Effect of charring on rice grain morphology and carbon isotopic composition

Abstract

Rice cultivation over Asia has several thousand years of history. Adequate water availability is a prime factor for the cultivation of rice in this region. The remains of rice at the archaeological sites, therefore, provide an indirect clue on rainfall in this region. The stable isotopic compositions in remains of rice grains allow estimation of rainfall condition during rice cultivation. Often, such remains found at the archaeological sites suffer from the process of charring, which is likely to modify the original isotopic signature. Here, we performed charring experiments on rice grains at two different temperatures, i.e. 230°C and 250°C and documented the changes in the morphology and carbon isotopic composition (δ 13C). A noticeable morphological shift was registered in the samples with progressive duration and temperature of charring. Further, cellulose was extracted and analysed for δ 13C. Our results showed that the shift in δ 13C observed for charred rice was relatively lower as compared to that observed in other cereals.