John Karkalas

Bio: John Karkalas is an academic researcher from Glasgow Caledonian University. The author has contributed to research in topics: Starch & Maize starch. The author has an hindex of 9, co-authored 9 publications receiving 1800 citations.

The Effects of Environmental Conditions on the Structural Features and Physico-chemical Properties of Starches

Abstract: The effects of environmental factors on the structural features and physico-chemical properties of starch (from various botanical sources) have been investigated over many decades. A close study of published data on the effects of environmental factors, especially growth temperature, reveals discrepancies with regard to its effects on the composition and properties of the major components of starch, namely amylose and amylopectin. These discrepancies can in part be explained on the basis of the different experimental protocols used by the various investigators to provide environmental variation although it is clear that environmental factors do influence the deposition and composition of starch granules. However, the effects of environmental conditions on the physical properties of starches are more easily reproduced and are consequently better understood. This review is an up to date survey of current knowledge in this area and draws extensively on the authors' own research.

The composition of maturing Omani dates

Abstract: The composition of two varieties of Omani dates, fard and khalas, was determined as maturity progressed. Free sugars and dietary fibre content were examined in detail. High-performance liquid chromatography (HPLC) of the extracts showed that at the early green stage (Arabic kimri), dates contained small amounts of glucose and fructose. At the intermediate yellow (khalal) and red (rutab) stages, large amounts (500–565 g kg−1 dry weight) of sucrose had accumulated, but no additional glucose or fructose was detected. At the final mature (tamar) stage, all sucrose was converted to glucose and fructose (>800 g kg−1 dry weight). Dietary fibre, determined as non-starch polysaccharides (NSPs) by gas chromatography (GC), decreased from 250 g kg−1 (kimri) to 50 g kg−1 (tamar) on a dry weight basis. The principal monomers of NSPs were glucose, galactose, xylose, mannose, arabinose and rhamnose. On a dry weight basis, pectin, protein and ash contents decreased as the dates matured. On a fresh weight basis, changes in NSPs, pectin, protein and ash could be attributed to loss of moisture and the accumulation of sucrose initially, or of invert sugar later as maturation progressed. © 1999 Society of Chemical Industry

Handbook of hydrocolloids.

Abstract: Introduction. Agar. Starch. Gelatin. Carrageenan. Xanthum Gum. Gellan Gum. Gallactomannans. Gum Arabic. Pectins. Milk Proteins. Cellulosis. Tragacanth and Karaya. Xyloglucan. Curdlan. Glucans. Soluble Soybean Polysaccharide. Bacterial Cellulose. Microcrystalline Cellulose. Gums for Coating and Adhesives.Chitosan Hydrogels. Alginates. Frutafit-Inulin. The CRC Emulsifying Biopolymer.

Catalytic conversion of lignocellulosic biomass to fine chemicals and fuels

Abstract: Lignocellulosic biomass is the most abundant and bio-renewable resource with great potential for sustainable production of chemicals and fuels. This critical review provides insights into the state-of the-art accomplishments in the chemocatalytic technologies to generate fuels and value-added chemicals from lignocellulosic biomass, with an emphasis on its major component, cellulose. Catalytic hydrolysis, solvolysis, liquefaction, pyrolysis, gasification, hydrogenolysis and hydrogenation are the major processes presently studied. Regarding catalytic hydrolysis, the acid catalysts cover inorganic or organic acids and various solid acids such as sulfonated carbon, zeolites, heteropolyacids and oxides. Liquefaction and fast pyrolysis of cellulose are primarily conducted over catalysts with proper acidity/basicity. Gasification is typically conducted over supported noble metal catalysts. Reaction conditions, solvents and catalysts are the prime factors that affect the yield and composition of the target products. Most of processes yield a complex mixture, leading to problematic upgrading and separation. An emerging technique is to integrate hydrolysis, liquefaction or pyrolysis with hydrogenation over multifunctional solid catalysts to convert lignocellulosic biomass to value-added fine chemicals and bio-hydrocarbon fuels. And the promising catalysts might be supported transition metal catalysts and zeolite-related materials. There still exist technological barriers that need to be overcome (229 references).

The molecular structures of starch components and their contribution to the architecture of starch granules: A comprehensive review

Abstract: Recent developments in methods and instrumentation have contributed to major advances in our understanding of the fine structure of amylose and amylopectin. The structure of the starch granule slowly unravels with new insight into key structural features. Following a brief presentation of the structural features common to all starches, the most recent findings for the structure of amylose and amylopectin are reported. The organization of different types of chains in amylopectin is discussed with a critical review of the 'cluster' model leading to the presentation of alternative models. The locations of molecular components in the starch granule are described according to a progress structural order. The description of the crystalline components is followed by a presentation of their supramolecular arrangements. The crystalline components comprise platelet nanocrystals which have already been identified and characterized, and other less well characterized 'blocklet components'. The location and state of amylose within the granule is also presented. This comprehensive review aims at distinguishing between those structural features that have received widespread acceptance and those that are still under debate, with the ambition of being educational and to provide stimulation for further fundamental investigation into the starch granule as a macromolecular assembly.