Tortilla chips are made from corn and sorghum by nixtamalization process. Nixtamalization caused some changes in physical apperaence of the protein and
starch of the kernel. Gelatinization and crystallinity are of cardinal importance in starch
technology. So, this study was performed to follow-up the degree of starch
gelatinization (loss of birefringence and structure disruption) and the changes in
starch crystallinity during tortilla chips processing. Starch granules in raw grains
appeared as distorted spherocrystals, with a typical dark cross. The majority of starch
granules in nixtamalized samples were swollen, adhered to other granules and
exhibited partial birefringence. Masa had irregular in shape and often the external part
of the granules exhibted birefringence. Tortilla chips lost about 95% of birefringence.
The structural changes as evaluated by scanning electronic microscope revealed that
raw samples had a mixture of round granules from the floury endosperm and angular
granules from the horny endosperm. Starches granules are disrupted and swollen by
cooking. Masa had irregular and swollen starch granules and a cohesive, glue like
structure was appeared. Misshape starch granules along with more uniform,
smoothes and more amorphous appearance of starch granules were appeared in
tortilla and tortilla chips samples. The X- ray diffractograms of raw samples show
pattern closely to A-type cereal straches. A diffraction peak of a feature of V-type
starch was appeared in the nixtamal samples. Masa samples had the main peaks of
A-type starch along with developing a diffraction peaks feature of V-patterns of starch.
Starch was changed from a crystalline to an amorphous state as a result of baking
and frying.