The multi-scale structure changes of γ-ray irradiated potato starch to mitigate pasting/digestion properties.

The comprehensive understanding of multi-scale structure of starch and how the structure regulates the pasting/digestion properties remain unclear. This work investigated the effects of γ-ray irradiation with different doses on multi-scale structure and pasting/digestion properties of potato starch. Results indicated that γ-ray at lower doses (<20 kGy) had little effect on micromorphology of starch, increased mainly the amylose content and the thickness of amorphous region while decreased crystallinity, double helix content and lamellar ordering. With the increase of dose, the internal structure of large granules was destroyed, resulting in the depolymerization of starch to form more short-chains and to reduce molecular weight. Meanwhile, amylose content decreased due to the depolymerization of amylose. The enhanced double helix content, crystallinity, lamellar ordering and structural compactness manifested the formation of the thicker and denser starch structure. These structure changes resulted in the decreased viscosity, the increased stability and anti- digestibility of paste.

Fine molecular structure and digestibility changes of potato starch irradiated with electron beam and X-ray.

The change of digestibility of starch irradiated with different types from the perspective of fine structure is not well understood. In this work, the change of internal structure, molecular weight and chain-length distribution, helical structure, lamellar structure, fractal structure and digestibility of native and treated potato starch with electron beam and X-ray was analyzed. Two irradiations caused the destruction of internal structure, the disappearance of growth rings and increase of pores. Irradiation degraded starch to produce short chains and to decrease molecular weight. Irradiation increased double helical content and the thickness and peak area of lamellar structure, resulting in the reorganization of amylopectin and increase of structure order degree. The protected glycosidic linkages increased starch resistance to hydrolase attack, thereby enhancing the anti-digestibility of irradiated starch. Pearson correlation matrix also verified the above-mentioned results. Moreover, X-ray more increased the anti-digestibility of starch by enhancing ability to change fine structure.

Comparative investigation of the effects of electron beam and X-ray irradiation on potato starch: Structure and functional properties.

Electron beam (particle radiation) and X-ray (electromagnetic radiation) without radioisotope in the application of material modification have received increasing attention in the last decade. To clarify the effect of electron beam and X-ray on the morphology, crystalline structure and functional properties of starch, potato starch was irradiated using electron beam and X-ray at 2, 5, 10, 20 and 30 kGy, respectively. Electron beam and X-ray treatment increased the amylose content of starch. The surface morphology of starch did not change at lower doses (< 5 kGy), but starch granules were aggregated with the increase of doses. All treatments decreased crystallinity, viscosity and swelling power but increased solubility and stability properties. The effects of electron beam and X-ray on the starch had a similar trend. Unlike X-ray, electron beam destructed the crystallinity of starch to a lesser extent, thereby increasing thermal stability and freeze-thaw stability. Furthermore, X-ray irradiation at higher doses (> 10 kGy) resulted in outstanding anti-retrogradation properties of starch compared with electron beam treatment. Thus, particle and electromagnetic irradiation displayed an excellent ability to modify starch with respective specific characteristics, which expands the potential application of these irradiations in the starch industry.

Genome-Wide Identification and Expression Analysis of the 4-Coumarate: CoA Ligase Gene Family in Solanum tuberosum.

4-coumarate: CoA ligase (4CL) is not only involved in the biosynthetic processes of flavonoids and lignin in plants but is also closely related to plant tolerance to abiotic stress. UV irradiation can activate the expression of 4CL genes in plants, and the expression of 4CL genes changed significantly in response to different phytohormone treatments. Although the 4CL gene has been cloned in potatoes, there have been fewer related studies of the 4CL gene family on the potato genome-wide scale. In this study, a total of 10 potato 4CL genes were identified in the potato whole genome. Through multiple sequence alignment, phylogenetic analysis as well as gene structure analysis indicated that the potato 4CL gene family could be divided into two subgroups. Combined with promoter cis-acting element analysis, transcriptome data, and RT-qPCR results indicated that potato 4CL gene family was involved in potato response to white light, UV irradiation, ABA treatment, MeJA treatment, and PEG simulated drought stress. Abiotic stresses such as UV, ABA, MeJA, and PEG could promote the up-regulated expression of St4CL6 and St4CL8 but inhibits the expression of St4CL5. The above results will increase our understanding of the evolution and expression regulation of the potato 4CL gene family and provide reference value for further research on the molecular biological mechanism of 4CL participating in response to diverse environmental signals in potatoes.

Phenolic compounds and antioxidant activity in red- and in green-fleshed kiwifruits.

Red-fleshed kiwifruits are receiving increasing attention because of their high phenolic contents. However, detailed information on their phenolic compounds and antioxidant capacities remains scarce. Here, six red-fleshed and six green-fleshed kiwifruits were investigated to determine their contents of phenolic compounds and their antioxidant capacities. The results showed chlorogenic acid, p-coumaric acid and ferulic acid were the main phenolic compounds found in kiwifruit. Most of red-fleshed kiwifruits contain higher amounts of total phenolics and anthocyanins, as well as higher activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). Moreover, they exhibited stronger antioxidant capacities than green-fleshed kiwifruits in ABTS, DPPH and FRAP assays. Furthermore, the reactive oxygen species (ROS) inhibition assay showed the phenolics extracted from red-fleshed kiwifruit can better protect tobacco leaves against hydrogen peroxide (H2O2)-induced oxidative damage. This is because of their abundant anthocyanins which in vitro contribute more to H2O2 scavenging than the other phenolic compounds. Based on these findings, it is fair to conclude the red-fleshed kiwifruits are promising sources of antioxidants in human nutrition.