Characterization and level of desorption of volatile compounds released from boiling sweet potato pulp (Ipomoea batatas)

Sweet potato (Ipomoea batatas) is an important root crop in the Caribbean Basin. This crop releases volatile compounds that can be used to determine quality for acceptance or rejection of the food. The volatile compounds released by boiling the pulp of eight sweet potato varieties were identified, and the desorption process of some of them was studied. Volatile compounds were identified by static headspace extraction coupled with solid phase micro extraction (SPME), all of which allowed volatile analysis in a high water and carbon dioxide atmosphere. The eight sweet potato varieties studied were Ninetynine, Pujols, Taiwan, Martina, Dominicana, Dune, Craneal and Miguela. Ten grams of sweet potato pulp paste (1:1 sweet potato-water) was sealed in a 20 ml headspace vial, and ethyl benzoate was added as internal standard (10 ng/g). The vial was heated to 80° C for one hour, and a polydimethyl siloxane (PDMS) solid phase micro extraction fiber was exposed to the sample headspace for one hour. The fiber was injected in a GC-MS. Some volatiles identified in all sweet potato varieties included hexanal, benzaldehido, 2-pentilfurano, isoledene, copaene and humelene. The Kovat indexes for DB-5MS analytical column were: 699, 846, 887, 1256, 1268 and 1342, respectively. Desorption isotherms of isoledene, copaene and humulene showed an initial non favored process. Hexanal and benzaldehyde desorption were higher than those of simultaneous control samples between 10 and 200 ng/g. These findings suggest that the above mentioned terpenes were released from the matrix whereas aldehydes were synthesized during the boiling process. Results obtained from this study help to better characterize sweet potato and might be used to develop a quantitative selection index.