Research

1. 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 - Read Full Article

2. 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 - Read Full Article

3. 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 - Read Full Article

4. 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. - Read Full Article

5. 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 - Read Full Article

6. 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. - Read Full Article

7. Variation in Properties of Starch in Cassava Varieties in Relation to Age of the Crop

   Cassava starch extracted from six varieties at different period of growth was examined for various physicochemical properties. The granule size increased in all the six varieties upto 6th month from time of tuber initiation and thereafter remained almost constant. The amylase content and reducing values did not vary much at different stages of growth. The swelling volume and swelling power of starch showed large variations particularly after 10th month. Such changes of four varieties were not noticed in other varieties. Associative binding forces of starch molecules largely determine the stability characteristics of starch under varied environmental conditions - Read Full Article

8. Cassava Fermentation and Associated Changes in Physicochemical and Functional Properties

   Fermentation of cassava is an important processing technique followed in different parts of the world. Although fermentation is known to bring about vast changes in the physicochemical and functional properties of the tubers, attempts have seldom been made to consolidate and critically analyze the available information. Glaring inconsistencies and contradictions noticeable in some of the results reflect the differences and variation in the artisanal processes followed in the preparation of these products. It also stresses the need for systematic study of not only the quoted products, but also a number of other fermented cassava products and have not been well documented. - Read Full Article

9. Effect of Pretreatment of Fresh Amorphophallus paeoniifolius on Physicocochemical Properties of Scratch

   Fresh roots of Amorphophallus paeoniifolius were separately pretreated with sodium hexametaphosphate (SHMP), potassium metabisulphite (KMS), sodium chloride (NaCL), and ammonium hydroxide (NH4OH) within a range of 1-5% (w/v) concentration and glyceryl monosterate (GMS) at 0.025-0.125% concentration. The quality of starch extracted from pretreated roots was compared with that obtained from fresh roots by direct aqueous extraction. The starch samples prepared from chemically pretreated roots showed characteristic changes in properties of water soluble amylase content, swelling and solubility and ά-amylase susceptibility. X-ray diffraction of starch samples from chemically pretreated roots although resembled that of control, there was noticeable shift with respect to their’d’ spacing and Io/Imax values - Read Full Article

10. Functional Properties of the Starchy Flour Extracted from Cassava on Fermentation with a Mixed Culture Inoculum

    The fundamental properties of the starchy flour extracted from six varieties of cassava subjected to fermentation by a mixed culture inoculum comprised of lactobacilli, streptococci, corynebacteria and yeast cells are examined. Apparent reduction in total and soluble amylose contents is observed. Differential scanning calorimetry of the samples indicated that the enthalpy of gelatinisation was reduced, while gelatinisation temperature was enhanced. A marked reduction in Brabender viscosity values of starch from fermented tuber was observed, but the X-ray diffraction pattern was unaffected. All these changes were attributed to the presence of fibrous material and consequent reduction of starch in unit volume rather than any change un the starch granule structure. - Read Full Article

11. Stereochemistry & Mechanism of Birch Reduction of Cyclic Allenes

    The sodium-ammonia reductions of 1,2-cyclononadiene, 1,2-cyclodecadiene, 1,2-cyclodecadiene, 1,2-cyclodecadiene , 1,2-cyclodecadiene, 1,2-cyclodecadiene , 1-methyl-1,2-cyclodecadiene, 1-methyl-1,2-cyclodecadiene and 1-methyl-1,2-cyclodecadiene have been described. All the cyclic allenes get reduced smoothly t o give good yields of olefinic product(s). Analysis of the products after partial reduction, use of lithium instead of sodium and the relative rates of reduction of cyclic allenes and acetylenes rule out the possibility of the rearrangement of cyclic allenes to acetylenes before reduction. From the ratios of cis to trans olefins obtained in the presence and absence of a proton donor, potential routes for the formation of isometric olefins have been proposed. The synthetic utility of this reduction procedure is borne out in the reduction of some trisubstituted cyclic allenes which offers a convenient stereoselective synthesis of C9?, C10?and C13? trisubstituted cyclic olefins - Read Full Article

