The vitamin B 12 content of lobster, crayfish, crab, and shrimp viscera was determined using a microbiological assay based on Lactobacillus delbrueckii subsp. lactis ATCC7830. These viscera contained high vitamin B 12 levels (7.2−118.6 μg/100 g of wet weight). We purified vitamin B 12 compounds from the extracts of these viscera using an immunoaffinity column. Corrinoid compounds were identified using liquid chromatography-electrospray ionization tandem mass spectrometry. The viscera tested contained vitamin B 12 -b-, -d-, and -e-monocarboxylic acids and vitamin B 12 -be-dicarboxylic acid, modified with peripheral propionamide side chains of the corrin ring. These vitamin B 12 carboxylic acids are specifically located in the viscera edible portions of lobster, crayfish, crab, and shrimp.

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After immunoaffinity purification, the vitamin B12 contents of 12 types of commercially available fish sauce products were determined using reversed-phase high-performance liquid chromatography. Vitamin B12 contents of fish sauce products varied from <0.1–1.7 μg per 100 g, with an average of 0.6 ± 0.1 μg of vitamin B12 per 100 g. Vitamin B12 was the major corrinoid compound in all fish sauce samples tested. Vitamin B12-d-monocarboxylic acid (approximately 4–38% of total vitamin B12) and vitamin B12-e-monocarboxylic acid (approximately 1–9%) were identified. Vitamin B12-b-monocarboxylic acid or pseudovitamin B12 were rarely detected at trace levels. Additionally unidentified vitamin B12 monocarboxylic acid (approximately 2–16%) was detected. These results suggest that pseudovitamin B12 and vitamin B12 monocarboxylic acids are derived from materials such as shrimp and shellfish.