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Three sweet potato varieties with white-, yellow- and purple-fleshed root tubers were harvested at 100, 120, 140 and 160 days after planting (DAP). Their starch structural, thermal, pasting and digestion properties were measured to reveal the influences of harvesting dates on the physicochemical properties of sweet potato root tuber starch. Though starches from different varieties displayed some differences in physicochemical properties due to their different genetic backgrounds, they were influenced by harvesting date in similar ways. Starches isolated from root tubers at 100 and 160 DAP exhibited lower granule sizes than those at 120 and 140 DAP. The amylose content was higher in root tubers at 100 and 120 DAP than at 140 and 160 DAP. Starches from root tubers at 100 DAP exhibited CA-type X-ray diffraction patterns, and then the B-type crystallinity gradually increased at later harvesting dates. The different harvesting dates had no significant effects on the short-ranged ordered structure and lamellar thickness of starch, but the lamellar peak intensity decreased significantly at later harvesting dates. Starch had a lower gelatinization temperature and a wider gelatinization temperature range in root tubers at 140 and 160 DAP than at 100 and 120 DAP. The higher peak viscosity and lower pasting temperature were associated with the late harvesting date. The digestion of starch had slight differences among root tubers at different harvesting dates. The harvesting dates of root tubers played more important roles in starch properties than the variety. This study would be helpful for breeders, farmers and sweet potato starch users. [ABSTRACT FROM AUTHOR]

Being a disubstituted δ‐valerolactone synthesized by the telomerization of carbon dioxide with 1,3‐butadiene, 3‐ethylidene‐6‐vinyltetrahydro‐2H‐pyran‐2‐one (EVL) contains a six‐membered ring and two unsaturated groups. This report describes the synthesis of an amphiphilic graft copolymer by the combination of thiol‐ene click polymerization and ring‐opening grafting reaction of EVL, ethyldithiol (EDT), and methoxy polyethylene glycol (mPEG‐OH). The alternating copolymer of P(EVL‐alt‐EDT) with 17.9 wt% CO2 content and weight‐average molecular weight (Mw) of 7 kg/mol was prepared by means of the free radical thiol‐ene click polymerization of EVL with EDT initiated by 2,2‐dimethoxy‐1,2‐diphenylethanone under UV irradiation. The following alcoholysis of the lactone ring of P(EVL‐alt‐EDT) backbone by mPEG‐OH is catalyzed by 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene, producing the amphiphilic graft copolymer P(EVL‐alt‐EDT)‐g‐PEG750 with Mw of 12 kg/mol. The polymers are characterized by nuclear magnetic resonance, Fourier transform infrared, matrix‐assisted laser desorption ionization‐time of flight mass spectra, size exclusion chromatography and differential scanning calorimetry. The one‐pot orthogonal strategy is a new utilization of EVL in synthetic polymers and it is significant to the carbon dioxide transformation. [ABSTRACT FROM AUTHOR]