Contents of nitrate, nitrite and the occurrence of bacteria in fermented cooked parboiled rice and their potential ingestion in the diet

In our region, people use the fermented cooked parboiled rice as their breakfast. Therefore, our present study was conducted to analyse the levels of nitrate, nitrite and the occurrence of bacteria in four different brands of rice which are found in Northern part of Sri Lanka especially in Jaffna Peninsula. Freshly and fermented cooked parboiled rice extracts were prepared for each variety separately and its nitrate and nitrite concentration was determined using spectrophotometric method. Naturally occurring bacteria were isolated from both parboiled rice and characterized based on morphological, physiological and biochemical characters. The results showed that higher levels of nitrate and nitrite were presence in the fermented cooked parboiled rice rather than the fresh par boiled rice. As well as, the bacterial population was higher in fermented cooked parboiled rice than fresh ones after 24 hours of incubation. Hence, among the isolated bacterial genera, Bacillus spp. was the wide spread bacteria in both parboiled rice. Daily intake estimates indicate that the nitrite content seems to satisfy the current acceptable daily intake, but nitrate does not satisfy the current acceptable level. Nevertheless, except in brand D, amount of nitrate and nitrite concentration in most of isolated fermented cooked parboiled rice were found in lower level due to the addition of additives such as pickled lime, onion, chilli. Therefore it is concluded that the presence of nitrite, nitrate and, Bacillus spp. (nitrate reducing bacteria) in fermented cooked par boiled rice may provide favourable environment to produce nitrosamine invivoand invitro in human beings. However, further studies should be done for the quantitative estimation of nitrosamine and also to characterize the bacteria in species level. Key words -fermented cooked parboiled rice, spectrophotometery, nitrosamine, Bacillus spp.