Some Quality Aspects of Persimmon Jam Manufactured by Osmotic Dehydration without Thermal Treatment

Abstract

The traditional way of preparing persimmon jam produces astringent flavours due to the conversion of insoluble tannins into soluble tannins as a consequence of the high temperatures used in the process. For this reason, a new method for preparing this kind of product based on osmotic dehydration was tested, in order to obtain persimmon jam without thermal treatment. In this work, 'Rojo Brillante’ persimmon slices were dehydrated to approximately 30 ºBrix in concentrated grape juice of 65.8 ºBrix at 30ºC, according to a previous kinetic study. Then, samples were mixed with concentrated grape juice, potassium sorbate, pectin and citric acid in order to reach a concentration of soluble solids of approximately 48 ºBrix. Samples were stored at room temperature, and at 4ºC. Determinations of ºBrix, humidity, astringency, water activity and analysis of optical and mechanical properties (consistency and extrusion) were performed after 1, 5, 7, 12 and 18 days of storage. Non-refrigerated jam spoiled after five days of storage, but the characteristics of the refrigerated samples barely changed, without the presence of astringency. In conclusion, this method of preparing jam from persimmons could increase the commercial possibilities of this fruit, using refrigerated storage.