Michael L. Jahncke

Low Dose Gamma Irradiation to Reduce Pathogenic Vibrios in Live Oysters (Crassostrea virginica)

Abstract Pathogenic strains of Vibrio (Vibrio vulnificus and V. parahaemolyticus), natural inhabitants of estuarine and ocean environments, can cause serious illness and death in susceptible persons from consumption of raw half-shell oysters. Objectives of this study were (1) to establish the irradiation dose needed to reduce pathogenic vibrios to nondetectable levels and (2) to determine consumers ability to differentiate between irradiated and control oysters. Live oysters, Crassostrea virginica, with naturally incurred and artificially inoculated pathogenic vibrios, were exposed to 0-3 kGy dose Cobalt-60 gamma radiation. Vibrio vulnificus (MO-624) was reduced from 106 cfu/g oyster meat to nondetectable levels (< 3 mpn/g oyster meat) with 0.75-1.0 kGy irradiation exposure. Vibrio parahaemolyticus, 03:K6 (TX-2103), required 1.0-1.5 kGy for reduction to nondetectable levels. Using triangle difference testing, sensory panelists were asked to identify differences between treated (1 kGy) and untreated oysters. Sensory difference tests, triangle method, by 146 volunteers confirmed that panelists, many of whom worked in the seafood industry, were unable to distinguish non-irradiated from irradiated oysters (p < 0.001).

Inactivation of Vibrio parahaemolyticus and Vibrio vulnificus in phosphate-buffered saline and in inoculated whole oysters by high-pressure processing

Inactivation studies for Vibrio parahaemolyticus TX-2103 (serotype O3:K6) and Vibrio vulnificus MO-624 (clinical isolate) were conducted in phosphate-buffered saline (PBS) and in inoculated oysters under high-pressure processing conditions. V. parahaemolyticus was more resistant than V. vulnificus in PBS at all pressures and times. A 6-log reduction of V. parahaemolyticus and V. vulnificus in PBS at 241 MPa required 11 and 5 min, respectively, which included a 3-min pressure come-up time. A 4.5-log reduction of V. parahaemolyticus in oysters at 345 MPa required 7.7 min, which included a 6.7-min pressure come-up time. More than a 5.4-log reduction of V. vulnificus in oysters at 345 MPa occurred during the 6-min pressure come-up time. Both V. parahaemolyticus and V. vulnificus in PBS and in oysters were reduced to nondetectable numbers at 586 MPa during the 8- and 7-min pressure come-up times, respectively.

Comparison of kinetic models to describe high pressure and gamma irradiation used to inactivate Vibrio vulnificus and Vibrio parahaemolyticus prepared in buffer solution and in whole oysters.

Comparisons of different models in inactivation kinetics were conducted on data obtained from high-pressure and gamma-irradiation processing. Vibrio vulnificus (MO-624) and Vibrio parahaemolyticus (O3:K6 TX-2103) suspended in phosphate-buffered saline (pH 7.4, 10(7) CFU/ml) were exposed to pressures from 207 to 379 MPa for 1 to 20 min. Inoculated whole oysters (106 CFU/g) were exposed to pressure from 276 to 379 MPa for 1 to 15 min. Pure cultures and inoculated oysters (10(6) CFU/g) also were irradiated (gamma irradiation) at doses of less than 3 kGy. Four mathematical models, the Bigelow model, Arrhenius equation, Fermi equation, and Weibull frequency distributions, were applied to microbial survival data, and performances of the different kinetic models were compared. Weibull frequency distributions can predict the high-pressure inactivation of Vibrio spp. with more accuracy in both pure cultures and inoculated oyster samples. The Fermi model provided a better description of gamma-irradiation inactivation kinetics compared with the traditional Bigelow model.

Effects of modified atmosphere packaging on toxin production by Clostridium botulinum in raw aquacultured summer flounder fillets (Paralichthys dentatus).

