Brian H. Himelbloom

Ozone Efficacy as a Bactericide in Seafood Processing

Abstract The efficacy of ozonated water (0.6-1.5 ppm) was evaluated as a bactericidal agent for sanitizing food contact surfaces and for treatment of raw seafood. The presence of ozone reduced the bacterial levels substantially on stainless steel surfaces and to a lesser extent on plastic cutting boards. Ozone was about as effective as chlorine in lowering levels of Listeria innocua on inoculated food contact surfaces. Fish processing residuals present on the surface greatly reduced sanitizer effectiveness. In high organic conditions, chlorinated water was slightly more effective than ozonated water. However, ozonated water applied to fish fillets and roe was not effective for bacterial control. The presence of organic material, particularly with fillets, reduced the effectiveness of ozone. Ozone accelerated the development of rancidity in frozen roe and fillets, resulting in reduced shelf life. We recommend ozone only as a sanitizer for cleaned seafood contact surfaces.

Chemical characterization of commercial liquid smoke products

The objective of this study was to determine important chemical characteristics of a full-strength liquid smoke, Code 10-Poly, and three refined liquid smoke products (AM-3, AM-10 and 1291) commercially available (Kerry Ingredients and Flavors, Monterey, TN). The pH of the products were significantly different (Pu2003<u20030.05) and ranged from 2.3 (Code 10-Poly) to 5.7 (1291). The pH was inversely correlated with titratable acidity (R2u2003=u20030.87), which was significantly different (Pu2003<u20030.05) among products ranging from 10.3% acetic acid (Code 10-Poly) to 0.7% acetic acid (1291). Total phenol content was quantified using the Gibbs reaction; the only liquid smoke containing appreciable level of phenolic compounds was Code 10-Poly at 3.22u2003mg mL−1. Gas chromatography-mass spectrometry (GC-MS) analysis of liquid smoke dichloromethane extracts revealed that carbonyl-containing compounds were major constituents of all products, in which 1-hydroxy-2-butanone, 2(5H)-furanone, propanal and cyclopentenone predominated. Organic acids were detected by GC-MS in all extracts and correlated positively (R2u2003=u20030.98) with titratable acidity. The GC-MS data showed that phenolic compounds constituted a major portion of Code 10-Poly, and were detected only in trace quantities in 1291. The refined liquid smokes had lighter color, lower acidity, and reduced level of carbonyl-containing compounds and organic acids. Our study revealed major differences in pH, titratable acidity, total phenol content, color and chemical make-up of the full-strength and refined liquid smokes. The three refined liquid smoke products studied have less flavor and color active compounds, when compared with the full-strength product. Furthermore, the three refined products studied have unique chemical characteristics and will impart specific sensorial properties to food systems. Understanding the chemical composition of liquid smokes, be these refined or full-strength products, is an important step to establish their functions and appropriate use in food systems.

Microbial Evaluation of Alaska Salmon Caviar

Microbial quality of pink salmon caviar (ikura) processed at one plant in Alaska during a 30-day season was examined. Ikura (aw = 0.98; pH 6.1) averaged 49% water, 32% protein, 11% fat, 7% ash, and 3% salt. Aerobic plate counts (APCs) ranged from < 10(2)/g to 4.5 x 10(7)/g with increasing APC toward seasons end. Coliform counts ranged from < 3/g to 2.4 x 10(3)/g. Escherichia coli, Staphylococcus aureus, yeasts, and molds were not detected. High-APC (10(7)/g) thawed caviar exhibited predominantly lactic acid bacteria; low-APC (10(3)/g) thawed caviar exhibited predominantly gram-negative bacteria. Freezing had little effect on the microbial counts, and shelf life of thawed caviar was 3 to 5 days at 2 degrees C.

Microbial Quality of an Alaska Native Smoked Salmon Process

A 4-day process of smoking and drying at ambient temperature (30°C) was used to produce Alaska Native-style salmon strips. A water activity of 0.95 during the first 3 days of smoking and drying allowed initial aerobic and facultative anaerobic microbial counts of 1.4 × 104/g and 6.5 × 103/g to reach 2.1 × 106/g and 2.8 × 106/g of fish, respectively. Coliform and yeast counts, which were less than 3/g and less than 4.0 × 102/g respectively, increased to 2.4 × 105/g and 4.2 × 104/g of fish by day 4. Staphylococcus aureus counts increased from 15/g to 2.4 × 105/g of fish during processing. The high S. aureus count in this product indicates consumers may be at risk.

Refined liquid smoke: a potential antilisterial additive to cold-smoked sockeye salmon (Oncorhynchus nerka).

