Oleic, Linoleic and Palmitic acids– Reduce % misclassified seeds

300350400450500550600650700750800850900

300 350 400 450 500 550 600 650 700 750 800 850 900

NIR predicted Oleic Acid (g kg-1)

GC

mea

sure

d O

leic

Aci

d (g

kg-1

)Previous calibration- Oleic Acid

Agreement between NIR and GC is very good

R2=0.98y = 1.01x – 4.4slope: p>|t|<0.0001intercept: p>|t|=0.6059n =132

GC

NIR

350400450500550600650700750800850900

350 400 450 500 550 600 650 700 750 800 850 900

NIR predicted Oleic Acid (%)

GC

Mea

sure

d O

leic

Aci

d (%

)Previous validation- Oleic Acid

4 out of 43 HO (4/94 total) kernels were misclassified by NIR

R2=0.84y = 1.01x – 2.0slope: p>|t|<0.0001intercept: p>|t|=0.9475n =94 GC

NIR

NIR Calibration - Fatty Acids in Peanut

• Previous Calibration & Validation – Predicts Oleic and Linoleic acids– Misclassifies 4-5% of single seeds tested

(Crop Sci. 46:2121–2126 (2006))

• Goals of New Calibration & Validation– Predict Oleic, Linoleic and Palmitic acids– Reduce % Misclassified seeds

New Model Oleic Acid Calibration(single seeds)

y = 0.9822x + 12.749R2 = 0.851

n = 243

360

440

520

600

680

760

840

380 430 480 530 580 630 680 730 780 830 880NIRS predicted Oleic acid (g kg-1)

GC

mea

sure

d O

leic

aci

d (g

kg

-1)

New validation- Oleic Acid1 out of 43 HO (1/94 total) kernels were misclassified by

NIR

y = 1.0034x - 8.4905R2 = 0.8882

n = 94

360

440

520

600

680

760

840

400 450 500 550 600 650 700 750 800 850NIRS predicted Oleic acid (g kg-1)

GC

mea

sure

d O

leic

aci

d (g

kg

-1)

New Model Palmitic acid calibration(single seeds)

y = 0.9541x + 3.2758 R2 = 0.7244

n = 243

45

55

65

75

85

95

105

115

125

45 55 65 75 85 95 105 115NIRS predicted Palmitic acid (g kg-1)

GC

mea

sure

d Pa

lmiti

c ac

id (g

kg

-1)

New Model Palmitic acid validation(single seeds)

y = 1.0383x - 5.0642R2 = 0.804

n = 94

45

55

65

75

85

95

105

115

125

45 55 65 75 85 95 105 115NIRS predicted Palmitic acid (g kg-1)

GC

mea

sure

d Pa

lmiti

c ac

id (g

kg

-1)

NIR Calibration - Fatty Acids in Peanut

• Previous Calibration & Validation – Predicts Oleic and Linoleic acids– Misclassifies 4-5% of single seeds tested

(Crop Sci. 46:2121–2126 (2006))

• Goals of New Calibration & Validation– Predict Oleic, Linoleic and Palmitic acids– Reduce % Misclassified seeds

• Results- New Calibration & Validation– Predicts Oleic, Linoleic and Palmitic acids– Misclassifies 1 % of single seeds tested

Old Model Oleic acid validation(average of 5 spectra)

y = 1.1065x - 66.78R2 = 0.8938

n = 434

360

440

520

600

680

760

840

400 450 500 550 600 650 700 750 800 850NIRS predicted Oleic acid (g kg-1)

GC

mea

sure

d O

leic

aci

d (g

kg

-1)

715

740

New Model Oleic acid validation(average of 5 spectra)

y = 1.016x - 15.107R2 = 0.9115

n = 434

360

440

520

600

680

760

840

400 450 500 550 600 650 700 750 800 850NIRS predicted Oleic acid (g kg-1)

GC

mea

sure

d O

leic

aci

d (g

kg

-1)

725

740

Previous Model - Oleic acid validation(average of 5 seeds)

y = 1.1083x - 69.289R2 = 0.89n = 434

360

440

520

600

680

760

840

400 450 500 550 600 650 700 750 800 850NIRS predicted Oleic acid (g kg-1)

GC

mea

sure

d O

leic

aci

d (g

kg

-1)

720

740

% Misclassified (average of spectra)

0

2

4

6

8

10

12

14

655 675 695 715 735 755

NIRS cutoff value (g kg-1 predicted Oleic acid)

% M

iscl

assi

fied

New model Old model

725

Old model % misclassified(average of seeds)

0

2

4

6

8

10

12

14

655 675 695 715 735 755

NIRS cutoff value (g kg-1 predicted Oleic acid)

% M

iscl

assi

fied

720