Quality of Potatoes by Sous Vide Processing

Quality of sous vide processed potatoes was studied in relation to the differences of processing temperatures (70, 80, 90 or 100°C) and degrees of vacuum (30 or 100Torr) in packaging. In addition, quality changes in sous vide processed potatoes during storage was also investigated. When processed at 80°C or higher temperatures, potatoes showed no changes in surface color in all treatments. Browning, however, occurred in processing at 70°C. There were no appreciable differences between the hardness of potatoes and the degree of vacuum during processing at 80 or 90°C. In the processing at 100°C, potatoes remained harder with a lowering of the degree of vacuum while those packaged under atmospheric pressure remained hardest. The content of total ascorbic acid in potatoes was kept higher during processing at 90 and 100°C. The content in packaged potatoes was higher than that in the conventional processing potatoes. Dehydroascorbic acid content showed almost the same value in all the treatments. There was no considerable difference between the sugar content and the degree of vacuum in packaged potatoes. The sugar content in the conventional processing, however, was lower when compared with that of the processing at 80 or 90°C of packaged potatoes. Anaerobic bacteria were detected after 3 days of storage at 20°C. Potatoes were putrefied after 3 days of storage at 20°C. No bacteria were detected for 7 days of the storage when stored at 5 or 10°C. Dehydroascorbic acid content increased during storage at all temperatures. Changes of reducing sugar content showed a similar tendency at all of the storage temperatures and increased slightly during storage. It is suggested that sous vide processing at 90°C or higher temperatures is good for the storage of potatoes and that storage at 5°C or a lower temperature is good for quality.