Dr. S. N. Moorthy - Research - Dr. S. N. Moorthy

Effect of Solvent Extraction on the Gelatinisation Properties of Flour and Starch of Five Cassava Varieties

The gelatinization properties of native and solvent-extracted (petroleum ether and ethanol) flour and starch processed from five cassava varieties grown in India were studied using a differential; scanning calorimeter (DSC) peaks but these remained unaffected by solvent extraction, indicating that the DSC profiles are characteristic of these starches. In general, the gelatinisation temperatures of the flours were significantly higher than those of the starches but the enthalpy of gelatinization was less for flour. Varietal differences were also observed in the gelatinisation profiles of starch and flour samples obtained using the Brabender amylograph. Lower viscosity values were obtained for the flour samples but values remained more stable throughout the temperature programme. In most varieties, solvent extraction of the samples caused only sight modification of the gelatinisation patterns. There was no apparent relationship between the gelatinisation properties of the starch derived from the different varieties and the size and amylose content of the starch granules. Results of these experiments indicate that differences in gelatinisation values obtained, between starch and flour samples for the same variety, are not due to the presence of sugars and flour samples for the same variety, are not due to the presence of sugars and fats which were removed by ethanol and petroleum ether extraction, respectively. The significant differences observed in some varieties are therefore due to the presence of other root constituents.

Quality Changes in Market Cassava Chips Infested by Insects

The biochemical changes occurring in dried cassava chips collected from various marketing centres in Kerala (India) due to insect infestation were studied. Araecerus fasciculatus (Degeer) was the most important pest of plain sun-dried cassava chips and Sitophilus oryzae (L.) and Rhyzopertha dominica (F.) were the important pests of parboiled chips. There was substantial reduction in starch and sugar content in fully infested plain dried chips as compared to the uninfested chips (83.5-77.9% for starch and 6.95-1.53% for sugar). Reduction in starch was more pronounced in fully infested parboiled chips (78-57%) while sugar increased nearly three fold (6.0-15.7%). Total and soluble amylase contents and reducing values were not significantly affected in plain dried chips due to infestation. Viscosity underwent only slight reduction in plain dried chips while in parboiled chips, the reduction was noticeable even at a partially infested stage. Although there was reduction in starch content due to insect infestation, starch quality did not change much in plain dried chips, indicating the possibility of using such infested chips in animal feed formulations and in the manufacture of commodity chemicals

Research work on tuber starches

During the period under report, I have been involved in four major projects in the institute, two ad-hoc projects ( viz. physicochemical and structural characterization of minor root crop starches and potentialities of tuber starches in tablets and capsules), advanced training in starch chemistry in the UK and sabbatical at Sweden. Five students have registered under my supervision for their Ph.D degree. The work over the period covered a wide variety of aspects which include studies on the cooking quality of cassava, extraction process for starch from minor tuber crops, basic studies on the starches of tropical root and tuber crops, production and properties of starch derivatives for application in food and industry and interaction with industry and entrepreneurs for extension of technologies.

Determination of amylose content in different starches using modulated differential scanning calorimetry

A simple calorimetric method for determination of amylose content in starch is reported. Modulated differential scanning calorimetry (MDSC) was used since there are continuous heating-cooling cycles taking place, which can help in release of amylose from starch granules, and therefore more accurate results can be expected. Two common surfactants viz. sodium dodecyl sulphate (SDS) and cetyltrimethylammonium bromide (CTAB) were used. A large number of native starches including cereal, root and pea starches were examined. The results were compared with those obtained by iodimtery and gel permeation chromatography (GPC) for all the starches. There was a good match between the values from iodimetry and GPC with those obtained using the surfactants. Both surfactants seemed to work equally well, even for those starches of around 40% in amylose content. However, in case of SDS higher standard deviations were usually obtained than for CTAB in the determination of transition enthalpies

Tropical Sources of Starches

The tropical belt which covers around 40% of the total land area encompassing five continents and many countries harbour a number of starch bearing crops which include cereals, tree, fruit and vegetable crops and most important the root crops [1-8]. However commercial use of these for starch extraction has been limited to a few of these crops. Most important of them are sago starch from sago palm, potato, cassava and sweet potato starches from the corresponding tubers

Physicochemical properties of enzymatically separated starch from sweet potato

The physicochemical properties of starch extracted from sweet potato tubers using five different concentrations of the enzyme system cellulase-pectinase was studied. The starch content of the extract was 90-93% on a dry weight basis. The reducing values were not noticeably increased by the enzyme treatment. The peak viscosity values of the extracted starches showed an increase up to 0.05% concentration of enzyme, and thereafter registered a minor fall. The viscosity stability also showed a small reduction at enzyme concentrations above 0.05%. The swelling volumes exhibited a slight decrease and solubility was almost doubled at the highest concentration of the enzyme. The SEM photographs did not indicate any major change in the surface morphology of the extracted starch. Thus the enzyme treatment does not adversely affect the starch properties up to 0.05% concentration