Packaging fishery products under vacuum atmosphere packaging (VAC) and modified atmosphere packaging (MAP) conditions can significantly extend the shelf life of raw, refrigerated fish products. There is considerable commercial interest in marketing VAC and MAP refrigerated (never frozen) raw fish fillets. The objective of this study was to determine if Clostridium botulinum toxin development precedes microbiological spoilage in raw, refrigerated flounder fillets. Aquacultured flounder (Paralichthys dentatus) individual fish fillets either were packed with a film having an oxygen transmission rate (OTR) of 3000 cm3 m(-2) 24 h(-1) at 22.8 degrees C or were vacuum packaged or packaged under 100% CO2 with a film having an OTR of 7.8 cm3 m(-2) 24 h(-1) at 21.1 degrees C and were stored at 4 and 10 degrees C. Samples were analyzed by aerobic plate count (APC) for spoilage and qualitatively for botulinum toxin with a mouse bioassay. The results demonstrate that flounder fillets (4 degrees C) packaged with a film having an OTR of 3,000 were microbiologically spoiled (APC, > 10(7) CFU/g) on day 15, but there was no toxin formation, even after 35 days of storage. However, at 10 degrees C, toxin production occurred (day 8), but it was after microbial spoilage and absolute sensory rejection (day 5). Vacuum-packaged fillets and 100% CO2 fillets (4 degrees C) packaged with a film having an OTR of 7.8 were toxic on days 20 and 25, respectively, with microbial spoilage (APC, >10(7) CFU/g) not occurring during the tested storage period (i.e., >35 days). At 10 degrees C, in vacuum-packaged flounder, toxin formation coincided with microbiological spoilage (days 8 to 9). In the 100% CO2-packaged fillets, toxin formation occurred on day 9, with microbial spoilage occurring on day 15. This study indicates that films with an OTR of 3,000 can be used for refrigerated fish fillets and still maintain the safety of the product.

Nutritional composition and microflora of the fresh and fermented skate (Raja Kenojei) skins

The proximate compositions of fresh and fermented skate skin were each 75.95% and 74.5% moisture, 22.7% and 21.8% protein, 0.5% and 0.7% lipid and 0.6% and 0.9% ash, respectively. The predominant minerals were potassium and phosphorus (i.e. 53.5 and 33.0 mg/100 g in fresh skin, and 10.46 and 10.51 mg/100 g in fermented skin, respectively). Amino acid concentrations were lower in the fermented skin compared with the fresh skin. Histidine, glycine, alanine and glutamic acid were the major free amino acids in both skins. Palmitic acid (C16:0) was the major fatty acid in both fresh (16.68%) and fermented (20.38%) skate skin. Omega-3 polyunsaturated fatty acids were higher in fresh skin (22.17%) and fermented skin (24.54%) compared with omega-6 polyunsaturated fatty acids. The predominant microflora present in the both fresh and fermented skin were Photobacterium sp. and Vibrio sp. Total plate counts for the fresh and fermented skin were 2.4×104 CFU/g and 7.7×107 CFU/g, respectively.

Effects of Codex and GATT

Abstract The role of the WHO/FAO Food Standards Programme has become increasingly important since the Uruguay Round of GATT since adherence to Codex Standards offers safe harborage in WTO disputes. This paper reviews some of the Programmes history and successes, discusses Codexs changing role due to GATT and WTOs endorsement of its work products, and discusses HACCP and other topical issues. It also details where the Codex Programme is in relation to streamlining its activities in terms of emphasizing the role of science in its deliberations, accelerating the timeliness of its activities, and recasting its recommendations for national government acceptance of its standards.

Optimum Cooking Conditions for Shrimp and Atlantic Salmon

The quality and safety of a cooked food product depends on many variables, including the cooking method and time-temperature combinations employed. The overall heating profile of the food can be useful in predicting the quality changes and microbial inactivation occurring during cooking. Mathematical modeling can be used to attain the complex heating profile of a food product during cooking. Studies were performed to monitor the product heating profile during the baking and boiling of shrimp and the baking and pan-frying of salmon. Product color, texture, moisture content, mass loss, and pressed juice were evaluated during the cooking processes as the products reached the internal temperature recommended by the FDA. Studies were also performed on the inactivation of Salmonella cocktails in shrimp and salmon. To effectively predict inactivation during cooking, the Bigelow, Fermi distribution, and Weibull distribution models were applied to the Salmonella thermal inactivation data. Minimum cooking temperatures necessary to destroy Salmonella in shrimp and salmon were determined. The heating profiles of the 2 products were modeled using the finite difference method. Temperature data directly from the modeled heating profiles were then used in the kinetic modeling of quality change and Salmonella inactivation during cooking. The optimum cooking times for a 3-log reduction of Salmonella and maintaining 95% of quality attributes are 100, 233, 159, 378, 1132, and 399 s for boiling extra jumbo shrimp, baking extra jumbo shrimp, boiling colossal shrimp, baking colossal shrimp, baking Atlantic salmon, and pan frying Atlantic Salmon, respectively.