12. Variability in starch extracted from taro

    Starch was extracted from ten cultivars of taro and various physiochemical properties were determined. The granule size was found to vary considerably among the different accessions, C-9 starch having the largest average granule size (5.19 µm) while the lowest was recorded for C-46 (2.96 µm). the total amylose content varied between 14 and 19% C-9 starch having the highest value. Soluble amylose content ranged from 4 to 11%. Although there was not much difference between varieties in the 2% viscosity determined using a Redwood viscometer, the Brabender viscosity patterns showed considerable variation, and C-9 starch had the highest peak viscosity, almost twice as much as the others. The swelling volumes ranged from 25.0 to 60.0 ml g-1 with C-266 starch having the highest swelling volume - Read Full Article

13. Stereoselective Partial Hydrogenation of Allenes by Diimide in situ

    Both cyclic and acyclic allenes have been hydrogenated by diimide formed in situ by oxidation of hydrazine by hydrogen peroxide as well as oxygen gas, to olefins in which the double bounds are found to have cis geometry. Terminal allenes give 2-alkenes. Both observations have been explained by the approach of diimide from the least hindered side of allenic bond. It is also noted that allenic bond is more reactive towards diimide than the olefinic double bond is. The efficiency of reduction increases as the degree of allenic substitution and the ring size of the cyclic allene decrease - Read Full Article

14. The Effect of Low Levels of Antioxidants on the Swelling and Solubility of Cassava Starch

    The addition of low levels of sodium sulphite had a dramatic effect on the structure of cassava (Manihot esculenta Crantz) starch pasted at 95oC. Inclusion of 100 ppm sulphite promoted granule disintegration resulting in a reduction in measured swelling volume to nearly 10% of its value in the absence of sulphite and release of almost all the carbohydrates from the starch granukle. It is suggested that sulphite addition promotes oxidative reductive depolymerization (ORD) of the polysaccharides since its effect on the granules is prevented when lower levels (around 20 ppm) of the polar antioxidant propyl gallate are added. Possible practical applications of the results and implications for the understanding of starch granule structure are discussed - Read Full Article

15. A Convenient Route to Medium-ring Trisubstituted cis-Olefins from Allenes

    The selective introduction of a trisusbstituted carbon-carbon double bond with a specific configuration is still an interesting problem to organic chemists, although several methods have been documented in the literature1-4. The sodium/ammonia reduction of allenes, in combination with an elegant synthesis of allenes has proven to be useful in synthesizing a homologue of an olefin or a diene in good yield 5-11. In this communication, we report a further extension of this general method to provide a new and a convenient procedure to synthesize medium-ring (9 and 10 membered) tri-alkyl-substituted cis-olefins - Read Full Article

16. Physicochemical and Functional Properties of Tropical Tuber Starches: A Review

    The tropical tuber crops contain starch as the major component and thus act as important source of starch. Except cassava and to a smaller extent sweet potato, starch from other tuber crops has not been exploited for industrial applications partly because of difficulty in the extraction of the pure starches and partly because of non-availability of information about the properties of these lesser known starches. This review attempts at collating data available on the physicochemical and functional characteristics of the tropical tuber starches, highlighting their unique properties and potential field of applications - Read Full Article

17. Studies on Dioscorea rotundata Starch Properties

    Starch from six clonal selections of Dioscorea rotundata was isolated by standard procedure. The yield was between 20-24%. Various properties of these starches were compared. Granule size, 2% viscosity, peak viscosity, clarity, sol stability, total and soluble amylase contents were studied and only small variations were observed in the properties except paste viscosities among the clonal selections. The phosphorus content of Dioscorea starch was found to be three times as much as cassava starch, but low compared to potato starch. The higher gel strength of D, rotundata starch paste compared to cassava gel may be attributed to the phosphate linkages among the starch molecules in the granules - Read Full Article

18. The Physicochemical properties of starch of some accessions of amorphophallus paeoniifolius

    Starch was extracted from the tubers of ten accessions of Amorphophallus paeoniifolius of the same maturity, with a yield varying from 7 to 14 % on a fresh weight basis. The starch was pure white in color. There was no significant difference in granule size between the different accessions. The starch granule size and viscosity values were lower in A. paeonifolius than in Dioscorea spp. And cassava, but the viscosity was higher than that of cereal starches. The viscosity stability was good, indicating suitability for many food applications - Read Full Article

