Osmotic and membrane distillation for the concentration of tomato juice: Effects on quality and safety characteristics

• Different concentration techniques used to obtain tomato paste were compared.
• Conventional thermal evaporation (CTE) caused increase in HMF and furan concentrations.
• Membrane concentration systems yielded less HMF and less furan containing products.
• Membrane concentration systems retained color values better than CTE.
• Total vitamin C contents were higher in samples concentrated by membrane systems.

The aim of this study was to evaluate the utilization of osmotic distillation, membrane distillation, and coupled operation of these systems as an alternative to the conventional thermal evaporation (CTE) technique for the concentration of tomato juice. Some physicochemical characteristics of the products obtained by different techniques were determined. The samples concentrated by membrane systems were more advantageous by means of many parameters investigated, especially for color, hydroxymethylfurfural (HMF) and furan formation. HMF and furan contents were increased up to three to four times after CTE while there was no statistical change after membrane concentrations. Ascorbic acid and dehydroascorbic acid levels were decreased significantly after all concentration operations. Nonetheless, as total vitamin C content, membrane systems were more advantageous compared to CTE. Sensorial evaluation also showed that, except consistence, products obtained by membrane techniques gained higher scores than thermally concentrated products.Industrial RelevanceThe quality of tomato paste is dependent on process conditions used to convert the tomato pulp into paste. Conventional thermal evaporation may result in the deterioration of product quality by damaging heat sensitive tomato juice components as well as inducing color changes. Moreover, some mutagenic and carcinogenic compounds such as furan and HMF may be formed. Concentration of tomato juice using membrane systems can be proposed as the promising alternative to the CTE since most of the characteristics, especially color, are preserved, and HMF and furan formations are reduced significantly by these processes.