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Extends fish shelf life.

By storing eviscerated fresh fish on ice that has been treated with a combination of citric acid and potassium sorbate, bacteria counts can be reduced and shelf life can be extended by several days. "We can now extend the shelf life of our fish ten days beyond the boat, where before it would have been six, maximum," Said Jerry Knecht, President of North Atlantic, Inc., a harvester and processor of fresh fish. Based on the results of studies performed last April, North Atlantic now uses treated ice for packing all fish at its Portland, ME operation.

Study conducted

Laboratory analyses were conducted to generate data to evaluate whether treated ice containing potassium sorbate and citric acid could benefit fish shelf life and quality. Atlantic cod, all taken from the same catch, were divided into experimental and control groups. The control group was stored on untreated ice, and the experimental group was stored on ice containing 0.20% citric acid and 0.05% potassium sorbate.

Fresh, eviscerated Atlantic cod were packed in 8-10 lb of treated ice. Duplicate boxes were prepared with untreated ice. Fish were stored at 34-38 F. Microbiological and organoleptic analyses were conducted at an independent laboratory on day 0, 3, 6, and 10.

For each checkpoint, treated and untreated fish were removed from the chiller from a fresh, unopened box. On each day, the cod were examined for appearance and odor of the skin surface, gill, and body cavity. An area of the skin 5 sq cm with a maximum depth of 3 mm was aseptically excised for microbiological evaluation.

Skin sample was placed in a sterile plastic bag with 45 ml of 0.1% peptone buffer and pummeled in a Stomacher for 2 min. Total viable counts were made in duplicate on pour plates using standard methods agar. Plates were incubated at 25 C for 96 hr to promote simultaneous growth of aerobic psychrotrophic and mesophilic bacteria.

Micro counts lowered

Results indicate a trend for potassium sorbate/citric acid to delay the log growth phase and maintain lower microbial counts on the treated fish. Organoleptic results showed after 6 days of storage that untreated fish had developed a slight sour odor in the body cavity, which was not detected in treated fish.

On the basis of this, and further trials with other fish species, North Atlantic now packs all fish on treated ice at its Portland location. Few physical modifications were required to incorporate treatment system with existing ice making equipment. Chemicals are premixed to specified concentrations and metered into ice make-up water.

Installation costs for the system were approximately $2,000. At current prices for potassium sorbate and citric acid, extra days of fish shelf life are realized at a cost of under 1/2 cent/lb.

Further information on applications of potassium sorbate and citric acid can be acquired from Haarmann & Reimer Corp., Food Ingredients Div., P.O Box 932, Elkhart, IN 46515.


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Title Annotation:ice containing potassium sorbate and citric acid
Author:Eilers, James R.
Publication:Food Processing
Date:Dec 1, 1992
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