19. A Regio-and Stereo-Specific Addition of Iodine Azide to C-9 and C-13 Cyclic Allenes

    Iodine azide is known to undergo addition to alkenes and alkynes with a remarkable high degree of regio- and stereoselectivity¹. However, there are no reports of such additions of iodine azide to allenes. In this Communication a regio- and sterospecific addition of iodine azide to 1, 2-cyclodecadiene and 1, 2-cyclotridecadiene is described. The results are summarized in the Table. - Read Full Article

20. Extraction of Starches from Tuber Crops Using Ammonia

    Ammonia solution(0.03 M) was used to extract starch from various tuber crops by the conventional settling method. It was found that there was noticeable improvement in the yield of starch from Colocasia (6-16%), while it fell for sweet potato starch and remained almost the same for the other starches. The various properties of starch, thus extracted, were compared with those for starch obtained by water extraction. It was found that total amylose of all starches were unaffected while the ’soluble amylose’ was slightly suppressed for Colocasia starch extracted with ammonia solution. Peak viscosity was found to be increased to a large extent for Colocasia and Dioscorea esculenta starches by ammonia extraction, while it was lowered for sweet potato starch. The swelling volume of Colocasia starch extracted with ammonia was similarly enhanced by 25%, but the Dioscorea esculenta starch did not show such a tendency. Sweet Potato starch suffered a reduction in swelling a reduction in swelling volume, Phosphorous content was found to be independent of the extraction medium - Read Full Article

21. Effect of Different Types of Surfactants on Cassava Starch Properties

    The effect of anionic, neutral, and cationic surfactants in three different concentrations on cassava starch properties was studied. The iodine affinity of total amylose was reduced by 20 -40% by all surfactants, with highest reduction being observed for cetyltrimethylammonium bromide. The iodine affinity of soluble amylase was suppressed by all reagents except cetyltrimethylammonium bromide, which lowered the value to almost zero. There was no significant difference between the concentrations 0.04 and 0.06 mol of surfactant per 100 g of starch. Viscosity was stabilized by potassium stearate and potassium palmitate without greatly affecting the peak viscosity of 660 BU of pure starch, but sodium lauryl sulphate and cetyltrimethylammonium bromide increased the peak of viscosity to 900 and 780 BU respectively at 0.06-mol concentration and did not show stable viscocity during the holding period - Read Full Article

22. Physicochemical and functional properties of Canna edulis starch

    Apart from the major root crops like cassava, sweet potato, aroids and yams, many types of rhizomatous and tuberous root crops are grown in different countries including India. Queensland arrowroot (Canna edulis) is a perennial herb grown in many countries for its edible rhizome (Joseph and Peter, 1985) . According to Hermann (1994), the bakery products prepared from canna starch are much lighter, and crisper than those from wheat. This Institute has three accessions of Canna edulis classified from the leaf colour as green, purple and dark purple. Only the tubers of dark purple accession are consumed since the others are fibrous and contain large quantity of phenols. This paper describes the physicochemical and functional properties of starch isolated from these three accessions - Read Full Article

23. Starch-lipid interactions of tuber starches

    Lipids and surfactants can form strong complexes with starch and thereby modify the properties of the starches. Unlike cereal starches which contain considerable quantities of lipids present in them, the tuber starches are devoid of the lipids. A study was conducted to compare the types of starches using DSC. The starches were moistened with equal quantity of water in aluminum pans and the DSC run using a Seiko Calorimeter using indium as standard - Read Full Article

24. Tropical Tuber Crops

    The tropical tuber crops play a dual role in being a source of food as well as industrial raw material. However, they have not received enough importance due to various factors. The main factors are that the tubers are considered poor mans crop and there is little awareness of the variability available in the starch properties of these crops. Again the knowledge about the innumerable products, which can be produced from starch, has been scanty. So all these aspects needed to be addressed to enhance the importance of these crops and research projects covering food and industrial applications of these neglected crops were formulated and carried out. In addition, an ad-hoc project on minor tuber starches was undertaken in collaboration with RRL, Trivandrum. - Read Full Article