Preparation Of Acid Thermal Dextirn: Mechanism And Application

Acid thermal dextrins are branched dextrins prepared by a process involvingacidification and heating of starch, they have good solubility and wide application prospects.However, its formation mechanism has yet not to form a conclusion. Therefore, this studyinvestigated the molecular and the side chain structure of different acid thermal dextrins madefrom starch with different amylose content at different reaction stages. Preliminary research ofits formation mechanism was proposed in this study. Finally, acid thermal dextrin embeddedcitral with its side chain helix was used to prepare slowly releasing fragrance gel pen ink.This research investigated the molecular weight of acid thermal dextrin made fromdifferent reaction stages. The results show that the acidification and heat treatments are veryintense to starch. After0.5hour, the molecular weight (Mw) of starch with different amylosecontent is reduced to a low level, which is located between1.93×104to2.03×104g/mol.Nevertheless, the Mwof three acid thermal dextrins gradually increased as the reaction inprogress, indicating that the polymerization reaction of dextrin molecules occurred. The Mwof acid thermal dextrin made from high amylose corn starch (HCAD), acid thermal dextrinmade from nomal corn starch (NCAD), and acid thermal dextrin made from waxy miasestarch (WMAD) reached2.94×104g/mol,3.84×104g/mol and4.57×104g/mol after3-hreaction, respectively.The side chain branching, the average chain length, the average ratio of A/B chains andother parameters of acid thermal dextrin made from different stages were studied. The resultsshowed that the content of short chains (DP=3-9) in acid thermal dextrin molecules generallyincreased above60%，the content of long side chains (DP≥10) decreased in the latterreaction. The average chain numbers of acid thermal dextrin were7-20, the average chainlength were between7-11DP, and each B chain contains2to5numbers of A chains.Effects of dextrin/citral mass ratio，dextrin concentration，temperature and time ofHCAD-citral, NCAD-citral, WMAD-ceitral inclusion complex were also investigated. Resultsshowed that HCAD is most suitable for embedding and the effects of these four factors on theembedding rate were: dextrin/citral mass ratio> dextrin concentration> temperature> time.The results obtained under the optimum conditions were addressed as follows: dextrin/citralmass ratio4:1, dextrin concentration0.08g/mL, temperature45℃, embedding time4h.Under the optimized conditions, the embedding rate of the inclusion complex reached51.7%.The citral releasing rate of HCAD-citral mixture reached59.3%in2d. Nevertheless, theinclusion complex was slowly released and the releasing rate reached56.9%after6d.Effects on the citral releasing behavior and the gel pen ink viscosity of HCAD-citralinclusion complex amount were investigated. The results showed that the time to achieve thehighest citral headspace concentration was prolonged nearly70h by the addition of theHCAD-citral inclusion complex. The viscosity of the ink could exceed its optimum range，when the inclusion amount exceeds0.20%.