PhD

A study entitled “Quality evaluation of medicinal rice (Oryza sativa L.) cv. Njavara for product development and therapeutic value” was conducted to assess the major quality parameters such as physico-chemical characteristics, nutritional composition and antioxidant activity.

Two eco types of Njavara rice Njavara black (NB) and Njavara yellow (NY) were procured from RRS, Moncompu and one eco type of Hraswa was obtained from ARS, Mannuthy. Hraswa was treated as the control.

The study was conducted in three phases. The first phase experiment envisaged the quality evaluation of the selected rice varieties. In the second phase of experimentation, a product (grits) was developed using both the ecotypes of Njavara; Its physical, chemical, nutritional composition, sensory and shelf life qualities was assessed and finally in the third phase of experiments the product was tested for its therapeutic value viz. glycemic index and antioxidant properties.

In the first experiment, the parameters selected to study under physico-chemical characteristics were moisture, size, shape, length, width, L/B ratio, colour, thousand grain weight, gel consistency, bulk density, gelatinization temperature, chalkiness index, viscography and hardness.

Regarding the colour of the rice samples all the samples were red in colour. The L/B ratio and moisture content was recorded highest for NY among the three selected rice varieties. Thousand grain weight was highest for the variety Hraswa (control) and lowest for NY.

The assessment of the calorific value/energy of the three rice varieties revealed that NY had the highest value for calories when compared to the other two varieties. The protein content was found to be higher in NB and lowest in Hraswa (control) variety. The evaluation of protein quality showed that values of essential amino acids like threonine, valine, methionine and isoleucine of Hraswa (control variety) was lower than the values of raw Njavara rice samples. Whereas leucine, phenylalanine, lysine and tryptophan values of Hraswa were higher than Njavara black and yellow varieties. Amino acid score (AAS) of the rice samples revealed that NY had more amino acid score than NB.

Soluble fibre content was more for NB and lower for Hraswa (control) variety. NB had the highest value for total phenol content. Trace element content of the rice samples revealed that NB had the highest value for Fe. As for Mn, Zn, Cu and Se, Hraswa (control) variety had the highest values.

The results of the antioxidant properties revealed that for DPPH scavenging activity and hydroxyl radical activity NY had highest antioxidant activity, with an IC50 value of 31.62 µg/ml for DPPH and 46.00 µg/ml for hydroxyl radical scavenging activity. For superoxide radical scavenging activity, NB had the highest activity with an IC50 value of 48.78 µg/ml.

In the second phase of the experiment, both the Njavara ecotypes were first parboiled and then converted to grits form and its nutritional composition, sensory and shelf life qualities were assessed.

The results revealed that the energy content of the NY (G) was higher when compared to NB (G). It was found that processing influences the calorific values of rice positively. The protein content was found to be highest in NY (G) and the results showed a decrease in protein content due to processing when compared to raw values. As a result of processing the essential and non-essential content of both the Njavara varieties were found to decrease and the decrease was found more in NY (G) when compared to NBG). The EAA index of the rice samples showed that NB (G) had higher value.

NY (G) had higher soluble fibre content; the results revealed that soluble fibre content has decreased as result of processing. NB (G) had the highest value for total phenol content and the results revealed that after processing the total phenol content had increased. Trace element analysis of the Njavara rice samples in the present study revealed that all the trace elements viz., Fe, Mn, Zn Cu and Se increased in content after processing with NB(G) having the highest value for all the trace elements.

Antioxidant properties showed that for DPPH scavenging activity NY grits had highest antioxidant activity with an IC50 value of 35.89 µg/ml. For hydroxyl radical scavenging activity also NY grits was having highest activity. (IC50 = 53.78 µg/ml). Superoxide radical scavenging activity showed that NB grits had highest activity (IC50 value = 48.78 µg/ml).

To ascertain the shelf life quality of the developed product, moisture percentage, peroxide value, insect count and microbial growth was determined.

The assessment of microbial growth revealed that the highest microbial load was found in NB(G) but these levels were within the prescribed specification.

Results of the selection of superior variety showed that NB (G) was found to be superior in quality, but statistically the values of NY (G) and NB(G) were not having much difference.

In the third phase of experiments, Njavara grits were tested for their therapeutic value viz. glycemic index and antioxidant properties.

For assessing the therapeutic value, different breakfast recipes like uppuma, porridge, kozhukatta and oratti were tried in the laboratory incorporating Njavara rice grits. The formulated recipes were then subjected to sensory evaluation. Njavara grits uppuma obtained the highest score for overall acceptability.

For assessing the efficacy of Njavara on the blood sugar levels, a feeding trial for 3 months was conducted among five diabetic subjects in the age group of 40-50 years. Blood sugar levels was monitored initially (before the supplementation) and finally (after the supplementation). The results revealed that, for all subjects, blood sugar levels decreased after supplementation study.
Mean glycemic index and Glycemic load of the Njavara rice was found to be 72 and 36 respectively.
Antioxidant properties in the blood samples of the subjects revealed that after the supplementation with Njavara the DPPH scavenging activity, hydroxyl radical activity and superoxide anion-radical scavenging activity of all the five subjects under study had appreciably increased.