Starch measurement

McCleary, B.V., Gibson, T.S., Solah, V., and Mug-ford, D.C. 1994. Total starch measurement in cereal products Interlaboratory evaluation of a rapid enzymic test procedure. Cereal Chem. 71 501-505. 

Figure 16.11 Pasting profiles of barley starches measured by a Rapid ViscoAnalyzer.27 Waxy ( ) normal ( ) (X) high-amylose and (A) high-amylose hull-less. (Reproduced with permission)...

Figure 16.12 Pasting profiles of (a) small and (b) large granules ofwaxy, normal and high-amylose barley starches measured by Brabender Amylography. (Adapted from reference 42 with permission)...

In a series of recent experiments in this laboratory where flours were extruded at a moisture content of only 28%, residual ungelatinised starch, measured by DSC, was shown to be less than 10% for all barrel temperatures above 110°C. 

Thermal analysis has also been used to characterize the structure of starch. A melting endotherm due to the crystalline portions of starch has been investigated, but it is not clearly resolved in all samples due to the small amount of crystalline material present in the samples. This transition is also dependent on the sample preparation and moisture content of the material. Melting points of 168-210°C have been reported. The glass transition temperature (Tg) in starch, measured using differential scanning calorimetry (DSC), was found to be dependent on the moisture content... 

Carbohydrates and phosphorylated intermediates were estimated at the growth temperature and after transfer to 13 C or 30 C. Soluble carbohydrates were analysed by gas chromatography, and starch measured enzymically after amyloglucosidase digestion. Phosphorylated intermediates were also estimated enzymically. 

Anselme Payen (Paris 17 January 1795-13 March 1871), at first director of a beet-sugar factory, was also professor of industrial chemistry in the Conservatoire des Arts et Metiers. He introduced the name cellulose (1839), published on starch (measuring the sizes of the granules of different kinds), dextrin, diastase, and many other subjects. His lectures were published. ... 

Haissig B E, Dickson R E (1979) Starch measurement in plant tissue using enzymatic hydrolysis. Physiol Plant 47 151 -15 7... 

Figure 4. a-Amylolysis kinetics porcine pancreatic a-amylase, 12U/mg starch at 37 C) of potato starch measured under following conditions native kept in the dark (A), starch-amylase solution illuminated for Ihr with the visible non polarized light (B), starch amylase solution illuminated for Ihr with the visible polarized Hght (C), amylase solution illuminated for Ihr with the visible non polarized light prior to the starch addition (D), amylase solution illuminated for 1 hr with the visible polarized light prior to the starch addition (E) (from [38] by permission). 

From the data in Fig. 4.8b, estimate the shift factors required to displace the data at 0 = 0.5 (consider only this point) so that all runs superimpose on the experiment conducted at 128 C at 0 = 0.5. Either a ruler or proportional dividers can be used to measure displacements. Criticize or defend the following proposition Whether a buffered aqueous solution of H2O2 and 1. containing small amounts of S2O3 and starch, appears blue or colorless depends on both the time and the temperature. This standard general chemistry experiment could be used to demonstrate the equivalency of time and temperature. The pertinent reactions for the iodine clock are... 

Starches used to increase the internal strength of paper as measured by tensile, edge cmsh resistance, Mullen burst, and Scott bond strength are added at the wet end, whereas starch used to increase surface strength as measured by pick and resistance to Hnting are added at the size press. 

In industrial production of acid-modified starches, a 40% slurry of normal com starch or waxy maize starch is acidified with hydrochloric or sulfuric acid at 25—55°C. Reaction time is controlled by measuring loss of viscosity and may vary from 6 to 24 hs. For product reproducibiUty, it is necessary to strictly control the type of starch, its concentration, the type of acid and its concentration, the temperature, and time of reaction. Viscosity is plotted versus time, and when the desired amount of thinning is attained the mixture is neutralized with soda ash or dilute sodium hydroxide. The acid-modified starch is then filtered and dried. If the starch is washed with a nonaqueous solvent (89), gelling time is reduced, but such drying is seldom used. Acid treatment may be used in conjunction with preparation of starch ethers (90), cationic starches, or cross-linked starches. Acid treatment of 34 different rice starches has been reported (91), as well as acidic hydrolysis of wheat and com starches followed by hydroxypropylation for the purpose of preparing thin-hoiling and nongelling adhesives (92). 

