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United States Department of Agriculture

Agricultural Research Service

Research Project: Management of Off-flavors and Undesirable Bacteria in Aquaculture

Location: Natural Products Utilization Research

Title: Evaluation of a modified Ph-shift process to reduce 2-methylisoborneol and geosmin in spiked catfish and produce a consumer acceptable fried catfish nugget-like product

Authors
item Brown, Teresa -
item Cerruto-Noya, Claudia -
item Schrader, Kevin
item Kleinholz, Conrad -
item Mireles Dewitt, Christina -

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 2012
Publication Date: October 1, 2012
Citation: Brown, T.M., Cerruto-Noya, C.A., Schrader, K., Kleinholz, C.W., Mireles Dewitt, C.A. 2012. Evaluation of a modified Ph-shift process to reduce 2-methylisoborneol and geosmin in spiked catfish and produce a consumer acceptable fried catfish nugget-like product. Journal of Food Science. 77(10):377-383.

Interpretive Summary: Channel catfish fillets containing “earthy” and “musty” off-flavor compounds were subjected to a processing method in which the fillets were treated with acidified water and then filtered. The process reduced off-flavors in mildly off-flavored catfish to acceptable levels. In addition, the texture of the resulting product was preferred to untreated fillets.

Technical Abstract: Farm-raised catfish weighing about 1 kg were selected and placed into 3 tanks each containing 1000 L of water. Treatment of tanks was blocked by week. In week 1, catfish in tanks were allowed to depurate 24 h, and then were held an additional 24 h. In weeks 2 and 3, catfish were treated as in week 1 except after the initial 24 h depuration tanks were treated with either 1 ppb geosmin (GEO) or 2-methylisoborneol (MIB). After each treatment, catfish were collected, pooled and then randomly redistributed into 3 groups (replicates) containing equal male:female ratios. Fillets from each replicate were collected and ground. A portion was treated by the acid pH-shift process which involved diluting fish with water (1:9), acidifying to pH 2.5, and filtering through a sieve to remove insoluble residuals. The acidified filtrate was adjusted to pH 5.5, dewatered with the aid of cheesecloth, and labeled as processed. Samples from all treatments and replicates were evaluated for residual GEO and MIB. Additionally, batter-coated fried catfish samples were prepared for a consumer sensory evaluation. Results demonstrated that the pH-shift process decreased % moisture, ash, and collagen content of catfish fillet tissue (p<0.05). Flavor of control samples was preferred (p<0.05). Texture of catfish samples treated by the pH-shift process was preferred (p<0.05). Results demonstrate the pH-shift process can be utilized to reduce off-flavors and increase the acceptability of a processed catfish product.

Last Modified: 10/25/2014
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