Value adding is one approach to maximising the ‘value’ of a new industry to its participants. The production of non-astringent persimmons (Diospyros kaki) is a new industry in Australia. Drying and freezing are well known processes of adding value to fruit, but these methods have not been applied to non-astringent persimmons.
The purpose of this research was to examine processing options as a means of value adding to non-astringent persimmon fruit that are not acceptable for the high quality fresh market. Up to 60% of marketable fruit is lost due to blemish marks, calyx separation and apex cracking. Other benefits for finding alternative uses for this fruit include accessing new markets which are closed to the fresh product because of quarantine or distribution problems, and increasing the exposure of domestic consumers to this new fruit.
Therefore, this research investigates the processing of ‘Fuyu’ and ‘Suruga’ non-astringent persimmon varieties that are not suitable for the high quality fresh market to determine optimum methods for producing sliced (10mm) dried and frozen non-astringent persimmons and to review product quality acceptance (water content, water activity, sulphur dioxide, pH, titratable acidity, total soluble solids, fruit firmness, colour (L a b), sensory characteristics) for commercial viability. Dried fruit was pre-treated with sodium metabisulphite (SMB) dip (2 and 3%), then dried by heat pump dryer (operating at 40°C (+/- 2°C) and 25% (+/- 2%) relative humidity) to between 15 and 20% water content. Frozen fruit was packed in 30% total soluble solids syrup with ascorbic acid (0.5%) and pH adjustment (pH 4.0), then blast frozen to a final product temperature of -18°C.
Results show that non-astringent persimmons can be dried following dipping in 2% SMB (general acceptability score 5.9, using 1-9 Hedonic scale 9 = like extremely, 1 = dislike extremely), or frozen with added 0.5% ascorbic acid (general acceptability score 5.8) to produce an acceptable product with a potential shelf life of at least four months. Unlike dried persimmons, frozen persimmons, regardless of the treatment applied, are found to be consistently rated by taste panellists as unacceptable when stored for up to eight months (general acceptability score < 4.9). This establishes that frozen persimmons deteriorate well short of the typical commercial freezing shelf life and food supply chain expectations. Therefore, dried non-astringent persimmons are the preferred value added product in this research.
In terms of variety, this research found no difference in preference for the ‘Fuyu’ or ‘Suruga’ varieties. In Australia, ‘Fuyu’ is the most commonly planted variety (around 70%), thus this positive outcome from the taste panel ratings indicates that the majority of the Australian non-astringent persimmon crop would be suitable for processing.
The research also demonstrates that the Minolta ‘colour a’ value is an acceptable indicator of the taste panel means for general acceptability (r=0.69) and appearance (r=0.65) of dried non-astringent persimmons. Hence, ‘colour a’ values could be used as an objective measurement for determining the acceptability of dried non-astringent persimmons.
The contribution of this research has been to establish a commercially acceptable process for drying non-astringent ‘Fuyu’ and ‘Suruga’ persimmon varieties and to link colour L a b values with sensory parameters as objective quality acceptance tools to monitor both the production and shelf life validation of processed non-astringent persimmon products.