Fructo-oligosaccharide changes during the storage of dehydrated commercial garlic and onion samples

The composition of fructo-oligosaccharides (FOS), together with glucose, fructose and sucrose, has been determined in commercial dehydrated samples of onion (Allium cepa L.) and garlic (Allium sativum L.). No qualitative differences were detected among the FOS identified in both onion and garlic. Results show a lower FOS content in garlic than in onion in all samples analysed. In garlic samples, FOS with degree of polymerisation from 3 to 7 were identified and quantified for the first time. In addition, a study on the effect of the storage in these carbohydrates has been carried out under controlled conditions (50 degrees C, a(w) 0.44). The storage seemed to promote important changes in the content of glucose and fructose, which could participate in the Maillard reaction and in the composition of sucrose and FOS, whose hydrolysis was noticeable during the storage time. Therefore, all these chemical changes should be considered to evaluate the quality of these foods.