FOOD SCIENCE ›› 2013, Vol. 34 ›› Issue (23): 77-82.doi: 10.7506/spkx1002-6630-201323017

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Solubility of Lac Resin in Aqueous Ammonia and Physico-chemical Properties of Its Ammonium Salt

CHEN Qi1,2,ZHANG Hong1,ZHENG Hua1,*,SUN Yan-lin2   

  1. 1. Research Institute of Resources Insects, Chinese Academy of Forestry, Kunming 650224, China;
    2. Faculty of Chemical Engineering, Kunming University of Science and Technology, Kunming 650500, China
  • Received:2013-07-10 Revised:2013-10-30 Online:2013-12-15 Published:2014-01-03
  • Contact: Hua ZHENG E-mail:eastgeneva@163.com

Abstract:

To improve the hydrophilicity of lac resin and broaden its application in the food industry, a chemical method
was used for preparing carboxyl-modified lac resin. Lac resin ammonium salt was prepared to improve the solubility. The
relationship between the quantity of dissolved lac resin and either total dissolved solids (TDS) or pH at 40 ℃ was elucidated
as well as the reaction mechanism between lac resin and aqueous ammonia. The physico-chemical properties of lac resin
and its ammonium salt were compared. The results indicated that the reaction between them was essentially an acid-base
neutralization reaction between RCOOH and NH3·H2O, leading to generation of water-soluble strong electrolytes. At
the ammonia concentration of 0.1 mol/L, 62.90% of the lac resin was achieved after reaction at 40 ℃. The swelling ratio
of lac resin ammonium salt film was as high as 275.03% at pH 5.0, and dissolving ratio was up to 67.04% at pH 7.0. In
addition, it was more soluble in acidic water than lac resin. The puncture intensity was 4.82-fold higher than that of lac resin,
accompanied with a 64.50% increase in toughness. The softening point of lac resin ammonium salt was elevated by over 10 ℃ and
it had significantly better heat resistance when compared to lac resin.

Key words: lac resin, ammonium salt, carboxyl, hydrophilicity, modification

CLC Number: