Rice preparation for cadmium and arsenic reduction while maintaining a healthy microbial load

  • Esesua Ebahi Pogoson

Student thesis: Doctoral ThesisDoctor of Philosophy


Paddy rice is a major source of exposure, globally, to the carcinogen and nephrotoxin cadmium and the carcinogen inorganic arsenic. As rice is a dietary staple, this makes rice production highly problematic. Thus, if cadmium and inorganic arsenic can be reduced in rice, even in rice based processed products such as flour, as opposed to rice grain, per se, then large production regions rice output can be made safer.

The study presented developed robust, low-technology approaches to rice post-harvest processing, through to food-preparation, to lower rice cadmium and arsenic species levels. Here it was identified that the food safe and common cadmium chelator, citric acid, efficiently removed cadmium via pre-soaking rice, while also reducing arsenic species. A twostep pre-soaking stage was developed, such that when 10 different individual types of rice were processed in such a way, this resulted in removal rates of 79% for cadmium and 81% for inorganic arsenic. Also, the use of food waste materials, orange and lemon peels, were evaluated for their adsorption capacities by pre-soaking specified amount of adsorbent and water in the rice grain. Both materials resulted to be efficient for the adsorption of both cadmium and arsenic, although to varying degrees, with lemon peel being responsible for an average of 60% cadmium removal, with up to 88% cadmium removal in one rice type, and 38% average arsenic removal. It was also ensured that, because rice could be laden with the pathogenic bacteria, Bacillus cereus, any interventions being considered did not aid the proliferation of the bacteria in rice.

These technologies are particularly suitable for bulk food processing, while putting food waste materials (lemon and orange peels) to good use and could be deployed in the most cadmium and arsenic impacted regions where rice is a staple.
Date of AwardJul 2021
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsQueen's University Belfast
SupervisorAndy Meharg (Supervisor) & Caroline Meharg (Supervisor)


  • Rice
  • paddy rice
  • cadmium
  • inorganic arsenic
  • citric acid
  • calcium salts
  • toxic metal chelation

Cite this