Quality preservation of stored rice using modified atmospheres in Portugal

Portugal is the largest consumer of white rice in Europe, and consequently a large number of farmers and industries are associated with rice production, transportation and processing. During five years, studies were conducted in six on-farm stores, and three rice industries in Portugal in order to identify the most important noxious agents (insects and fungi associated to stored rice) and implement IPM strategies, such as sanitation, tools for risk assessment, sampling programs, and non-chemical alternatives like ventilation/refrigeration and modified atmospheres as sustainable technologies to replace conventional chemical treatments. The implementation of these strategies and the dissemination of the results, illustrates an advancement in stored rice protection in Portugal. Currently, many of the rice processing companies apply monitoring programs to assist in decision-making and in the use of strategies such as modified atmospheres (MA) on stored rice. MA based CO2 was tested to control Sitophilus zeamais and S. oryzae in bulk stored milled rice. The trials were conducted in a silo containing 40 tonnes of polished rice and four hermetic big bags of 1 tonne capacity; two with paddy and two with polished rice. The composition of the atmosphere was 90-95% CO2 and 0.7-2.1% O2. Three trials were carried out using different temperature and different treatment times: stored rice in the silo at 30ºC for 26 days (first trial) and at 34ºC for 10 days, (second trial) and in big bags at 22ºC during 26 days (third trial). The exposure of eggs and adults of Sitophilus spp. to modified atmospheres showed mortality close to 100% and no F1 emergency was recorded after each treatment. This was the first time that a Portuguese rice mill used modified atmospheres. This paper presents some of the most preeminent strategies and results on stored rice in Portugal.