Thermal Optima for the Culture of Juvenile Summer Flounder, Paralichthys dentatus

Abstract Summer flounder, Paralichthys dentatus, aquaculture has shown promise over the recent past and a considerable body of knowledge is amassing for this species of flatfish. Even with the amassing data, basic information on environmental parameter ranges to maintain in indoor culture systems is still lacking. Therefore, the current study was undertaken to elucidate a temperature range that may be best suited for juvenile summer flounder production in indoor recirculating aquaculture. A 10-week study was designed to address 19, 24 and 29°C as potential temperatures for the culture of summer flounder. Fish averaging 9.5 g initial weight were stocked into triplicate 20-L aquaria per treatment after conditioning to their respective temperatures for 1 week. Fish were fed to apparent satiation twice daily a 50% crude protein fingerling diet and weighed every 2 weeks to assess growth rates. Juvenile summer flounder grew better at 24 and 29°C (167 and 197% increase initial weight, respectively) than at 19°C (97% increase in initial weight) with increased individual fish variation within a treatment as temperature increased above 19°C. Feed efficiency was greatest at 24 and 29°C (0.65 and 0.57, respectively), but survival decreased at temperatures above 19°C (93, 60 and 57% for 19, 24 and 29°C, respectively). There was no effect of temperature on the hepatosomatic index or interior muscle ratio, but the finray muscle ratio was slightly elevated when flounder were cultured at 29°C. The lipid content of the finray muscle and liver also increased at 29°C. Therefore, 24°C appears to be the best culture temperature for summer flounder with respect to growth rates and efficiency, but survival and homogeneity of flounder may be lowered at temperatures above 19°C.

Applications of HACCP Principles to Address Food Safety and Other Issues in Aquaculture: An Overview

Abstract Aquaculture is important to our United States fishery system. Import and export markets for such products can be expected to expand, particularly as increased research begins to remove physiological and animal husbandry barriers, and over fishing of wild stocks require replenishment through increased aquaculture efforts. Some unique risk factors associated with aquacultured products must be addressed and controlled as the United States relies more on aquacultured species. This is particularly the case due to concerns about increased risk exposure to our national sea animals, vegetation in the marineestuarine, and fresh water environments when live animals are transferred across state, provincial, and national borders. Nonetheless, application of the Hazard Analysis Critical Control Point (HACCP) principles as a risk management tool in aquaculture will work provided the proper infrastructures are executed. We must also overcome the historical regulatory pitfalls of HACCP dealing with concept understanding, critical control point definitions, misunderstanding of and between the complimentary roles of sanitation and process controls, agency and industry commitment, inspector and consumer acceptance and effective training.

Determination of Quality Attributes of Blue Crab (Callinectes sapidus) Meat by Electronic Nose and Draeger-Tube Analysis

ABSTRACT In this study, five groups of sequentially spoiled crabmeat were evaluated by a trained sensory panel, and these results were compared with the findings from a Cyranose 320 Electronic Nose and Draeger gas analyzer. Using the electronic nose with filtered compressed breathing air yielded the best results. Although this approach resulted in 100 % separation of the known groups, only 30% of the coded unknown samples were correctly identified. All 5 groups of samples analyzed using Draeger-Tubes were found to be significantly different at α = 0.05 using a Tukey-Kramer ANOVA statistical procedure. The coded unknown samples were correctly identified at a rate of 83%. The simplicity and precision of this latter procedure may present opportunities for use of Draeger-Tubes by crab processing industries and other food processing industries as an objective method for quality control.