Effects of Tea Residue Extracts with Different Molecular Weight on the Pasting Characteristics of Potato Starch

Tea residues are the remaining residue of tea after processing and utilization, which are rich in multiple active components. To investigate the effects of different types and molecular weights of tea residue extracts on the pasting characteristics of potato starch (PS), the ethanol extract (TRE), water extract (TRW) and alkali extract (TRA) of tea residue were obtained by continuous extraction method. On this basis, the different molecular weights of ethanol extract (TRE-1, <30 kDa. TRE-2, >30 kDa) and water extract (TRW-1, <100 kDa. TRW-2, >100 kDa) were prepared by a membrane separation. The effects of different tea residue extracts on the viscosity properties were investigated, and the microstructure of potato starch added with tea residue extract was observed by scanning electron microscopy (SEM). The results showed that different types and molecular weights of tea residue extracts could significantly (P<0.05) reduce the peak viscosity and swelling power of potato starch and inhibit the pasting behaviors of potato starch. The inhibition order was as follows: TRA>TRW-2>TRE-2>TRW-1>TRE-1. The peak viscosity of potato starch was gradually decreased with the increase of different extracts. After adding 10% TRA, TRW-2, TRE-2, TRW-1 and TRE-1, the peak viscosity of potato starch was 4624, 5013, 5431, 5911 and 6195 cP, respectively. TRE-2, TRW-2 and TRA could better promote the link between potato starch fragments and result in a more complete and smooth lamellar structure, compared with TRE-1, TRW-1. In summary, the addition of different types and molecular weights of tea residue extracts could effectively inhibit the gelatinization of potato starch, and the inhibitory effect of 10% alkali extract was the best.