Rheological Properties of Alkali-extracted Pectin from Tea Residue and Preparation of Its Edible Film
Tea residue contains approximately 10％pectin,which has the potential to serve as a raw material for edible film production.In this study,alkali-extracted tea residue pectin(ATRP)was employed that its basic composition was determined,and the influence of pectin concentration and the addition of Ca2+on the rheological properties of ATRP was investigated.Edible films were prepared using ATRP as the matrix material,combined with sodium alginate,konjac glu-comannan,and sodium carboxymethyl cellulose,to explore the changes in tensile elongation.The results showed that the ATRP contained 72.3％HG domain,while the side chain'RG-I domain'accounted for 24.0％,and the solution exhibit-ed non-Newtonian fluid behavior.When the ATRP mass concentration reached 70 g/L,the viscosity of the solution was 5×104mPa.s,and the resulting gel showed a storage modulus(G')of approximately 157 Pa and a loss modulus(G")of approximately 21 Pa,and the gelation transition occurred at 300 s-1,demonstrating a significant increase in viscosity and gel properties compared to the 40 g/L ATRP solution.Furthermore,after adding Ca2+to a 40 g/L ARTP solution,the maximum increases in its viscosity and gel strength could reach 80 times and 20 times their original values,respectively.but the Ca2+concentration should not exceed 30 mmol/L.Compared to the film made by only ATRP,the films made by complex reagents exhibited improved appearance and superior tensile elongation properties.Among them,the film made by ATRP-konjac glucomannan(prepare according to a volume ratio of 1∶1)showed the highest tensile elongation,with a maximum load of 280 g(at a stretching time of 70s),which was seven times higher than that of film made by only ATRP and 70 times higher in terms of elongation.Therefore,ATRP exhibits promising potential as a raw material for edible film production.
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