Study of the thermal properties of corn urs produced by thermal-alkaline treatment

摘要

A design of a controlled cooking system (CCS) for corn urs production is presented. The system allows reproducibility in the samples preparation withcontrol of the time and the temperature. The treatment of corn was performed with a cooking time of 120 minutes at 92.5, by adding calcium hydroxide (Ca(OH)2) in concentration between 0 and 0.5% compared to the corn weight.The cooking process was monitored via measures of moisture absorbed by the corn kernels and pH of the solution. The samples were manufactured by operation steps like wet milling, dehydration, dry milling and sieving. The samples were analyzed using modulated di€erential scanning calorimetry (MDSC)and thermogravimetric analysis (TGA) techniques, which were focused in the thermal stability of the urs and their physical variables: gelatinization range (), enthalpy (), change in heat capacity (p), temperature decomposition of maximum decomposition rate (Tmd) and residue after decomposition (Rs). The adding of Ca(OH)2 moves the peak gelatinization and the maximum peak of decomposition towards higher temperature. The TGA analysis showed that the addition of calcium hydroxide improves the thermal stability of the ur, since the degradation temperature shifts to higher temperatures as the amount of calcium hydroxide increases. The results were compared with the same analysis performed on raw corn. This study proposes an experimental method, including a controlled cooking system for the production of ur enriched with calcium, which could have a major impact in the ld of nutrition.PACS:64.60.-i, 61.25.hk, 61.25.hp, 83.10.Tv