Bacterial Spoilage of Thawed Frozen Peas

Abstract

The main groups of bacteria developing in peas were isolated on differential media. Leuconostoc mesenteroides and Streptococcus lactis predominated and smaller numbers of catalase positive ‘coryneform’bacteria were also regularly present. Strep. cremoris , streptococci (group D), catalase positive cocci and Gram negative rods were less regularly isolated. Bacterial spoilage of untreated peas was usually accompanied by the development of a yellow colour and a reduction in pH. In pure culture in peas leuconostocs and group N streptococci produced an acid pH while the catalase positive organisms produced alkali, sometimes with ammoniacal odours. In mixed cultures in peas the products of a leuconostoc and a ‘coryneform’tended to neutralize each other. A leuconostoc and a ‘coryneform’did not interfere with each others’growth when grown from similar inocula. The behaviour of streptococci is still being investigated. The type and rate of spoilage probably depends on the balance between ammonia production and acid production in the system.