Cold-smoked salmon (CSS) is a potentially hazardous ready-to-eat food product due to the high risk of contamination with Listeria monocytogenes and lack of a listericidal step. We investigated the antilisterial property of liquid smokes (LS) against Listeria innocua ATCC 33090 (surrogate to L. monocytogenes) as a potential supplement to vacuum-packaged CSS. A full-strength LS (Code 10-Poly), and three commercially refined fractions (AM-3, AM-10, and 1291) having less color and flavor (lower content of phenols and carbonyl-containing compounds) were tested. In vitro assays showed strong inhibition for all LS except for 1291. The CSS strips were surface coated with AM-3 and AM-10 at 1% LS (vol/wt) with an L-shaped glass rod and then inoculated with L. innocua at 3.5 log CFU/g, vacuum packaged, and stored at 4°C. The LS did not completely eliminate L. innocua but provided a 2-log reduction by day 14, with no growth up to 35 days of refrigerated storage. A simple difference sensory test by 180 untrained panelists showed the application of AM-3 did not significantly influence the overall sensorial quality of CSS. In essence, the application of the refined LS as an antilisterial additive to CSS is recommended.

False-positive fluorescence by pink salmon tissue and staphylococci in a rapid test for Escherichia coli

Fluorescence from 4-methylumbelliferyl-beta-D-glucuronide (MUG) hydrolysis is a common, rapid method for determining Escherichia coli in water and food. False-positive fluorescence occurred when either pink salmon fillets were tested or beta-glucuronidase-positive Staphylococcus species were present in other fish products. Salmon fillet, E. coli, S. xylosus, and S. warneri produced 2, 17, 39, and 43 nmol of 4-methylumbelliferone per ml, respectively, in a one-step detection broth (lauryl salts tryptose broth with MUG) for E. coli after 48 h at 35 degrees C. These false-positive reactions need to be considered when testing fish products, especially those contaminated through human handling.

Microbial analysis of a fish waste dump site in Alaska

The bacteriological impact of fish waste dumping in the ocean was evaluated by comparing heterotropic bacterial counts for seawater and sediment at the dump site with those from a control site. Prior to dumping, fish waste contained 3·0 × 107 bacteria g−1. Seawater near the ocean floor (bottom water) and sediment from the dump site contained 4·0 × 102 bacteria ml−1 and 2·2 × 106 bacteria g−1, respectively. Bottom water and sediment samples from the control site contained significantly lower bacterial counts (<102 bacteria g−1 and 6·1 × 104 bacteria g−1, respectively) than the dump site samples. For the five aerobic media tested, significant differences in bacterial counts occurred only for the fish waste samples. Anaerobic bacterial counts, for all samples except fish waste, were slightly less than the aerobic bacterial counts.

Supplementing long-chain n-3 polyunsaturated fatty acids in canned wild Pacific pink salmon with Alaska salmon oil.

Establishing n-3 polyunsaturated fatty acid contents in canned wild Alaska pink salmon products is challenging due to ample natural variation found in lipid content of pink salmon muscle. This study investigated the effect of adding salmon oil (SO) to canned pink salmon produced from fish exhibiting two opposite degrees of skin watermarking, bright (B) and dark (D). Specific goals of the study were to evaluate the benefits of adding SO to canned pink salmon with regard to nutritional value of the product, sensory characteristics, and the oxidative and hydrolytic stability of the lipids over thermal processing. Six groups of canned pink salmon were produced with variable levels of SO, either using bright (with 0, 1, or 2% SO) or dark (with 0, 2, or 4% SO) pink salmon. Compositional analysis revealed highest (Pu2003<u20030.05) lipid content in sample B2 (8.7%) and lowest (Pu2003<u20030.05) lipid content in sample D0 (3.5%). Lipid content of samples B0, B1, D2, and D4 was not significantly different (Pu2003>u20030.05) ranging from 5.7% to 6.8%. Consequently, addition of SO to canned pink salmon allowed for consistent lipid content between bright and dark fish. Addition of 1% or 2% SO to canned bright pink salmon was not detrimental to the sensory properties of the product. It is recommended that canned bright pink salmon be supplemented with at least 1% SO, while supplementation with 2% SO would guarantee a minimum quantity of 1.9u2003g of n-3 fatty acids per 100u2003g of product. Addition of 4% SO to canned dark pink salmon was detrimental to product texture and taste, while supplementation with 2% SO did not negatively affect sensorial properties of the product. Accordingly, canned dark pink salmon should be supplemented with 2% SO so that a minimum n-3 fatty acids content of 1.5u2003g per 100u2003g of product.

Portable ATP Luminometry for Evaluating Salmon Roe Processing Facilities

Abstract Sanitation conditions in two salmon roe processing operations were evaluated by adenosine triphosphate (ATP) assays using a portable luminometer and single-use reaction swabs. The bioluminescent reaction provided real-time testing (< 1 min) when compared to standard microbiological analyses (48-72 hr). The ATP assay was quicker and more sensitive than a rapid protein assay (10 min) in detecting presence of biological contamination. High levels of ATP indicated the presence of fish residues and/or bacteria on processing surfaces. The ATP values correlated well with aerobic bacterial counts but the protein values were poorly correlated with either data set. Luminometry showed the effect of proper cleaning and sanitizing between the seafood processing plants tested. A common reservoir of bacterial contamination was the plastic baskets used for transferring salmon roe between sorting, grading, washing and packing stations. The handheld luminometer is suitable as a rapid quality control tool for seafood processors.