Effect of γ‐radiation and microwave heating of wheat grain on some starch properties in irradiated grain as well as in grain of the next generation crops

Abstract

Grains of the Polish winter wheat variety Begra were subjected to gamma-radiation (grain harvested in 1996) within the dose range of 0.05-10 kGy and microwave heating (grain harvested in 1997) from 28 degrees C to 98 degrees C. Later the grains were divided into two parts, the first was used for direct analyses after treatment. The second part was sown on the experimental fields. The obtained crop was described as the first generation and divided into two parts. One part was destined to determination of starch properties and the second part was sown in order to obtain the second generation crop. The same pattern was conducted in order to achieve the third generation crop. gamma-Irradiation directly applied on the wheat grain reduced statistically significant falling number values and gelatinisation enthalpy (deltaH) of the grain treated by 5 and 10 kGy. Calculated linear regression correlation coefficient between the falling number values and the gelatinisation enthalpy was equal to 0.94 (p < or = 0.001) and showed that these two starch characteristics are well correlated in the case of directly irradiated wheat grain. The falling number values, peak temperatures (Tp) and gelatinisation enthalpy (deltaH), in three generations of wheat grain crop studied, did not show any statistically significant differences as a result of indirect effect of gamma-irradiation. Microwave direct heating of wheat grain to 98 degrees C caused a statistically significant increase in the falling number value and decrease in starch gelatinisation power expressed by the enthalpy of gelatinisation (deltaH). The statistically significant changes in the falling number values, slight changes in the peak temperatures (Tp) and enthalpy of gelatinisation (deltaH) were found in all three generation crops as an indirect effect of microwave heating.

Microwave technology for disinfestation of cereals and pulses: An overview

“…A hot spot can be defined as a local area of very high temperature that results from the temperature dependence of material properties. The treatment of infested grain by microwave treatment appears a reliable alternative to conventional post-harvest in the near future, either with stationary or mobile applicators on the farm or quarantine purposes during the loading process before grain storage and seed sowing (Dolinska et al 2004)…”

Changes in Microwave-Treated Wheat Grain Properties

“…When applying microwaves to reduce grain damage by stored-grain pests, it should be consider also the question of how this heat-treatment will affect wheat grain properties not only directly, but also indirectly, on seeds secondary infested as well used for the production of next-generation grain crops. So far only a few papers on indirect influence of microwaves on wheat seeds have been published (Dolińska & Warchalewski, 2002;Dolińska et al, 2004;Warchalewski et al, 2007;Grundas et al, 2008). The major problem in the use of microwave energy for the eradication of pests and pathogens in seeds has been its adverse effect on seed quality (Stephenson et al, 1996).…”

“…Grain temperatures ≤48 o C probably enhance amylases activity within the grain during the heating process. Moreover, some changes in starch properties are possible due to differences reported by Dolińska et al (2004) in falling number values, peak temperatures (T p ), and gelatinization enthalpy (∆H). This could explain the increase in extractability of reducing sugars ≤60 sec of heating time, when grain temperature was not exceeded 48 o C. Changes in reducing sugars content was well correlated with endogenous amylolytic activity determined in samples of grain at ≥64 o C during microwave heating.…”

“…fed on three generation wheat grain crops bred from seeds microwave heated shown some statistically significant differences as can be seen in factors such as heritability and possible genetic modification of the wheat crop. However, each year, the climate, soil and fertilization treatment of wheat seeds were exactly the same, the influence of different climate conditions during the three cultivation periods should not be excluded (Dolińska, 2004;Dolińska et al, 2004;Grundas et al, 2008).…”

“…In the case of grain treatment as seeds, the germination potency should be preserved with acceptance of some unintentionally mutation in next generation of wheat crops. The treatment of infested grain by microwave appears a reliable alternative to conventional post-harvest insect control in the near future, either with stationary or mobile applicators on the farm or quarantine purposes during the loading process (pre-or post-shipment) before grain storage and seed sowing (Plarre et al, 1999;Dolińska et al, 2004).…”