Oligo- and higher saccharides are produced extensively by acid-and/or enzyme-catalyzed hydrolysis of starch, generally in the form of symps of mixtures (12). These products are classified by thek dextrose equivalency (DE), which is an indication of thek molecular size and is a measure of thek reducing power with the DE value of anhydrous D-glucose defined as 100. 

In this reaction, iodine is liberated from a solution of potassium iodide. This reaction can be used to assess the amount of ozone in either air or water. For determination in air or oxygen, a measured volume of gas is drawn through a wash bottle containing potassium iodide solution. Upon lowering the pH with acid, titration is effected with sodium thiosulfate, using a starch solution as an indicator. There is a similar procedure for determining ozone in water. 

Using a burette or a pipette with a safety pump (this is necessary owing to the poisonous properties of the solution) measure out 25.0 mL of the arsenite solution into a 250 mL conical flask, add 25-50 mL of water, 5g of sodium hydrogencarbonate, and 2 mL of starch solution. Swirl the solution carefully until the hydrogencarbonate has dissolved. Then titrate slowly with the iodine solution, contained in a burette, to the first blue colour. 

C) With a standard solution of iodine. If a standard solution of iodine is available (see Section 10.112), this may be used to standardise the thiosulphate solution. Measure a 25.0 mL portion of the standard iodine solution into a 250 mL conical flask, add about 150 mL distilled water and titrate with the thiosulphate solution, adding 2 mL of starch solution when the liquid is pale yellow in colour. 

Measure out a 100 mL portion of the solution with a pipette and titrate the iodine with approximately Mj80 standard sodium thiosulphate solution adding 2mL of starch solution as indicator as the titration proceeds and after the titration liquid has become pale yellow in colour. 

Among the chemical methods proposed for the objective measurement of maturity may be listed total solids, alcohol-insoluble solids, and starch, based upon the fact that these constituents increase in concentration with maturity. Each has its limitations and advantages, and all are equally applicable as long as the limitations are taken into account. These methods as they apply to frozen peas have been discussed by Nielsen and co-workers (31) and by Lee (22). 

The tenderometer is not readily adaptable for measurement of maturity in the finished product, and any method used for estimating maturity at this point should yield results well correlated with those obtained by the tenderometer. Estimation of total solids or starch content appears to fulfill this requirement very well. 

Protein concentration can be determined by using method of Bradford,9 which utilises Pierce reagent 23200 (Pierce Chemical Company, Rockford, IL, USA) in combination with an acidic Coomassie Brilliant Blue G-20 solution to absorb at 595 nm when reagent binds to the protein. A 20 mg/1 bovine serum albumin (Pierce Chemical) solution was used as the standard. Starch concentration was measured by the orcinol method4,9-11 using synthetic starch as the reference. A yellow to orange colour is obtained and measured at 420 nm when orcinol reacts with carbohydrates. Absorbance is determined by spectrometry. 

In the matrix of PLA/ polycaprilactone (PCL)/OMMT nano-composites, the silicate layers of the organoclay were intercalated and randomly distributed (Zhenyang et at, 2007). The PLA/PCL blend significantly improved the tensile and other mechanical properties by addition of OMMT. Thermal stability of PLA/PCL blends was also explicitly improved when the OMMT content is less than 5%wt. Preparation of PLA/thermoplastic starch/MMT nano-composites have been investigated and the products have been characterized using X-Ray diffraction, transmission electron microscopy and tensile measurements. The results show improvement in the tensile and modulus, and reduction in fracture toughness (Arroyo et ah, 2010). 

Electrical conductivity measurements revealed that ionic conductivity of Ag-starch nanocomposites increased as a function of temperature (Fig.l7) which is an indication of a thermally activated conduction mechanism [40]. This behavior is attributed to increase of charge carrier (Ag+ ions) energy with rise in temperature. It is also foimd to increase with increasing concentration of Ag ion precursor (inset of Fig.l7). This potentiality can lead to development of novel biosensors for biotechnological applications such as DNA detection. 

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