PhD

The present study was undertaken to standardise processing treatments for
optimising resistant starch (RS) formation in rice starch and to evaluate the changes
in rice starch properties. The study also aimed to standardise rice flour supplemented
with RS, to evaluate its quality attributes during storage and the effect of RS
supplemented food products on postprandial glycaemic response.
Starch was isolated from the raw and parboiled rice of variety Uma. Raw rice
had lower starch content and higher RS, compared to parboiled rice.
The effect of processing conditions on the RS content of rice starch was
studied in 48 treatments by autoclaving at 121°C and 141°C for 20, 40 and 60
minutes without moisture and with 10, 20 and 40 percentage moisture levels. After
autoclaving, the samples were cooled at room temperature and at -20°C. The yield of
RS was found to be maximum in samples autoclaved at 141°C for 40 minutes with 10
per cent moisture and cooled at -20°C. Increasing the duration of autoclaving up to 60
minutes at a lower temperature of 121°C was also found to be effective in improving
the RS content of rice starch. RS formation not only depends on a single factor but
also on multiple factors like time and temperature of autoclaving, moisture as well as
cooling conditions.
To study the effect of repeated autoclaving and cooling, five treatments
yielding maximum RS content were selected. The RS content increased with increase
in the number of autoclaving and cooling cycles irrespective of the temperature and
time of autoclaving, moisture content and cooling conditions. Repeated autoclaving
and cooling lowered the content of rapidly and slowly digestible starch.
The moisture and protein content of repeatedly autoclaved and cooled samples
were significantly lower than the native starch. The total carbohydrate and amylose
content increased during processing and found to be maximum in samples autoclaved
at 141°C for 40 minutes and cooled at -20°C.
The standardisation of resistant starch supplemented rice flour (RSRF) was
carried out by incorporating 10, 15 and 20g of RS to 100g of puttu and idiappam
flour. For this, two treatments with maximum RS content were selected. Physical
qualities of the flour, in vitro starch digestibility and organoleptic qualities of the
products were evaluated. Incorporation of RS decreased the bulk density (BD) and
water absorption index (WAI) of flour whereas water solubility index (WSI)
increased. In vitro starch digestibility was found to be inversely proportional to the
RS content of rice flour. The puttu and idiappam prepared with RS supplemented rice
flour were found to be organoleptically acceptable.
The storage studies of RSRF were carried out by selecting RS incorporated
puttu and idiappam flour having better organoleptic acceptance of their products. The
flour was stored for six months under ambient condition after packing in polythene
bags.
The physical qualities like BD, WAI and WSI of puttu and idiappam flour
decreased during six months of storage. A decrease in protein and total carbohydrate
content was noticed with an increase in the moisture level. The RS content of flour
improved during storage. The count of bacteria, yeast and fungi increased towards the
end of storage in both the flour. Insect infestation was not observed throughout the
storage period. The organoleptic qualities of the puttu and idiappam decreased
slightly, when they were prepared from stored flour.
Postprandial glycaemic responses of puttu and idiappam supplemented with
RS was assessed among diabetic and non-diabetic individuals in comparison with
non-supplemented products. The increase in blood glucose level was relatively at a
lower rate when RS supplemented puttu and idiappam were given to diabetic as well