Studies on pasting and structural characteristics of thermally treated wheat germ

Abstract

In order to utilize wheat germ, a nutrient-dense by-product of wheat milling industry, in various food products, different moist and dry heat treatments were used to stabilize and to investigate its influence on protein sub-unit composition, starch pasting characteristics and structural characteristics. The raw germ contained 11% moisture, 31.4% crude protein, 18.4% dietary fibre and 7% fat. Different heat treatments, except for fluidized bed drying, inactivated the lipase activity in germ completely. On the other hand, various heat treatments inactivated lipoxygenase activity to varying extents (78–92%). Extent of gelatinisation, as assessed in electron micrographs was least in steamed and fluidized bed dried samples, while steamed and oven-dried germ and drum dried germ samples exhibited greater extent of gelatinisation. The extent of gelatinisation seemed to be more in drum-dried sample as no intact starch granule was observed. Electrophoretic pattern and sub-unit composition of germ samples remained similar, irrespective of their nature of treatment. Raw germ showed a gelatinisation temperature of 67.9 °C as measured in visco-amylograph and increased to 80.3–88.3 °C for differently treated germ samples, except for drum-dried sample. Differently heated germ samples, depending on their extent of pre-gelatinisation, gave significantly lower peak viscosity (221–268 BU) and break down values (0–9 BU).