Formation of resistant starch and cracker products from leftover rice in Saudi Arabia

Food leftovers are a worldwide concern and the Food and Agriculture Organization reported about 400 billion USD worth of food is wasted yearly. In the Kingdom of Saudi Arabia, food waste is increasing; the loss is about 33.6% of the rice commodity only. To achieve sustainable development goals including zero hunger and sustainable consumption, the current investigation aimed to study the recycling possibilities of rice leftovers through the production of resistant starch (a nutraceutical active component). Proximate analysis, in vitro digestibility (rapidly, slowly, and resistant starches), and conformational techniques (SEM, FTIR, and DSC) were accomplished before and after treating heated or not samples with acetic, citric, and tartaric acids. Also, crackers were produced from rice starch and its sensory evaluations were completed. Results reported variations in starch content between the controls and acid treatments, but interestingly, amounts of protein, and fiber were not different. The highest production of resistant starch (more than 35%) was when treated with tartaric acid and heat treatment, followed by citric acid and heat treatment (32.5%), then acetic acid and heat treatment (28%). The FTIR pictograms revealed the acetylation of heat and acid-treated rice samples. The gelatinization enthalpy (ΔH) decreased from 10.51 to 7.81 J/g for control and treated rice by acetic acid without heat. Surprisingly, the panelists reported no differences in the sensory evaluations of crackers produced from treated rice with a high content of resistant starch, which considered as functional food. These findings help achieve food sustainability through commercial-scale functional food production.