Raisins as a source of prebiotic compounds in the diet

Fructans, oligo‐ and polysaccharides of fructose, include both frucooligosaccharides and inulins. They are not digested in the human small intestine and are therefore considered as dietary fiber. Fructans may provide a wide range of health benefits. Acting as prebiotic compounds, they promote the growth of beneficial intestinal flora and suppress the growth of potential pathogens in the colon. They may also increase stool‐bulking capacity; stimulate the gastrointestinal immune system and may reduce the risk of colon cancer. While fresh grapes have no detectable fructans, the dehydration process converts grape sugars into fructans. The objective of this study was to characterize the dietary composition of four different commercially important raisin types: sun‐dried raisins (conventional and dried on the vine); golden raisins and Zante currants. Total, soluble and insoluble fiber was determined by AOAC method 991.43, inulin by AOAC method 997.08 and fructan by AOAC method 999.03. Total dietary fiber values agreed with published results. Raisin inulin content ranged between 0.71% to 1.2% and fructan between 0.78% and 0.96%, thus having among the highest prebiotic content of commonly consumed fruits. Results suggest that the type of dehydration, storage and grape variety influence raisins fructan content.