Utilization of tomato peel waste from canning factory as a potential source for pectin production and application as tin corrosion inhibitor

Background: The possibility of utilizing the bioorganic tomato peel as a cheap source for pectin production and its application as a corrosion inhibitor was investigated to implement viable cyclical economy principle in solving the main problem of waste disposal. Methodology: Pectin, from two batches (A and B) from canning factory, was extracted in two steps with ammonium oxalate/oxalic acid, under reflux. Physico-chemical properties, characterisation of structure (FTIR and NMR spectroscopy) and application as corrosion inhibitor of pure tin for isolated pectin were investigated. Results: The highest pectin yield of 32.6 and 31.9% in two batches, respectively, but the lowest pectin quality, i.e. methoxy and anhydrouronic acid contents and degree of esterification, were obtained in the second extraction step, which points out that higher pectin yields are not necessarily connected with higher pectin quality. The results of total anhydrouronic acid content for batches A (52.9%) and B (39.6%) show that sample origin have a considerable effect on pectin quality. Degree of esterification around 82% categorizes extracted pectin as high methoxy pectin. Corrosion results point out that pectin is efficient inhibitor (73%) even at very low concentrations, much better then commercially available pectin. Conclusion: According to chemical profile, rheological properties and structural characterisation of extracted pectins, it can be concluded that tomato peel is a suitable source for pectin isolation. The obtained results show that under-utilised biomass waste from tomato canning industry can be used for development of new generation of corrosion inhibitors and as valuable additive in food industry. (C) 2015 Elsevier Ltd. All rights reserved.