Highland barley (HB) is a nutritious crop with excellent health benefits, and shows promise as an economically important crop with diverse applications. Starch is the main component of HB and has great application potential owing to its unique structural and functional properties. This review details the latest status of research on the isolation, chemical composition, structure, properties, and applications of highland barley starch (HBS). Suggestions regarding how to better comprehend and utilize starches are proposed. The amylopectin content of HBS ranged from 74% to 78%, and can reach 100% in some varieties. Milling and air classification of barley, followed by wet extraction, can yield high-purity HBS. The surface of HBS granules is smooth, and most are oval and disc-shaped. Normal, waxy, and high-amylose HBS have an A-type crystalline. Due to its superb freeze-thaw stability, outstanding stability, and high solubility, HBS is widely used in the food and non-food industries. The digestibility of starch in different HB whole grain products varies widely. Therefore, the suitable HB variety can be selected to achieve the desired glycemic index. Further physicochemical modifications can be applied to expand the variability in starch structures and properties. The findings provide a thorough reference for future research on the utilization of HBS.
The nature of amino acid residue 47 shows a clear discrimination between the different groups of cyclodextrin glycosyltransferase (CGTase). The effects of amino acid side chain at position 47 on cyclodextrin product specificity were investigated by replacing Lys47 in the CGTase from Paenibacillus macerans strain JFB05-01 with arginine, histidine, threonine, serine, or leucine. All of the mutations reduced alpha-cyclodextrin-forming activity, whereas significant increases in beta-cyclodextrin-forming activity were achieved. Especially, the mutations of Lys47 into threonine, serine, or leucine converted P. macerans CGTase from alpha-type to beta/alpha-type. As a result, all of the mutants displayed a shift in product specificity toward the production of beta-cyclodextrin. Thus, they were more suitable for the industrial production of beta-cyclodextrin than the wild-type enzyme. The enhancement of beta-cyclodextrin specificity might be due to weakening or removal of hydrogen-bonding interactions between the side chain of residue 47 and the bent intermediate specific for alpha-cyclodextrin formation.
The detection of furfural in transformer oil through surface enhanced Raman spectroscopy (SERS) is one of the most promising online monitoring techniques in the process of transformer aging. In this work, the Raman of individual furfural molecules and SERS of furfural-Mx (M = Ag, Au, Cu) complexes are investigated through density functional theory (DFT). In the Raman spectrum of individual furfural molecules, the vibration mode of each Raman peak is figured out, and the deviation from experimental data is analyzed by surface charge distribution. In the SERS of furfural-Mx complexes, the influence of atom number and species on SERS chemical enhancement factors (EFs) are studied, and are further analyzed by charge transfer effect. Our studies strengthen the understanding of charge transfer effect in the SERS of furfural molecules, which is important in the online monitoring of the transformer aging process through SERS.
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