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Variation in Thermal Properties of Corn Starch as Affected by Hybrid Selection and Drying Temperature

Proceedings of the Corn Utilization Conference IV.
National Corn Growers’ Association. St. Louis, MO.
Johnson, L.A., P.J. White, and L.M. Pollak. 1992.

Several research programs focus on identifying corn hybrids with starches having unique functional properties by using differential scanning calorimetry (DSC) as a technique for screening large numbers of samples. Thus, it is important to have baseline DSC data on the variation among commonly grown dent hybrids and to know the effect of laboratory drying conditions. Our objective was to quantify these variations to understand the significance of differences observed among genotypes.

Twenty-seven samples were selected from a pool of 184 hybrids grown in central Iowa. Those with the greatest variation in physical and compositional properties were selected for laboratory wet milling. The sample set is the same one as used by Fox et al 1992. Methods for analysis have been reported by White et al 1990.

Statistically significant differences in thermal properties for gelatinization of starch from dent corn hybrids exist (table below). However, differences observed were probably of minimal practical importance. Few differences in retrogradation characteristics were observed. Drying at 60?C, a process recognized as annealing.

 

Gelatinization

 

Retrogradation

 

Onset (°C)

Range (°C)

 

DH (Cal/g)

P.H.I.a (Cal/g°C)

 

Onset (°C)

Range (°C)

 

DH (Cal/g)

Retro (%)

Starch dried at 45°C

Mean

68.0

10.6

3.13

0.60

 

43.3

18.5

1.30

41.5

High

70.4

14.6

3.36

0.80

 

45.4

21.3

1.50

47.5

Low

65.8

7.7

2.75

0.48

 

40.9

16.5

0.96

32.3

LSD (p<0.05)

1.2

1.3

0.30

0.10

 

4.2

3.5

0.46

15.5

Starch dried at 60°C

Mean

70.5

9.8

2.93

0.60

 

43.1

18.7

1.47

50.1

High

73.4

12.6

3.18

0.80

 

44.4

24.0

1.76

63.5

Low

68.9

7.7

2.39

0.44

 

41.1

15.7

1.15

38.8

LSD (p<0.05)

3.4

2.9

0.52

0.16

 

2.9

3.2

0.48

15.7

 

aPeak Height Index

Fox, S.R., L.A. Johnson, C.R. Hurburgh, and C. Dorsey-Redding, 1992. Cereal Chem. 69(2): 191-197.

White, P.J., I.R. Abbas, L. Pollak, and L.A. Johnson. 1990. Starch/Staerke 41: 179-180.