Quality changes during the storage of sous vide processed soybean sprouts soup

Soybean sprouts soup was made by mixing 100 g blanched soybean sprouts with 400 mL tap water containing 0.8% salt. The soup was vacuum packed in a plastic bag and cooked at 97°C with subsequent rapid cooling. Packaged samples were stored in a refrigerating chamber at 3 and 10°C. Sous vide (cook-chill) soybean sprouts soup was evaluated for physicochemical quality changes and microbial safety during storage to examine the possibility of shelf-life extension and industrial application. The physicochemical changes examined were colour, texture and concentration of ascorbic acid. More deterioration in the quality of the soybean sprouts soup was found when stored at 10°C than at 3°C. Initial numbers of aerobic, anaerobic and psychrophilic bacteria were high but those of heat resistant bacteria, yeast and molds were low in the raw soybean sprouts. Finally no microorganisms were detected after sous vide processing. The sous vide soybean sprouts soup received high scores in all sensory evaluations and did not differ significantly from the freshly cooked soup. We conclude that soybean sprouts soup prepared in the described manner may be stored for at least 6 days under chilled conditions and used by the food service industry with good quality characteristics.