Reference "Pasting Properties of gamma-Irradiated Rice Starches as Affected by pH"

Reference ID

6770

Title

Pasting Properties of gamma-Irradiated Rice Starches as Affected by pH

Source

Journal of agricultural and food chemistry, 2002, vol. 50, pp. 336-341

Authors (2)

Bao-J

Corke-H

Abstract

Changes in the viscosity properties of gamma-irradiated rice starches (from 1 to
25% amylose content) from four genotypes (JY293, Jiayu 293; XS, Xiushui; ZF504,
Zhefu 504; and ZXN, Zaoxiannuo) during pasting in water (pH 7) or in different
pH solutions were studied using a rapid visco analyzer. Peak viscosity (PV) of
all native rice starches was little affected at pH 4 and 10, while hot paste
viscosity (HPV) and cool paste (final) viscosity (CPV) were generally lower at
pH 4 and higher at pH 10 as compared with that at pH 7. The PV, HPV, and CPV of
gamma-irradiated starches were higher at pH 4 and lower at pH 10 than pH 7. All
viscosity characteristics of native rice starches were reduced in stronger
alkali (pH 11.5) or acidic (pH 2.5) solutions. However, the gamma-irradiated
starches were substantially higher at pH 2.5 but lower at pH 11.5, indicating
that the effect of irradiation was highly pH dependent. The swelling volume of
irradiated ZF504 and JY293 starch at all irradiation levels was higher at pH 4
than pH 7, while the values were lowest at pH 2.5. The irradiated ZXN and XS
starches had higher swelling volumes at pH 4 and pH 2.5 than pH 7. Differential
scanning calorimetry analysis showed that gamma-irradiation caused progressively
lower gelatinization peak temperature (T(p)) and higher gelatinization range
(T(r)) at pH 7. T(p) was higher and T(r) was lower at a much stronger acidic
condition (pH 1) for both native and irradiated starches. The possibility of
using viscosity changes in low pH for the detection of irradiated starch was
discussed.