Studies on the Preservation of Cooked Beans

Abstract

Bacteriological examination was conducted on cooked beans packed in film under vacuum, and the effect of sorbic acid (SOA) and furylfuramide (FF) was investigated for the preservation of the product. Three-layered plate method was very useful for bacteria counting, preventing the rapid spreading of colonies of Bacillus strains. More than thirty strains belonging to B. pumilus, B. megaterium, B. cereus, B. subtilis, B. licheniformis, B. circulans, B. coagulans, Clostridium acetobutyricum, and C. bifermentans were isolated from the products prepared with or without SOA and stored at 37°C for a few days, one and six months. For preventing the growth of non-spore forming bacteria found in the products pasteurized at 85°C for 45min., 1500μg/ml SOA or 10μg/ml FF was necessary at pH 5. 8. The effectiveness of these preservatives decreased significantly with the increase in the number of inoculated bacteria. Some strains isolated from the product, especially of Clostridium, exhibited an ability to decompose SOA. By addition of 1000μg/g SOA or 2.5μg/g FF, the product was preserved for 21 days at 37°C without any spoilage in appearance and without increase in number of bacteria more than 10102-103/g. About half of added FF was lost by heat-treatment and the rest disappeared rapidly during the storage, while SOA decreased to only a limited extent.