Sweet corn is one of the most consumed vegetables in the US. Fresh sweet corn contains about 20 g/100 g carbohydrates, which makes it an important source of carbohydrates in American diet. Studies have shown that cooking can alter carbohydrate profiles of vegetables. In this study, the effects of two common cooking methods (boiling and steaming) on the carbohydrates of sweet corns were examined. Yellow and bi-color sweet corns were selected as raw materials. The contents of individual simple sugars, oligosaccharides, water-soluble carbohydrates (WSC), starch, total dietary fiber (DF), resistant starch (RS), as well as sugar alcohols were measured in these two varieties before and after cooking. The simple sugars, oligosaccharides and sugar alcohols were quantified by high performance anion exchange chromatography-pulsed amperometric detection (HPAEC-PAD). Other components were measured by AOAC methods with optimization and modification. The results showed that the amounts of carbohydrate components in the two varieties were different. Four simple sugars, sucrose, glucose, fructose and maltose, were identified and sucrose is the predominant one. Boiling and steaming did not change the concentrations of sucrose but resulted in the decreases of the other three sugars. No detectable oligosaccharides were found in these two varieties. Both boiling and steaming did not alter the contents of WSC, starch and DF, but led to huge reduction of RS. RS content decreased by 75.8% and 74.3% after steaming and boiling for bi-color sweet corn, and 84.2% and 83.0% after steaming and boiling for yellow sweet corn, respectively. Sorbitol and mannitol were identified as main sugar alcohols in sweet corn. Sorbitol decreased in cooked samples, while mannitol remained unchanged. In conclusion, boiling and steaming mostly alter RS and simple sugars in sweet corn. The effects of these changes on the digestibility of sweet corn carbohydrates and their biological functions warrant further investigation.

Effect of boiling and steaming on the carbohydrates of sweet corns

ACS Spring 2022

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