Organelle Imaging with Terahertz Scattering-Type Scanning Near-Field Microscope.

Organelles play core roles in living beings, especially in internal cellular actions, but the hidden information inside the cell is difficult to extract in a label-free manner. In recent years, terahertz (THz) imaging has attracted much attention because of its penetration depth in nonpolar and non-metallic materials and label-free, non-invasive and non-ionizing ability to obtain the interior information of bio-samples. However, the low spatial resolution of traditional far-field THz imaging systems and the weak dielectric contrast of biological samples hinder the application of this technology in the biological field. In this paper, we used an advanced THz scattering near-field imaging method for detecting chloroplasts on gold substrate with nano-flatness combined with an image processing method to remove the background noise and successfully obtained the subcellular-grade internal reticular structure from an Arabidopsis chloroplast THz image. In contrast, little inner information could be observed in the tea chloroplast in similar THz images. Further, transmission electron microscopy (TEM) and mass spectroscopy (MS) were also used to detect structural and chemical differences inside the chloroplasts of Arabidopsis and tea plants. The preliminary results suggested that the interspecific different THz information is related to the internal spatial structures of chloroplasts and metabolite differences among species. Therefore, this method could open a new way to study the structure of individual organelles.

Comparative studies on physicochemical properties of three potato varieties different in RS2 and RS3 contents.

BACKGROUND: At present, increasing importance has been attracted to healthy food enriched in resistant starch (RS), which has great benefits in health-promoting. Raw potato has rich RS2, whereas most RS2 may become digestible after gelatinization, resulting in few RS being left in processed potato. Breeding potatoes with high RS2 or RS3 or both can meet the demand for various healthy potato products. RESULTS: There were apparent discrepancies among three potatoes with contrast RS2 and RS3 content in thermal properties, viscosity and digestibility. ZS-5 had the highest RS2 with 50.17% but the lowest RS3 with 3.31%. Meanwhile, ZS-5 had the largest starch granule, the highest proportion of B3, viscosity and hardness, and the highest digestibility. DN303 with the highest content of RS3 (5.08%) had the lowest hardness and fracturability. MG56-42 with both higher RS2 and RS3 content showed the highest resistance to digestion and moderate hardness and fracturability. CONCLUSION: The present study enriches the potential resources and provides a reliable scientific basis for high RS potatoes breeding. The various features of different potatoes make it possible to screen potatoes according to different demands. © 2023 Society of Chemical Industry.

Physicochemical characterizations of five Dioscorea alata L. starches from China.

D. alata is an important edible and medicinal plant in China. Its tuber is rich in starch but the understanding of the physiochemical properties of D. alata starch is limited. In order to explore the processing and application potential of different D. alata accessions in China, five kinds of D. alata starch (LY, WC, XT, GZ, SM) were isolated and characterized. The study showed that D. alata tubers contained abundant starch, enriched in amylose and resistant starch (RS). D. alata starches showed B-type or C-type diffraction pattern, had higher RS content and gelatinization temperature (GT), lower fa and viscosity when compared to D. opposita, D. esculenta, and D. nipponica. Among D. alata starches, D. alata (SM) showing the C-type diffraction pattern, had the lowest proportion of fa with 10.18 %, the highest amylose, RS2 and RS3 content of 40.24 %, 84.17 % and 10.48 % respectively, and the highest GT and viscosity. The results indicated that D. alata tubers are potential sources for novel starch with high amylose and RS content, and provided a theoretical basis for further utilizations of D. alata starch in food processing and industry application.

A novel starch: Characterizations of starches separated from tea (Camellia sinensis (L.) O. Ktze) seed.

The physicochemical, thermal and crystal properties of starches isolated from 3 different tea (Camellia sinensis (L.) O. Ktze) seeds were analyzed in this study. The shape of tea starch granules were flat spherical or oval shape, showed unimodal or bimodal distribution with average size of around 9 µm. Tea starch was typical A-type starch. Apparent amylose contents of three tea seed starches ranged from 27.06% to 33.17%. The chains having degree of polymerization (DP) 13-24 were over 50% of the total detectable chains for tea amylopectin. Peak gelatinization temperature of tea starch ranged from 65 to 77 °C and the water solubility reached up to 9.70%. The peak viscosity of tea starches were as high as 5300 cP and final viscosity ranged from 4000 to 6700 cP. The results indicated that tea seed starch had potential as gel reagents and provide some guides for comprehensive utilization of tea starch in food and non-food applications.