I refer to John Kaneko's message of 3 August concerning water activity of fish cakes.
He writes that the Aw of the fish cakes is between 0.96 and 0.97. He does not state what solutes he uses to reduce the water activity to this level, but I note that a 1.0 molal solution of sodium chloride, 5.85gNaCl/100g water, has an Aw of 0.967 (Robinson & Stokes, Electrolyte Solution, Butterworths, 1959, Appendix 8.3, Table 1). If much of the lowering of Aw in the fish cakes is due to sodium chloride then its concentration is well above the 3.5%, water phase, which, in conjunction with refrigeration below 5ºC, is adequate to prevent production of botulinum toxin in smoked fish products.
Has John considered challenging his fish cakes with C. botulinum to see if they support growth of the organism and toxin formation?
Does John consider only the vacuum packed fish cakes pose a risk of producing botulinum toxin? The manufacture of fish cakes involves mixing of ingredients, and if the mix is contaminated with C. botulinum, the organism will be distributed throughout a cake. Cooking will not inactivate spores and conditions within the cake could allow for localised anaerobic regions even in cakes that were air packed.
Peter Howgate
----- Original Message -----
From: Pacific Management Resources, Inc.
To: seafood@ucdavis.edu
Sent: Friday, August 04, 2000 3:05 AM
Subject: water activity in fishcakes.
Date: August 3, 2000
To: Seafood List
Email: seafood@ucdavis.edu
Re: water activity in fishcakes.
I have a question about water activity in surimi-based fishcakes. Fishcakes (steamed, fried and broiled) are usually vacuum-packed and sold refrigerated. C. bot is a concern. The water activity of these fishcakes runs about 0.96-0.97.
What can be added to lower the water activity to below 0.935 to inhibit growth of C. bot? I have looked at many different fishcakes and imitation crab products sold in the refrigerated case. Either they are all out of compliance (possible) or else they have a recipe that results in a product with lower water activity.
What will do the job without fundamentally changing the nature of the fishcakes? Candidates. Carageenan? Sorbitol? Tripolyphosphate? More sugar and salt? More starch? Any other ideas?
Thanks for any help....John
John Kaneko MS, DVM
Project Director,
PacMar, Inc.
3615 Harding Avenue, Suite 409
Honolulu, Hawaii USA 96816
Ph: (808) 735-2602
Fax: (808) 734-2315
Email: pacusa@pixi.com
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